Changelog — Python 3.12.9 documentation
Description: Python 3.12.9 final: Release date: 2025-02-04 Tests: gh-127906: Test the limited C API in test_cppext. Patch by Victor Stinner., gh-127906: Backport test_cext from the main branch. Patch by Victor ...

# Changelog

## Python 3.12.9 final

Release date: 2025-02-04

### Tests

- gh-127906: Test the limited C API in test_cppext. Patch by Victor Stinner.

- gh-127906: Backport test_cext from the main branch. Patch by Victor Stinner.

- gh-127637: Add tests for the `dis` command-line interface. Patch by Bénédikt Tran.

### Security

- gh-105704: When using `urllib.parse.urlsplit()` and `urllib.parse.urlparse()` host parsing would not reject domain names containing square brackets (`[` and `]`). Square brackets are only valid for IPv6 and IPvFuture hosts according to RFC 3986 Section 3.2.2.

- gh-127655: Fixed the `asyncio.selector_events._SelectorSocketTransport` transport not pausing writes for the protocol when the buffer reaches the high water mark when using `asyncio.WriteTransport.writelines()`.

- gh-126108: Fix a possible `NULL` pointer dereference in `PySys_AddWarnOptionUnicode()`.

- gh-80222: Fix bug in the folding of quoted strings when flattening an email message using a modern email policy. Previously when a quoted string was folded so that it spanned more than one line, the surrounding quotes and internal escapes would be omitted. This could theoretically be used to spoof header lines using a carefully constructed quoted string if the resulting rendered email was transmitted or re-parsed.

- gh-119511: Fix a potential denial of service in the `imaplib` module. When connecting to a malicious server, it could cause an arbitrary amount of memory to be allocated. On many systems this is harmless as unused virtual memory is only a mapping, but if this hit a virtual address size limit it could lead to a `MemoryError` or other process crash. On unusual systems or builds where all allocated memory is touched and backed by actual ram or storage it could’ve consumed resources doing so until similarly crashing.

### Library

- gh-129502: Unlikely errors in preparing arguments for `ctypes` callback are now handled in the same way as errors raised in the callback of in converting the result of the callback – using `sys.unraisablehook()` instead of `sys.excepthook()` and not setting `sys.last_exc` and other variables.

- gh-129403: Corrected `ValueError` message for `asyncio.Barrier` and `threading.Barrier`.

- gh-129409: Fix an integer overflow in the `csv` module when writing a data field larger than 2GB.

- gh-118761: Improve import time of `subprocess` by lazy importing `locale` and `signal`. Patch by Taneli Hukkinen.

- gh-129346: In `sqlite3`, handle out-of-memory when creating user-defined SQL functions.

- gh-128550: Removed an incorrect optimization relating to eager tasks in `asyncio.TaskGroup` that resulted in cancellations being missed.

- gh-128991: Release the enter frame reference within `bdb` callback

- gh-128961: Fix a crash when setting state on an exhausted `array.array` iterator.

- gh-128916: Do not attempt to set `SO_REUSEPORT` on sockets of address families other than `AF_INET` and `AF_INET6`, as it is meaningless with these address families, and the call with fail with Linux kernel 6.12.9 and newer.

- gh-128679: Fix `tracemalloc.stop()` race condition. Fix `tracemalloc` to support calling `tracemalloc.stop()` in one thread, while another thread is tracing memory allocations. Patch by Victor Stinner.

- gh-128562: Fix possible conflicts in generated `tkinter` widget names if the widget class name ends with a digit.

- gh-128552: Fix cyclic garbage introduced by `asyncio.loop.create_task()` and `asyncio.TaskGroup.create_task()` holding a reference to the created task if it is eager.

- gh-128479: Fix `asyncio.staggered.staggered_race()` leaking tasks and issuing an unhandled exception.

- gh-88834: Unify the instance check for `typing.Union` and `types.UnionType`: `Union` now uses the instance checks against its parameters instead of the subclass checks.

- gh-128302: Fix `xml.dom.xmlbuilder.DOMEntityResolver.resolveEntity()`, which was broken by the Python 3.0 transition.

- gh-128302: Allow `xml.dom.xmlbuilder.DOMParser.parse()` to correctly handle `xml.dom.xmlbuilder.DOMInputSource` instances that only have a `systemId` attribute set.

- gh-112064: Fix incorrect handling of negative read sizes in `HTTPResponse.read`. Patch by Yury Manushkin.

- gh-58956: Fixed a frame reference leak in `bdb`.

- gh-128131: Completely support random access of uncompressed unencrypted read-only zip files obtained by `ZipFile.open`.

- gh-127975: Avoid reusing quote types in `ast.unparse()` if not needed.

- gh-128014: Fix resetting the default window icon by passing `default=''` to the `tkinter` method `wm_iconbitmap()`.

- gh-115514: Fix exceptions and incomplete writes after `asyncio._SelectorTransport` is closed before writes are completed.

- gh-41872: Fix quick extraction of module docstrings from a file in `pydoc`. It now supports docstrings with single quotes, escape sequences, raw string literals, and other Python syntax.

- gh-126742: Fix support of localized error messages reported by dlerror(3) and gdbm_strerror in `ctypes` and `dbm.gnu` functions respectively. Patch by Bénédikt Tran.

- gh-127870: Detect recursive calls in ctypes `_as_parameter_` handling. Patch by Victor Stinner.

- gh-127847: Fix the position when doing interleaved seeks and reads in uncompressed, unencrypted zip files returned by `zipfile.ZipFile.open()`.

- gh-127732: The `platform` module now correctly detects Windows Server 2025.

- gh-93312: Include `<sys/pidfd.h>` to get `os.PIDFD_NONBLOCK` constant. Patch by Victor Stinner.

- gh-83662: Add missing `__class_getitem__` method to the Python implementation of `functools.partial()`, to make it compatible with the C version. This is mainly relevant for alternative Python implementations like PyPy and GraalPy, because CPython will usually use the C-implementation of that function.

- gh-127586: `multiprocessing.pool.Pool` now properly restores blocked signal handlers of the parent thread when creating processes via either spawn or forkserver.

- gh-98188: Fix an issue in `email.message.Message.get_payload()` where data cannot be decoded if the Content Transfer Encoding mechanism contains trailing whitespaces or additional junk text. Patch by Hui Liu.

- gh-127257: In `ssl`, system call failures that OpenSSL reports using `ERR_LIB_SYS` are now raised as `OSError`.

- gh-126775: Make `linecache.checkcache()` thread safe and GC re-entrancy safe.

- gh-58956: Fixed a bug in `pdb` where sometimes the breakpoint won’t trigger if it was set on a function which is already in the call stack.

- gh-123401: The `http.cookies` module now supports parsing obsolete RFC 850 date formats, in accordance with RFC 9110 requirements. Patch by Nano Zheng.

- gh-123085: In a bare call to `importlib.resources.files()`, ensure the caller’s frame is properly detected when `importlib.resources` is itself available as a compiled module only (no source).

- gh-122431: `readline.append_history_file()` now raises a `ValueError` when given a negative value.

### Documentation

- gh-125722: Require Sphinx 8.1.3 or later to build the Python documentation. Patch by Adam Turner.

- gh-67206: Document that `string.printable` is not printable in the POSIX sense. In particular, `string.printable.isprintable()` returns `False`. Patch by Bénédikt Tran.

### Core and Builtins

- gh-129345: Fix null pointer dereference in `syslog.openlog()` when an audit hook raises an exception.

- gh-129093: Fix f-strings such as `f'{expr=}'` sometimes not displaying the full expression when the expression contains `!=`.

- gh-124363: Treat debug expressions in f-string as raw strings. Patch by Pablo Galindo

- gh-128799: Add frame of `except*` to traceback when it wraps a naked exception.

- gh-128078: Fix a `SystemError` when using `anext()` with a default tuple value. Patch by Bénédikt Tran.

- gh-128079: Fix a bug where `except*` does not properly check the return value of an `ExceptionGroup`’s `split()` function, leading to a crash in some cases. Now when `split()` returns an invalid object, `except*` raises a `TypeError` with the original raised `ExceptionGroup` object chained to it.

- gh-127903: `Objects/unicodeobject.c`: fix a crash on DEBUG builds in `_copy_characters` when there is nothing to copy.

- gh-127599: Fix statistics for increments of object reference counts (in particular, when a reference count was increased by more than 1 in a single operation).

- gh-111609: Respect end_offset in `SyntaxError` subclasses.

- gh-126862: Fix a possible overflow when a class inherits from an absurd number of super-classes. Reported by Valery Fedorenko. Patch by Bénédikt Tran.

- gh-117195: Avoid assertion failure for debug builds when calling `object.__sizeof__(1)`

### C API

- gh-126554: Fix error handling in `ctypes.CDLL` objects which could result in a crash in rare situations.

- gh-107249: Implement the `Py_UNUSED` macro for Windows MSVC compiler. Patch by Victor Stinner.

### Build

- gh-129539: Don’t redefine `EX_OK` when the system has the `sysexits.h` header.

- gh-128472: Skip BOLT optimization of functions using computed gotos, fixing errors on build with LLVM 19.

- gh-123925: Fix building the `curses` module on platforms with libncurses but without libncursesw.

- gh-128321: Set `LIBS` instead of `LDFLAGS` when checking if `sqlite3` library functions are available. This fixes the ordering of linked libraries during checks, which was incorrect when using a statically linked `libsqlite3`.

## Python 3.12.8 final

Release date: 2024-12-03

### macOS

- gh-124448: Update bundled Tcl/Tk in macOS installer to 8.6.15.

### Windows

- gh-126911: Update credits command output.

- gh-125315: Avoid crashing in `platform` due to slow WMI calls on some Windows machines.

- gh-125550: Enable the Python Launcher for Windows to detect Python 3.14 installs from the Windows Store.

- gh-124448: Updated bundled Tcl/Tk to 8.6.15.

### Tools/Demos

- gh-126807: Fix extraction warnings in pygettext.py caused by mistaking function definitions for function calls.

### Tests

- gh-126909: Fix test_os extended attribute tests to work on filesystems with 1 KiB xattr size limit.

- gh-125041: Re-enable skipped tests for `zlib` on the s390x architecture: only skip checks of the compressed bytes, which can be different between zlib’s software implementation and the hardware-accelerated implementation.

- gh-124295: Add translation tests to the `argparse` module.

### Security

- gh-126623: Upgrade libexpat to 2.6.4

### Library

- gh-127303: Publicly expose `EXACT_TOKEN_TYPES` in `token.__all__`.

- gh-123967: Fix faulthandler for trampoline frames. If the top-most frame is a trampoline frame, skip it. Patch by Victor Stinner.

- gh-127182: Fix `io.StringIO.__setstate__()` crash, when `None` was passed as the first value.

- gh-127217: Fix `urllib.request.pathname2url()` for paths starting with multiple slashes on Posix.

- gh-127035: Fix `shutil.which` on Windows. Now it looks at direct match if and only if the command ends with a PATHEXT extension or X_OK is not in mode. Support extensionless files if “.” is in PATHEXT. Support PATHEXT extensions that end with a dot.

- gh-127078: Fix issue where `urllib.request.url2pathname()` failed to discard an extra slash before a UNC drive in the URL path on Windows.

- gh-126766: Fix issue where `urllib.request.url2pathname()` failed to discard any ‘localhost’ authority present in the URL.

- gh-126997: Fix support of STRING and GLOBAL opcodes with non-ASCII arguments in `pickletools`. `pickletools.dis()` now outputs non-ASCII bytes in STRING, BINSTRING and SHORT_BINSTRING arguments as escaped (`\xXX`).

- gh-126618: Fix the representation of `itertools.count` objects when the count value is `sys.maxsize`.

- gh-85168: Fix issue where `urllib.request.url2pathname()` and `pathname2url()` always used UTF-8 when quoting and unquoting file URIs. They now use the filesystem encoding and error handler.

- gh-67877: Fix memory leaks when `regular expression` matching terminates abruptly, either because of a signal or because memory allocation fails.

- gh-126789: Fixed the values of `sysconfig.get_config_vars()`, `sysconfig.get_paths()`, and their siblings when the `site` initialization happens after `sysconfig` has built a cache for `sysconfig.get_config_vars()`.

- gh-126188: Update bundled pip to 24.3.1

- gh-126766: Fix issue where `urllib.request.url2pathname()` failed to discard two leading slashes introducing an empty authority section.

- gh-126727: `locale.nl_langinfo(locale.ERA)` now returns multiple era description segments separated by semicolons. Previously it only returned the first segment on platforms with Glibc.

- gh-126699: Allow `collections.abc.AsyncIterator` to be a base for Protocols.

- gh-104745: Limit starting a patcher (from `unittest.mock.patch()` or `unittest.mock.patch.object()`) more than once without stopping it

- gh-126595: Fix a crash when instantiating `itertools.count` with an initial count of `sys.maxsize` on debug builds. Patch by Bénédikt Tran.

- gh-120423: Fix issue where `urllib.request.pathname2url()` mishandled Windows paths with embedded forward slashes.

- gh-126565: Improve performances of `zipfile.Path.open()` for non-reading modes.

- gh-126505: Fix bugs in compiling case-insensitive `regular expressions` with character classes containing non-BMP characters: upper-case non-BMP character did was ignored and the ASCII flag was ignored when matching a character range whose upper bound is beyond the BMP region.

- gh-117378: Fixed the `multiprocessing` `"forkserver"` start method forkserver process to correctly inherit the parent’s `sys.path` during the importing of `multiprocessing.set_forkserver_preload()` modules in the same manner as `sys.path` is configured in workers before executing work items.

  This bug caused some forkserver module preloading to silently fail to preload. This manifested as a performance degration in child processes when the `sys.path` was required due to additional repeated work in every worker.

  It could also have a side effect of `""` remaining in `sys.path` during forkserver preload imports instead of the absolute path from `os.getcwd()` at multiprocessing import time used in the worker `sys.path`.

  The `sys.path` differences between phases in the child process could potentially have caused preload to import incorrect things from the wrong location. We are unaware of that actually having happened in practice.

- gh-125679: The `multiprocessing.Lock` and `multiprocessing.RLock` `repr` values no longer say “unknown” on macOS.

- gh-126476: Raise `calendar.IllegalMonthError` (now a subclass of `IndexError`) for `calendar.month()` when the input month is not correct.

- gh-126489: The Python implementation of `pickle` no longer calls `pickle.Pickler.persistent_id()` for the result of `persistent_id()`.

- gh-126303: Fix pickling and copying of `os.sched_param` objects.

- gh-126138: Fix a use-after-free crash on `asyncio.Task` objects whose underlying coroutine yields an object that implements an evil `__getattribute__()`. Patch by Nico Posada.

- gh-126220: Fix crash in `cProfile.Profile` and `_lsprof.Profiler` when their callbacks were directly called with 0 arguments.

- gh-126212: Fix issue where `urllib.request.pathname2url()` and `url2pathname()` removed slashes from Windows DOS drive paths and URLs.

- gh-126205: Fix issue where `urllib.request.pathname2url()` generated URLs beginning with four slashes (rather than two) when given a Windows UNC path.

- gh-126105: Fix a crash in `ast` when the `ast.AST._fields` attribute is deleted.

- gh-126106: Fixes a possible `NULL` pointer dereference in `ssl`.

- gh-126080: Fix a use-after-free crash on `asyncio.Task` objects for which the underlying event loop implements an evil `__getattribute__()`. Reported by Nico-Posada. Patch by Bénédikt Tran.

- gh-126083: Fixed a reference leak in `asyncio.Task` objects when reinitializing the same object with a non-`None` context. Patch by Nico Posada.

- gh-125984: Fix use-after-free crashes on `asyncio.Future` objects for which the underlying event loop implements an evil `__getattribute__()`. Reported by Nico-Posada. Patch by Bénédikt Tran.

- gh-125969: Fix an out-of-bounds crash when an evil `asyncio.loop.call_soon()` mutates the length of the internal callbacks list. Patch by Bénédikt Tran.

- gh-125966: Fix a use-after-free crash in `asyncio.Future.remove_done_callback()`. Patch by Bénédikt Tran.

- gh-125789: Fix possible crash when mutating list of callbacks returned by `asyncio.Future._callbacks`. It now always returns a new copy in C implementation `_asyncio`. Patch by Kumar Aditya.

- gh-124452: Fix an issue in `email.policy.EmailPolicy.header_source_parse()` and `email.policy.Compat32.header_source_parse()` that introduced spurious leading whitespaces into header values when the header includes a newline character after the header name delimiter (`:`) and before the value.

- gh-125884: Fixed the bug for `pdb` where it can’t set breakpoints on functions with certain annotations.

- gh-125355: Fix several bugs in `argparse.ArgumentParser.parse_intermixed_args()`.

  - The parser no longer changes temporarily during parsing.

  - Default values are not processed twice.

  - Required mutually exclusive groups containing positional arguments are now supported.

  - The missing arguments report now includes the names of all required optional and positional arguments.

  - Unknown options can be intermixed with positional arguments in parse_known_intermixed_args().

- gh-125682: Reject non-ASCII digits in the Python implementation of `json.loads()` conforming to the JSON specification.

- gh-125660: Reject invalid unicode escapes for Python implementation of `json.loads()`.

- gh-125259: Fix the notes removal logic for errors thrown in enum initialization.

- gh-125519: Improve traceback if `importlib.reload()` is called with an object that is not a module. Patch by Alex Waygood.

- gh-125451: Fix deadlock when `concurrent.futures.ProcessPoolExecutor` shuts down concurrently with an error when feeding a job to a worker process.

- gh-125422: Fixed the bug where `pdb` and `bdb` can step into the bottom caller frame.

- gh-100141: Fixed the bug where `pdb` will be stuck in an infinite loop when debugging an empty file.

- gh-53203: Fix `time.strptime()` for `%c`, `%x` and `%X` formats in many locales that use non-ASCII digits, like Persian, Burmese, Odia and Shan.

- gh-125254: Fix a bug where ArgumentError includes the incorrect ambiguous option in `argparse`.

- gh-61011: Fix inheritance of nested mutually exclusive groups from parent parser in `argparse.ArgumentParser`. Previously, all nested mutually exclusive groups lost their connection to the group containing them and were displayed as belonging directly to the parser.

- gh-52551: Fix encoding issues in `time.strftime()`, the `strftime()` method of the `datetime` classes `datetime`, `date` and `time` and formatting of these classes. Characters not encodable in the current locale are now acceptable in the format string. Surrogate pairs and sequence of surrogatescape-encoded bytes are no longer recombinated. Embedded null character no longer terminates the format string.

- gh-125118: Don’t copy arbitrary values to _Bool in the `struct` module.

- gh-125069: Fix an issue where providing a `pathlib.PurePath` object as an initializer argument to a second `PurePath` object with a different flavour resulted in arguments to the former object’s initializer being joined by the latter object’s flavour.

- gh-124969: Fix `locale.nl_langinfo(locale.ALT_DIGITS)` on platforms with glibc. Now it returns a string consisting of up to 100 semicolon-separated symbols (an empty string in most locales) on all Posix platforms. Previously it only returned the first symbol or an empty string.

- gh-124958: Fix refcycles in exceptions raised from `asyncio.TaskGroup` and the python implementation of `asyncio.Future`

- gh-53203: Fix `time.strptime()` for `%c` and `%x` formats in many locales: Arabic, Bislama, Breton, Bodo, Kashubian, Chuvash, Estonian, French, Irish, Ge’ez, Gurajati, Manx Gaelic, Hebrew, Hindi, Chhattisgarhi, Haitian Kreyol, Japanese, Kannada, Korean, Marathi, Malay, Norwegian, Nynorsk, Punjabi, Rajasthani, Tok Pisin, Yoruba, Yue Chinese, Yau/Nungon and Chinese.

- gh-124917: Allow calling `os.path.exists()` and `os.path.lexists()` with keyword arguments on Windows. Fixes a regression in 3.12.4.

- gh-124653: Fix detection of the minimal Queue API needed by the `logging` module. Patch by Bénédikt Tran.

- gh-124858: Fix reference cycles left in tracebacks in `asyncio.open_connection()` when used with `happy_eyeballs_delay`

- gh-124390: Fixed `AssertionError` when using `asyncio.staggered.staggered_race()` with `asyncio.eager_task_factory`.

- gh-124651: Properly quote template strings in `venv` activation scripts.

- gh-124594: All `asyncio` REPL prompts run in the same `context`. Contributed by Bartosz Sławecki.

- gh-120378: Fix a crash related to an integer overflow in `curses.resizeterm()` and `curses.resize_term()`.

- gh-123884: Fixed bug in itertools.tee() handling of other tee inputs (a tee in a tee). The output now has the promised n independent new iterators. Formerly, the first iterator was identical (not independent) to the input iterator. This would sometimes give surprising results.

- gh-123978: Remove broken `time.thread_time()` and `time.thread_time_ns()` on NetBSD.

- gh-124008: Fix possible crash (in debug build), incorrect output or returning incorrect value from raw binary `write()` when writing to console on Windows.

- gh-123370: Fix the canvas not clearing after running turtledemo clock.

- gh-120754: Update unbounded `read` calls in `zipfile` to specify an explicit `size` putting a limit on how much data they may read. This also updates handling around ZIP max comment size to match the standard instead of reading comments that are one byte too long.

- gh-70764: Fixed an issue where `inspect.getclosurevars()` would incorrectly classify an attribute name as a global variable when the name exists both as an attribute name and a global variable.

- gh-119826: Always return an absolute path for `os.path.abspath()` on Windows.

- gh-117766: Always use `str()` to print `choices` in `argparse`.

- gh-101955: Fix SystemError when match regular expression pattern containing some combination of possessive quantifier, alternative and capture group.

- gh-88110: Fixed `multiprocessing.Process` reporting a `.exitcode` of 1 even on success when using the `"fork"` start method while using a `concurrent.futures.ThreadPoolExecutor`.

- gh-71936: Fix a race condition in `multiprocessing.pool.Pool`.

- bpo-46128: Strip `unittest.IsolatedAsyncioTestCase` stack frames from reported stacktraces.

- bpo-14074: Fix `argparse` metavar processing to allow positional arguments to have a tuple metavar.

### IDLE

- gh-122392: Increase currently inadequate vertical spacing for the IDLE browsers (path, module, and stack) on high-resolution monitors.

### Documentation

- gh-125277: Require Sphinx 7.2.6 or later to build the Python documentation. Patch by Adam Turner.

- gh-125018: The `importlib.metadata` documentation now includes semantic cross-reference targets for the significant documented APIs. This means intersphinx references like `importlib.metadata.version()` will now work as expected.

- gh-121277: Writers of CPython’s documentation can now use `next` as the version for the `versionchanged`, `versionadded`, `deprecated` directives.

- gh-60712: Include the `object` type in the lists of documented types. Change by Furkan Onder and Martin Panter.

### Core and Builtins

- gh-113841: Fix possible undefined behavior division by zero in `complex`’s `_Py_c_pow()`.

- gh-126341: Now `ValueError` is raised instead of `SystemError` when trying to iterate over a released `memoryview` object.

- gh-126066: Fix `importlib` to not write an incomplete .pyc files when a ulimit or some other operating system mechanism is preventing the write to go through fully.

- gh-126139: Provide better error location when attempting to use a future statement with an unknown future feature.

- gh-125008: Fix `tokenize.untokenize()` producing invalid syntax for double braces preceded by certain escape characters.

- gh-123378: Fix a crash in the `__str__()` method of `UnicodeError` objects when the `UnicodeError.start` and `UnicodeError.end` values are invalid or out-of-range. Patch by Bénédikt Tran.

- gh-116510: Fix a crash caused by immortal interned strings being shared between sub-interpreters that use basic single-phase init. In that case, the string can be used by an interpreter that outlives the interpreter that created and interned it. For interpreters that share obmalloc state, also share the interned dict with the main interpreter.

- gh-118950: Fix bug where SSLProtocol.connection_lost wasn’t getting called when OSError was thrown on writing to socket.

- gh-113570: Fixed a bug in `reprlib.repr` where it incorrectly called the repr method on shadowed Python built-in types.

- gh-109746: If `_thread.start_new_thread()` fails to start a new thread, it deletes its state from interpreter and thus avoids its repeated cleanup on finalization.

### C API

- gh-113601: Removed debug build assertions related to interning strings, which were falsely triggered by stable ABI extensions.

### Build

- gh-89640: Hard-code float word ordering as little endian on WASM.

- gh-89640: Improve detection of float word ordering on Linux when link-time optimizations are enabled.

## Python 3.12.7 final

Release date: 2024-10-01

### Windows

- gh-123915: Ensure that `Tools\msi\buildrelease.bat` uses different directories for AMD64 and ARM64 builds.

- gh-117505: Fixes an issue with the Windows installer not running ensurepip in a fully isolated environment. This could cause unexpected interactions with the user site-packages.

### Tests

- gh-124378: Updated `test_ttk` to pass with Tcl/Tk 8.6.15.

### Security

- gh-122792: Changed IPv4-mapped `ipaddress.IPv6Address` to consistently use the mapped IPv4 address value for deciding properties. Properties which have their behavior fixed are `is_multicast`, `is_reserved`, `is_link_local`, `is_global`, and `is_unspecified`.

### Library

- gh-116850: Fix `argparse` for namespaces with not directly writable dict (e.g. classes).

- gh-58573: Fix conflicts between abbreviated long options in the parent parser and subparsers in `argparse`.

- gh-61181: Fix support of choices with string value in `argparse`. Substrings of the specified string no longer considered valid values.

- gh-80259: Fix `argparse` support of positional arguments with `nargs='?'`, `default=argparse.SUPPRESS` and specified `type`.

- gh-124498: Fix `typing.TypeAliasType` not to be generic, when `type_params` is an empty tuple.

- gh-124345: `argparse` vim supports abbreviated single-dash long options separated by `=` from its value.

- gh-104860: Fix disallowing abbreviation of single-dash long options in `argparse` with `allow_abbrev=False`.

- gh-63143: Fix parsing mutually exclusive arguments in `argparse`. Arguments with the value identical to the default value (e.g. booleans, small integers, empty or 1-character strings) are no longer considered “not present”.

- gh-72795: Positional arguments with nargs equal to `'*'` or `argparse.REMAINDER` are no longer required. This allows to use positional argument with `nargs='*'` and without `default` in mutually exclusive group and improves error message about required arguments.

- gh-59317: Fix parsing positional argument with nargs equal to `'?'` or `'*'` if it is preceded by an option and another positional argument.

- gh-53780: `argparse` now ignores the first `"--"` (double dash) between an option and command.

- gh-124217: Add RFC 9637 reserved IPv6 block `3fff::/20` in `ipaddress` module.

- gh-124248: Fixed potential crash when using `struct` to process zero-width ‘Pascal string’ fields (`0p`).

- gh-81691: Fix handling of multiple `"--"` (double dashes) in `argparse`. Only the first one has now been removed, all subsequent ones are now taken literally.

- gh-87041: Fix a bug in `argparse` where lengthy subparser argument help is incorrectly indented.

- gh-124171: Add workaround for broken `fmod()` implementations on Windows, that loose zero sign (e.g. `fmod(-10, 1)` returns `0.0`). Patch by Sergey B Kirpichev.

- gh-123934: Fix `unittest.mock.MagicMock` reseting magic methods return values after `.reset_mock(return_value=True)` was called.

- gh-123935: Fix parent slots detection for dataclasses that inherit from classes with `__dictoffset__`.

- gh-123892: Add `"_wmi"` to `sys.stdlib_module_names`. Patch by Victor Stinner.

- gh-116810: Resolve a memory leak introduced in CPython 3.10’s `ssl` when the `ssl.SSLSocket.session` property was accessed. Speeds up read and write access to said property by no longer unnecessarily cloning session objects via serialization.

- gh-121735: When working with zip archives, importlib.resources now properly honors module-adjacent references (e.g. `files(pkg.mod)` and not just `files(pkg)`).

- gh-119004: Fix a crash in OrderedDict.__eq__ when operands are mutated during the check. Patch by Bénédikt Tran.

- bpo-44864: Do not translate user-provided strings in `argparse.ArgumentParser`.

### IDLE

- gh-112938: Fix uninteruptable hang when Shell gets rapid continuous output.

### Core and Builtins

- gh-116510: Fix a bug that can cause a crash when sub-interpreters use “basic” single-phase extension modules. Shared objects could refer to PyGC_Head nodes that had been freed as part of interpreter cleanup.

- gh-124188: Fix reading and decoding a line from the source file witn non-UTF-8 encoding for syntax errors raised in the compiler.

- gh-77894: Fix possible crash in the garbage collector when it tries to break a reference loop containing a `memoryview` object. Now a `memoryview` object can only be cleared if there are no buffers that refer it.

- gh-98442: Fix too wide source locations of the cleanup instructions of a with statement.

- gh-113993: Strings interned with `sys.intern()` are again garbage-collected when no longer used, as per the documentation. Strings interned with the C function `PyUnicode_InternInPlace()` are still immortal. Internals of the string interning mechanism have been changed. This may affect performance and identities of `str` objects.

### C API

- gh-113993: `PyUnicode_InternInPlace()` no longer prevents its argument from being garbage collected.

  Several functions that take `char *` are now documented as possibly preventing string objects from being garbage collected; refer to their documentation for details: `PyUnicode_InternFromString()`, `PyDict_SetItemString()`, `PyObject_SetAttrString()`, `PyObject_DelAttrString()`, `PyUnicode_InternFromString()`, and `PyModule_Add*` convenience functions.

### Build

- gh-124487: Windows builds now use Windows 8.1 as their API baseline (installation already required Windows 8.1).

- gh-123917: Fix the check for the `crypt()` function in the configure script. Patch by Paul Smith and Victor Stinner.

## Python 3.12.6 final

Release date: 2024-09-06

### macOS

- gh-123418: Updated macOS installer build to use OpenSSL 3.0.15.

### Windows

- gh-123418: Updated Windows build to use OpenSSL 3.0.15.

- gh-100256: `mimetypes` no longer fails when it encounters an inaccessible registry key.

- gh-79846: Makes `ssl.create_default_context()` ignore invalid certificates in the Windows certificate store

### Tools/Demos

- gh-123418: Update GitHub CI workflows to use OpenSSL 3.0.15 and multissltests to use 3.0.15, 3.1.7, and 3.2.3.

### Tests

- gh-101525: Skip `test_gdb` if the binary is relocated by BOLT. Patch by Donghee Na.

### Security

- gh-123678: Upgrade libexpat to 2.6.3

- gh-121285: Remove backtracking from tarfile header parsing for `hdrcharset`, PAX, and GNU sparse headers.

### Library

- gh-123270: Applied a more surgical fix for malformed payloads in `zipfile.Path` causing infinite loops (gh-122905) without breaking contents using legitimate characters.

- gh-123213: `xml.etree.ElementTree.Element.extend()` and `Element` assignment no longer hide the internal exception if an erronous generator is passed. Patch by Bar Harel.

- gh-85110: Preserve relative path in URL without netloc in `urllib.parse.urlunsplit()` and `urllib.parse.urlunparse()`.

- gh-123067: Fix quadratic complexity in parsing `"`-quoted cookie values with backslashes by `http.cookies`.

- gh-122903: `zipfile.Path.glob` now correctly matches directories instead of silently omitting them.

- gh-122905: `zipfile.Path` objects now sanitize names from the zipfile.

- gh-122695: Fixed double-free when using `gc.get_referents()` with a freed `asyncio.Future` iterator.

- gh-116263: `logging.handlers.RotatingFileHandler` no longer rolls over empty log files.

- gh-118814: Fix the `typing.TypeVar` constructor when name is passed by keyword.

- gh-122478: Remove internal frames from tracebacks shown in `code.InteractiveInterpreter` with non-default `sys.excepthook()`. Save correct tracebacks in `sys.last_traceback` and update `__traceback__` attribute of `sys.last_value` and `sys.last_exc`.

- gh-113785: `csv` now correctly parses numeric fields (when used with `csv.QUOTE_NONNUMERIC`) which start with an escape character.

- gh-112182: `asyncio.futures.Future.set_exception()` now transforms `StopIteration` into `RuntimeError` instead of hanging or other misbehavior. Patch contributed by Jamie Phan.

- gh-108172: `webbrowser` honors OS preferred browser on Linux when its desktop entry name contains the text of a known browser name.

- gh-102988: `email.utils.getaddresses()` and `email.utils.parseaddr()` now return `('', '')` 2-tuples in more situations where invalid email addresses are encountered instead of potentially inaccurate values. Add optional strict parameter to these two functions: use `strict=False` to get the old behavior, accept malformed inputs. `getattr(email.utils, 'supports_strict_parsing', False)` can be use to check if the strict paramater is available. Patch by Thomas Dwyer and Victor Stinner to improve the CVE-2023-27043 fix.

- gh-99437: `runpy.run_path()` now decodes path-like objects, making sure __file__ and sys.argv[0] of the module being run are always strings.

### IDLE

- gh-120083: Add explicit black IDLE Hovertip foreground color needed for recent macOS. Fixes Sonoma showing unreadable white on pale yellow. Patch by John Riggles.

### Core and Builtins

- gh-123321: Prevent Parser/myreadline race condition from segfaulting on multi-threaded use. Patch by Bar Harel and Amit Wienner.

- gh-122982: Extend the deprecation period for bool inversion (`~`) by two years.

- gh-123229: Fix valgrind warning by initializing the f-string buffers to 0 in the tokenizer. Patch by Pablo Galindo

- gh-123142: Fix too-wide source location in exception tracebacks coming from broken iterables in comprehensions.

- gh-123048: Fix a bug where pattern matching code could emit a `JUMP_FORWARD` with no source location.

- gh-123083: Fix a potential use-after-free in `STORE_ATTR_WITH_HINT`.

- gh-122527: Fix a crash that occurred when a `PyStructSequence` was deallocated after its type’s dictionary was cleared by the GC. The type’s `tp_basicsize` now accounts for non-sequence fields that aren’t included in the `Py_SIZE` of the sequence.

- gh-93691: Fix source locations of instructions generated for with statements.

### Build

- gh-123297: Propagate the value of `LDFLAGS` to `LDCXXSHARED` in `sysconfig`. Patch by Pablo Galindo

## Python 3.12.5 final

Release date: 2024-08-06

### Windows

- gh-122573: The Windows build of CPython now requires 3.10 or newer.

### Tests

- gh-59022: Add tests for `pkgutil.extend_path()`. Patch by Andreas Stocker.

- gh-99242: `os.getloadavg()` may throw `OSError` when running regression tests under certain conditions (e.g. chroot). This error is now caught and ignored, since reporting load average is optional.

- gh-121084: Fix test_typing random leaks. Clear typing ABC caches when running tests for refleaks (`-R` option): call `_abc_caches_clear()` on typing abstract classes and their subclasses. Patch by Victor Stinner.

- gh-121160: Add a test for `readline.set_history_length()`. Note that this test may fail on readline libraries.

- gh-121200: Fix `test_expanduser_pwd2()` of `test_posixpath`. Call `getpwnam()` to get `pw_dir`, since it can be different than `getpwall()` `pw_dir`. Patch by Victor Stinner.

- gh-121188: When creating the JUnit XML file, regrtest now escapes characters which are invalid in XML, such as the chr(27) control character used in ANSI escape sequences. Patch by Victor Stinner.

### Security

- gh-121957: Fixed missing audit events around interactive use of Python, now also properly firing for `python -i`, as well as for `python -m asyncio`. The event in question is `cpython.run_stdin`.

- gh-122133: Authenticate the socket connection for the `socket.socketpair()` fallback on platforms where `AF_UNIX` is not available like Windows.

  Patch by Gregory P. Smith <greg@krypto.org> and Seth Larson <seth@python.org>. Reported by Ellie <el@horse64.org>

### Library

- gh-122744: Bump the version of pip bundled in ensurepip to version 24.2.

- gh-122334: Fix crash when importing `ssl` after the main interpreter restarts.

- gh-87320: In `code.InteractiveInterpreter`, handle exceptions caused by calling a non-default `sys.excepthook()`. Before, the exception bubbled up to the caller, ending the REPL.

- gh-122400: Handle `ValueError`s raised by `os.stat()` in `filecmp.dircmp` and `filecmp.cmpfiles()`. Patch by Bénédikt Tran.

- gh-122311: Fix some error messages in `pickle`.

- gh-121650: `email` headers with embedded newlines are now quoted on output. The `generator` will now refuse to serialize (write) headers that are unsafely folded or delimited; see `verify_generated_headers`. (Contributed by Bas Bloemsaat and Petr Viktorin in gh-121650.)

- gh-122332: Fixed segfault with `asyncio.Task.get_coro()` when using an eager task factory.

- gh-122170: Handle `ValueError`s raised by `os.stat()` in `linecache`. Patch by Bénédikt Tran.

- gh-121723: Make `logging.config.dictConfig()` accept any object implementing the Queue public API. See the queue configuration section for details. Patch by Bénédikt Tran.

- gh-82951: Serializing objects with complex `__qualname__` (such as unbound methods and nested classes) by name no longer involves serializing parent objects by value in pickle protocols < 4.

- gh-120930: Fixed a bug introduced by gh-92081 that added an incorrect extra blank to encoded words occurring in wrapped headers.

- gh-121474: Fix missing sanity check for `parties` arg in `threading.Barrier` constructor. Patch by Clinton Christian (pygeek).

- gh-121025: Improve the `__repr__()` of `functools.partialmethod`. Patch by Bénédikt Tran.

- gh-121018: Fixed issues where `argparse.ArgumentParser.parse_args()` did not honor `exit_on_error=False`. Based on patch by Ben Hsing.

- gh-119614: Fix truncation of strings with embedded null characters in some internal operations in `tkinter`.

- gh-120910: When reading installed files from an egg, use `relative_to(walk_up=True)` to honor files installed outside of the installation root.

- gh-101830: Accessing the `tkinter` object’s string representation no longer converts the underlying Tcl object to a string on Windows.

- gh-120811: Fix possible memory leak in `contextvars.Context.run()`.

- gh-120769: Make empty line in `pdb` repeats the last command even when the command is from `cmdqueue`.

- gh-120732: Fix `name` passing to `unittest.mock.Mock` object when using `unittest.mock.create_autospec()`.

- gh-120495: Fix incorrect exception handling in Tab Nanny. Patch by Wulian233.

- gh-120343: Fix column offset reporting for tokens that come after multiline f-strings in the `tokenize` module.

- gh-119600: Fix `unittest.mock.patch()` to not read attributes of the target when `new_callable` is set. Patch by Robert Collins.

- gh-120289: Fixed the use-after-free issue in `cProfile` by disallowing `disable()` and `clear()` in external timers.

- gh-114053: Fix edge-case bug where `typing.get_type_hints()` would produce incorrect results if type parameters in a class scope were overridden by assignments in a class scope and `from __future__ import annotations` semantics were enabled. Patch by Alex Waygood.

- gh-114053: Fix erroneous `NameError` when calling `inspect.get_annotations()` with `eval_str=True`` on a class that made use of PEP 695 type parameters in a module that had `from __future__ import annotations` at the top of the file. Patch by Alex Waygood.

- gh-120268: Prohibit passing `None` to pure-Python `datetime.date.fromtimestamp()` to achieve consistency with C-extension implementation.

- gh-120244: Fix memory leak in `re.sub()` when the replacement string contains backreferences.

- gh-120211: Fix `tkinter.ttk` with Tcl/Tk 9.0.

- gh-71587: Fix crash in C version of `datetime.datetime.strptime()` when called again on the restarted interpreter.

- gh-117983: Defer the `threading` import in `importlib.util` until lazy loading is used.

- gh-119698: Fix `symtable.Class.get_methods()` and document its behaviour. Patch by Bénédikt Tran.

- gh-120121: Add `concurrent.futures.InvalidStateError` to module’s `__all__`.

- gh-112672: Support building `tkinter` with Tcl 9.0.

- gh-65454: `unittest.mock.Mock.attach_mock()` no longer triggers a call to a `PropertyMock` being attached.

- gh-81936: `help()` and `showtopic()` methods now respect a configured output argument to `pydoc.Helper` and not use the pager in such cases. Patch by Enrico Tröger.

- gh-119577: The `DeprecationWarning` emitted when testing the truth value of an `xml.etree.ElementTree.Element` now describes unconditionally returning `True` in a future version rather than raising an exception in Python 3.14.

- gh-119506: Fix `io.TextIOWrapper.write()` method breaks internal buffer when the method is called again during flushing internal buffer.

- gh-119189: When using the `**` operator or `pow()` with `Fraction` as the base and an exponent that is not rational, a float, or a complex, the fraction is no longer converted to a float.

- gh-105623: Fix performance degradation in `logging.handlers.RotatingFileHandler`. Patch by Craig Robson.

- bpo-39324: Add mime type mapping for .md <-> text/markdown

### IDLE

- gh-122482: Change About IDLE to direct users to discuss.python.org instead of the now unused idle-dev email and mailing list.

- gh-78889: Stop Shell freezes by blocking user access to non-method sys.stdout.shell attributes, which are all private.

- gh-120104: Fix padding in config and search dialog windows in IDLE.

### Documentation

- gh-121749: Fix documentation for `PyModule_AddObjectRef()`.

- gh-120012: Clarify the behaviours of `multiprocessing.Queue.empty()` and `multiprocessing.SimpleQueue.empty()` on closed queues. Patch by Bénédikt Tran.

### Core and Builtins

- gh-122208: Dictionary watchers now only deliver the PyDict_EVENT_ADDED event when the insertion is in a known good state to succeed.

- gh-122300: Preserve AST nodes for f-string with single-element format specifiers. Patch by Pablo Galindo

- gh-122029: Emit `c_call` events in `sys.setprofile()` when a `PyMethodObject` pointing to a `PyCFunction` is called.

- gh-122026: Fix a bug that caused the tokenizer to not correctly identify mismatched parentheses inside f-strings in some situations. Patch by Pablo Galindo

- gh-121657: Improve the `SyntaxError` message if the user tries to use `yield from` outside a function.

- gh-117482: Unexpected slot wrappers are no longer created for builtin static types in subinterpreters.

- gh-121439: Allow tuples of length 20 in the freelist to be reused.

- gh-121130: Fix f-strings with debug expressions in format specifiers. Patch by Pablo Galindo

- gh-120722: Correctly set the bytecode position on return instructions within lambdas. Patch by Jelle Zijlstra.

- gh-120384: Fix an array out of bounds crash in `list_ass_subscript`, which could be invoked via some specificly tailored input: including concurrent modification of a list object, where one thread assigns a slice and another clears it.

- gh-120380: Fix Python implementation of `pickle.Pickler` for `bytes` and `bytearray` objects when using protocol version 5. Patch by Bénédikt Tran.

- gh-93691: Fix source locations of instructions generated for the iterator of a for statement.

- gh-120198: Fix a crash when multiple threads read and write to the same `__class__` of an object concurrently.

- gh-120298: Fix use-after free in `list_richcompare_impl` which can be invoked via some specificly tailored evil input.

- gh-119666: Fix a compiler crash in the case where two comprehensions in class scope both reference `__class__`.

- bpo-24766: Fix handling of `doc` argument to subclasses of `property`.

### Build

- gh-120671: Fix failing configure tests due to a missing space when appending to CFLAGS.

- gh-115983: Skip building test modules that must be built as shared under WASI.

## Python 3.12.4 final

Release date: 2024-06-06

### Security

- gh-118486: `os.mkdir()` on Windows now accepts mode of `0o700` to restrict the new directory to the current user. This fixes CVE 2024-4030 affecting `tempfile.mkdtemp()` in scenarios where the base temporary directory is more permissive than the default.

- gh-116741: Update bundled libexpat to 2.6.2

- gh-117233: Detect BLAKE2, SHA3, Shake, & truncated SHA512 support in the OpenSSL-ish libcrypto library at build time. This allows `hashlib` to be used with libraries that do not to support every algorithm that upstream OpenSSL does.

### Core and Builtins

- gh-119821: Fix execution of annotation scopes within classes when `globals` is set to a non-dict. Patch by Jelle Zijlstra.

- gh-119311: Fix bug where names are unexpectedly mangled in the bases of generic classes.

- gh-119395: Fix bug where names appearing after a generic class are mangled as if they are in the generic class.

- gh-119213: Non-builtin modules built with argument clinic were crashing if used in a subinterpreter before the main interpreter. The objects that were causing the problem by leaking between interpreters carelessly have been fixed.

- gh-119011: Fixes `type.__type_params__` to return an empty tuple instead of a descriptor.

- gh-118997: Fix _Py_ClearImmortal() assertion: use _Py_IsImmortal() to tolerate reference count lower than _Py_IMMORTAL_REFCNT. Fix the assertion for the stable ABI, when a C extension is built with Python 3.11 or lower. Patch by Victor Stinner.

- gh-118513: Fix incorrect `UnboundLocalError` when two comprehensions in the same function both reference the same name, and in one comprehension the name is bound while in the other it’s an implicit global.

- gh-118164: Break a loop between the Python implementation of the `decimal` module and the Python code for integer to string conversion. Also optimize integer to string conversion for values in the range from 9_000 to 135_000 decimal digits.

- gh-118272: Fix bug where `generator.close` does not free the generator frame’s locals.

- gh-116767: Fix crash in compiler on ‘async with’ that has many context managers.

- gh-117894: Prevent `agen.aclose()` objects being re-used after `.throw()`.

- gh-117881: prevent concurrent access to an async generator via athrow().throw() or asend().throw()

- gh-115874: Fixed a possible segfault during garbage collection of `_asyncio.FutureIter` objects

### Library

- gh-119819: Fix regression to allow logging configuration with multiprocessing queue types.

- gh-89727: Fix issue with `shutil.rmtree()` where a `RecursionError` is raised on deep directory trees.

- gh-89727: Partially fix issue with `shutil.rmtree()` where a `RecursionError` is raised on deep directory trees. A recursion error is no longer raised when `rmtree.avoids_symlink_attacks` is false.

- gh-119118: Fix performance regression in the `tokenize` module by caching the `line` token attribute and calculating the column offset more efficiently.

- gh-89727: Fix issue with `os.fwalk()` where a `RecursionError` was raised on deep directory trees by adjusting the implementation to be iterative instead of recursive.

- gh-118263: Speed up `os.path.normpath()` with a direct C call.

- gh-113892: Now, the method `sock_connect` of `asyncio.ProactorEventLoop` raises a `ValueError` if given socket is not in non-blocking mode, as well as in other loop implementations.

- gh-118507: Fix `os.path.isfile()` on Windows for pipes.

- gh-119174: Fix high DPI causes turtledemo(turtle-graphics examples) windows blurry Patch by Wulian233 and Terry Jan Reedy

- gh-118643: Fix an AttributeError in the `email` module when re-fold a long address list. Also fix more cases of incorrect encoding of the address separator in the address list.

- gh-58933: Make `pdb` return to caller frame correctly when `f_trace` of the caller frame is not set

- gh-118868: Fixed issue where kwargs were no longer passed to the logging handler QueueHandler

- gh-118164: The Python implementation of the `decimal` module could appear to hang in relatively small power cases (like `2**117`) if context precision was set to a very high value. A different method to check for exactly representable results is used now that doesn’t rely on computing `10**precision` (which could be effectively too large to compute).

- gh-118404: Fix `inspect.signature()` for non-comparable callables.

- gh-118314: Fix an edge case in `binascii.a2b_base64()` strict mode, where excessive padding is not detected when no padding is necessary.

- gh-118042: Fix an unraisable exception in `telnetlib.Telnet.__del__()` when the `__init__()` method was not called.

- gh-118221: Fix a bug where `sqlite3.iterdump()` could fail if a custom `row factory` was used. Patch by Erlend Aasland.

- gh-118013: Fix regression introduced in gh-103193 that meant that calling `inspect.getattr_static()` on an instance would cause a strong reference to that instance’s class to persist in an internal cache in the `inspect` module. This caused unexpected memory consumption if the class was dynamically created, the class held strong references to other objects which took up a significant amount of memory, and the cache contained the sole strong reference to the class. The fix for the regression leads to a slowdown in `getattr_static()`, but the function should still be significantly faster than it was in Python 3.11. Patch by Alex Waygood.

- gh-90848: Fixed `unittest.mock.create_autospec()` to configure parent mock with keyword arguments.

- gh-118168: Fix incorrect argument substitution when `typing.Unpack` is used with the builtin `tuple`. `typing.Unpack` now raises `TypeError` when used with certain invalid types. Patch by Jelle Zijlstra.

- gh-118033: Fix `dataclasses.dataclass()` not creating a `__weakref__` slot when subclassing `typing.Generic`.

- gh-117535: Do not try to get the source line for made up file name “sys” in `warnings`.

- gh-114053: Fix erroneous `NameError` when calling `typing.get_type_hints()` on a class that made use of PEP 695 type parameters in a module that had `from __future__ import annotations` at the top of the file. Patch by Alex Waygood.

- gh-117995: Don’t raise `DeprecationWarning` when a sequence of parameters is used to bind indexed, nameless placeholders. See also gh-100668.

- gh-80361: Fix TypeError in `email.message.Message.get_payload()` when the charset is RFC 2231 encoded.

- gh-86650: Fix IndexError when parse some emails with invalid Message-ID (including one-off addresses generated by Microsoft Outlook).

- gh-117691: Improve the error messages emitted by `tarfile` deprecation warnings relating to PEP 706. If a `filter` argument is not provided to `extract()` or `extractall`, the deprecation warning now points to the line in the user’s code where the relevant function was called. Patch by Alex Waygood.

- gh-77102: `site` module now parses `.pth` file with UTF-8 first, and locale encoding if `UnicodeDecodeError` happened. It supported only locale encoding before.

- gh-117692: Fixes a bug when `doctest.DocTestFinder` was failing on wrapped `builtin_function_or_method`.

- gh-117566: `ipaddress.IPv6Address.is_loopback()` will now return `True` for IPv4-mapped loopback addresses, i.e. addresses in the `::ffff:127.0.0.0/104` address space.

- gh-117503: Fix support of non-ASCII user names in bytes paths in `os.path.expanduser()` on Posix.

- gh-117313: Only treat `'\n'`, `'\r'` and `'\r\n'` as line separators in re-folding the `email` messages. Preserve control characters `'\v'`, `'\f'`, `'\x1c'`, `'\x1d'` and `'\x1e'` and Unicode line separators `'\x85'`, `'\u2028'` and `'\u2029'` as is.

- gh-113171: Fixed various false positives and false negatives in

  - `ipaddress.IPv4Address.is_private` (see these docs for details)

  - `ipaddress.IPv4Address.is_global`

  - `ipaddress.IPv6Address.is_private`

  - `ipaddress.IPv6Address.is_global`

  Also in the corresponding `ipaddress.IPv4Network` and `ipaddress.IPv6Network` attributes.

- gh-103956: Fix lack of newline characters in `trace` module output when line tracing is enabled but source code line for current frame is not available.

- gh-92081: Fix missing spaces in email headers when the spaces are mixed with encoded 8-bit characters.

- gh-103194: Prepare Tkinter for C API changes in Tcl 8.7/9.0 to avoid `_tkinter.Tcl_Obj` being unexpectedly returned instead of `bool`, `str`, `bytearray`, or `int`.

- gh-87106: Fixed handling in `inspect.Signature.bind()` of keyword arguments having the same name as positional-only arguments when a variadic keyword argument (e.g. `**kwargs`) is present.

- bpo-45767: Fix integer conversion in `os.major()`, `os.minor()`, and `os.makedev()`. Support device numbers larger than `2**63-1`. Support non-existent device number (`NODEV`).

- bpo-40943: Fix several IndexError when parse emails with truncated Message-ID, address, routes, etc, e.g. `example@`.

- bpo-30988: Fix parsing of emails with invalid address headers having a leading or trailing dot. Patch by tsufeki.

- gh-67693: Fix `urllib.parse.urlunparse()` and `urllib.parse.urlunsplit()` for URIs with path starting with multiple slashes and no authority. Based on patch by Ashwin Ramaswami.

- bpo-15010: `unittest.TestLoader.discover()` now saves the original value of `unittest.TestLoader._top_level_dir` and restores it at the end of the call.

### Documentation

- gh-117928: The minimum Sphinx version required for the documentation is now 6.2.1.

- gh-91565: Changes to documentation files and config outputs to reflect the new location for reporting bugs - i.e. GitHub rather than bugs.python.org.

### Tests

- gh-119050: regrtest test runner: Add XML support to the refleak checker (-R option). Patch by Victor Stinner.

### Windows

- gh-119690: Adds Unicode support and fixes audit events for `_winapi.CreateNamedPipe`.

- gh-119070: Fixes `py.exe` handling of shebangs like `/usr/bin/env python3.12`, which were previously interpreted as `python3.exe` instead of `python3.12.exe`.

- gh-118347: Fixes launcher updates not being installed.

- gh-115009: Update Windows installer to use SQLite 3.45.3.

- gh-90329: Suppress the warning displayed on virtual environment creation when the requested and created paths differ only by a short (8.3 style) name. Warnings will continue to be shown if a junction or symlink in the path caused the venv to be created in a different location than originally requested.

### macOS

- gh-115009: Update macOS installer to use SQLite 3.45.3.

- gh-116145: Update macOS installer to Tcl/Tk 8.6.14.

### IDLE

- bpo-34774: Use user-selected color theme for Help => IDLE Doc.

### C API

- gh-119585: Fix crash when a thread state that was created by `PyGILState_Ensure()` calls a destructor that during `PyThreadState_Clear()` that calls back into `PyGILState_Ensure()` and `PyGILState_Release()`. This might occur when in the free-threaded build or when using thread-local variables whose destructors call `PyGILState_Ensure()`.

- gh-117534: Improve validation logic in the C implementation of `datetime.fromisoformat()` to better handle invalid years. Patch by Vlad Efanov.

## Python 3.12.3 final

Release date: 2024-04-09

### Security

- gh-115398: Allow controlling Expat >=2.6.0 reparse deferral (CVE 2023-52425) by adding five new methods:

  - `xml.etree.ElementTree.XMLParser.flush()`

  - `xml.etree.ElementTree.XMLPullParser.flush()`

  - `xml.parsers.expat.xmlparser.GetReparseDeferralEnabled()`

  - `xml.parsers.expat.xmlparser.SetReparseDeferralEnabled()`

  - `xml.sax.expatreader.ExpatParser.flush()`

- gh-115399: Update bundled libexpat to 2.6.0

- gh-115243: Fix possible crashes in `collections.deque.index()` when the deque is concurrently modified.

- gh-114572: `ssl.SSLContext.cert_store_stats()` and `ssl.SSLContext.get_ca_certs()` now correctly lock access to the certificate store, when the `ssl.SSLContext` is shared across multiple threads.

### Core and Builtins

- gh-109120: Added handle of incorrect star expressions, e.g `f(3, *)`. Patch by Grigoryev Semyon

- gh-99108: Updated the `hashlib` built-in HACL* project C code from upstream that we use for many implementations when they are not present via OpenSSL in a given build. This also avoids the rare potential for a C symbol name one definition rule linking issue.

- gh-116735: For `INSTRUMENTED_CALL_FUNCTION_EX`, set `arg0` to `sys.monitoring.MISSING` instead of `None` for `CALL` event.

- gh-113964: Starting new threads and process creation through `os.fork()` are now only prevented once all non-daemon threads exit.

- gh-116604: Respect the status of the garbage collector when indirect calls are made via `PyErr_CheckSignals()` and the evaluation breaker. Patch by Pablo Galindo

- gh-116626: Ensure `INSTRUMENTED_CALL_FUNCTION_EX` always emits `CALL`

- gh-116296: Fix possible refleak in `object.__reduce__()` internal error handling.

- gh-116034: Fix location of the error on a failed assertion.

- gh-115823: Properly calculate error ranges in the parser when raising `SyntaxError` exceptions caused by invalid byte sequences. Patch by Pablo Galindo

- gh-112087: For an empty reverse iterator for list will be reduced to `reversed()`. Patch by Donghee Na.

- gh-115154: Fix a bug that was causing the `tokenize.untokenize()` function to handle unicode named literals incorrectly. Patch by Pablo Galindo

- gh-114828: Fix compilation crashes in uncommon code examples using `super()` inside a comprehension in a class body.

- gh-115011: Setters for members with an unsigned integer type now support the same range of valid values for objects that has a `__index__()` method as for `int`.

- gh-112215: Change the C recursion limits to more closely reflect the underlying platform limits.

- gh-96497: Fix incorrect resolution of mangled class variables used in assignment expressions in comprehensions.

### Library

- gh-117467: Preserve mailbox ownership when rewriting in `mailbox.mbox.flush()`. Patch by Tony Mountifield.

- gh-117310: Fixed an unlikely early & extra `Py_DECREF` triggered crash in `ssl` when creating a new `_ssl._SSLContext` if CPython was built implausibly such that the default cipher list is empty or the SSL library it was linked against reports a failure from its C `SSL_CTX_set_cipher_list()` API.

- gh-117178: Fix regression in lazy loading of self-referential modules, introduced in gh-114781.

- gh-117084: Fix `zipfile` extraction for directory entries with the name containing backslashes on Windows.

- gh-117110: Fix a bug that prevents subclasses of `typing.Any` to be instantiated with arguments. Patch by Chris Fu.

- gh-90872: On Windows, `subprocess.Popen.wait()` no longer calls `WaitForSingleObject()` with a negative timeout: pass `0` ms if the timeout is negative. Patch by Victor Stinner.

- gh-116957: configparser: Don’t leave ConfigParser values in an invalid state (stored as a list instead of a str) after an earlier read raised DuplicateSectionError or DuplicateOptionError.

- gh-90095: Ignore empty lines and comments in `.pdbrc`

- gh-116764: Restore support of `None` and other false values in `urllib.parse` functions `parse_qs()` and `parse_qsl()`. Also, they now raise a TypeError for non-zero integers and non-empty sequences.

- gh-116811: In `PathFinder.invalidate_caches`, delegate to `MetadataPathFinder.invalidate_caches`.

- gh-116600: Fix `repr()` for global `Flag` members.

- gh-116484: Change automatically generated `tkinter.Checkbutton` widget names to avoid collisions with automatically generated `tkinter.ttk.Checkbutton` widget names within the same parent widget.

- gh-116401: Fix blocking `os.fwalk()` and `shutil.rmtree()` on opening named pipe.

- gh-116143: Fix a race in pydoc `_start_server`, eliminating a window in which `_start_server` can return a thread that is “serving” but without a `docserver` set.

- gh-116325: `typing`: raise `SyntaxError` instead of `AttributeError` on forward references as empty strings.

- gh-90535: Fix support of interval values > 1 in `logging.TimedRotatingFileHandler` for `when='MIDNIGHT'` and `when='Wx'`.

- gh-115978: Disable preadv(), readv(), pwritev(), and writev() on WASI.

  Under wasmtime for WASI 0.2, these functions don’t pass test_posix (https://github.com/bytecodealliance/wasmtime/issues/7830).

- gh-88352: Fix the computation of the next rollover time in the `logging.TimedRotatingFileHandler` handler. `computeRollover()` now always returns a timestamp larger than the specified time and works correctly during the DST change. `doRollover()` no longer overwrite the already rolled over file, saving from data loss when run at midnight or during repeated time at the DST change.

- gh-87115: Set `__main__.__spec__` to `None` when running a script with `pdb`

- gh-76511: Fix UnicodeEncodeError in `email.Message.as_string()` that results when a message that claims to be in the ascii character set actually has non-ascii characters. Non-ascii characters are now replaced with the U+FFFD replacement character, like in the `replace` error handler.

- gh-116040: [Enum] fix by-value calls when second value is falsey; e.g. Cardinal(1, 0)

- gh-75988: Fixed `unittest.mock.create_autospec()` to pass the call through to the wrapped object to return the real result.

- gh-115881: Fix issue where `ast.parse()` would incorrectly flag conditional context managers (such as `with (x() if y else z()): ...`) as invalid syntax if `feature_version=(3, 8)` was passed. This reverts changes to the grammar made as part of gh-94949.

- gh-115886: Fix silent truncation of the name with an embedded null character in `multiprocessing.shared_memory.SharedMemory`.

- gh-115809: Improve algorithm for computing which rolled-over log files to delete in `logging.TimedRotatingFileHandler`. It is now reliable for handlers without `namer` and with arbitrary deterministic `namer` that leaves the datetime part in the file name unmodified.

- gh-74668: `urllib.parse` functions `parse_qs()` and `parse_qsl()` now support bytes arguments containing raw and percent-encoded non-ASCII data.

- gh-67044: `csv.writer()` now always quotes or escapes `'\r'` and `'\n'`, regardless of lineterminator value.

- gh-115712: `csv.writer()` now quotes empty fields if delimiter is a space and skipinitialspace is true and raises exception if quoting is not possible.

- gh-112364: Fixed `ast.unparse()` to handle format_spec with `"`, `'` or `\\`. Patched by Frank Hoffmann.

- gh-111358: Fix a bug in `asyncio.BaseEventLoop.shutdown_default_executor()` to ensure the timeout passed to the coroutine behaves as expected.

- gh-115618: Fix improper decreasing the reference count for `None` argument in `property` methods `getter()`, `setter()` and `deleter()`.

- gh-115570: A `DeprecationWarning` is no longer omitted on access to the `__doc__` attributes of the deprecated `typing.io` and `typing.re` pseudo-modules.

- gh-112006: Fix `inspect.unwrap()` for types with the `__wrapper__` data descriptor.

- gh-101293: Support callables with the `__call__()` method and types with `__new__()` and `__init__()` methods set to class methods, static methods, bound methods, partial functions, and other types of methods and descriptors in `inspect.Signature.from_callable()`.

- gh-115392: Fix a bug in `doctest` where incorrect line numbers would be reported for decorated functions.

- gh-114563: Fix several `format()` bugs when using the C implementation of `Decimal`: * memory leak in some rare cases when using the `z` format option (coerce negative 0) * incorrect output when applying the `z` format option to type `F` (fixed-point with capital `NAN` / `INF`) * incorrect output when applying the `#` format option (alternate form)

- gh-115197: `urllib.request` no longer resolves the hostname before checking it against the system’s proxy bypass list on macOS and Windows.

- gh-115165: Most exceptions are now ignored when attempting to set the `__orig_class__` attribute on objects returned when calling `typing` generic aliases (including generic aliases created using `typing.Annotated`). Previously only `AttributeError` was ignored. Patch by Dave Shawley.

- gh-115133: Fix tests for `XMLPullParser` with Expat 2.6.0.

- gh-115059: `io.BufferedRandom.read1()` now flushes the underlying write buffer.

- gh-79382: Trailing `**` no longer allows to match files and non-existing paths in recursive `glob()`.

- gh-114071: Support tuple subclasses using auto() for enum member value.

- gh-114763: Protect modules loaded with `importlib.util.LazyLoader` from race conditions when multiple threads try to access attributes before the loading is complete.

- gh-97959: Fix rendering class methods, bound methods, method and function aliases in `pydoc`. Class methods no longer have “method of builtins.type instance” note. Corresponding notes are now added for class and unbound methods. Method and function aliases now have references to the module or the class where the origin was defined if it differs from the current. Bound methods are now listed in the static methods section. Methods of builtin classes are now supported as well as methods of Python classes.

- gh-112281: Allow creating union of types for `typing.Annotated` with unhashable metadata.

- gh-111775: Fix `importlib.resources.simple.ResourceHandle.open()` for text mode, added missed `stream` argument.

- gh-90095: Make .pdbrc and -c work with any valid pdb commands.

- gh-107155: Fix incorrect output of `help(x)` where `x` is a `lambda` function, which has an `__annotations__` dictionary attribute with a `"return"` key.

- gh-105866: Fixed `_get_slots` bug which caused error when defining dataclasses with slots and a weakref_slot.

- gh-60346: Fix ArgumentParser inconsistent with parse_known_args.

- gh-100985: Update HTTPSConnection to consistently wrap IPv6 Addresses when using a proxy.

- gh-100884: email: fix misfolding of comma in address-lists over multiple lines in combination with unicode encoding.

- gh-95782: Fix `io.BufferedReader.tell()`, `io.BufferedReader.seek()`, `_pyio.BufferedReader.tell()`, `io.BufferedRandom.tell()`, `io.BufferedRandom.seek()` and `_pyio.BufferedRandom.tell()` being able to return negative offsets.

- gh-96310: Fix a traceback in `argparse` when all options in a mutually exclusive group are suppressed.

- gh-93205: Fixed a bug in `logging.handlers.TimedRotatingFileHandler` where multiple rotating handler instances pointing to files with the same name but different extensions would conflict and not delete the correct files.

- bpo-44865: Add missing call to localization function in `argparse`.

- bpo-43952: Fix `multiprocessing.connection.Listener.accept()` to accept empty bytes as authkey. Not accepting empty bytes as key causes it to hang indefinitely.

- bpo-42125: linecache: get module name from `__spec__` if available. This allows getting source code for the `__main__` module when a custom loader is used.

- gh-66543: Make `mimetypes.guess_type()` properly parsing of URLs with only a host name, URLs containing fragment or query, and filenames with only a UNC sharepoint on Windows. Based on patch by Dong-hee Na.

- bpo-33775: Add ‘default’ and ‘version’ help text for localization in argparse.

### Documentation

- gh-115399: Document CVE 2023-52425 of Expat <2.6.0 under “XML vulnerabilities”.

- gh-115233: Fix an example for `LoggerAdapter` in the Logging Cookbook.

### Tests

- gh-83434: Disable JUnit XML output (`--junit-xml=FILE` command line option) in regrtest when hunting for reference leaks (`-R` option). Patch by Victor Stinner.

- gh-117187: Fix XML tests for vanilla Expat <2.6.0.

- gh-116333: Tests of TLS related things (error codes, etc) were updated to be more lenient about specific error message strings and behaviors as seen in the BoringSSL and AWS-LC forks of OpenSSL.

- gh-115979: Update test_importlib so that it passes under WASI SDK 21.

- gh-112536: Add –tsan to test.regrtest for running TSAN tests in reasonable execution times. Patch by Donghee Na.

- gh-116307: Added import helper `isolated_modules` as `CleanImport` does not remove modules imported during the context. Use it in importlib.resources tests to avoid leaving `mod` around to impede importlib.metadata tests.

- gh-115720: Leak tests (`-R`, `--huntrleaks`) now show a summary of the number of leaks found in each iteration.

- gh-115122: Add `--bisect` option to regrtest test runner: run failed tests with `test.bisect_cmd` to identify failing tests. Patch by Victor Stinner.

- gh-115596: Fix `ProgramPriorityTests` in `test_os` permanently changing the process priority.

### Build

- gh-116313: Get WASI builds to work under wasmtime 18 w/ WASI 0.2/preview2 primitives.

- gh-116117: Backport `libb2`’s PR #42 to fix compiling CPython on 32-bit Windows with `clang-cl`.

- gh-115167: Avoid vendoring `vcruntime140_threads.dll` when building with Visual Studio 2022 version 17.8.

- gh-112536: Add support for thread sanitizer (TSAN)

### Windows

- gh-117267: Ensure `DirEntry.stat().st_ctime` behaves consistently with `os.stat()` during the deprecation period of `st_ctime` by containing the same value as `st_birthtime`. After the deprecation period, `st_ctime` will be the metadata change time (or unavailable through `DirEntry`), and only `st_birthtime` will contain the creation time.

- gh-116773: Fix instances of `<_overlapped.Overlapped object at 0xXXX> still has pending operation at deallocation, the process may crash`.

- gh-91227: Fix the asyncio ProactorEventLoop implementation so that sending a datagram to an address that is not listening does not prevent receiving any more datagrams.

- gh-115554: The installer now has more strict rules about updating the Python Launcher for Windows. In general, most users only have a single launcher installed and will see no difference. When multiple launchers have been installed, the option to install the launcher is disabled until all but one have been removed. Downgrading the launcher (which was never allowed) is now more obviously blocked.

- gh-115543: Python Launcher for Windows can now detect Python 3.13 when installed from the Microsoft Store, and will install Python 3.12 by default when `PYLAUNCHER_ALLOW_INSTALL` is set.

- gh-115049: Fixes `py.exe` launcher failing when run as users without user profiles.

- gh-115009: Update Windows installer to use SQLite 3.45.1.

### IDLE

- gh-88516: On macOS show a proxy icon in the title bar of editor windows to match platform behaviour.

### Tools/Demos

- gh-113516: Don’t set `LDSHARED` when building for WASI.

### C API

- gh-117021: Fix integer overflow in `PyLong_AsPid()` on non-Windows 64-bit platforms.

- gh-116869: Make the C API compatible with `-Werror=declaration-after-statement` compiler flag again. Patch by Victor Stinner.

## Python 3.12.2 final

Release date: 2024-02-06

### Security

- gh-113659: Skip `.pth` files with names starting with a dot or hidden file attribute.

### Core and Builtins

- gh-114887: Changed socket type validation in `create_datagram_endpoint()` to accept all non-stream sockets. This fixes a regression in compatibility with raw sockets.

- gh-114388: Fix a `RuntimeWarning` emitted when assign an integer-like value that is not an instance of `int` to an attribute that corresponds to a C struct member of type T_UINT and T_ULONG. Fix a double `RuntimeWarning` emitted when assign a negative integer value to an attribute that corresponds to a C struct member of type T_UINT.

- gh-113703: Fix a regression in the `codeop` module that was causing it to incorrectly identify incomplete f-strings. Patch by Pablo Galindo

- gh-89811: Check for a valid `tp_version_tag` before performing bytecode specializations that rely on this value being usable.

- gh-113602: Fix an error that was causing the parser to try to overwrite existing errors and crashing in the process. Patch by Pablo Galindo

- gh-113297: Fix segfault in the compiler on with statement with 19 context managers.

- gh-106905: Use per AST-parser state rather than global state to track recursion depth within the AST parser to prevent potential race condition due to simultaneous parsing.

  The issue primarily showed up in 3.11 by multithreaded users of `ast.parse()`. In 3.12 a change to when garbage collection can be triggered prevented the race condition from occurring.

- gh-112943: Correctly compute end column offsets for multiline tokens in the `tokenize` module. Patch by Pablo Galindo

- gh-112716: Fix SystemError in the `import` statement and in `__reduce__()` methods of builtin types when `__builtins__` is not a dict.

- gh-94606: Fix UnicodeEncodeError when `email.message.get_payload()` reads a message with a Unicode surrogate character and the message content is not well-formed for surrogateescape encoding. Patch by Sidney Markowitz.

### Library

- gh-114965: Update bundled pip to 24.0

- gh-114959: `tarfile` no longer ignores errors when trying to extract a directory on top of a file.

- gh-109475: Fix support of explicit option value “–” in `argparse` (e.g. `--option=--`).

- gh-110190: Fix ctypes structs with array on Windows ARM64 platform by setting `MAX_STRUCT_SIZE` to 32 in stgdict. Patch by Diego Russo

- gh-113280: Fix a leak of open socket in rare cases when error occurred in `ssl.SSLSocket` creation.

- gh-77749: `email.policy.EmailPolicy.fold()` now always encodes non-ASCII characters in headers if `utf8` is false.

- gh-114492: Make the result of `termios.tcgetattr()` reproducible on Alpine Linux. Previously it could leave a random garbage in some fields.

- gh-113267: Revert changes in gh-106584 which made calls of `TestResult` methods `startTest()` and `stopTest()` unbalanced.

- gh-75128: Ignore an `OSError` in `asyncio.BaseEventLoop.create_server()` when IPv6 is available but the interface cannot actually support it.

- gh-114257: Dismiss the `FileNotFound` error in `ctypes.util.find_library()` and just return `None` on Linux.

- gh-114328: The `tty.setcbreak()` and new `tty.cfmakecbreak()` no longer clears the terminal input ICRLF flag. This fixes a regression introduced in 3.12 that no longer matched how OSes define cbreak mode in their `stty(1)` manual pages.

- gh-101438: Avoid reference cycle in ElementTree.iterparse. The iterator returned by `ElementTree.iterparse` may hold on to a file descriptor. The reference cycle prevented prompt clean-up of the file descriptor if the returned iterator was not exhausted.

- gh-104522: `OSError` raised when run a subprocess now only has filename attribute set to cwd if the error was caused by a failed attempt to change the current directory.

- gh-114149: Enum: correctly handle tuple subclasses in custom `__new__`.

- gh-109534: Fix a reference leak in `asyncio.selector_events.BaseSelectorEventLoop` when SSL handshakes fail. Patch contributed by Jamie Phan.

- gh-114077: Fix possible `OverflowError` in `socket.socket.sendfile()` when pass count larger than 2 GiB on 32-bit platform.

- gh-114014: Fixed a bug in `fractions.Fraction` where an invalid string using `d` in the decimals part creates a different error compared to other invalid letters/characters. Patch by Jeremiah Gabriel Pascual.

- gh-113951: Fix the behavior of `tag_unbind()` methods of `tkinter.Text` and `tkinter.Canvas` classes with three arguments. Previously, `widget.tag_unbind(tag, sequence, funcid)` destroyed the current binding for sequence, leaving sequence unbound, and deleted the funcid command. Now it removes only funcid from the binding for sequence, keeping other commands, and deletes the funcid command. It leaves sequence unbound only if funcid was the last bound command.

- gh-113877: Fix `tkinter` method `winfo_pathname()` on 64-bit Windows.

- gh-113661: unittest runner: Don’t exit 5 if tests were skipped. The intention of exiting 5 was to detect issues where the test suite wasn’t discovered at all. If we skipped tests, it was correctly discovered.

- gh-113781: Silence unraisable AttributeError when warnings are emitted during Python finalization.

- gh-112932: Restore the ability for `zipfile` to `extractall` from zip files with a “/” directory entry in them as is commonly added to zips by some wiki or bug tracker data exporters.

- gh-113594: Fix `UnicodeEncodeError` in `email` when re-fold lines that contain unknown-8bit encoded part followed by non-unknown-8bit encoded part.

- gh-113538: In `asyncio.StreamReaderProtocol.connection_made()`, there is callback that logs an error if the task wrapping the “connected callback” fails. This callback would itself fail if the task was cancelled. Prevent this by checking whether the task was cancelled first. If so, close the transport but don’t log an error.

- gh-85567: Fix resource warnings for unclosed files in `pickle` and `pickletools` command line interfaces.

- gh-101225: Increase the backlog for `multiprocessing.connection.Listener` objects created by `multiprocessing.manager` and `multiprocessing.resource_sharer` to significantly reduce the risk of getting a connection refused error when creating a `multiprocessing.connection.Connection` to them.

- gh-113543: Make sure that `webbrowser.MacOSXOSAScript` sends `webbrowser.open` audit event.

- gh-113028: When a second reference to a string appears in the input to `pickle`, and the Python implementation is in use, we are guaranteed that a single copy gets pickled and a single object is shared when reloaded. Previously, in protocol 0, when a string contained certain characters (e.g. newline) it resulted in duplicate objects.

- gh-113421: Fix multiprocessing logger for `%(filename)s`.

- gh-111784: Fix segfaults in the `_elementtree` module. Fix first segfault during deallocation of `_elementtree.XMLParser` instances by keeping strong reference to `pyexpat` module in module state for capsule lifetime. Fix second segfault which happens in the same deallocation process by keeping strong reference to `_elementtree` module in `XMLParser` structure for `_elementtree` module lifetime.

- gh-113407: Fix import of `unittest.mock` when CPython is built without docstrings.

- gh-113320: Fix regression in Python 3.12 where `Protocol` classes that were not marked as `runtime-checkable` would be unnecessarily introspected, potentially causing exceptions to be raised if the protocol had problematic members. Patch by Alex Waygood.

- gh-113358: Fix rendering tracebacks for exceptions with a broken `__getattr__`.

- gh-113214: Fix an `AttributeError` during asyncio SSL protocol aborts in SSL-over-SSL scenarios.

- gh-113246: Update bundled pip to 23.3.2.

- gh-113199: Make `http.client.HTTPResponse.read1` and `http.client.HTTPResponse.readline` close IO after reading all data when content length is known. Patch by Illia Volochii.

- gh-113188: Fix `shutil.copymode()` and `shutil.copystat()` on Windows. Previously they worked differenly if dst is a symbolic link: they modified the permission bits of dst itself rather than the file it points to if follow_symlinks is true or src is not a symbolic link, and did not modify the permission bits if follow_symlinks is false and src is a symbolic link.

- gh-61648: Detect line numbers of properties in doctests.

- gh-112559: `signal.signal()` and `signal.getsignal()` no longer call `repr` on callable handlers. `asyncio.run()` and `asyncio.Runner.run()` no longer call `repr` on the task results. Patch by Yilei Yang.

- gh-110190: Fix ctypes structs with array on PPC64LE platform by setting `MAX_STRUCT_SIZE` to 64 in stgdict. Patch by Diego Russo.

- gh-79429: Ignore FileNotFoundError when remove a temporary directory in the multiprocessing finalizer.

- gh-81194: Fix a crash in `socket.if_indextoname()` with specific value (UINT_MAX). Fix an integer overflow in `socket.if_indextoname()` on 64-bit non-Windows platforms.

- gh-112343: Improve handling of pdb convenience variables to avoid replacing string contents.

- gh-111615: Fix a regression caused by a fix to gh-93162 whereby you couldn’t configure a `QueueHandler` without specifying handlers.

- gh-111049: Fix crash during garbage collection of the `io.BytesIO` buffer object.

- gh-110345: Show the Tcl/Tk patchlevel (rather than version) in `tkinter._test()`.

- gh-109858: Protect `zipfile` from “quoted-overlap” zipbomb. It now raises BadZipFile when try to read an entry that overlaps with other entry or central directory.

- gh-114440: On Windows, closing the connection writer when cleaning up a broken `multiprocessing.Queue` queue is now done for all queues, rather than only in `concurrent.futures` manager thread. This can prevent a deadlock when a `multiprocessing` worker process terminates without cleaning up. This completes the backport of patches by Victor Stinner and Serhiy Storchaka.

- gh-38807: Fix race condition in `trace`. Instead of checking if a directory exists and creating it, directly call `os.makedirs()` with the kwarg `exist_ok=True`.

- gh-75705: Set unixfrom envelope in `mailbox.mbox` and `mailbox.MMDF`.

- gh-106233: Fix stacklevel in `InvalidTZPathWarning` during `zoneinfo` module import.

- gh-105102: Allow `ctypes.Union` to be nested in `ctypes.Structure` when the system endianness is the opposite of the classes.

- gh-104282: Fix null pointer dereference in `lzma._decode_filter_properties()` due to improper handling of BCJ filters with properties of zero length. Patch by Radislav Chugunov.

- gh-102512: When `os.fork()` is called from a foreign thread (aka `_DummyThread`), the type of the thread in a child process is changed to `_MainThread`. Also changed its name and daemonic status, it can be now joined.

- bpo-35928: `io.TextIOWrapper` now correctly handles the decoding buffer after `read()` and `write()`.

- bpo-26791: `shutil.move()` now moves a symlink into a directory when that directory is the target of the symlink. This provides the same behavior as the mv shell command. The previous behavior raised an exception. Patch by Jeffrey Kintscher.

- bpo-36959: Fix some error messages for invalid ISO format string combinations in `strptime()` that referred to directives not contained in the format string. Patch by Gordon P. Hemsley.

- bpo-18060: Fixed a class inheritance issue that can cause segfaults when deriving two or more levels of subclasses from a base class of Structure or Union.

### Documentation

- gh-110746: Improved markup for valid options/values for methods ttk.treeview.column and ttk.treeview.heading, and for Layouts.

- gh-95649: Document that the `asyncio` module contains code taken from v0.16.0 of the uvloop project, as well as the required MIT licensing information.

### Tests

- gh-109980: Fix `test_tarfile_vs_tar` in `test_shutil` for macOS, where system tar can include more information in the archive than `shutil.make_archive`.

- gh-105089: Fix `test.test_zipfile.test_core.TestWithDirectory.test_create_directory_with_write` test in AIX by doing a bitwise AND of 0xFFFF on mode , so that it will be in sync with `zinfo.external_attr`

- bpo-40648: Test modes that file can get with chmod() on Windows.

### Build

- gh-112305: Fixed the `check-clean-src` step performed on out of tree builds to detect errant `$(srcdir)/Python/frozen_modules/*.h` files and recommend appropriate source tree cleanup steps to get a working build again.

- gh-112867: Fix the build for the case that WITH_PYMALLOC_RADIX_TREE=0 set.

- bpo-11102: The `os.major()`, `os.makedev()`, and `os.minor()` functions are now available on HP-UX v3.

- bpo-36351: Do not set ipv6type when cross-compiling.

### Windows

- gh-109991: Update Windows build to use OpenSSL 3.0.13.

- gh-111239: Update Windows builds to use zlib v1.3.1.

- gh-100107: The `py.exe` launcher will no longer attempt to run the Microsoft Store redirector when launching a script containing a `/usr/bin/env` shebang

- gh-114096: Process privileges that are activated for creating directory junctions are now restored afterwards, avoiding behaviour changes in other parts of the program.

- gh-111877: `os.stat()` calls were returning incorrect time values for files that could not be accessed directly.

- gh-113009: `multiprocessing`: On Windows, fix a race condition in `Process.terminate()`: no longer set the `returncode` attribute to always call `WaitForSingleObject()` in `Process.wait()`. Previously, sometimes the process was still running after `TerminateProcess()` even if `GetExitCodeProcess()` is not `STILL_ACTIVE`. Patch by Victor Stinner.

- gh-87868: Correctly sort and remove duplicate environment variables in `_winapi.CreateProcess()`.

- bpo-37308: Fix mojibake in `mmap.mmap` when using a non-ASCII tagname argument on Windows.

### macOS

- gh-115009: Update macOS installer to use SQLite 3.45.1.

- gh-109991: Update macOS installer to use OpenSSL 3.0.13.

- gh-110459: Running `configure ... --with-openssl-rpath=X/Y/Z` no longer fails to detect OpenSSL on macOS.

- gh-74573: Document that `dbm.ndbm` can silently corrupt DBM files on updates when exceeding undocumented platform limits, and can crash (segmentation fault) when reading such a corrupted file. (FB8919203)

- gh-65701: The freeze tool doesn’t work with framework builds of Python. Document this and bail out early when running the tool with such a build.

- gh-108269: Set `CFBundleAllowMixedLocalizations` to true in the Info.plist for the framework, embedded Python.app and IDLE.app with framework installs on macOS. This allows applications to pick up the user’s preferred locale when that’s different from english.

- gh-102362: Make sure the result of `sysconfig.get_plaform()` includes at least a major and minor versions, even if `MACOSX_DEPLOYMENT_TARGET` is set to only a major version during build to match the format expected by pip.

- gh-110017: Disable a signal handling stress test on macOS due to a bug in macOS (FB13453490).

- gh-110820: Make sure the preprocessor definitions for `ALIGNOF_MAX_ALIGN_T`, `SIZEOF_LONG_DOUBLE` and `HAVE_GCC_ASM_FOR_X64` are correct for Universal 2 builds on macOS.

### IDLE

- gh-96905: In idlelib code, stop redefining built-ins ‘dict’ and ‘object’.

- gh-72284: Improve the lists of features, editor key bindings, and shell key bingings in the IDLE doc.

- gh-113903: Fix rare failure of test.test_idle, in test_configdialog.

- gh-113729: Fix the “Help -> IDLE Doc” menu bug in 3.11.7 and 3.12.1.

- gh-113269: Fix test_editor hang on macOS Catalina.

- gh-112898: Fix processing unsaved files when quitting IDLE on macOS.

- gh-103820: Revise IDLE bindings so that events from mouse button 4/5 on non-X11 windowing systems (i.e. Win32 and Aqua) are not mistaken for scrolling.

- bpo-13586: Enter the selected text when opening the “Replace” dialog.

### Tools/Demos

- gh-109991: Update GitHub CI workflows to use OpenSSL 3.0.13 and multissltests to use 1.1.1w, 3.0.13, 3.1.5, and 3.2.1.

- gh-115015: Fix a bug in Argument Clinic that generated incorrect code for methods with no parameters that use the METH_METHOD | METH_FASTCALL | METH_KEYWORDS calling convention. Only the positional parameter count was checked; any keyword argument passed would be silently accepted.

## Python 3.12.1 final

Release date: 2023-12-07

### Core and Builtins

- gh-112125: Fix None.__ne__(None) returning NotImplemented instead of False

- gh-112625: Fixes a bug where a bytearray object could be cleared while iterating over an argument in the `bytearray.join()` method that could result in reading memory after it was freed.

- gh-105967: Workaround a bug in Apple’s macOS platform zlib library where `zlib.crc32()` and `binascii.crc32()` could produce incorrect results on multi-gigabyte inputs. Including when using `zipfile` on zips containing large data.

- gh-112356: Stopped erroneously deleting a `LOAD_NULL` bytecode instruction when optimized twice.

- gh-111058: Change coro.cr_frame/gen.gi_frame to return `None` after the coroutine/generator has been closed. This fixes a bug where `getcoroutinestate()` and `getgeneratorstate()` return the wrong state for a closed coroutine/generator.

- gh-112388: Fix an error that was causing the parser to try to overwrite tokenizer errors. Patch by pablo Galindo

- gh-112387: Fix error positions for decoded strings with backwards tokenize errors. Patch by Pablo Galindo

- gh-112367: Avoid undefined behaviour when using the perf trampolines by not freeing the code arenas until shutdown. Patch by Pablo Galindo

- gh-112243: Don’t include comments in f-string debug expressions. Patch by Pablo Galindo

- gh-112266: Change docstrings of `__dict__` and `__weakref__`.

- gh-111654: Fix runtime crash when some error happens in opcode `LOAD_FROM_DICT_OR_DEREF`.

- gh-109181: Speed up `Traceback` object creation by lazily compute the line number. Patch by Pablo Galindo

- gh-102388: Fix a bug where `iso2022_jp_3` and `iso2022_jp_2004` codecs read out of bounds

- gh-111366: Fix an issue in the `codeop` that was causing `SyntaxError` exceptions raised in the presence of invalid syntax to not contain precise error messages. Patch by Pablo Galindo

- gh-111380: Fix a bug that was causing `SyntaxWarning` to appear twice when parsing if invalid syntax is encountered later. Patch by Pablo galindo

- gh-94438: Fix a regression that prevented jumping across `is None` and `is not None` when debugging. Patch by Savannah Ostrowski.

- gh-110938: Fix error messages for indented blocks with functions and classes with generic type parameters. Patch by Pablo Galindo

- gh-109894: Fixed crash due to improperly initialized static `MemoryError` in subinterpreter.

- gh-110782: Fix crash when `typing.TypeVar` is constructed with a keyword argument. Patch by Jelle Zijlstra.

- gh-110696: Fix incorrect error message for invalid argument unpacking. Patch by Pablo Galindo

- gh-110543: Fix regression in Python 3.12 where `types.CodeType.replace()` would produce a broken code object if called on a module or class code object that contains a comprehension. Patch by Jelle Zijlstra.

- gh-110514: Add `PY_THROW` to `sys.setprofile()` events

- gh-110455: Guard `assert(tstate->thread_id > 0)` with `#ifndef HAVE_PTHREAD_STUBS`. This allows for for pydebug builds to work under WASI which (currently) lacks thread support.

- gh-110259: Correctly identify the format spec in f-strings (with single or triple quotes) that have multiple lines in the expression part and include a formatting spec. Patch by Pablo Galindo

- gh-110237: Fix missing error checks for calls to `PyList_Append` in `_PyEval_MatchClass`.

- gh-109889: Fix the compiler’s redundant NOP detection algorithm to skip over NOPs with no line number when looking for the next instruction’s lineno.

- gh-109853: `sys.path[0]` is now set correctly for subinterpreters.

- gh-105716: Subinterpreters now correctly handle the case where they have threads running in the background. Before, such threads would interfere with cleaning up and destroying them, as well as prevent running another script.

- gh-109793: The main thread no longer exits prematurely when a subinterpreter is cleaned up during runtime finalization. The bug was a problem particularly because, when triggered, the Python process would always return with a 0 exitcode, even if it failed.

- gh-109596: Fix some tokens in the grammar that were incorrectly marked as soft keywords. Also fix some repeated rule names and ensure that repeated rules are not allowed. Patch by Pablo Galindo

- gh-109351: Fix crash when compiling an invalid AST involving a named (walrus) expression.

- gh-109216: Fix possible memory leak in `BUILD_MAP`.

- gh-109207: Fix a SystemError in `__repr__` of symtable entry object.

- gh-109179: Fix bug where the C traceback display drops notes from `SyntaxError`.

- gh-109052: Use the base opcode when comparing code objects to avoid interference from instrumentation

- gh-88943: Improve syntax error for non-ASCII character that follows a numerical literal. It now points on the invalid non-ASCII character, not on the valid numerical literal.

- gh-106931: Statically allocated string objects are now interned globally instead of per-interpreter. This fixes a situation where such a string would only be interned in a single interpreter. Normal string objects are unaffected.

### Library

- gh-79325: Fix an infinite recursion error in `tempfile.TemporaryDirectory()` cleanup on Windows.

- gh-112645: Remove deprecation error on passing `onerror` to `shutil.rmtree()`.

- gh-112618: Fix a caching bug relating to `typing.Annotated`. `Annotated[str, True]` is no longer identical to `Annotated[str, 1]`.

- gh-112334: Fixed a performance regression in 3.12’s `subprocess` on Linux where it would no longer use the fast-path `vfork()` system call when it should have due to a logic bug, instead always falling back to the safe but slower `fork()`.

  Also fixed a related 3.12 security regression: If a value of `extra_groups=[]` was passed to `subprocess.Popen` or related APIs, the underlying `setgroups(0, NULL)` system call to clear the groups list would not be made in the child process prior to `exec()`. This has been assigned CVE 2023-6507.

  This was identified via code inspection in the process of fixing the first bug.

- gh-110190: Fix ctypes structs with array on Arm platform by setting `MAX_STRUCT_SIZE` to 32 in stgdict. Patch by Diego Russo.

- gh-112578: Fix a spurious `RuntimeWarning` when executing the `zipfile` module.

- gh-112509: Fix edge cases that could cause a key to be present in both the `__required_keys__` and `__optional_keys__` attributes of a `typing.TypedDict`. Patch by Jelle Zijlstra.

- gh-112414: Fix regression in Python 3.12 where calling `repr()` on a module that had been imported using a custom loader could fail with `AttributeError`. Patch by Alex Waygood.

- gh-112358: Revert change to `struct.Struct` initialization that broke some cases of subclassing.

- gh-94722: Fix bug where comparison between instances of `DocTest` fails if one of them has `None` as its lineno.

- gh-112105: Make `readline.set_completer_delims()` work with libedit

- gh-111942: Fix SystemError in the TextIOWrapper constructor with non-encodable “errors” argument in non-debug mode.

- gh-109538: Issue warning message instead of having `RuntimeError` be displayed when event loop has already been closed at `StreamWriter.__del__()`.

- gh-111942: Fix crashes in `io.TextIOWrapper.reconfigure()` when pass invalid arguments, e.g. non-string encoding.

- gh-111460: `curses`: restore wide character support (including `curses.unget_wch()` and `get_wch()`) on macOS, which was unavailable due to a regression in Python 3.12.

- gh-103791: `contextlib.suppress` now supports suppressing exceptions raised as part of a `BaseExceptionGroup`, in addition to the recent support for `ExceptionGroup`.

- gh-111804: Remove posix.fallocate() under WASI as the underlying posix_fallocate() is not available in WASI preview2.

- gh-111841: Fix truncating arguments on an embedded null character in `os.putenv()` and `os.unsetenv()` on Windows.

- gh-111541: Fix `doctest` for `SyntaxError` not-builtin subclasses.

- gh-110894: Call loop exception handler for exceptions in `client_connected_cb` of `asyncio.start_server()` so that applications can handle it. Patch by Kumar Aditya.

- gh-111531: Fix reference leaks in `bind_class()` and `bind_all()` methods of `tkinter` widgets.

- gh-111356: Added `io.text_encoding()`, `io.DEFAULT_BUFFER_SIZE`, and `io.IncrementalNewlineDecoder` to `io.__all__`.

- gh-111342: Fixed typo in `math.sumprod()`.

- gh-68166: Remove mention of not supported “vsapi” element type in `tkinter.ttk.Style.element_create()`. Add tests for `element_create()` and other `ttk.Style` methods. Add examples for `element_create()` in the documentation.

- gh-75666: Fix the behavior of `tkinter` widget’s `unbind()` method with two arguments. Previously, `widget.unbind(sequence, funcid)` destroyed the current binding for sequence, leaving sequence unbound, and deleted the funcid command. Now it removes only funcid from the binding for sequence, keeping other commands, and deletes the funcid command. It leaves sequence unbound only if funcid was the last bound command.

- gh-79033: Another attempt at fixing `asyncio.Server.wait_closed()`. It now blocks until both conditions are true: the server is closed, and there are no more active connections. (This means that in some cases where in 3.12.0 this function would incorrectly have returned immediately, it will now block; in particular, when there are no active connections but the server hasn’t been closed yet.)

- gh-111295: Fix `time` not checking for errors when initializing.

- gh-111253: Add error checking during `_socket` module init.

- gh-111251: Fix `_blake2` not checking for errors when initializing.

- gh-111174: Fix crash in `io.BytesIO.getbuffer()` called repeatedly for empty BytesIO.

- gh-111187: Postpone removal version for locale.getdefaultlocale() to Python 3.15.

- gh-111159: Fix `doctest` output comparison for exceptions with notes.

- gh-110910: Fix invalid state handling in `asyncio.TaskGroup` and `asyncio.Timeout`. They now raise proper RuntimeError if they are improperly used and are left in consistent state after this.

- gh-111092: Make turtledemo run without default root enabled.

- gh-110488: Fix a couple of issues in `pathlib.PurePath.with_name()`: a single dot was incorrectly considered a valid name, and in `PureWindowsPath`, a name with an NTFS alternate data stream, like `a:b`, was incorrectly considered invalid.

- gh-110392: Fix `tty.setraw()` and `tty.setcbreak()`: previously they returned partially modified list of the original tty attributes. `tty.cfmakeraw()` and `tty.cfmakecbreak()` now make a copy of the list of special characters before modifying it.

- gh-110590: Fix a bug in `_sre.compile()` where `TypeError` would be overwritten by `OverflowError` when the code argument was a list of non-ints.

- gh-65052: Prevent `pdb` from crashing when trying to display undisplayable objects

- gh-110519: Deprecation warning about non-integer number in `gettext` now alwais refers to the line in the user code where gettext function or method is used. Previously it could refer to a line in `gettext` code.

- gh-110395: Ensure that `select.kqueue()` objects correctly appear as closed in forked children, to prevent operations on an invalid file descriptor.

- gh-110378: `contextmanager()` and `asynccontextmanager()` context managers now close an invalid underlying generator object that yields more then one value.

- gh-110365: Fix `termios.tcsetattr()` bug that was overwritting existing errors during parsing integers from `term` list.

- gh-109653: Fix a Python 3.12 regression in the import time of `random`. Patch by Alex Waygood.

- gh-110196: Add `__reduce__` method to `IPv6Address` in order to keep `scope_id`

- gh-110036: On Windows, multiprocessing `Popen.terminate()` now catchs `PermissionError` and get the process exit code. If the process is still running, raise again the `PermissionError`. Otherwise, the process terminated as expected: store its exit code. Patch by Victor Stinner.

- gh-110038: Fixed an issue that caused `KqueueSelector.select()` to not return all the ready events in some cases when a file descriptor is registered for both read and write.

- gh-109631: `re` functions such as `re.findall()`, `re.split()`, `re.search()` and `re.sub()` which perform short repeated matches can now be interrupted by user.

- gh-109747: Improve errors for unsupported look-behind patterns. Now re.error is raised instead of OverflowError or RuntimeError for too large width of look-behind pattern.

- gh-109818: Fix `reprlib.recursive_repr()` not copying `__type_params__` from decorated function.

- gh-109047: `concurrent.futures`: The executor manager thread now catches exceptions when adding an item to the call queue. During Python finalization, creating a new thread can now raise `RuntimeError`. Catch the exception and call `terminate_broken()` in this case. Patch by Victor Stinner.

- gh-109782: Ensure the signature of `os.path.isdir()` is identical on all platforms. Patch by Amin Alaee.

- gh-109590: `shutil.which()` will prefer files with an extension in `PATHEXT` if the given mode includes `os.X_OK` on win32. If no `PATHEXT` match is found, a file without an extension in `PATHEXT` can be returned. This change will have `shutil.which()` act more similarly to previous behavior in Python 3.11.

- gh-109786: Fix possible reference leaks and crash when re-enter the `__next__()` method of `itertools.pairwise`.

- gh-109593: Avoid deadlocking on a reentrant call to the multiprocessing resource tracker. Such a reentrant call, though unlikely, can happen if a GC pass invokes the finalizer for a multiprocessing object such as SemLock.

- gh-109613: Fix `os.stat()` and `os.DirEntry.stat()`: check for exceptions. Previously, on Python built in debug mode, these functions could trigger a fatal Python error (and abort the process) when a function succeeded with an exception set. Patch by Victor Stinner.

- gh-109375: The `pdb` `alias` command now prevents registering aliases without arguments.

- gh-107219: Fix a race condition in `concurrent.futures`. When a process in the process pool was terminated abruptly (while the future was running or pending), close the connection write end. If the call queue is blocked on sending bytes to a worker process, closing the connection write end interrupts the send, so the queue can be closed. Patch by Victor Stinner.

- gh-50644: Attempts to pickle or create a shallow or deep copy of `codecs` streams now raise a TypeError. Previously, copying failed with a RecursionError, while pickling produced wrong results that eventually caused unpickling to fail with a RecursionError.

- gh-108987: Fix `_thread.start_new_thread()` race condition. If a thread is created during Python finalization, the newly spawned thread now exits immediately instead of trying to access freed memory and lead to a crash. Patch by Victor Stinner.

- gh-108791: Improved error handling in `pdb` command line interface, making it produce more concise error messages.

- gh-105829: Fix concurrent.futures.ProcessPoolExecutor deadlock

- gh-106584: Fix exit code for `unittest` if all tests are skipped. Patch by Egor Eliseev.

- gh-102956: Fix returning of empty byte strings after seek in zipfile module

- gh-84867: `unittest.TestLoader` no longer loads test cases from exact `unittest.TestCase` and `unittest.FunctionTestCase` classes.

- gh-91133: Fix a bug in `tempfile.TemporaryDirectory` cleanup, which now no longer dereferences symlinks when working around file system permission errors.

- gh-73561: Omit the interface scope from an IPv6 address when used as Host header by `http.client`.

- gh-86826: `zipinfo` now supports the full range of values in the TZ string determined by RFC 8536 and detects all invalid formats. Both Python and C implementations now raise exceptions of the same type on invalid data.

- bpo-43153: On Windows, `tempfile.TemporaryDirectory` previously masked a `PermissionError` with `NotADirectoryError` during directory cleanup. It now correctly raises `PermissionError` if errors are not ignored. Patch by Andrei Kulakov and Ken Jin.

- bpo-35332: The `shutil.rmtree()` function now ignores errors when calling `os.close()` when ignore_errors is `True`, and `os.close()` no longer retried after error.

- bpo-41422: Fixed memory leaks of `pickle.Pickler` and `pickle.Unpickler` involving cyclic references via the internal memo mapping.

- bpo-40262: The `ssl.SSLSocket.recv_into()` method no longer requires the buffer argument to implement `__len__` and supports buffers with arbitrary item size.

### Documentation

- gh-111699: Relocate `smtpd` deprecation notice to its own section rather than under `locale` in What’s New in Python 3.12 document

- gh-108826: `dis` module command-line interface is now mentioned in documentation.

### Tests

- gh-112769: The tests now correctly compare zlib version when `zlib.ZLIB_RUNTIME_VERSION` contains non-integer suffixes. For example zlib-ng defines the version as `1.3.0.zlib-ng`.

- gh-110367: Make regrtest `--verbose3` option compatible with `--huntrleaks -jN` options. The `./python -m test -j1 -R 3:3 --verbose3` command now works as expected. Patch by Victor Stinner.

- gh-111165: Remove no longer used functions `run_unittest()` and `run_doctest()` from the `test.support` module.

- gh-110932: Fix regrtest if the `SOURCE_DATE_EPOCH` environment variable is defined: use the variable value as the random seed. Patch by Victor Stinner.

- gh-110995: test_gdb: Fix detection of gdb built without Python scripting support. Patch by Victor Stinner.

- gh-110918: Test case matching patterns specified by options `--match`, `--ignore`, `--matchfile` and `--ignorefile` are now tested in the order of specification, and the last match determines whether the test case be run or ignored.

- gh-110647: Fix test_stress_modifying_handlers() of test_signal. Patch by Victor Stinner.

- gh-103053: Fix test_tools.test_freeze on FreeBSD: run “make distclean” instead of “make clean” in the copied source directory to remove also the “python” program. Patch by Victor Stinner.

- gh-110167: Fix a deadlock in test_socket when server fails with a timeout but the client is still running in its thread. Don’t hold a lock to call cleanup functions in doCleanups(). One of the cleanup function waits until the client completes, whereas the client could deadlock if it called addCleanup() in such situation. Patch by Victor Stinner.

- gh-110388: Add tests for `tty`.

- gh-81002: Add tests for `termios`.

- gh-110267: Add tests for pickling and copying PyStructSequence objects. Patched by Xuehai Pan.

- gh-110031: Skip test_threading tests using thread+fork if Python is built with Address Sanitizer (ASAN). Patch by Victor Stinner.

- gh-110088: Fix test_asyncio timeouts: don’t measure the maximum duration, a test should not measure a CI performance. Only measure the minimum duration when a task has a timeout or delay. Add `CLOCK_RES` to `test_asyncio.utils`. Patch by Victor Stinner.

- gh-109974: Fix race conditions in test_threading lock tests. Wait until a condition is met rather than using `time.sleep()` with a hardcoded number of seconds. Patch by Victor Stinner.

- gh-110033: Fix `test_interprocess_signal()` of `test_signal`. Make sure that the `subprocess.Popen` object is deleted before the test raising an exception in a signal handler. Otherwise, `Popen.__del__()` can get the exception which is logged as `Exception ignored in: ...` and the test fails. Patch by Victor Stinner.

- gh-109594: Fix test_timeout() of test_concurrent_futures.test_wait. Remove the future which may or may not complete depending if it takes longer than the timeout ot not. Keep the second future which does not complete before wait() timeout. Patch by Victor Stinner.

- gh-109972: Split test_gdb.py file into a test_gdb package made of multiple tests, so tests can now be run in parallel. Patch by Victor Stinner.

- gh-103053: Skip test_freeze_simple_script() of test_tools.test_freeze if Python is built with `./configure --enable-optimizations`, which means with Profile Guided Optimization (PGO): it just makes the test too slow. The freeze tool is tested by many other CIs with other (faster) compiler flags. Patch by Victor Stinner.

- gh-109580: Skip `test_perf_profiler` if Python is built with ASAN, MSAN or UBSAN sanitizer. Python does crash randomly in this test on such build. Patch by Victor Stinner.

- gh-104736: Fix test_gdb on Python built with LLVM clang 16 on Linux ppc64le (ex: Fedora 38). Search patterns in gdb “bt” command output to detect when gdb fails to retrieve the traceback. For example, skip a test if `Backtrace stopped: frame did not save the PC` is found. Patch by Victor Stinner.

- gh-108927: Fixed order dependence in running tests in the same process when a test that has submodules (e.g. test_importlib) follows a test that imports its submodule (e.g. test_importlib.util) and precedes a test (e.g. test_unittest or test_compileall) that uses that submodule.

### Build

- gh-112088: Add `Tools/build/regen-configure.sh` script to regenerate the `configure` with an Ubuntu container image. The `quay.io/tiran/cpython_autoconf:271` container image (tiran/cpython_autoconf) is no longer used. Patch by Victor Stinner.

- gh-111046: For wasi-threads, memory is now exported to fix compatibility issues with some wasm runtimes.

- gh-103053: “make check-clean-src” now also checks if the “python” program is found in the source directory: fail with an error if it does exist. Patch by Victor Stinner.

- gh-109191: Fix compile error when building with recent versions of libedit.

### Windows

- gh-111856: Fixes `fstat()` on file systems that do not support file ID requests. This includes FAT32 and exFAT.

- gh-111293: Fix `os.DirEntry.inode` dropping higher 64 bits of a file id on some filesystems on Windows.

- gh-110913: WindowsConsoleIO now correctly chunks large buffers without splitting up UTF-8 sequences.

- gh-110437: Allows overriding the source of VC redistributables so that releases can be guaranteed to never downgrade between updates.

- gh-109286: Update Windows installer to use SQLite 3.43.1.

### macOS

- gh-109981: Use `/dev/fd` on macOS to determine the number of open files in `test.support.os_helper.fd_count` to avoid a crash with “guarded” file descriptors when probing for open files.

- gh-110950: Update macOS installer to include an upstream Tcl/Tk fix for the `Secure coding is not enabled for restorable state!` warning encountered in Tkinter on macOS 14 Sonoma.

- gh-111015: Ensure that IDLE.app and Python Launcher.app are installed with appropriate permissions on macOS builds.

- gh-109286: Update macOS installer to use SQLite 3.43.1.

- gh-71383: Update macOS installer to include an upstream Tcl/Tk fix for the `ttk::ThemeChanged` error encountered in Tkinter.

- gh-92603: Update macOS installer to include a fix accepted by upstream Tcl/Tk for a crash encountered after the first `tkinter.Tk()` instance is destroyed.

### IDLE

- bpo-35668: Add docstrings to the IDLE debugger module. Fix two bugs: initialize Idb.botframe (should be in Bdb); in Idb.in_rpc_code, check whether prev_frame is None before trying to use it. Greatly expand test_debugger.

### C API

- gh-106560: Fix redundant declarations in the public C API. Declare PyBool_Type and PyLong_Type only once. Patch by Victor Stinner.

- gh-112438: Fix support of format units “es”, “et”, “es#”, and “et#” in nested tuples in `PyArg_ParseTuple()`-like functions.

- gh-109521: `PyImport_GetImporter()` now sets RuntimeError if it fails to get `sys.path_hooks` or `sys.path_importer_cache` or they are not list and dict correspondingly. Previously it could return NULL without setting error in obscure cases, crash or raise SystemError if these attributes have wrong type.

## Python 3.12.0 final

Release date: 2023-10-02

### Core and Builtins

- gh-109823: Fix bug where compiler does not adjust labels when removing an empty basic block which is a jump target.

- gh-109719: Fix missing jump target labels when compiler reorders cold/warm blocks.

- gh-109627: Fix bug where the compiler does not assign a new jump target label to a duplicated small exit block.

### Library

- gh-110045: Update the `symtable` module to support the new scopes introduced by PEP 695.

### Documentation

- gh-109209: The minimum Sphinx version required for the documentation is now 4.2.

### Windows

- gh-109991: Update Windows build to use OpenSSL 3.0.11.

### macOS

- gh-109991: Update macOS installer to use OpenSSL 3.0.11.

### Tools/Demos

- gh-109991: Update GitHub CI workflows to use OpenSSL 3.0.11 and multissltests to use 1.1.1w, 3.0.11, and 3.1.3.

## Python 3.12.0 release candidate 3

Release date: 2023-09-18

### Core and Builtins

- gh-109496: On a Python built in debug mode, `Py_DECREF()` now calls `_Py_NegativeRefcount()` if the object is a dangling pointer to deallocated memory: memory filled with `0xDD` “dead byte” by the debug hook on memory allocators. The fix is to check the reference count before checking for `_Py_IsImmortal()`. Patch by Victor Stinner.

- gh-109371: Deopted instructions correctly for tool initialization and modified the incorrect assertion in instrumentation, when a previous tool already sets INSTRUCTION events

- gh-105658: Fix bug where the line trace of an except block ending with a conditional includes an excess event with the line of the conditional expression.

- gh-109219: Fix compiling type param scopes that use a name which is also free in an inner scope.

- gh-109341: Fix crash when compiling an invalid AST involving a `ast.TypeAlias`.

- gh-109195: Fix source location for the `LOAD_*` instruction preceding a `LOAD_SUPER_ATTR` to load the `super` global (or shadowing variable) so that it encompasses only the name `super` and not the following parentheses.

- gh-109118: Disallow nested scopes (lambdas, generator expressions, and comprehensions) within PEP 695 annotation scopes that are nested within classes.

- gh-109114: Relax the detection of the error message for invalid lambdas inside f-strings to not search for arbitrary replacement fields to avoid false positives. Patch by Pablo Galindo

- gh-109118: Fix interpreter crash when a NameError is raised inside the type parameters of a generic class.

- gh-108976: Fix crash that occurs after de-instrumenting a code object in a monitoring callback.

- gh-108732: Make iteration variables of module- and class-scoped comprehensions visible to pdb and other tools that use `frame.f_locals` again.

- gh-108959: Fix caret placement for error locations for subscript and binary operations that involve non-semantic parentheses and spaces. Patch by Pablo Galindo

### Library

- gh-108682: Enum: require `names=()` or `type=...` to create an empty enum using the functional syntax.

- gh-108843: Fix an issue in `ast.unparse()` when unparsing f-strings containing many quote types.

### Documentation

- gh-102823: Document the return type of `x // y` when `x` and `y` have type `float`.

### Tests

- gh-109396: Fix `test_socket.test_hmac_sha1()` in FIPS mode. Use a longer key: FIPS mode requires at least of at least 112 bits. The previous key was only 32 bits. Patch by Victor Stinner.

- gh-104736: Fix test_gdb on Python built with LLVM clang 16 on Linux ppc64le (ex: Fedora 38). Search patterns in gdb “bt” command output to detect when gdb fails to retrieve the traceback. For example, skip a test if `Backtrace stopped: frame did not save the PC` is found. Patch by Victor Stinner.

- gh-109237: Fix `test_site.test_underpth_basic()` when the working directory contains at least one non-ASCII character: encode the `._pth` file to UTF-8 and enable the UTF-8 Mode to use UTF-8 for the child process stdout. Patch by Victor Stinner.

- gh-109230: Fix `test_pyexpat.test_exception()`: it can now be run from a directory different than Python source code directory. Before, the test failed in this case. Skip the test if Modules/pyexpat.c source is not available. Skip also the test on Python implementations other than CPython. Patch by Victor Stinner.

- gh-109015: Fix test_asyncio, test_imaplib and test_socket tests on FreeBSD if the TCP blackhole is enabled (`sysctl net.inet.tcp.blackhole`). Skip the few tests which failed with `ETIMEDOUT` which such non standard configuration. Currently, the FreeBSD GCP image enables TCP and UDP blackhole (`sysctl net.inet.tcp.blackhole=2` and `sysctl net.inet.udp.blackhole=1`). Patch by Victor Stinner.

- gh-91960: Skip `test_gdb` if gdb is unable to retrieve Python frame objects: if a frame is `<optimized out>`. When Python is built with “clang -Og”, gdb can fail to retrive the frame parameter of `_PyEval_EvalFrameDefault()`. In this case, tests like `py_bt()` are likely to fail. Without getting access to Python frames, `python-gdb.py` is mostly clueless on retrieving the Python traceback. Moreover, `test_gdb` is no longer skipped on macOS if Python is built with Clang. Patch by Victor Stinner.

- gh-108962: Skip `test_tempfile.test_flags()` if `chflags()` fails with “OSError: [Errno 45] Operation not supported” (ex: on FreeBSD 13). Patch by Victor Stinner.

- gh-108851: Fix `test_tomllib` recursion tests for WASI buildbots: reduce the recursion limit and compute the maximum nested array/dict depending on the current available recursion limit. Patch by Victor Stinner.

- gh-108851: Add `get_recursion_available()` and `get_recursion_depth()` functions to the `test.support` module. Patch by Victor Stinner.

- gh-108834: Add `--fail-rerun option` option to regrtest: if a test failed when then passed when rerun in verbose mode, exit the process with exit code 2 (error), instead of exit code 0 (success). Patch by Victor Stinner.

- gh-108834: Rename regrtest `--verbose2` option (`-w`) to `--rerun`. Keep `--verbose2` as a deprecated alias. Patch by Victor Stinner.

- gh-108834: When regrtest reruns failed tests in verbose mode (`./python -m test --rerun`), tests are now rerun in fresh worker processes rather than being executed in the main process. If a test does crash or is killed by a timeout, the main process can detect and handle the killed worker process. Tests are rerun in parallel if the `-jN` option is used to run tests in parallel. Patch by Victor Stinner.

- gh-103186: Suppress and assert expected RuntimeWarnings in test_sys_settrace.py

### Build

- gh-108740: Fix a race condition in `make regen-all`. The `deepfreeze.c` source and files generated by Argument Clinic are now generated or updated before generating “global objects”. Previously, some identifiers may miss depending on the order in which these files were generated. Patch by Victor Stinner.

## Python 3.12.0 release candidate 2

Release date: 2023-09-05

### Security

- gh-108310: Fixed an issue where instances of `ssl.SSLSocket` were vulnerable to a bypass of the TLS handshake and included protections (like certificate verification) and treating sent unencrypted data as if it were post-handshake TLS encrypted data. Security issue reported as CVE 2023-40217 by Aapo Oksman. Patch by Gregory P. Smith.

- gh-107774: PEP 669 specifies that `sys.monitoring.register_callback` will generate an audit event. Pre-releases of Python 3.12 did not generate the audit event. This is now fixed.

### Core and Builtins

- gh-108520: Fix `multiprocessing.synchronize.SemLock.__setstate__()` to properly initialize `multiprocessing.synchronize.SemLock._is_fork_ctx`. This fixes a regression when passing a SemLock accross nested processes.

  Rename `multiprocessing.synchronize.SemLock.is_fork_ctx` to `multiprocessing.synchronize.SemLock._is_fork_ctx` to avoid exposing it as public API.

- gh-108654: Restore locals shadowed by an inlined comprehension if the comprehension raises an exception.

- gh-108487: Change an assert that would cause a spurious crash in a devious case that should only trigger deoptimization.

- gh-106176: Use a `WeakValueDictionary` to track the lists containing the modules each thread is currently importing. This helps avoid a reference leak from keeping the list around longer than necessary. Weakrefs are used as GC can’t interrupt the cleanup.

- gh-107901: Fix missing line number on `JUMP_BACKWARD` at the end of a for loop.

- gh-108390: Raise an exception when setting a non-local event (`RAISE`, `EXCEPTION_HANDLED`, etc.) in `sys.monitoring.set_local_events`.

  Fixes crash when tracing in recursive calls to Python classes.

- gh-91051: Fix abort / segfault when using all eight type watcher slots, on platforms where `char` is signed by default.

- gh-107724: In pre-release versions of 3.12, up to rc1, the sys.monitoring callback function for the `PY_THROW` event was missing the third, exception argument. That is now fixed.

- gh-107080: Trace refs builds (`--with-trace-refs`) were crashing when used with isolated subinterpreters. The problematic global state has been isolated to each interpreter. Other fixing the crashes, this change does not affect users.

- gh-77377: Ensure that multiprocessing synchronization objects created in a fork context are not sent to a different process created in a spawn context. This changes a segfault into an actionable RuntimeError in the parent process.

### Library

- gh-108469: `ast.unparse()` now supports new f-string syntax introduced in Python 3.12. Note that the f-string quotes are reselected for simplicity under the new syntax. (Patch by Steven Sun)

- gh-108682: Enum: raise `TypeError` if `super().__new__()` is called from a custom `__new__`.

- gh-108295: Fix crashes related to use of weakrefs on `typing.TypeVar`.

- gh-64662: Fix support for virtual tables in `sqlite3.Connection.iterdump()`. Patch by Aviv Palivoda.

- gh-108111: Fix a regression introduced in gh-101251 for 3.12, resulting in an incorrect offset calculation in `gzip.GzipFile.seek()`.

- gh-105736: Harmonized the pure Python version of `OrderedDict` with the C version. Now, both versions set up their internal state in `__new__`. Formerly, the pure Python version did the set up in `__init__`.

- gh-108083: Fix bugs in the constructor of `sqlite3.Connection` and `sqlite3.Connection.close()` where exceptions could be leaked. Patch by Erlend E. Aasland.

- gh-107963: Fix `multiprocessing.set_forkserver_preload()` to check the given list of modules names. Patch by Donghee Na.

- gh-106242: Fixes `os.path.normpath()` to handle embedded null characters without truncating the path.

- gh-107913: Fix possible losses of `errno` and `winerror` values in `OSError` exceptions if they were cleared or modified by the cleanup code before creating the exception object.

- gh-107845: `tarfile.data_filter()` now takes the location of symlinks into account when determining their target, so it will no longer reject some valid tarballs with `LinkOutsideDestinationError`.

- gh-107805: Fix signatures of module-level generated functions in `turtle`.

- gh-107715: Fix `doctest.DocTestFinder.find()` in presence of class names with special characters. Patch by Gertjan van Zwieten.

- gh-100814: Passing a callable object as an option value to a Tkinter image now raises the expected TclError instead of an AttributeError.

- gh-106684: Close `asyncio.StreamWriter` when it is not closed by application leading to memory leaks. Patch by Kumar Aditya.

- gh-107396: tarfiles; Fixed use before assignment of self.exception for gzip decompression

- gh-106052: `re` module: fix the matching of possessive quantifiers in the case of a subpattern containing backtracking.

- gh-100061: Fix a bug that causes wrong matches for regular expressions with possessive qualifier.

- gh-99203: Restore following CPython <= 3.10.5 behavior of `shutil.make_archive()`: do not create an empty archive if `root_dir` is not a directory, and, in that case, raise `FileNotFoundError` or `NotADirectoryError` regardless of `format` choice. Beyond the brought-back behavior, the function may now also raise these exceptions in `dry_run` mode.

### Documentation

- gh-105052: Update `timeit` doc to specify that time in seconds is just the default.

### Tests

- gh-89392: Removed support of `test_main()` function in tests. They now always use normal unittest test runner.

- gh-108388: Convert test_concurrent_futures to a package of 7 sub-tests. Patch by Victor Stinner.

- gh-108388: Split test_multiprocessing_fork, test_multiprocessing_forkserver and test_multiprocessing_spawn into test packages. Each package is made of 4 sub-tests: processes, threads, manager and misc. It allows running more tests in parallel and so reduce the total test duration. Patch by Victor Stinner.

- gh-105776: Fix test_cppext when the C compiler command `-std=c11` option: remove `-std=` options from the compiler command. Patch by Victor Stinner.

- gh-107178: Add the C API test for functions in the Mapping Protocol, the Sequence Protocol and some functions in the Object Protocol.

### Build

- gh-63760: Fix Solaris build: no longer redefine the `gethostname()` function. Solaris defines the function since 2005. Patch by Victor Stinner, original patch by Jakub Kulík.

- gh-107814: When calling `find_python.bat` with `-q` it did not properly silence the output of nuget. That is now fixed.

### Windows

- gh-107565: Update Windows build to use OpenSSL 3.0.10.

- gh-106242: Fixes `realpath()` to behave consistently when passed a path containing an embedded null character on Windows. In strict mode, it now raises `OSError` instead of the unexpected `ValueError`, and in non-strict mode will make the path absolute.

- gh-106844: Fix integer overflow and truncating by the null character in `_winapi.LCMapStringEx()` which affects `ntpath.normcase()`.

### macOS

- gh-107565: Update macOS installer to use OpenSSL 3.0.10.

### Tools/Demos

- gh-107565: Update multissltests and GitHub CI workflows to use OpenSSL 1.1.1v, 3.0.10, and 3.1.2.

- gh-95065: Argument Clinic now supports overriding automatically generated signature by using directive `@text_signature`.

### C API

- gh-107916: C API functions `PyErr_SetFromErrnoWithFilename()`, `PyErr_SetExcFromWindowsErrWithFilename()` and `PyErr_SetFromWindowsErrWithFilename()` save now the error code before calling `PyUnicode_DecodeFSDefault()`.

- gh-107915: Such C API functions as `PyErr_SetString()`, `PyErr_Format()`, `PyErr_SetFromErrnoWithFilename()` and many others no longer crash or ignore errors if it failed to format the error message or decode the filename. Instead, they keep a corresponding error.

- gh-107810: Improve `DeprecationWarning` for uses of `PyType_Spec` with metaclasses that have custom `tp_new`.

## Python 3.12.0 release candidate 1

Release date: 2023-08-05

### Security

- gh-102988: Reverted the `email.utils` security improvement change released in 3.12beta4 that unintentionally caused `email.utils.getaddresses` to fail to parse email addresses with a comma in the quoted name field. See gh-106669.

- gh-102509: Start initializing `ob_digit` during creation of `PyLongObject` objects. Patch by Illia Volochii.

### Core and Builtins

- gh-107263: Increase C recursion limit for functions other than the main interpreter from 800 to 1500. This should allow functions like `list.__repr__` and `json.dumps` to handle all the inputs that they could prior to 3.12

- gh-104432: Fix potential unaligned memory access on C APIs involving returned sequences of `char *` pointers within the `grp` and `socket` modules. These were revealed using a `-fsaniziter=alignment` build on ARM macOS. Patch by Christopher Chavez.

- gh-106898: Add the exception as the third argument to `PY_UNIND` callbacks in `sys.monitoring`. This makes the `PY_UNWIND` callback consistent with the other exception hanlding callbacks.

- gh-106895: Raise a `ValueError` when a monitoring callback funtion returns `DISABLE` for events that cannot be disabled locally.

- gh-106897: Add a `RERAISE` event to `sys.monitoring`, which occurs when an exception is reraised, either explicitly by a plain `raise` statement, or implicitly in an `except` or `finally` block.

- gh-104621: Unsupported modules now always fail to be imported.

- gh-106917: Fix classmethod-style `super()` method calls (i.e., where the second argument to `super()`, or the implied second argument drawn from `self/cls` in the case of zero-arg super, is a type) when the target of the call is not a classmethod.

- gh-105699: Python no longer crashes due an infrequent race when initialzing per-interpreter interned strings. The crash would manifest when the interpreter was finalized.

- gh-105699: Python no longer crashes due to an infrequent race in setting `Py_FileSystemDefaultEncoding` and `Py_FileSystemDefaultEncodeErrors` (both deprecated), when simultaneously initializing two isolated subinterpreters. Now they are only set during runtime initialization.

- gh-106092: Fix a segmentation fault caused by a use-after-free bug in `frame_dealloc` when the trashcan delays the deallocation of a `PyFrameObject`.

- gh-106719: No longer suppress arbitrary errors in the `__annotations__` getter and setter in the type and module types.

- gh-106723: Propagate `frozen_modules` to multiprocessing spawned process interpreters.

- gh-105235: Prevent out-of-bounds memory access during `mmap.find()` calls.

### Library

- gh-107077: Seems that in some conditions, OpenSSL will return `SSL_ERROR_SYSCALL` instead of `SSL_ERROR_SSL` when a certification verification has failed, but the error parameters will still contain `ERR_LIB_SSL` and `SSL_R_CERTIFICATE_VERIFY_FAILED`. We are now detecting this situation and raising the appropiate `ssl.SSLCertVerificationError`. Patch by Pablo Galindo

- gh-107576: Fix `types.get_original_bases()` to only return `__orig_bases__` if it is present on `cls` directly. Patch by James Hilton-Balfe.

- gh-46376: Prevent memory leak and use-after-free when using pointers to pointers with ctypes

- gh-62519: Make `gettext.pgettext()` search plural definitions when translation is not found.

- gh-83006: Document behavior of `shutil.disk_usage()` for non-mounted filesystems on Unix.

- gh-106186: Do not report `MultipartInvariantViolationDefect` defect when the `email.parser.Parser` class is used to parse emails with `headersonly=True`.

- gh-105002: Fix invalid result from `PurePath.relative_to()` method when attempting to walk a “`..`” segment in other with walk_up enabled. A `ValueError` exception is now raised in this case.

- gh-106831: Fix potential missing `NULL` check of `d2i_SSL_SESSION` result in `_ssl.c`.

- gh-106774: Update the bundled copy of pip to version 23.2.1.

- gh-106752: Fixed several bugs in zipfile.Path, including: in `Path.match`, Windows separators are no longer honored (and never were meant to be); Fixed `name`/`suffix`/`suffixes`/`stem` operations when no filename is present and the Path is not at the root of the zipfile; Reworked glob for performance and more correct matching behavior.

- gh-106602: Add __copy__ and __deepcopy__ in `enum`

- gh-106530: Revert a change to `colorsys.rgb_to_hls()` that caused division by zero for certain almost-white inputs. Patch by Terry Jan Reedy.

- gh-106403: Instances of `typing.TypeVar`, `typing.ParamSpec`, `typing.ParamSpecArgs`, `typing.ParamSpecKwargs`, and `typing.TypeVarTuple` once again support weak references, fixing a regression introduced in Python 3.12.0 beta 1. Patch by Jelle Zijlstra.

- gh-106350: Detect possible memory allocation failure in the libtommath function `mp_init()` used by the `_tkinter` module.

- gh-106263: Fix crash when calling `repr` with a manually constructed SignalDict object. Patch by Charlie Zhao.

- gh-105626: Change the default return value of `http.client.HTTPConnection.get_proxy_response_headers()` to be `None` and not `{}`.

- bpo-18319: Ensure `gettext(msg)` retrieve translations even if a plural form exists. In other words: `gettext(msg) == ngettext(msg, '', 1)`.

### Documentation

- gh-107305: Add documentation for `PyInterpreterConfig` and `Py_NewInterpreterFromConfig()`. Also clarify some of the nearby docs relative to per-interpreter GIL.

- gh-107008: Document the `curses` module variables `LINES` and `COLS`.

- gh-106948: Add a number of standard external names to `nitpick_ignore`.

- gh-54738: Add documentation on how to localize the `argparse` module.

### Tests

- gh-107237: `test_logging`: Fix `test_udp_reconnection()` by increasing the timeout from 100 ms to 5 minutes (LONG_TIMEOUT). Patch by Victor Stinner.

- gh-106714: test_capi: Fix test_no_FatalError_infinite_loop() to no longer write a coredump, by using test.support.SuppressCrashReport. Patch by Victor Stinner.

- gh-104090: Avoid creating a reference to the test object in `collectedDurations()`.

- gh-106752: Moved tests for `zipfile.Path` into `Lib/test/test_zipfile/_path`. Made `zipfile._path` a package.

### Build

- gh-106881: Check for `linux/limits.h` before including it in `Modules/posixmodule.c`.

- gh-106962: Detect MPI compilers in `configure`.

- gh-101538: Add experimental wasi-threads support. Patch by Takashi Yamamoto.

### Windows

- gh-99079: Update Windows build to use OpenSSL 3.0.9

### macOS

- gh-99079: Update macOS installer to use OpenSSL 3.0.9.

### Tools/Demos

- gh-106970: Fix bugs in the Argument Clinic `destination <name> clear` command; the destination buffers would never be cleared, and the `destination` directive parser would simply continue to the fault handler after processing the command. Patch by Erlend E. Aasland.

- gh-103186: `freeze` now fetches `CONFIG_ARGS` from the original CPython instance the Makefile uses to call utility scripts. Patch by Ijtaba Hussain.

### C API

- gh-107226: `PyModule_AddObjectRef()` is now only available in the limited API version 3.10 or later.

## Python 3.12.0 beta 4

Release date: 2023-07-11

### Security

- gh-102988: CVE 2023-27043: Prevent `email.utils.parseaddr()` and `email.utils.getaddresses()` from returning the realname portion of an invalid RFC2822 email header in the email address portion of the 2-tuple returned after being parsed by `email._parseaddr.AddressList`.

### Core and Builtins

- gh-106396: When the format specification of an f-string expression is empty, the parser now generates an empty `ast.JoinedStr` node for it instead of an one-element `ast.JoinedStr` with an empty string `ast.Constant`.

- gh-106145: Make `end_lineno` and `end_col_offset` required on `type_param` ast nodes.

- gh-105979: Fix crash in `_imp.get_frozen_object()` due to improper exception handling.

- gh-98931: Ensure custom `SyntaxError` error messages are raised for invalid imports with multiple targets. Patch by Pablo Galindo

- gh-105908: Fixed bug where gh-99111 breaks future import `barry_as_FLUFL` in the Python REPL.

- gh-105340: Include the comprehension iteration variable in `locals()` inside a module- or class-scope comprehension.

- gh-105486: Change the repr of `ParamSpec` list of args in `types.GenericAlias`.

- gh-101006: Improve error handling when read `marshal` data.

### Library

- gh-106524: Fix crash in `_sre.template()` with templates containing invalid group indices.

- gh-106510: Improve debug output for atomic groups in regular expressions.

- gh-106503: Fix ref cycle in `asyncio._SelectorSocketTransport` by removing `_write_ready` in `close`.

- gh-105497: Fix flag mask inversion when unnamed flags exist.

- gh-90876: Prevent `multiprocessing.spawn` from failing to import in environments where `sys.executable` is `None`. This regressed in 3.11 with the addition of support for path-like objects in multiprocessing.

- gh-106292: Check for an instance-dict cached value in the `__get__()` method of `functools.cached_property()`. This better matches the pre-3.12 behavior and improves compatibility for users subclassing `functools.cached_property()` and adding a `__set__()` method.

- gh-106330: Fix incorrect matching of empty paths in `pathlib.PurePath.match()`. This bug was introduced in Python 3.12.0 beta 1.

- gh-102541: Make pydoc.doc catch bad module ImportError when output stream is not None.

- gh-106152: Added PY_THROW event hook for `cProfile` for generators

- gh-106075: Added `asyncio.taskgroups.__all__` to `asyncio.__all__` for export in star imports.

- gh-105987: Fix crash due to improper reference counting in `asyncio` eager task factory internal routines.

- gh-105974: Fix bug where a `typing.Protocol` class that had one or more non-callable members would raise `TypeError` when `issubclass()` was called against it, even if it defined a custom `__subclasshook__` method. The behaviour in Python 3.11 and lower – which has now been restored – was not to raise `TypeError` in these situations if a custom `__subclasshook__` method was defined. Patch by Alex Waygood.

- gh-96145: Reverted addition of `json.AttrDict`.

- gh-105497: Fix flag inversion when alias/mask members exist.

- gh-104554: Add RTSPS scheme support in urllib.parse

- gh-94777: Fix hanging `multiprocessing` `ProcessPoolExecutor` when a child process crashes while data is being written in the call queue.

### Documentation

- gh-106232: Make timeit doc command lines compatible with Windows by using double quotes for arguments. This works on linux and macOS also.

### Tests

- gh-101634: When running the Python test suite with `-jN` option, if a worker stdout cannot be decoded from the locale encoding report a failed testn so the exitcode is non-zero. Patch by Victor Stinner.

### Build

- gh-106118: Fix compilation for platforms without `O_CLOEXEC`. The issue was introduced with Python 3.12b1 in gh-103295. Patch by Erlend Aasland.

- gh-104692: Include `commoninstall` as a prerequisite for `bininstall`

  This ensures that `commoninstall` is completed before `bininstall` is started when parallel builds are used (`make -j install`), and so the `python3` symlink is only installed after all standard library modules are installed.

### Tools/Demos

- gh-106359: Argument Clinic now explicitly forbids “kwarg splats” in function calls used as annotations.

### C API

- gh-105227: The new `PyType_GetDict()` provides the dictionary for the given type object that is normally exposed by `cls.__dict__`. Normally it’s sufficient to use `tp_dict`, but for the static builtin types `tp_dict` is now always `NULL`. `PyType_GetDict()` provides the correct dict object instead.

## Python 3.12.0 beta 3

Release date: 2023-06-19

### Core and Builtins

- gh-105840: Fix possible crashes when specializing function calls with too many `__defaults__`.

- gh-105831: Fix an f-string bug, where using a debug expression (the `=` sign) that appears in the last line of a file results to the debug buffer that holds the expression text being one character too small.

- gh-105800: Correctly issue `SyntaxWarning` in f-strings if invalid sequences are used. Patch by Pablo Galindo

- gh-105587: The runtime can’t guarantee that immortal objects will not be mutated by Extensions. Thus, this modifies _PyStaticObject_CheckRefcnt to warn instead of asserting.

- gh-105564: Don’t include artificil newlines in the `line` attribute of tokens in the APIs of the `tokenize` module. Patch by Pablo Galindo

- gh-105549: Tokenize separately `NUMBER` and `NAME` tokens that are not ambiguous. Patch by Pablo Galindo.

- gh-105588: Fix an issue that could result in crashes when compiling malformed `ast` nodes.

- gh-105375: Fix bugs in the `builtins` module where exceptions could end up being overwritten.

- gh-105375: Fix bug in the compiler where an exception could end up being overwritten.

- gh-105375: Improve error handling in `PyUnicode_BuildEncodingMap()` where an exception could end up being overwritten.

- gh-105435: Fix spurious newline character if file ends on a comment without a newline. Patch by Pablo Galindo

- gh-105390: Correctly raise `tokenize.TokenError` exceptions instead of `SyntaxError` for tokenize errors such as incomplete input. Patch by Pablo Galindo

- gh-104812: The “pending call” machinery now works for all interpreters, not just the main interpreter, and runs in all threads, not just the main thread. Some calls are still only done in the main thread, ergo in the main interpreter. This change does not affect signal handling nor the existing public C-API (`Py_AddPendingCall()`), which both still only target the main thread. The new functionality is meant strictly for internal use for now, since consequences of its use are not well understood yet outside some very restricted cases. This change brings the capability in line with the intention when the state was made per-interpreter several years ago.

### Library

- gh-105808: Fix a regression introduced in gh-101251 for 3.12, causing `gzip.GzipFile.flush()` to not flush the compressor (nor pass along the `zip_mode` argument).

- gh-104799: Enable `ast.unparse()` to unparse function and class definitions created without the new `type_params` field from PEP 695. Patch by Jelle Zijlstra.

- gh-105745: Fix `webbrowser.Konqueror.open` method.

- gh-105375: Fix a bug in `_Unpickler_SetInputStream()` where an exception could end up being overwritten in case of failure.

- gh-105375: Fix bugs in `sys` where exceptions could end up being overwritten because of deferred error handling.

- gh-105605: Harden `pyexpat` error handling during module initialisation to prevent exceptions from possibly being overwritten, and objects from being dereferenced twice.

- gh-105375: Fix bug in `decimal` where an exception could end up being overwritten.

- gh-105375: Fix bugs in `_datetime` where exceptions could be overwritten in case of module initialisation failure.

- gh-105375: Fix bugs in `_ssl` initialisation which could lead to leaked references and overwritten exceptions.

- gh-105375: Fix a bug in `array.array` where an exception could end up being overwritten.

- gh-105375: Fix bugs in `_ctypes` where exceptions could end up being overwritten.

- gh-105375: Fix a bug in the `posix` module where an exception could be overwritten.

- gh-105375: Fix bugs in `_elementtree` where exceptions could be overwritten.

- gh-105375: Fix bugs in `zoneinfo` where exceptions could be overwritten.

- gh-105375: Fix bugs in `errno` where exceptions could be overwritten.

- gh-105375: Fix bugs in `pickle` where exceptions could be overwritten.

- gh-105375: Fix a bug in `sqlite3` where an exception could be overwritten in the `collation` callback.

- gh-105332: Revert pickling method from by-name back to by-value.

- gh-104310: In the beta 1 release we added a utility function for extension module authors, to use when testing their module for support in multiple interpreters or under a per-interpreter GIL. The name of that function has changed from `allowing_all_extensions` to `_incompatible_extension_module_restrictions`. The default for the “disable_check” argument has change from `True` to `False`, to better match the new function name.

- gh-104996: Improve performance of `pathlib.PurePath` initialisation by deferring joining of paths when multiple arguments are given.

- gh-102541: Hide traceback in `help()` prompt, when import failed.

### Tests

- gh-105084: When the Python build is configured `--with-wheel-pkg-dir`, tests requiring the `setuptools` and `wheel` wheels will search for the wheels in `WHEEL_PKG_DIR`.

### Windows

- gh-105436: Ensure that an empty environment block is terminated by two null characters, as is required by Windows.

### C API

- gh-105375: Fix a bug in `PyErr_WarnExplicit()` where an exception could end up being overwritten if the API failed internally.

- gh-105603: We’ve renamed the new (in 3.12) `PyInterpreterConfig.own_gil` to `PyInterpreterConfig.gil` and changed the meaning of the value from “bool” to an integer with supported values of `PyInterpreterConfig_DEFAULT_GIL`, `PyInterpreterConfig_SHARED_GIL`, and `PyInterpreterConfig_OWN_GIL`. The default is “shared”.

- gh-105387: In the limited C API version 3.12, `Py_INCREF()` and `Py_DECREF()` functions are now implemented as opaque function calls to hide implementation details. Patch by Victor Stinner.

- gh-103968: `PyType_FromMetaclass()` now allows metaclasses with `tp_new` set to `NULL`.

## Python 3.12.0 beta 2

Release date: 2023-06-06

### Security

- gh-103142: The version of OpenSSL used in our binary builds has been upgraded to 1.1.1u to address several CVEs.

- gh-99108: Refresh our new HACL* built-in `hashlib` code from upstream. Built-in SHA2 should be faster and an issue with SHA3 on 32-bit platforms is fixed.

### Core and Builtins

- gh-105259: Don’t include newline character for trailing `NEWLINE` tokens emitted in the `tokenize` module. Patch by Pablo Galindo

- gh-105324: Fix the main function of the `tokenize` module when reading from `sys.stdin`. Patch by Pablo Galindo

- gh-98963: Restore the ability for a subclass of `property` to define `__slots__` or otherwise be dict-less by ignoring failures to set a docstring on such a class. This behavior had regressed in 3.12beta1. An `AttributeError` where there had not previously been one was disruptive to existing code.

- gh-105194: Do not escape with backslashes f-string format specifiers. Patch by Pablo Galindo

- gh-105162: Fixed bug in generator.close()/throw() where an inner iterator would be ignored when the outer iterator was instrumented.

- gh-105164: Ensure annotations are set up correctly if the only annotation in a block is within a `match` block. Patch by Jelle Zijlstra.

- gh-104799: Attributes of `ast` nodes that are lists now default to the empty list if omitted. This means that some code that previously raised `TypeError` when the AST node was used will now proceed with the empty list instead. Patch by Jelle Zijlstra.

- gh-105035: Fix `super()` calls on types with custom `tp_getattro` implementation (e.g. meta-types.)

- gh-105017: Show CRLF lines in the tokenize string attribute in both NL and NEWLINE tokens. Patch by Marta Gómez.

- gh-105013: Fix handling of multiline parenthesized lambdas in `inspect.getsource()`. Patch by Pablo Galindo

- gh-105017: Do not include an additional final `NL` token when parsing files having CRLF lines. Patch by Marta Gómez.

- gh-104976: Ensure that trailing `DEDENT` `tokenize.TokenInfo` objects emitted by the `tokenize` module are reported as in Python 3.11. Patch by Pablo Galindo

- gh-104972: Ensure that the `line` attribute in `tokenize.TokenInfo` objects in the `tokenize` module are always correct. Patch by Pablo Galindo

- gh-104955: Fix signature for the new `__release_buffer__()` slot. Patch by Jelle Zijlstra.

- gh-104690: Starting new threads and process creation through `os.fork()` during interpreter shutdown (such as from `atexit` handlers) is no longer supported. It can lead to race condition between the main Python runtime thread freeing thread states while internal `threading` routines are trying to allocate and use the state of just created threads. Or forked children trying to use the mid-shutdown runtime and thread state in the child process.

- gh-104879: Fix crash when accessing the `__module__` attribute of type aliases defined outside a module. Patch by Jelle Zijlstra.

- gh-104825: Tokens emitted by the `tokenize` module do not include an implicit `\n` character in the `line` attribute anymore. Patch by Pablo Galindo

### Library

- gh-105280: Fix bug where `isinstance([], collections.abc.Mapping)` could evaluate to `True` if garbage collection happened at the wrong time. The bug was caused by changes to the implementation of `typing.Protocol` in Python 3.12.

- gh-105239: Fix longstanding bug where `issubclass(object, typing.Protocol)` would evaluate to `True` in some edge cases. Patch by Alex Waygood.

- gh-105080: Fixed inconsistent signature on derived classes for `inspect.signature()`

- gh-105144: Fix a recent regression in the `typing` module. The regression meant that doing `class Foo(X, typing.Protocol)`, where `X` was a class that had `abc.ABCMeta` as its metaclass, would then cause subsequent `isinstance(1, X)` calls to erroneously raise `TypeError`. Patch by Alex Waygood.

- gh-105113: Improve performance of `pathlib.PurePath.match()` by compiling an `re.Pattern` object for the entire pattern.

- gh-101588: Deprecate undocumented copy/deepcopy/pickle support for itertools.

- gh-103631: Fix `pathlib.PurePosixPath(pathlib.PureWindowsPath(...))` not converting path separators to restore 3.11 compatible behavior.

- gh-104947: Make comparisons between `pathlib.PureWindowsPath` objects consistent across Windows and Posix to match 3.11 behavior.

- gh-104935: Fix bugs with the interaction between `typing.runtime_checkable()` and `typing.Generic` that were introduced by the PEP 695 implementation. Patch by Jelle Zijlstra.

- gh-104874: Document the `__name__` and `__supertype__` attributes of `typing.NewType`. Patch by Jelle Zijlstra.

- gh-104799: Adjust the location of the (see PEP 695) `type_params` field on `ast.ClassDef`, `ast.AsyncFunctionDef`, and `ast.FunctionDef` to better preserve backward compatibility. Patch by Jelle Zijlstra

- gh-104797: Allow `typing.Protocol` classes to inherit from `collections.abc.Buffer`. Patch by Jelle Zijlstra.

- gh-104372: On Linux where `subprocess` can use the `vfork()` syscall for faster spawning, prevent the parent process from blocking other threads by dropping the GIL while it waits for the vfork’ed child process `exec()` outcome. This prevents spawning a binary from a slow filesystem from blocking the rest of the application.

- gh-99108: We now release the GIL around built-in `hashlib` computations of reasonable size for the SHA families and MD5 hash functions, matching what our OpenSSL backed hash computations already does.

- gh-104399: Prepare the `_tkinter` module for building with Tcl 9.0 and future libtommath by replacing usage of deprecated functions `mp_to_unsigned_bin_n()` and `mp_unsigned_bin_size()` when necessary.

- gh-102024: Reduce calls of `_idle_semaphore.release()` in `concurrent.futures.thread._worker()`.

### Documentation

- gh-89455: Add missing documentation for the `max_group_depth` and `max_group_width` parameters and the `exceptions` attribute of the `traceback.TracebackException` class.

- gh-89412: Add missing documentation for the `end_lineno` and `end_offset` attributes of the `traceback.TracebackException` class.

- gh-104943: Remove mentions of old Python versions in `typing.NamedTuple`.

### Build

- gh-90005: Fix a regression in `configure` where we could end up unintentionally linking with `libbsd`.

- gh-89886: Autoconf 2.71 and aclocal 1.16.4 is now required to regenerate `!configure`.

### Windows

- gh-105146: Updated the links at the end of the installer to point to Discourse rather than the mailing lists.

- gh-103646: When installed from the Microsoft Store, `pip` no longer defaults to per-user installs. However, as the install directory is unwritable, it should automatically decide to do a per-user install anyway. This should resolve issues when `pip` is passed an option that conflicts with `--user`.

- gh-88745: Improve performance of `shutil.copy2()` by using the operating system’s `CopyFile2` function. This may result in subtle changes to metadata copied along with some files, bringing them in line with normal OS behavior.

- gh-104820: Fixes `stat()` and related functions on file systems that do not support file ID requests. This includes FAT32 and exFAT.

- gh-104803: Add `os.path.isdevdrive()` to detect whether a path is on a Windows Dev Drive. Returns `False` on platforms that do not support Dev Drive, and is absent on non-Windows platforms.

### macOS

- gh-103142: Update macOS installer to use OpenSSL 1.1.1u.

### IDLE

- gh-104719: Remove IDLE’s modification of tokenize.tabsize and test other uses of tokenize data and methods.

### C API

- gh-105115: `PyTypeObject.tp_bases` (and `tp_mro`) for builtin static types are now shared by all interpreters, whereas in 3.12-beta1 they were stored on `PyInterpreterState`. Also note that now the tuples are immortal objects.

- gh-105071: Add `PyUnstable_Exc_PrepReraiseStar` to the unstable C api to expose the implementation of `except*`.

- gh-104668: Don’t call `PyOS_InputHook` or `PyOS_ReadlineFunctionPointer` in subinterpreters, since it’s generally difficult to avoid using global state in their registered callbacks. This also avoids situations where extensions may find themselves running in a subinterpreter they don’t support (or haven’t yet been loaded in).

## Python 3.12.0 beta 1

Release date: 2023-05-22

### Security

- gh-99889: Fixed a security in flaw in `uu.decode()` that could allow for directory traversal based on the input if no `out_file` was specified.

- gh-104049: Do not expose the local on-disk location in directory indexes produced by `http.client.SimpleHTTPRequestHandler`.

- gh-99108: Upgrade built-in `hashlib` SHA3 implementation to a verified implementation from the `HACL*` project. Used when OpenSSL is not present or lacks SHA3.

- gh-102153: `urllib.parse.urlsplit()` now strips leading C0 control and space characters following the specification for URLs defined by WHATWG in response to CVE 2023-24329. Patch by Illia Volochii.

### Core and Builtins

- gh-102856: Implement PEP 701 changes in the `tokenize` module. Patch by Marta Gómez Macías and Pablo Galindo Salgado

- gh-104615: Fix wrong ordering of assignments in code like `a, a = x, y`. Contributed by Carl Meyer.

- gh-104572: Improve syntax error message for invalid constructs in PEP 695 contexts and in annotations when `from __future__ import annotations` is active.

- gh-104482: Fix three error handling bugs in ast.c’s validation of pattern matching statements.

- gh-102818: Do not add a frame to the traceback in the `sys.setprofile` and `sys.settrace` trampoline functions. This ensures that frames are not duplicated if an exception is raised in the callback function, and ensures that frames are not omitted if a C callback is used and that does not add the frame.

- gh-104405: Fix an issue where some bytecode instructions could ignore PEP 523 when “inlining” calls.

- gh-103082: Change behavior of `sys.monitoring.events.LINE` events in `sys.monitoring`: Line events now occur when a new line is reached dynamically, instead of using a static approximation, as before. This makes the behavior very similar to that of “line” events in `sys.settrace`. This should ease porting of tools from 3.11 to 3.12.

- gh-104263: Fix `float("nan")` to produce a quiet NaN on platforms (like MIPS) where the meaning of the signalling / quiet bit is inverted from its usual meaning. Also introduce a new macro `Py_INFINITY` matching C99’s `INFINITY`, and refactor internals to rely on C99’s `NAN` and `INFINITY` macros instead of hard-coding bit patterns for infinities and NaNs. Thanks Sebastian Berg.

- gh-99113: Multi-phase init extension modules may now indicate that they support running in subinterpreters that have their own GIL. This is done by using `Py_MOD_PER_INTERPRETER_GIL_SUPPORTED` as the value for the `Py_mod_multiple_interpreters` module def slot. Otherwise the module, by default, cannot be imported in such subinterpreters. (This does not affect the main interpreter or subinterpreters that do not have their own GIL.) In addition to the isolation that multi-phase init already normally requires, support for per-interpreter GIL involves one additional constraint: thread-safety. If the module has external (linked) dependencies and those libraries have any state that isn’t thread-safe then the module must do the additional work to add thread-safety. This should be an uncommon case.

- gh-99113: The GIL is now (optionally) per-interpreter. This is the fundamental change for PEP 684. This is all made possible by virtue of the isolated state of each interpreter in the process. The behavior of the main interpreter remains unchanged. Likewise, interpreters created using `Py_NewInterpreter()` are not affected. To get an interpreter with its own GIL, call `Py_NewInterpreterFromConfig()`.

- gh-104108: Multi-phase init extension modules may now indicate whether or not they actually support multiple interpreters. By default such modules are expected to support use in multiple interpreters. In the uncommon case that one does not, it may use the new `Py_mod_multiple_interpreters` module def slot. A value of `0` means the module does not support them. `1` means it does. The default is `1`.

- gh-104142: Fix an issue where `list` or `tuple` repetition could fail to respect PEP 683.

- gh-104078: Improve the performance of `PyObject_HasAttrString()`

- gh-104066: Improve the performance of `hasattr()` for module objects with a missing attribute.

- gh-104028: Reduce object creation while calling callback function from gc. Patch by Donghee Na.

- gh-104018: Disallow the “z” format specifier in %-format of bytes objects.

- gh-102213: Fix performance loss when accessing an object’s attributes with `__getattr__` defined.

- gh-103895: Improve handling of edge cases in showing `Exception.__notes__`. Ensures that the messages always end with a newline and that string/bytes are not exploded over multiple lines. Patch by Carey Metcalfe.

- gh-103907: Don’t modify the refcounts of known immortal objects (`True`, `False`, and `None`) in the main interpreter loop.

- gh-103899: Provide a helpful hint in the `TypeError` message when accidentally calling a module object that has a callable attribute of the same name (such as `dis.dis()` or `datetime.datetime`).

- gh-103845: Remove both line and instruction instrumentation before adding new ones for monitoring, to avoid newly added instrumentation being removed immediately.

- gh-103763: Implement PEP 695, adding syntactic support for generic classes, generic functions, and type aliases.

  A new `type X = ...` syntax is added for type aliases, which resolves at runtime to an instance of the new class `typing.TypeAliasType`. The value is lazily evaluated and is accessible through the `.__value__` attribute. This is implemented as a new AST node `ast.TypeAlias`.

  New syntax (`class X[T]: ...`, `def func[T](): ...`) is added for defining generic functions and classes. This is implemented as a new `type_params` attribute on the AST nodes for classes and functions. This node holds instances of the new AST classes `ast.TypeVar`, `ast.ParamSpec`, and `ast.TypeVarTuple`.

  `typing.TypeVar`, `typing.ParamSpec`, `typing.ParamSpecArgs`, `typing.ParamSpecKwargs`, `typing.TypeVarTuple`, and `typing.Generic` are now implemented in C rather than Python.

  There are new bytecode instructions `LOAD_LOCALS`, `LOAD_CLASSDICT_OR_GLOBAL`, and `LOAD_CLASSDICT_OR_DEREF` to support correct resolution of names in class namespaces.

  Patch by Eric Traut, Larry Hastings, and Jelle Zijlstra.

- gh-103801: Adds three minor linting fixes to the wasm module caught that were caught by ruff.

- gh-103793: Optimized asyncio Task creation by deferring expensive string formatting (task name generation) from Task creation to the first time `get_name` is called. This makes asyncio benchmarks up to 5% faster.

- gh-102310: Change the error range for invalid bytes literals.

- gh-103590: Do not wrap a single exception raised from a `try-except*` construct in an `ExceptionGroup`.

- gh-103650: Change the perf map format to remove the ‘0x’ prefix from the addresses

- gh-102856: Implement the required C tokenizer changes for PEP 701. Patch by Pablo Galindo Salgado, Lysandros Nikolaou, Batuhan Taskaya, Marta Gómez Macías and sunmy2019.

- gh-100530: Clarify the error message raised when the called part of a class pattern isn’t actually a class.

- gh-101517: Fix bug in line numbers of instructions emitted for `except*`.

- gh-103492: Clarify `SyntaxWarning` with literal `is` comparison by specifying which literal is problematic, since comparisons using `is` with e.g. `None` and bool literals are idiomatic.

- gh-87729: Add `LOAD_SUPER_ATTR` (and a specialization for `super().method()`) to speed up `super().method()` and `super().attr`. This makes `super().method()` roughly 2.3x faster and brings it within 20% of the performance of a simple method call. Patch by Vladimir Matveev and Carl Meyer.

- gh-103488: Change the internal offset distinguishing yield and return target addresses, so that the instruction pointer is correct for exception handling and other stack unwinding.

- gh-82012: The bitwise inversion operator (`~`) on bool is deprecated. It returns the bitwise inversion of the underlying `int` representation such that `bool(~True) == True`, which can be confusing. Use `not` for logical negation of bools. In the rare case that you really need the bitwise inversion of the underlying `int`, convert to int explicitly `~int(x)`.

- gh-77757: Exceptions raised in a typeobject’s `__set_name__` method are no longer wrapped by a `RuntimeError`. Context information is added to the exception as a PEP 678 note.

- gh-103333: `AttributeError` now retains the `name` attribute when pickled and unpickled.

- gh-103242: Migrate `set_ecdh_curve()` method not to use deprecated OpenSSL APIs. Patch by Donghee Na.

- gh-103323: We’ve replaced our use of `_PyRuntime.tstate_current` with a thread-local variable. This is a fairly low-level implementation detail, and there should be no change in behavior.

- gh-84436: The implementation of PEP-683 which adds Immortal Objects by using a fixed reference count that skips reference counting to make objects truly immutable.

- gh-102700: Allow built-in modules to be submodules. This allows submodules to be statically linked into a CPython binary.

- gh-103082: Implement PEP 669 Low Impact Monitoring for CPython.

- gh-88691: Reduce the number of inline `CACHE` entries for `CALL`.

- gh-102500: Make the buffer protocol accessible in Python code using the new `__buffer__` and `__release_buffer__` magic methods. See PEP 688 for details. Patch by Jelle Zijlstra.

- gh-97933: PEP 709: inline list, dict and set comprehensions to improve performance and reduce bytecode size.

- gh-99184: Bypass instance attribute access of `__name__` in `repr` of `weakref.ref`.

- gh-98003: Complex function calls are now faster and consume no C stack space.

- bpo-39610: `len()` for 0-dimensional `memoryview` objects (such as `memoryview(ctypes.c_uint8(42))`) now raises a `TypeError`. Previously this returned `1`, which was not consistent with `mem_0d[0]` raising an `IndexError`.

- bpo-31821: Fix `pause_reading()` to work when called from `connection_made()` in `asyncio`.

### Library

- gh-104600: `functools.update_wrapper()` now sets the `__type_params__` attribute (added by PEP 695).

- gh-104340: When an `asyncio` pipe protocol loses its connection due to an error, and the caller doesn’t await `wait_closed()` on the corresponding `StreamWriter`, don’t log a warning about an exception that was never retrieved. After all, according to the `StreamWriter.close()` docs, the `wait_closed()` call is optional (“not mandatory”).

- gh-104555: Fix issue where an `issubclass()` check comparing a class `X` against a `runtime-checkable protocol` `Y` with non-callable members would not cause `TypeError` to be raised if an `isinstance()` call had previously been made comparing an instance of `X` to `Y`. This issue was present in edge cases on Python 3.11, but became more prominent in 3.12 due to some unrelated changes that were made to runtime-checkable protocols. Patch by Alex Waygood.

- gh-104372: Refactored the `_posixsubprocess` internals to avoid Python C API usage between fork and exec when marking `pass_fds=` file descriptors inheritable.

- gh-104484: Added case_sensitive argument to `pathlib.PurePath.match()`

- gh-75367: Fix data descriptor detection in `inspect.getattr_static()`.

- gh-104536: Fix a race condition in the internal `multiprocessing.process` cleanup logic that could manifest as an unintended `AttributeError` when calling `process.close()`.

- gh-103857: Update datetime deprecations’ stracktrace to point to the calling line

- gh-101520: Move the core functionality of the `tracemalloc` module in the `Python/` folder, leaving just the module wrapper in `Modules/`.

- gh-104392: Remove undocumented and unused `_paramspec_tvars` attribute from some classes in `typing`.

- gh-102613: Fix issue where `pathlib.Path.glob()` raised `RecursionError` when walking deep directory trees.

- gh-103000: Improve performance of `dataclasses.asdict()` for the common case where dict_factory is `dict`. Patch by David C Ellis.

- gh-104301: Allow leading whitespace in disambiguated statements in `pdb`.

- gh-104139: Teach `urllib.parse.unsplit()` to retain the `"//"` when assembling `itms-services://?action=generate-bugs` style Apple Platform Deployment URLs.

- gh-104307: `socket.getnameinfo()` now releases the GIL while contacting the DNS server

- gh-104310: Users may now use `importlib.util.allowing_all_extensions()` (a context manager) to temporarily disable the strict compatibility checks for importing extension modules in subinterpreters.

- gh-87695: Fix issue where `pathlib.Path.glob()` raised `OSError` when it encountered a symlink to an overly long path.

- gh-104265: Prevent possible crash by disallowing instantiation of the `_csv.Reader` and `_csv.Writer` types. The regression was introduced in 3.10.0a4 with PR 23224 (bpo-14935). Patch by Radislav Chugunov.

- gh-102613: Improve performance of `pathlib.Path.glob()` when expanding recursive wildcards (”`**`”) by merging adjacent wildcards and de-duplicating results only when necessary.

- gh-65772: Remove unneeded comments and code in turtle.py.

- gh-90208: Fixed issue where `pathlib.Path.glob()` returned incomplete results when it encountered a `PermissionError`. This method now suppresses all `OSError` exceptions, except those raised from calling `is_dir()` on the top-level path.

- gh-104144: Optimize `asyncio.TaskGroup` when using `asyncio.eager_task_factory()`. Skip scheduling a done callback if a TaskGroup task completes eagerly.

- gh-104144: Optimize `asyncio.gather()` when using `asyncio.eager_task_factory()` to complete eagerly if all fututres completed eagerly. Avoid scheduling done callbacks for futures that complete eagerly.

- gh-104114: Fix issue where `pathlib.Path.glob()` returns paths using the case of non-wildcard segments for corresponding path segments, rather than the real filesystem case.

- gh-104104: Improve performance of `pathlib.Path.glob()` by using `re.IGNORECASE` to implement case-insensitive matching.

- gh-104102: Improve performance of `pathlib.Path.glob()` when evaluating patterns that contain `'../'` segments.

- gh-103822: Update the return type of `weekday` to the newly added Day attribute

- gh-103629: Update the `repr` of `typing.Unpack` according to PEP 692.

- gh-103963: Make `dis` display the names of the args for `CALL_INTRINSIC_*`.

- gh-104035: Do not ignore user-defined `__getstate__` and `__setstate__` methods for slotted frozen dataclasses.

- gh-103987: In `mmap`, fix several bugs that could lead to access to memory-mapped files after they have been invalidated.

- gh-103977: Improve import time of `platform` module.

- gh-88773: Added `turtle.teleport()` to the `turtle` module to move a turtle to a new point without tracing a line, visible or invisible. Patch by Liam Gersten.

- gh-103935: Use `io.open_code()` for files to be executed instead of raw `open()`

- gh-68968: Fixed garbled output of `assertEqual()` when an input lacks final newline.

- gh-100370: Fix potential `OverflowError` in `sqlite3.Connection.blobopen()` for 32-bit builds. Patch by Erlend E. Aasland.

- gh-102628: Substitute CTRL-D with CTRL-Z in `sqlite3` CLI banner when running on Windows.

- gh-103636: Module-level attributes `January` and `February` are deprecated from `calendar`.

- gh-103583: Isolate `_multibytecodec` and codecs extension modules. Patches by Erlend E. Aasland.

- gh-103848: Add checks to ensure that `[` bracketed `]` hosts found by `urllib.parse.urlsplit()` are of IPv6 or IPvFuture format.

- gh-103872: Update the bundled copy of pip to version 23.1.2.

- gh-99944: Make `dis` display the value of oparg of `KW_NAMES`.

- gh-74940: The C.UTF-8 locale is no longer converted to en_US.UTF-8, enabling the use of UTF-8 encoding on systems which have no locales installed.

- gh-103861: Fix `zipfile.Zipfile` creating invalid zip files when `force_zip64` was used to add files to them. Patch by Carey Metcalfe.

- gh-103857: Deprecated `datetime.datetime.utcnow()` and `datetime.datetime.utcfromtimestamp()`. (Patch by Paul Ganssle)

- gh-103839: Avoid compilation error due to tommath.h not being found when building Tkinter against Tcl 8.7 built with bundled libtommath.

- gh-103791: `contextlib.suppress` now supports suppressing exceptions raised as part of an `ExceptionGroup`. If other exceptions exist on the group, they are re-raised in a group that does not contain the suppressed exceptions.

- gh-90750: Use `datetime.datetime.fromisocalendar()` in the implementation of `datetime.datetime.strptime()`, which should now accept only valid ISO dates. (Patch by Paul Ganssle)

- gh-103685: Prepare `tkinter.Menu.index()` for Tk 8.7 so that it does not raise `TclError: expected integer but got ""` when it should return `None`.

- gh-81403: `urllib.request.CacheFTPHandler` no longer raises `URLError` if a cached FTP instance is reused. ftplib’s endtransfer method calls voidresp to drain the connection to handle FTP instance reuse properly.

- gh-103699: Add `__orig_bases__` to non-generic TypedDicts, call-based TypedDicts, and call-based NamedTuples. Other TypedDicts and NamedTuples already had the attribute.

- gh-103693: Add convenience variable feature to `pdb`

- gh-92248: Deprecate `type`, `choices`, and `metavar` parameters of `argparse.BooleanOptionalAction`.

- gh-89415: Add `socket` constants for source-specific multicast. Patch by Reese Hyde.

- gh-103673: `socketserver` gains `ForkingUnixStreamServer` and `ForkingUnixDatagramServer` classes. Patch by Jay Berry.

- gh-103636: Added Enum for months and days in the calendar module.

- gh-84976: Create a new `Lib/_pydatetime.py` file that defines the Python version of the `datetime` module, and make `datetime` import the contents of the new library only if the C implementation is missing. Currently, the full Python implementation is defined and then deleted if the C implementation is not available, slowing down `import datetime` unnecessarily.

- gh-103596: Attributes/methods are no longer shadowed by same-named enum members, although they may be shadowed by enum.property’s.

- gh-103584: Updated `importlib.metadata` with changes from `importlib_metadata` 5.2 through 6.5.0, including: Support `installed-files.txt` for `Distribution.files` when present. `PackageMetadata` now stipulates an additional `get` method allowing for easy querying of metadata keys that may not be present. `packages_distributions` now honors packages and modules with Python modules that not `.py` sources (e.g. `.pyc`, `.so`). Expand protocol for `PackageMetadata.get_all` to match the upstream implementation of `email.message.Message.get_all` in python/typeshed#9620. Deprecated use of `Distribution` without defining abstract methods. Deprecated expectation that `PackageMetadata.__getitem__` will return `None` for missing keys. In the future, it will raise a `KeyError`.

- gh-103578: Fixed a bug where `pdb` crashes when reading source file with different encoding by replacing `io.open()` with `io.open_code()`. The new method would also call into the hook set by `PyFile_SetOpenCodeHook()`.

- gh-103556: Now creating `inspect.Signature` objects with positional-only parameter with a default followed by a positional-or-keyword parameter without one is impossible.

- gh-103559: Update the bundled copy of pip to version 23.1.1.

- gh-103548: Improve performance of `pathlib.Path.absolute()` and `cwd()` by joining paths only when necessary. Also improve performance of `pathlib.PurePath.is_absolute()` on Posix by skipping path parsing and normalization.

- gh-103538: Remove `_tkinter` module code guarded by definition of the `TK_AQUA` macro which was only needed for Tk 8.4.7 or earlier and was never actually defined by any build system or documented for manual use.

- gh-103533: Update `cProfile` to use PEP 669 API

- gh-103525: Fix misleading exception message when mixed `str` and `bytes` arguments are supplied to `pathlib.PurePath` and `Path`.

- gh-103489: Add `getconfig()` and `setconfig()` to `Connection` to make configuration changes to a database connection. Patch by Erlend E. Aasland.

- gh-103365: Set default Flag boundary to `STRICT` and fix bitwise operations.

- gh-103472: Avoid a potential `ResourceWarning` in `http.client.HTTPConnection` by closing the proxy / tunnel’s CONNECT response explicitly.

- gh-103462: Fixed an issue with using `writelines()` in `asyncio` to send very large payloads that exceed the amount of data that can be written in one call to `socket.socket.send()` or `socket.socket.sendmsg()`, resulting in the remaining buffer being left unwritten.

- gh-103449: Fix a bug in doc string generation in `dataclasses.dataclass()`.

- gh-103092: Isolate `_collections` (apply PEP 687). Patch by Erlend E. Aasland.

- gh-103357: Added support for `logging.Formatter` `defaults` parameter to `logging.config.dictConfig()` and `logging.config.fileConfig()`. Patch by Bar Harel.

- gh-103092: Adapt the `winreg` extension module to PEP 687.

- gh-74690: The performance of `isinstance()` checks against `runtime-checkable protocols` has been considerably improved for protocols that only have a few members. To achieve this improvement, several internal implementation details of the `typing` module have been refactored, including `typing._ProtocolMeta.__instancecheck__`, `typing._is_callable_members_only`, and `typing._get_protocol_attrs`. Patches by Alex Waygood.

- gh-74690: The members of a runtime-checkable protocol are now considered “frozen” at runtime as soon as the class has been created. See “What’s new in Python 3.12” for more details.

- gh-103256: Fixed a bug that caused `hmac` to raise an exception when the requested hash algorithm was not available in OpenSSL despite being available separately as part of `hashlib` itself. It now falls back properly to the built-in. This could happen when, for example, your OpenSSL does not include SHA3 support and you want to compute `hmac.digest(b'K', b'M', 'sha3_256')`.

- gh-102778: Support `sys.last_exc` in `idlelib`.

- gh-103285: Improve performance of `ast.get_source_segment()`.

- gh-103225: Fix a bug in `pdb` when displaying line numbers of module-level source code.

- gh-103092: Adapt the `msvcrt` extension module to PEP 687.

- gh-103092: Adapt the `winsound` extension module to PEP 687.

- gh-93910: Remove deprecation of enum `member.member` access.

- gh-102978: Fixes `unittest.mock.patch()` not enforcing function signatures for methods decorated with `@classmethod` or `@staticmethod` when patch is called with `autospec=True`.

- gh-103092: Isolate `_socket` (apply PEP 687). Patch by Erlend E. Aasland.

- gh-100479: Add `pathlib.PurePath.with_segments()`, which creates a path object from arguments. This method is called whenever a derivative path is created, such as from `pathlib.PurePath.parent`. Subclasses may override this method to share information between path objects.

- gh-103220: Fix issue where `os.path.join()` added a slash when joining onto an incomplete UNC drive with a trailing slash on Windows.

- gh-103204: Fixes `http.server` accepting HTTP requests with HTTP version numbers preceded by ‘+’, or ‘-’, or with digit-separating ‘_’ characters. The length of the version numbers is also constrained.

- gh-75586: Fix various Windows-specific issues with `shutil.which`.

- gh-103193: Improve performance of `inspect.getattr_static()`. Patch by Alex Waygood.

- gh-103176: `sys._current_exceptions()` now returns a mapping from thread-id to an exception instance, rather than to a `(typ, exc, tb)` tuple.

- gh-103143: Polish the help messages and docstrings of `pdb`.

- gh-103015: Add entrypoint keyword-only parameter to `sqlite3.Connection.load_extension()`, for overriding the SQLite extension entry point. Patch by Erlend E. Aasland.

- gh-103000: Improve performance of `dataclasses.astuple()` and `dataclasses.asdict()` in cases where the contents are common Python types.

- gh-102953: The extraction methods in `tarfile`, and `shutil.unpack_archive()`, have a new a filter argument that allows limiting tar features than may be surprising or dangerous, such as creating files outside the destination directory. See Extraction filters for details.

- gh-97696: Implemented an eager task factory in asyncio. When used as a task factory on an event loop, it performs eager execution of coroutines. Coroutines that are able to complete synchronously (e.g. return or raise without blocking) are returned immediately as a finished task, and the task is never scheduled to the event loop. If the coroutine blocks, the (pending) task is scheduled and returned.

- gh-81079: Add case_sensitive keyword-only argument to `pathlib.Path.glob()` and `rglob()`.

- gh-101819: Isolate the `io` extension module by applying PEP 687. Patch by Kumar Aditya, Victor Stinner, and Erlend E. Aasland.

- gh-91896: Deprecate `collections.abc.ByteString`

- gh-101362: Speed up `pathlib.Path` construction by omitting the path anchor from the internal list of path parts.

- gh-102114: Functions in the `dis` module that accept a source code string as argument now print a more concise traceback when the string contains a syntax or indentation error.

- gh-62432: The `unittest` runner will now exit with status code 5 if no tests were run. It is common for test runner misconfiguration to fail to find any tests, this should be an error.

- gh-78079: Fix incorrect normalization of UNC device path roots, and partial UNC share path roots, in `pathlib.PurePath`. Pathlib no longer appends a trailing slash to such paths.

- gh-85984: Add `tty.cfmakeraw()` and `tty.cfmakecbreak()` to `tty` and modernize, the behavior of `tty.setraw()` and `tty.setcbreak()` to use POSIX.1-2017 Chapter 11 “General Terminal Interface” flag masks by default.

- gh-101688: Implement `types.get_original_bases()` to provide further introspection for types.

- gh-101640: `argparse.ArgumentParser` now catches errors when writing messages, such as when `sys.stderr` is `None`. Patch by Oleg Iarygin.

- gh-83861: Fix datetime.astimezone method return value when invoked on a naive datetime instance that represents local time falling in a timezone transition gap. PEP 495 requires that instances with fold=1 produce earlier times than those with fold=0 in this case.

- gh-89550: Decrease execution time of some `gzip` file writes by 15% by adding more appropriate buffering.

- gh-95299: Remove the bundled setuptools wheel from `ensurepip`, and stop installing setuptools in environments created by `venv`.

- gh-99353: Respect the `http.client.HTTPConnection` `.debuglevel` flag in `urllib.request.AbstractHTTPHandler` when its constructor parameter `debuglevel` is not set. And do the same for `*HTTPS*`.

- gh-98040: Remove the long-deprecated `imp` module.

- gh-97850: Deprecate `pkgutil.find_loader()` and `pkgutil.get_loader()` in favor of `importlib.util.find_spec()`.

- gh-94473: Flatten arguments in `tkinter.Canvas.coords()`. It now accepts not only `x1, y1, x2, y2, ...` and `[x1, y1, x2, y2, ...]`, but also `(x1, y1), (x2, y2), ...` and `[(x1, y1), (x2, y2), ...]`.

- gh-98040: Remove more deprecated importlib APIs: `find_loader()`, `find_module()`, `importlib.abc.Finder`, `pkgutil.ImpImporter`, `pkgutil.ImpLoader`.

- gh-96522: Fix potential deadlock in pty.spawn()

- gh-96534: Support divert(4) added in FreeBSD 14.

- gh-87474: Fix potential file descriptor leaks in `subprocess.Popen`.

- gh-94906: Support multiple steps in `math.nextafter()`. Patch by Shantanu Jain and Matthias Gorgens.

- gh-51574: Make `tempfile.mkdtemp()` return absolute paths when its dir parameter is relative.

- gh-94518: Convert private `_posixsubprocess.fork_exec()` to use Argument Clinic.

- gh-92184: When creating zip files using `zipfile`, `os.altsep`, if not `None`, will always be treated as a path separator even when it is not `/`. Patch by Carey Metcalfe.

- bpo-46797: Deprecation warnings are now emitted for `ast.Num`, `ast.Bytes`, `ast.Str`, `ast.NameConstant` and `ast.Ellipsis`. These have been documented as deprecated since Python 3.8, and will be removed in Python 3.14.

- bpo-44844: Enables `webbrowser` to detect and launch Microsoft Edge browser.

- bpo-45606: Fixed the bug in `pathlib.Path.glob()` – previously a dangling symlink would not be found by this method when the pattern is an exact match, but would be found when the pattern contains a wildcard or the recursive wildcard (`**`). With this change, a dangling symlink will be found in both cases.

- bpo-23041: Add `QUOTE_STRINGS` and `QUOTE_NOTNULL` to the suite of `csv` module quoting styles.

- bpo-24964: Added `http.client.HTTPConnection.get_proxy_response_headers()` that provides access to the HTTP headers on a proxy server response to the `CONNECT` request.

- bpo-17258: `multiprocessing` now supports stronger HMAC algorithms for inter-process connection authentication rather than only HMAC-MD5.

- bpo-39744: Make `asyncio.subprocess.Process.communicate()` close the subprocess’s stdin even when called with `input=None`.

- bpo-22708: http.client CONNECT method tunnel improvements: Use HTTP 1.1 protocol; send a matching Host: header with CONNECT, if one is not provided; convert IDN domain names to Punycode. Patch by Michael Handler.

### Documentation

- gh-67056: Document that the effect of registering or unregistering an `atexit` cleanup function from within a registered cleanup function is undefined.

- gh-103629: Mention the new way of typing `**kwargs` with `Unpack` and `TypedDict` introduced in PEP 692.

- gh-48241: Clarifying documentation about the url parameter to urllib.request.urlopen and urllib.request.Request needing to be encoded properly.

- gh-86094: Add support for Unicode Path Extra Field in ZipFile. Patch by Yeojin Kim and Andrea Giudiceandrea

- gh-99202: Fix extension type from documentation for compiling in C++20 mode

### Tests

- gh-104494: Update `test_pack_configure_in` and `test_place_configure_in` for changes to error message formatting in Tk 8.7.

- gh-104461: Run test_configure_screen on X11 only, since the `DISPLAY` environment variable and `-screen` option for toplevels are not useful on Tk for Win32 or Aqua.

- gh-86275: Added property-based tests to the `zoneinfo` tests, along with stubs for the `hypothesis` interface. (Patch by Paul Ganssle)

- gh-103329: Regression tests for the behaviour of `unittest.mock.PropertyMock` were added.

- gh-102795: fix use of poll in test_epoll’s test_control_and_wait

- gh-75729: Fix the `os.spawn*` tests failing on Windows when the working directory or interpreter path contains spaces.

### Build

- gh-101282: BOLT optimization is now applied to the libpython shared library if building a shared library. BOLT instrumentation and application settings can now be influenced via the `BOLT_INSTRUMENT_FLAGS` and `BOLT_APPLY_FLAGS` configure variables.

- gh-99017: `PYTHON_FOR_REGEN` now require Python 3.10 or newer.

- gh-104490: Define `.PHONY` / virtual make targets consistently and properly.

- gh-104106: Add gcc fallback of mkfifoat/mknodat for macOS. Patch by Donghee Na.

- gh-103532: The `TKINTER_PROTECT_LOADTK` macro is no longer defined or used in the `_tkinter` module. It was previously only defined when building against Tk 8.4.13 and older, but Tk older than 8.5.12 has been unsupported since gh-91152.

- gh-99069: Extended workaround defining `static_assert` when missing from the libc headers to all clang and gcc builds. In particular, this fixes building on macOS <= 10.10.

- gh-100220: Changed the default value of the `SHELL` Makefile variable from `/bin/sh` to `/bin/sh -e` to ensure that complex recipes correctly fail after an error. Previously, `make install` could fail to install some files and yet return a successful result.

- gh-90656: Add platform triplets for 64-bit LoongArch:

  - loongarch64-linux-gnusf

  - loongarch64-linux-gnuf32

  - loongarch64-linux-gnu

  Patch by Zhang Na.

### Windows

- gh-104623: Update Windows installer to use SQLite 3.42.0.

- gh-82814: Fix a potential `[Errno 13] Permission denied` when using `shutil.copystat()` within Windows Subsystem for Linux (WSL) on a mounted filesystem by adding `errno.EACCES` to the list of ignored errors within the internal implementation.

- gh-103088: Fix virtual environment `activate` script having incorrect line endings for Cygwin.

- gh-103088: Fixes venvs not working in bash on Windows across different disks

- gh-102997: Update Windows installer to use SQLite 3.41.2.

- gh-88013: Fixed a bug where `TypeError` was raised when calling `ntpath.realpath()` with a bytes parameter in some cases.

### macOS

- gh-99834: Update macOS installer to Tcl/Tk 8.6.13.

- gh-104623: Update macOS installer to SQLite 3.42.0.

- gh-103545: Add `os.PRIO_DARWIN_THREAD`, `os.PRIO_DARWIN_PROCESS`, `os.PRIO_DARWIN_BG` and `os.PRIO_DARWIN_NONUI`. These can be used with `os.setpriority` to run the process at a lower priority and make use of the efficiency cores on Apple Silicon systems.

- gh-104180: Support reading SOCKS proxy configuration from macOS System Configuration. Patch by Sam Schott.

- gh-60436: update curses textbox to additionally handle backspace using the `curses.ascii.DEL` key press.

- gh-102997: Update macOS installer to SQLite 3.41.2.

### IDLE

- gh-104499: Fix completions for Tk Aqua 8.7 (currently blank).

- gh-104496: About prints both tcl and tk versions if different (expected someday).

- gh-88496: Fix IDLE test hang on macOS.

### Tools/Demos

- gh-104389: Argument Clinic C converters now accept the `unused` keyword, for wrapping a parameter with `Py_UNUSED`. Patch by Erlend E. Aasland.

### C API

- gh-101291: Added unstable C API for extracting the value of “compact” integers: `PyUnstable_Long_IsCompact()` and `PyUnstable_Long_CompactValue()`.

- gh-104109: We’ve added `Py_NewInterpreterFromConfig()` and `PyInterpreterConfig` to the public C-API (but not the stable ABI; not yet at least). The new function may be used to create a new interpreter with various features configured. The function was added to support PEP 684 (per-interpreter GIL).

- gh-103968: `PyType_FromSpec()` and its variants now allow creating classes whose metaclass overrides `tp_new`. The `tp_new` is ignored. This behavior is deprecated and will be disallowed in 3.14+. The new `PyType_FromMetaclass()` already disallows it.

- gh-103743: Add `PyUnstable_Object_GC_NewWithExtraData()` function that can be used to allocate additional memory after an object for data not managed by Python.

- gh-103295: Introduced `PyUnstable_WritePerfMapEntry()`, `PyUnstable_PerfMapState_Init()` and `PyUnstable_PerfMapState_Fini()`. These allow extension modules (JIT compilers in particular) to write to perf-map files in a thread safe manner. The Python support for the Linux perf profiler also uses these APIs to write entries in the perf-map file.

- gh-103509: Added C API for extending types whose instance memory layout is opaque: `PyType_Spec.basicsize` can now be zero or negative, `PyObject_GetTypeData()` can be used to get subclass-specific data, and `Py_TPFLAGS_ITEMS_AT_END` can be used to safely extend variable-size objects. See PEP 697 for details.

- gh-103091: Add a new C-API function to eagerly assign a version tag to a PyTypeObject: `PyUnstable_Type_AssignVersionTag()`.

- gh-101408: `PyObject_GC_Resize` should calculate preheader size if needed. Patch by Donghee Na.

- gh-98836: Add support of more formatting options (left aligning, octals, uppercase hexadecimals, `intmax_t`, `ptrdiff_t`, `wchar_t` C strings, variable width and precision) in `PyUnicode_FromFormat()` and `PyUnicode_FromFormatV()`.

- gh-96803: Add unstable C-API functions to get the code object, lasti and line number from the internal `_PyInterpreterFrame` in the limited API. The functions are:

  - `PyCodeObject * PyUnstable_InterpreterFrame_GetCode(struct _PyInterpreterFrame *frame)`

  - `int PyUnstable_InterpreterFrame_GetLasti(struct _PyInterpreterFrame *frame)`

  - `int PyUnstable_InterpreterFrame_GetLine(struct _PyInterpreterFrame *frame)`

## Python 3.12.0 alpha 7

Release date: 2023-04-04

### Core and Builtins

- gh-102192: Deprecated `_PyErr_ChainExceptions` in favour of `_PyErr_ChainExceptions1`.

- gh-89987: Reduce the number of inline `CACHE` entries for `BINARY_SUBSCR`.

- gh-102859: Removed `JUMP_IF_FALSE_OR_POP` and `JUMP_IF_TRUE_OR_POP` instructions.

- gh-101975: Fixed `stacktop` value on tracing entries to avoid corruption on garbage collection.

- gh-102778: Add `sys.last_exc` and deprecate `sys.last_type`, `sys.last_value` and `sys.last_traceback`, which hold the same information in its legacy form.

- gh-100982: Replace all occurrences of `COMPARE_AND_BRANCH` with `COMPARE_OP`.

- gh-102701: Fix overflow when creating very large dict.

- gh-102755: Add `PyErr_DisplayException()` which takes just an exception instance, to replace the legacy `PyErr_Display()` which takes the `(typ, exc, tb)` triplet.

- gh-102594: Add note to exception raised in `PyErr_SetObject` when normalization fails.

- gh-90997: Shrink the number of inline `CACHE` entries used by `LOAD_GLOBAL`.

- gh-102491: Improve import time of `platform` by removing IronPython version parsing. The IronPython version parsing was not functional (see https://github.com/IronLanguages/ironpython3/issues/1667).

- gh-101291: Rearrage bits in first field (after header) of PyLongObject. * Bits 0 and 1: 1 - sign. I.e. 0 for positive numbers, 1 for zero and 2 for negative numbers. * Bit 2 reserved (probably for the immortal bit) * Bits 3+ the unsigned size.

  This makes a few operations slightly more efficient, and will enable a more compact and faster 2s-complement representation of most ints in future.

- gh-102397: Fix segfault from race condition in signal handling during garbage collection. Patch by Kumar Aditya.

- gh-102406: `codecs` encoding/decoding errors now get the context information (which operation and which codecs) attached as PEP 678 notes instead of through chaining a new instance of the exception.

- gh-102281: Fix potential nullptr dereference and use of uninitialized memory in fileutils. Patch by Max Bachmann.

- gh-102300: Reuse operands with refcount of 1 in float specializations of BINARY_OP.

- gh-102213: Fix performance loss when accessing an object’s attributes with `__getattr__` defined.

- gh-102255: Improve build support for the Xbox. Patch by Max Bachmann.

- gh-102027: Fix SSE2 and SSE3 detection in `_blake2` internal module. Patch by Max Bachmann.

- gh-101865: Deprecate `co_lnotab` in code objects, schedule it for removal in Python 3.14

- bpo-1635741: Adapt `_pickle` to PEP 687. Patch by Mohamed Koubaa and Erlend Aasland.

### Library

- gh-103085: Pure python `locale.getencoding()` will not warn deprecation.

- gh-103068: It’s no longer possible to register conditional breakpoints in `Pdb` that raise `SyntaxError`. Patch by Tian Gao.

- gh-102549: Don’t ignore exceptions in member type creation.

- gh-103056: Ensure final `_generate_next_value_` is a `staticmethod`.

- gh-103046: Display current line label correctly in `dis` when `show_caches` is False and `lasti` points to a CACHE entry.

- gh-102433: `isinstance()` checks against `runtime-checkable protocols` now use `inspect.getattr_static()` rather than `hasattr()` to lookup whether attributes exist. This means that descriptors and `__getattr__()` methods are no longer unexpectedly evaluated during `isinstance()` checks against runtime-checkable protocols. However, it may also mean that some objects which used to be considered instances of a runtime-checkable protocol may no longer be considered instances of that protocol on Python 3.12+, and vice versa. Most users are unlikely to be affected by this change. Patch by Alex Waygood.

- gh-103023: It’s no longer possible to register expressions to display in `Pdb` that raise `SyntaxError`. Patch by Tian Gao.

- gh-102947: Improve traceback when `dataclasses.fields()` is called on a non-dataclass. Patch by Alex Waygood

- gh-102780: The `asyncio.Timeout` context manager now works reliably even when performing cleanup due to task cancellation. Previously it could raise a `CancelledError` instead of an `TimeoutError` in such cases.

- gh-102871: Remove support for obsolete browsers from `webbrowser`. Removed browsers include Grail, Mosaic, Netscape, Galeon, Skipstone, Iceape, Firebird, and Firefox versions 35 and below.

- gh-102839: Improve performance of `math.log()` arguments handling by removing the argument clinic.

- gh-102828: Add the `onexc` arg to `shutil.rmtree()`, which is like `onerror` but expects an exception instance rather than an exc_info tuple. Deprecate `onerror`.

- gh-88965: typing: Fix a bug relating to substitution in custom classes generic over a `ParamSpec`. Previously, if the `ParamSpec` was substituted with a parameters list that itself contained a `TypeVar`, the `TypeVar` in the parameters list could not be subsequently substituted. This is now fixed.

  Patch by Nikita Sobolev.

- gh-76846: Fix issue where `__new__()` and `__init__()` methods of `pathlib.PurePath` and `Path` subclasses were not called in some circumstances.

- gh-78530: `asyncio.wait()` now accepts generators yielding tasks. Patch by Kumar Aditya.

- gh-102748: `asyncio.iscoroutine()` now returns `False` for generators as `asyncio` does not support legacy generator-based coroutines. Patch by Kumar Aditya.

- gh-102670: Optimized fmean(), correlation(), covariance(), and linear_regression() using the new math.sumprod() function.

- gh-102615: Typing: Improve the `repr` of generic aliases for classes generic over a `ParamSpec`. (Use square brackets to represent a parameter list.)

- gh-100112: `asyncio.Task.get_coro()` now always returns a coroutine when wrapping an awaitable object. Patch by Kumar Aditya.

- gh-102578: Speed up setting or deleting mutable attributes on non-dataclass subclasses of frozen dataclasses. Due to the implementation of `__setattr__` and `__delattr__` for frozen dataclasses, this previously had a time complexity of O(n). It now has a time complexity of O(1).

- gh-102519: Add `os.listdrives()`, `os.listvolumes()` and `os.listmounts()` functions on Windows for enumerating drives, volumes and mount points

- gh-74468: Attribute name of the extracted `tarfile` file object now holds filename of itself rather than of the archive it is contained in. Patch by Oleg Iarygin.

- gh-102378: Private helper method `inspect._signature_strip_non_python_syntax` will no longer strip `/` from the input string.

- gh-79940: Add `inspect.getasyncgenstate()` and `inspect.getasyncgenlocals()`. Patch by Thomas Krennwallner.

- gh-102103: Add `module` argument to `dataclasses.make_dataclass()` and make classes produced by it pickleable.

- gh-102069: Fix `__weakref__` descriptor generation for custom dataclasses.

- gh-102038: Skip a `stat` in `site` if we have already found a `pyvenv.cfg`

- gh-98886: Fix issues when defining dataclasses that have fields with specific underscore names that aren’t clearly reserved by `dataclasses`.

- gh-101673: Fix a `pdb` bug where `ll` clears the changes to local variables.

- gh-101313: Added -h and –help arguments to the webbrowser CLI

- gh-100372: `ssl.SSLContext.load_verify_locations()` no longer incorrectly accepts some cases of trailing data when parsing DER.

- gh-89727: Fix pathlib.Path.walk RecursionError on deep directory trees by rewriting it using iteration instead of recursion.

- gh-100131: Added an optional `delete` keyword argument to `tempfile.TemporaryDirectory`.

- gh-48330: Added `--durations` command line option, showing the N slowest test cases. `unittest.TextTestRunner` and `unittest.TextTestResult` constructors accept a new durations keyword argument. Subclasses should take this into account or accept `**kwargs`. Added `unittest.TestResult.addDuration()` method and `unittest.TestResult.collectedDurations` attribute.

  (Contributed by Giampaolo Rodola)

- gh-98169: Fix `dataclasses.astuple()` crash when `collections.defaultdict` is present in the attributes.

- gh-96931: Fix incorrect results from `ssl.SSLSocket.shared_ciphers()`

- gh-95495: When built against OpenSSL 3.0, the `ssl` module had a bug where it reported unauthenticated EOFs (i.e. without close_notify) as a clean TLS-level EOF. It now raises `SSLEOFError`, matching the behavior in previous versions of OpenSSL. The `options` attribute on `SSLContext` also no longer includes `OP_IGNORE_UNEXPECTED_EOF` by default. This option may be set to specify the previous OpenSSL 3.0 behavior.

- gh-94684: Now `uuid.uuid3()` and `uuid.uuid5()` functions support `bytes` objects as their name argument.

- gh-94440: Fix a `concurrent.futures.process` bug where `ProcessPoolExecutor` shutdown could hang after a future has been quickly submitted and canceled.

- gh-72346: Added deprecation warning to isdst parameter of `email.utils.localtime()`.

- bpo-36305: Fix handling of Windows filenames that resemble drives, such as `./a:b`, in `pathlib`.

### Documentation

- gh-103112: Add docstring to `http.client.HTTPResponse.read()` to fix `pydoc` output.

### Tests

- gh-102980: Improve test coverage on `pdb`.

- gh-102537: Adjust the error handling strategy in `test_zoneinfo.TzPathTest.python_tzpath_context`. Patch by Paul Ganssle.

- gh-101377: Improved test_locale_calendar_formatweekday of calendar.

### Build

- gh-102973: Add a dev container (along with accompanying Dockerfile) for development purposes.

- gh-102711: Fix `-Wstrict-prototypes` compiler warnings.

### Windows

- gh-102690: Update `webbrowser` to fall back to Microsoft Edge instead of Internet Explorer.

- gh-99726: Improves correctness of stat results for Windows, and uses faster API when available

### Tools/Demos

- gh-102809: `Misc/gdbinit` was removed.

### C API

- gh-102013: Add a new (unstable) C-API function for iterating over GC’able objects using a callback: `PyUnstable_VisitObjects`.

## Python 3.12.0 alpha 6

Release date: 2023-03-07

### Security

- gh-99108: Replace builtin hashlib implementations of MD5 and SHA1 with verified ones from the HACL* project.

- gh-101727: Updated the OpenSSL version used in Windows and macOS binary release builds to 1.1.1t to address CVE 2023-0286, CVE 2022-4303, and CVE 2022-4303 per the OpenSSL 2023-02-07 security advisory.

- gh-99108: Replace the builtin `hashlib` implementations of SHA2-384 and SHA2-512 originally from LibTomCrypt with formally verified, side-channel resistant code from the HACL* project. The builtins remain a fallback only used when OpenSSL does not provide them.

- gh-101283: `subprocess.Popen` now uses a safer approach to find `cmd.exe` when launching with `shell=True`. Patch by Eryk Sun, based on a patch by Oleg Iarygin.

### Core and Builtins

- gh-102493: Fix regression in semantics of normalisation in `PyErr_SetObject`.

- gh-102416: Do not memoize incorrectly automatically generated loop rules in the parser. Patch by Pablo Galindo.

- gh-102356: Fix a bug that caused a crash when deallocating deeply nested filter objects. Patch by Marta Gómez Macías.

- gh-102336: Cleanup Windows 7 specific special handling. Patch by Max Bachmann.

- gh-102250: Fixed a segfault occurring when the interpreter calls a `__bool__` method that raises.

- gh-102126: Fix deadlock at shutdown when clearing thread states if any finalizer tries to acquire the runtime head lock. Patch by Kumar Aditya.

- gh-102027: Use `GetCurrentProcessId` on Windows when `getpid` is unavailable. Patch by Max Bachmann.

- gh-102056: Fix error handling bugs in interpreter’s exception printing code, which could cause a crash on infinite recursion.

- gh-100982: Restrict the scope of the `FOR_ITER_RANGE` instruction to the scope of the original `FOR_ITER` instruction, to allow instrumentation.

- gh-101967: Fix possible segfault in `positional_only_passed_as_keyword` function, when new list created.

- gh-101952: Fix possible segfault in `BUILD_SET` opcode, when new set created.

- gh-74895: `socket.getaddrinfo` no longer raises `OverflowError` for `int` port values outside of the C long range. Out of range values are left up to the underlying string based C library API to report. A `socket.gaierror` `SAI_SERVICE` may occur instead, or no error at all as not all platform C libraries generate an error.

- gh-101799: Add `CALL_INTRINSIC_2` and use it instead of `PREP_RERAISE_STAR`.

- gh-101857: Fix xattr support detection on Linux systems by widening the check to linux, not just glibc. This fixes support for musl.

- gh-84783: Make the slice object hashable. Patch by Will Bradshaw and Furkan Onder.

- gh-87849: Change the `SEND` instruction to leave the receiver on the stack. This allows the specialized form of `SEND` to skip the chain of C calls and jump directly to the `RESUME` in the generator or coroutine.

- gh-101765: Fix SystemError / segmentation fault in iter `__reduce__` when internal access of `builtins.__dict__` keys mutates the iter object.

- gh-101430: Update `tracemalloc` to handle presize of object properly. Patch by Donghee Na.

- gh-101696: Invalidate type version tag in `_PyStaticType_Dealloc` for static types, avoiding bug where a false cache hit could crash the interpreter. Patch by Kumar Aditya.

- gh-101632: Adds a new `RETURN_CONST` instruction.

- gh-100719: Remove gi_code field from generator (and coroutine and async generator) objects as it is redundant. The frame already includes a reference to the code object.

- gh-98627: When an interpreter is configured to check (and only then), importing an extension module will now fail when the extension does not support multiple interpreters (i.e. doesn’t implement PEP 489 multi-phase init). This does not apply to the main interpreter, nor to subinterpreters created with `Py_NewInterpreter()`.

### Library

- gh-102302: Micro-optimise hashing of `inspect.Parameter`, reducing the time it takes to hash an instance by around 40%.

- gh-101979: Fix a bug where parentheses in the `metavar` argument to `argparse.ArgumentParser.add_argument()` were dropped. Patch by Yeojin Kim.

- gh-91038: `platform.platform()` now has boolean default arguments.

- gh-81652: Add `mmap.MAP_ALIGNED_SUPER` FreeBSD and `mmap.MAP_CONCEAL` OpenBSD constants to `mmap`. Patch by Yeojin Kim.

- gh-102179: Fix `os.dup2()` error message for negative fds.

- gh-101961: For the binary mode, `fileinput.hookcompressed()` doesn’t set the `encoding` value even if the value is `None`. Patch by Gihwan Kim.

- gh-101936: The default value of `fp` becomes `io.BytesIO` if `HTTPError` is initialized without a designated `fp` parameter. Patch by Long Vo.

- gh-101566: In zipfile, sync Path with zipp 3.14, including fix for extractall on the underlying zipfile after being wrapped in `Path`.

- gh-97930: Apply changes from importlib_resources 5.12, including fix for `MultiplexedPath` to support directories in multiple namespaces (python/importlib_resources#265).

- gh-101997: Upgrade pip wheel bundled with ensurepip (pip 23.0.1)

- gh-99108: The built-in extension modules for `hashlib` SHA2 algorithms, used when OpenSSL does not provide them, now live in a single internal `_sha2` module instead of separate `_sha256` and `_sha512` modules.

- gh-101892: Callable iterators no longer raise `SystemError` when the callable object exhausts the iterator but forgets to either return a sentinel value or raise `StopIteration`.

- gh-87634: Remove locking behavior from `functools.cached_property()`.

- gh-97786: Fix potential undefined behaviour in corner cases of floating-point-to-time conversions.

- gh-101517: Fixed bug where `bdb` looks up the source line with `linecache` with a `lineno=None`, which causes it to fail with an unhandled exception.

- gh-101773: Optimize `fractions.Fraction` for small components. The private argument `_normalize` of the `fractions.Fraction` constructor has been removed.

- gh-101693: In `sqlite3.Cursor.execute()`, `DeprecationWarning` is now emitted when named placeholders are used together with parameters supplied as a sequence instead of as a `dict`. Starting from Python 3.14, using named placeholders with parameters supplied as a sequence will raise a `ProgrammingError`. Patch by Erlend E. Aasland.

- gh-101446: Change repr of `collections.OrderedDict` to use regular dictionary formatting instead of pairs of keys and values.

- gh-101362: Speed up `pathlib.PurePath` construction by handling arguments more uniformly. When a `pathlib.Path` argument is supplied, we use its string representation rather than joining its parts with `os.path.join()`.

- gh-101362: Speed up `pathlib.PurePath` construction by calling `os.path.join()` only when two or more arguments are given.

- gh-101362: Speed up `pathlib.Path` construction by running the path flavour compatibility check only when pathlib is imported.

- gh-85984: Refactored the implementation of `pty.fork()` to use `os.login_tty()`.

  A `DeprecationWarning` is now raised by `pty.master_open()` and `pty.slave_open()`. They were undocumented and deprecated long long ago in the docstring in favor of `pty.openpty()`.

- gh-101561: Add a new decorator `typing.override()`. See PEP 698 for details. Patch by Steven Troxler.

- gh-63301: Set exit code when `tabnanny` CLI exits on error.

- gh-101360: Fix anchor matching in `pathlib.PureWindowsPath.match()`. Path and pattern anchors are now matched with `fnmatch`, just like other path parts. This allows patterns such as `"*:/Users/*"` to be matched.

- gh-101277: Remove global state from `itertools` module (PEP 687). Patches by Erlend E. Aasland.

- gh-100809: Fix handling of drive-relative paths (like ‘C:’ and ‘C:foo’) in `pathlib.Path.absolute()`. This method now uses the OS API to retrieve the correct current working directory for the drive.

- gh-99138: Apply PEP 687 to `zoneinfo`. Patch by Erlend E. Aasland.

- gh-96764: `asyncio.wait_for()` now uses `asyncio.timeout()` as its underlying implementation. Patch by Kumar Aditya.

- gh-88233: Correctly preserve “extra” fields in `zipfile` regardless of their ordering relative to a zip64 “extra.”

- bpo-23224: Fix segfaults when creating `lzma.LZMADecompressor` and `bz2.BZ2Decompressor` objects without calling `__init__()`, and fix leakage of locks and internal buffers when calling the `__init__()` methods of `lzma.LZMADecompressor`, `lzma.LZMACompressor`, `bz2.BZ2Compressor`, and `bz2.BZ2Decompressor` objects multiple times.

### Documentation

- gh-85417: Update `cmath` documentation to clarify behaviour on branch cuts.

- gh-97725: Fix `asyncio.Task.print_stack()` description for `file=None`. Patch by Oleg Iarygin.

### Tests

- gh-102019: Fix deadlock on shutdown if `test_current_{exception,frames}` fails. Patch by Jacob Bower.

- gh-85984: Utilize new “winsize” functions from termios in pty tests.

- gh-89792: `test_tools` now copies up to 10x less source data to a temporary directory during the `freeze` test by ignoring git metadata and other artifacts. It also limits its python build parallelism based on os.cpu_count instead of hard coding it as 8 cores.

### Build

- gh-99942: On Android, in a static build, python-config in embed mode no longer incorrectly reports a library to link to.

- gh-99942: On Android, python.pc now correctly reports the library to link to, the same as python-config.sh.

- gh-100221: Fix creating install directories in `make sharedinstall` if they exist outside `DESTDIR` already.

- gh-96821: Explicitly mark C extension modules that need defined signed integer overflow, and add a configure option `--with-strict-overflow`. Patch by Matthias Görgens and Shantanu Jain.

### Windows

- gh-102344: Implement `winreg.QueryValue` using `QueryValueEx` and `winreg.SetValue` using `SetValueEx`. Patch by Max Bachmann.

- gh-101881: Handle read and write operations on non-blocking pipes properly on Windows.

- gh-101881: Add support for the os.get_blocking() and os.set_blocking() functions on Windows.

- gh-101849: Ensures installer will correctly upgrade existing `py.exe` launcher installs.

- gh-101763: Updates copy of libffi bundled with Windows installs to 3.4.4.

- gh-101759: Update Windows installer to SQLite 3.40.1.

- gh-101614: Correctly handle extensions built against debug binaries that reference `python3_d.dll`.

- gh-101196: The functions `os.path.isdir`, `os.path.isfile`, `os.path.islink` and `os.path.exists` are now 13% to 28% faster on Windows, by making fewer Win32 API calls.

### macOS

- gh-101759: Update macOS installer to SQLite 3.40.1.

### C API

- gh-101907: Removes use of non-standard C++ extension in public header files.

- gh-99293: Document that the Py_TPFLAGS_VALID_VERSION_TAG is an internal feature, should not be used, and will be removed.

- gh-101578: Add `PyErr_GetRaisedException()` and `PyErr_SetRaisedException()` for saving and restoring the current exception. These functions return and accept a single exception object, rather than the triple arguments of the now-deprecated `PyErr_Fetch()` and `PyErr_Restore()`. This is less error prone and a bit more efficient.

  Add `PyException_GetArgs()` and `PyException_SetArgs()` as convenience functions for retrieving and modifying the `args` passed to the exception’s constructor.

- gh-91744: Introduced the Unstable C API tier, marking APi that is allowed to change in minor releases without a deprecation period. See PEP 689 for details.

## Python 3.12.0 alpha 5

Release date: 2023-02-07

### Security

- gh-99108: Replace the builtin `hashlib` implementations of SHA2-224 and SHA2-256 originally from LibTomCrypt with formally verified, side-channel resistant code from the HACL* project. The builtins remain a fallback only used when OpenSSL does not provide them.

### Core and Builtins

- gh-92173: Fix the `defs` and `kwdefs` arguments to `PyEval_EvalCodeEx()` and a reference leak in that function.

- gh-59956: The GILState API is now partially compatible with subinterpreters. Previously, `PyThreadState_GET()` and `PyGILState_GetThisThreadState()` would get out of sync, causing inconsistent behavior and crashes.

- gh-101400: Fix wrong lineno in exception message on `continue` or `break` which are not in a loop. Patch by Donghee Na.

- gh-101372: Fix `is_normalized()` to properly handle the UCD 3.2.0 cases. Patch by Donghee Na.

- gh-101266: Fix `sys.getsizeof()` reporting for `int` subclasses.

- gh-101291: Refactor the `PyLongObject` struct into a normal Python object header and a `PyLongValue` struct.

- gh-101046: Fix a possible memory leak in the parser when raising `MemoryError`. Patch by Pablo Galindo

- gh-101037: Fix potential memory underallocation issue for instances of `int` subclasses with value zero.

- gh-100762: Record the (virtual) exception block depth in the oparg of `YIELD_VALUE`. Use this to avoid the expensive `throw()` when closing generators (and coroutines) that can be closed trivially.

- gh-100982: Adds a new `COMPARE_AND_BRANCH` instruction. This is a bit more efficient when performing a comparison immediately followed by a branch, and restores the design intent of PEP 659 that specializations are local to a single instruction.

- gh-100942: Fixed segfault in property.getter/setter/deleter that occurred when a property subclass overrode the `__new__` method to return a non-property instance.

- gh-100923: Remove the `mask` cache entry for the `COMPARE_OP` instruction and embed the mask into the oparg.

- gh-100892: Fix race while iterating over thread states in clearing `threading.local`. Patch by Kumar Aditya.

- gh-91351: Fix a case where re-entrant imports could corrupt the import deadlock detection code and cause a `KeyError` to be raised out of `importlib/_bootstrap`. In addition to the straightforward cases, this could also happen when garbage collection leads to a warning being emitted – as happens when it collects an open socket or file)

- gh-100726: Optimize construction of `range` object for medium size integers.

- gh-100712: Added option to build cpython with specialization disabled, by setting `ENABLE_SPECIALIZATION=False` in `opcode`, followed by `make regen-all`.

- bpo-32780: Inter-field padding is now inserted into the PEP3118 format strings obtained from `ctypes.Structure` objects, reflecting their true representation in memory.

### Library

- gh-101541: [Enum] - fix psuedo-flag creation

- gh-101570: Upgrade pip wheel bundled with ensurepip (pip 23.0)

- gh-101323: Fix a bug where errors where not thrown by zlib._ZlibDecompressor if encountered during decompressing.

- gh-101317: Add ssl_shutdown_timeout parameter for `asyncio.StreamWriter.start_tls()`.

- gh-101326: Fix regression when passing `None` as second or third argument to `FutureIter.throw`.

- gh-92123: Adapt the `_elementtree` extension module to multi-phase init (PEP 489). Patches by Erlend E. Aasland.

- gh-100795: Avoid potential unexpected `freeaddrinfo` call (double free) in `socket` when when a libc `getaddrinfo()` implementation leaves garbage in an output pointer when returning an error. Original patch by Sergey G. Brester.

- gh-101143: Remove unused references to `TimerHandle` in `asyncio.base_events.BaseEventLoop._add_callback`.

- gh-101144: Make `zipfile.Path.open()` and `zipfile.Path.read_text()` also accept `encoding` as a positional argument. This was the behavior in Python 3.9 and earlier. 3.10 introduced a regression where supplying it as a positional argument would lead to a `TypeError`.

- gh-94518: Group-related variables of `_posixsubprocess` module are renamed to stress that supplimentary group affinity is added to a fork, not replace the inherited ones. Patch by Oleg Iarygin.

- gh-101015: Fix `typing.get_type_hints()` on `'*tuple[...]'` and `*tuple[...]`. It must not drop the `Unpack` part.

- gh-101000: Add `os.path.splitroot()`, which splits a path into a 3-item tuple `(drive, root, tail)`. This new function is used by `pathlib` to improve the performance of path construction by up to a third.

- gh-100573: Fix a Windows `asyncio` bug with named pipes where a client doing `os.stat()` on the pipe would cause an error in the server that disabled serving future requests.

- gh-39615: `warnings.warn()` now has the ability to skip stack frames based on code filename prefix rather than only a numeric `stacklevel` via the new `skip_file_prefixes` keyword argument.

- gh-100750: pass encoding kwarg to subprocess in platform

- gh-100160: Emit a deprecation warning in `asyncio.DefaultEventLoopPolicy.get_event_loop()` if there is no current event loop set and it decides to create one.

- gh-96290: Fix handling of partial and invalid UNC drives in `ntpath.splitdrive()`, and in `ntpath.normpath()` on non-Windows systems. Paths such as ‘\server’ and ‘\’ are now considered by `splitdrive()` to contain only a drive, and consequently are not modified by `normpath()` on non-Windows systems. The behaviour of `normpath()` on Windows systems is unaffected, as native OS APIs are used. Patch by Eryk Sun, with contributions by Barney Gale.

- gh-99952: Fix a reference undercounting issue in `ctypes.Structure` with `from_param()` results larger than a C pointer.

- gh-67790: Add float-style formatting support for `fractions.Fraction` instances.

- gh-99266: Preserve more detailed error messages in `ctypes`.

- gh-86682: Ensure runtime-created collections have the correct module name using the newly added (internal) `sys._getframemodulename()`.

- gh-88597: `uuid` now has a command line interface. Try `python -m uuid -h`.

- gh-60580: `ctypes.wintypes.BYTE` definition changed from `c_byte` to `c_ubyte` to match Windows SDK. Patch by Anatoly Techtonik and Oleg Iarygin.

- gh-94518: `_posixsubprocess` now initializes all UID and GID variables using a reserved `-1` value instead of a separate flag. Patch by Oleg Iarygin.

- bpo-38941: The `xml.etree.ElementTree` module now emits `DeprecationWarning` when testing the truth value of an `xml.etree.ElementTree.Element`. Before, the Python implementation emitted `FutureWarning`, and the C implementation emitted nothing.

- bpo-40077: Convert `elementtree` types to heap types. Patch by Erlend E. Aasland.

- bpo-29847: Fix a bug where `pathlib.Path` accepted and ignored keyword arguments. Patch provided by Yurii Karabas.

- gh-77772: `ctypes.CDLL`, `ctypes.OleDLL`, `ctypes.WinDLL`, and `ctypes.PyDLL` now accept path-like objects as their `name` argument. Patch by Robert Hoelzl.

### Documentation

- gh-88324: Reword `subprocess` to emphasize default behavior of stdin, stdout, and stderr arguments. Remove inaccurate statement about child file handle inheritance.

### Tests

- gh-101334: `test_tarfile` has been updated to pass when run as a high UID.

### Build

- gh-101282: Update BOLT configuration not to use deprecated usage of `--split functions`. Patch by Donghee Na.

- gh-101522: Allow overriding Windows dependencies versions and paths using MSBuild properties.

- gh-77532: Minor fixes to allow building with `PlatformToolset=ClangCL` on Windows.

- gh-101152: In accordance with PEP 699, the `ma_version_tag` field in `PyDictObject` is deprecated for extension modules. Accessing this field will generate a compiler warning at compile time. This field will be removed in Python 3.14.

- gh-100340: Allows -Wno-int-conversion for wasm-sdk 17 and onwards, thus enables building WASI builds once against the latest sdk.

- gh-101060: Conditionally add `-fno-reorder-blocks-and-partition` in configure. Effectively fixes `--enable-bolt` when using Clang, as this appears to be a GCC-only flag.

- gh-98705: `__bool__` is defined in AIX system header files which breaks the build in AIX, so undefine it.

- gh-98636: Fix a regression in detecting `gdbm_compat` library for the `_gdbm` module build.

- gh-96305: `_aix_support` now uses a simple code to get platform details rather than the now non-existent `_bootsubprocess` during bootstrap.

### Windows

- gh-101543: Ensure the install path in the registry is only used when the standard library hasn’t been located in any other way.

- gh-101467: The `py.exe` launcher now correctly filters when only a single runtime is installed. It also correctly handles prefix matches on tags so that `-3.1` does not match `3.11`, but would still match `3.1-32`.

- gh-99834: Updates bundled copy of Tcl/Tk to 8.6.13.0

- gh-101135: Restore ability to launch older 32-bit versions from the `py.exe` launcher when both 32-bit and 64-bit installs of the same version are available.

- gh-82052: Fixed an issue where writing more than 32K of Unicode output to the console screen in one go can result in mojibake.

- gh-100320: Ensures the `PythonPath` registry key from an install is used when launching from a different copy of Python that relies on an existing install to provide a copy of its modules and standard library.

- gh-100247: Restores support for the `py.exe` launcher finding shebang commands in its configuration file using the full command name.

## Python 3.12.0 alpha 4

Release date: 2023-01-10

### Core and Builtins

- gh-100776: Fix misleading default value in `input()`’s `__text_signature__`.

- gh-99005: Remove `UNARY_POSITIVE`, `ASYNC_GEN_WRAP` and `LIST_TO_TUPLE`, replacing them with intrinsics.

- gh-99005: Add new `CALL_INTRINSIC_1` instruction. Remove `IMPORT_STAR`, `PRINT_EXPR` and `STOPITERATION_ERROR`, replacing them with the `CALL_INTRINSIC_1` instruction.

- gh-100288: Remove the LOAD_ATTR_METHOD_WITH_DICT specialized instruction. Stats show it is not useful.

- gh-100720: Added `_PyFrame_NumSlotsForCodeObject`, which returns the number of slots needed in a frame for a given code object.

- gh-100719: Removed the co_nplaincellvars field from the code object, as it is redundant.

- gh-100637: Fix `int.__sizeof__()` calculation to include the 1-element `ob_digit` array for `0` and `False`.

- gh-100649: Update the native_thread_id field of PyThreadState after fork.

- gh-100126: Fix an issue where “incomplete” frames could be briefly visible to C code while other frames are being torn down, possibly resulting in corruption or hard crashes of the interpreter while running finalizers.

- gh-87447: Fix `SyntaxError` on comprehension rebind checking with names that are not actually redefined.

  Now reassigning `b` in `[(b := 1) for a, b.prop in some_iter]` is allowed. Reassigning `a` is still disallowed as per PEP 572.

- gh-100268: Add `int.is_integer()` to improve duck type compatibility between `int` and `float`.

- gh-100425: Improve the accuracy of `sum()` with compensated summation.

- gh-100374: Fix incorrect result and delay in `socket.getfqdn()`. Patch by Dominic Socular.

- gh-100357: Convert `vars`, `dir`, `next`, `getattr`, and `iter` to argument clinic.

- gh-100117: Improve the output of `codeobject.co_lines()` by emitting only one entry for each line range.

- gh-90043: Handle NaNs when specializing `COMPARE_OP` for `float` values.

- gh-100222: Redefine the `_Py_CODEUNIT` typedef as a union to describe its layout to the C compiler, avoiding type punning and improving clarity.

- gh-99955: Internal compiler functions (in compile.c) now consistently return -1 on error and 0 on success.

- gh-100188: The `BINARY_SUBSCR_LIST_INT` and `BINARY_SUBSCR_TUPLE_INT` instructions are no longer used for negative integers because those instructions always miss when encountering negative integers.

- gh-99110: Initialize frame->previous in frameobject.c to fix a segmentation fault when accessing frames created by `PyFrame_New()`.

- gh-94155: Improved the hashing algorithm for code objects, mitigating some hash collisions.

- gh-99540: `None` now hashes to a constant value. This is not a requirements change.

- gh-100143: When built with `--enable-pystats`, stats collection is now off by default. To enable it early at startup, pass the `-Xpystats` flag. Stats are now always dumped, even if switched off.

- gh-100146: Improve `BUILD_LIST` opcode so that it works similarly to the `BUILD_TUPLE` opcode, by stealing references from the stack rather than repeatedly using stack operations to set list elements. Implementation details are in a new private API `_PyList_FromArraySteal()`.

- gh-100110: Specialize `FOR_ITER` for tuples.

- gh-100050: Honor existing errors obtained when searching for mismatching parentheses in the tokenizer. Patch by Pablo Galindo

- gh-92216: Improve the performance of `hasattr()` for type objects with a missing attribute.

- gh-99582: Freeze `zipimport` module into `_bootstrap_python`.

- gh-99554: Pack debugging location tables more efficiently during bytecode compilation.

- gh-98522: Add an internal version number to code objects, to give better versioning of inner functions and comprehensions, and thus better specialization of those functions. This change is invisible to both Python and C extensions.

- gh-94603: Improve performance of `list.pop` for small lists.

- gh-89051: Add `ssl.OP_LEGACY_SERVER_CONNECT`

- bpo-32782: `ctypes` arrays of length 0 now report a correct itemsize when a `memoryview` is constructed from them, rather than always giving a value of 0.

### Library

- gh-100833: Speed up `math.fsum()` by removing defensive `volatile` qualifiers.

- gh-100805: Modify `random.choice()` implementation to once again work with NumPy arrays.

- gh-100813: Add `socket.IP_PKTINFO` constant.

- gh-100792: Make `email.message.Message.__contains__()` twice as fast.

- gh-91851: Microoptimizations for `fractions.Fraction.__round__()`, `fractions.Fraction.__ceil__()` and `fractions.Fraction.__floor__()`.

- gh-90104: Avoid RecursionError on `repr` if a dataclass field definition has a cyclic reference.

- gh-100689: Fix crash in `pyexpat` by statically allocating `PyExpat_CAPI` capsule.

- gh-100740: Fix `unittest.mock.Mock` not respecting the spec for attribute names prefixed with `assert`.

- gh-91219: Change `SimpleHTTPRequestHandler` to support subclassing to provide a different set of index file names instead of using `__init__` parameters.

- gh-100690: `Mock` objects which are not unsafe will now raise an `AttributeError` when accessing an attribute that matches the name of an assertion but without the prefix `assert_`, e.g. accessing `called_once` instead of `assert_called_once`. This is in addition to this already happening for accessing attributes with prefixes `assert`, `assret`, `asert`, `aseert`, and `assrt`.

- gh-89727: Simplify and optimize `os.walk()` by using `isinstance()` checks to check the top of the stack.

- gh-100485: Add math.sumprod() to compute the sum of products.

- gh-86508: Fix `asyncio.open_connection()` to skip binding to local addresses of different family. Patch by Kumar Aditya.

- gh-97930: `importlib.resources.files` now accepts a module as an anchor instead of only accepting packages. If a module is passed, resources are resolved adjacent to that module (in the same package or at the package root). The parameter was renamed from `package` to `anchor` with a compatibility shim for those passing by keyword. Additionally, the new `anchor` parameter is now optional and will default to the caller’s module.

- gh-100585: Fixed a bug where importlib.resources.as_file was leaving file pointers open

- gh-100562: Improve performance of `pathlib.Path.absolute()` by nearly 2x. This comes at the cost of a performance regression in `pathlib.Path.cwd()`, which is generally used less frequently in user code.

- gh-100519: Small simplification of `http.cookiejar.eff_request_host()` that improves readability and better matches the RFC wording.

- gh-100287: Fix the interaction of `unittest.mock.seal()` with `unittest.mock.AsyncMock`.

- gh-100488: Add `Fraction.is_integer()` to check whether a `fractions.Fraction` is an integer. This improves duck type compatibility with `float` and `int`.

- gh-100474: `http.server` now checks that an index page is actually a regular file before trying to serve it. This avoids issues with directories named `index.html`.

- gh-100363: Speed up `asyncio.get_running_loop()` by removing redundant `getpid` checks. Patch by Kumar Aditya.

- gh-78878: Fix crash when creating an instance of `_ctypes.CField`.

- gh-100348: Fix ref cycle in `asyncio._SelectorSocketTransport` by removing `_read_ready_cb` in `close`.

- gh-100344: Provide C implementation for `asyncio.current_task()` for a 4x-6x speedup.

- gh-100272: Fix JSON serialization of OrderedDict. It now preserves the order of keys.

- gh-83076: Instantiation of `Mock()` and `AsyncMock()` is now 3.8x faster.

- gh-100234: Set a default value of 1.0 for the `lambd` parameter in random.expovariate().

- gh-100228: A `DeprecationWarning` may be raised when `os.fork()` or `os.forkpty()` is called from multi-threaded processes. Forking with threads is unsafe and can cause deadlocks, crashes and subtle problems. Lack of a warning does not indicate that the fork call was actually safe, as Python may not be aware of all threads.

- gh-100039: Improve signatures for enums and flags.

- gh-100133: Fix regression in `asyncio` where a subprocess would sometimes lose data received from pipe.

- bpo-44592: Fixes inconsistent handling of case sensitivity of extrasaction arg in `csv.DictWriter`.

- gh-100098: Fix `tuple` subclasses being cast to `tuple` when used as enum values.

- gh-85432: Rename the fmt parameter of the pure-Python implementation of `datetime.time.strftime()` to format. Rename the t parameter of `datetime.datetime.fromtimestamp()` to timestamp. These changes mean the parameter names in the pure-Python implementation now match the parameter names in the C implementation. Patch by Alex Waygood.

- gh-98778: Update `HTTPError` to be initialized properly, even if the `fp` is `None`. Patch by Donghee Na.

- gh-99925: Unify error messages in JSON serialization between `json.dumps(float('nan'), allow_nan=False)` and `json.dumps(float('nan'), allow_nan=False, indent=<SOMETHING>)`. Now both include the representation of the value that could not be serialized.

- gh-89727: Fix issue with `os.walk()` where a `RecursionError` would occur on deep directory structures by adjusting the implementation of `os.walk()` to be iterative instead of recursive.

- gh-94943: Add Dataclass support to the `Enum` `__repr__()`. When inheriting from a `dataclass`, only show the field names in the value section of the member `repr()`, and not the dataclass’ class name.

- gh-83035: Fix `inspect.getsource()` handling of decorator calls with nested parentheses.

- gh-99576: Fix `.save()` method for `LWPCookieJar` and `MozillaCookieJar`: saved file was not truncated on repeated save.

- gh-94912: Add `inspect.markcoroutinefunction()` decorator which manually marks a function as a coroutine for the benefit of `iscoroutinefunction()`.

- gh-99509: Add PEP 585 support for `multiprocessing.queues.Queue`.

- gh-99482: Remove `Jython` partial compatibility code from several stdlib modules.

- gh-99433: Fix `doctest` failure on `types.MethodWrapperType` in modules.

- gh-85267: Several improvements to `inspect.signature()`’s handling of `__text_signature`. - Fixes a case where `inspect.signature()` dropped parameters - Fixes a case where `inspect.signature()` raised `tokenize.TokenError` - Allows `inspect.signature()` to understand defaults involving binary operations of constants - `inspect.signature()` is documented as only raising `TypeError` or `ValueError`, but sometimes raised `RuntimeError`. These cases now raise `ValueError` - Removed a dead code path

- gh-91166: `asyncio` is optimized to avoid excessive copying when writing to socket and use `sendmsg()` if the platform supports it. Patch by Kumar Aditya.

- gh-98030: Add missing TCP socket options from Linux: `TCP_MD5SIG`, `TCP_THIN_LINEAR_TIMEOUTS`, `TCP_THIN_DUPACK`, `TCP_REPAIR`, `TCP_REPAIR_QUEUE`, `TCP_QUEUE_SEQ`, `TCP_REPAIR_OPTIONS`, `TCP_TIMESTAMP`, `TCP_CC_INFO`, `TCP_SAVE_SYN`, `TCP_SAVED_SYN`, `TCP_REPAIR_WINDOW`, `TCP_FASTOPEN_CONNECT`, `TCP_ULP`, `TCP_MD5SIG_EXT`, `TCP_FASTOPEN_KEY`, `TCP_FASTOPEN_NO_COOKIE`, `TCP_ZEROCOPY_RECEIVE`, `TCP_INQ`, `TCP_TX_DELAY`.

- gh-88500: Reduced the memory usage of `urllib.parse.unquote()` and `urllib.parse.unquote_to_bytes()` on large values.

- gh-96127: `inspect.signature` was raising `TypeError` on call with mock objects. Now it correctly returns `(*args, **kwargs)` as inferred signature.

- gh-95882: Fix a 3.11 regression in `asynccontextmanager()`, which caused it to propagate exceptions with incorrect tracebacks and fix a 3.11 regression in `contextmanager()`, which caused it to propagate exceptions with incorrect tracebacks for `StopIteration`.

- gh-78707: Deprecate passing more than one positional argument to `pathlib.PurePath.relative_to()` and `is_relative_to()`.

- gh-92122: Fix reStructuredText syntax errors in docstrings in the `enum` module.

- gh-91851: Optimize the `Fraction` arithmetics for small components.

- bpo-24132: Make `pathlib.PurePath` and `Path` subclassable (private to start). Previously, attempting to instantiate a subclass resulted in an `AttributeError` being raised. Patch by Barney Gale.

- bpo-40447: Accept `os.PathLike` (such as `pathlib.Path`) in the `stripdir` arguments of `compileall.compile_file()` and `compileall.compile_dir()`.

- bpo-36880: Fix a reference counting issue when a `ctypes` callback with return type `py_object` returns `None`, which could cause crashes.

### Documentation

- gh-100616: Document existing `attr` parameter to `curses.window.vline()` function in `curses`.

- gh-100472: Remove claim in documentation that the `stripdir`, `prependdir` and `limit_sl_dest` parameters of `compileall.compile_dir()` and `compileall.compile_file()` could be `bytes`.

- bpo-25377: Clarify use of octal format of mode argument in help(os.chmod) as well as help(os.fchmod)

### Tests

- gh-100454: Start running SSL tests with OpenSSL 3.1.0-beta1.

- gh-100086: The Python test runner (libregrtest) now logs Python build information like “debug” vs “release” build, or LTO and PGO optimizations. Patch by Victor Stinner.

- gh-93018: Make two tests forgiving towards host system libexpat with backported security fixes applied.

### Build

- gh-100540: Removed the `--with-system-ffi` `configure` option; `libffi` must now always be supplied by the system on all non-Windows platforms. The option has had no effect on non-Darwin platforms for several releases, and in 3.11 only had the non-obvious effect of invoking `pkg-config` to find `libffi` and never setting `-DUSING_APPLE_OS_LIBFFI`. Now on Darwin platforms `configure` will first check for the OS `libffi` and then fall back to the same processing as other platforms if it is not found.

- gh-88267: Avoid exporting Python symbols in linked Windows applications when the core is built as static.

- bpo-41916: Allow override of ac_cv_cxx_thread so that cross compiled python can set -pthread for CXX.

### Windows

- gh-100180: Update Windows installer to OpenSSL 1.1.1s

- gh-99191: Use `_MSVC_LANG >= 202002L` instead of less-precise `_MSC_VER >=1929` to more accurately test for C++20 support in `PC/_wmimodule.cpp`.

- gh-79218: Define `MS_WIN64` for Mingw-w64 64bit, fix cython compilation failure.

- gh-99941: Ensure that `asyncio.Protocol.data_received()` receives an immutable `bytes` object (as documented), instead of `bytearray`.

- bpo-43984: `winreg.SetValueEx()` now leaves the target value untouched in the case of conversion errors. Previously, `-1` would be written in case of such errors.

- bpo-34816: `hasattr(ctypes.windll, 'nonexistant')` now returns `False` instead of raising `OSError`.

### macOS

- gh-100180: Update macOS installer to OpenSSL 1.1.1s

- gh-100540: Removed obsolete `dlfcn.h` shim from the `_ctypes` extension module, which has not been necessary since Mac OS X 10.2.

### Tools/Demos

- bpo-45256: Fix a bug that caused an `AttributeError` to be raised in `python-gdb.py` when `py-locals` is used without a frame.

- gh-100342: Add missing `NULL` check for possible allocation failure in `*args` parsing in Argument Clinic.

### C API

- gh-99947: Raising SystemError on import will now have its cause be set to the original unexpected exception.

- gh-99240: In argument parsing, after deallocating newly allocated memory, reset its pointer to NULL.

- gh-98724: The `Py_CLEAR`, `Py_SETREF` and `Py_XSETREF` macros now only evaluate their arguments once. If an argument has side effects, these side effects are no longer duplicated. Patch by Victor Stinner.

## Python 3.12.0 alpha 3

Release date: 2022-12-06

### Security

- gh-100001: `python -m http.server` no longer allows terminal control characters sent within a garbage request to be printed to the stderr server log.

  This is done by changing the `http.server` `BaseHTTPRequestHandler` `.log_message` method to replace control characters with a `\xHH` hex escape before printing.

- gh-87604: Avoid publishing list of active per-interpreter audit hooks via the `gc` module

### Core and Builtins

- gh-99891: Fix a bug in the tokenizer that could cause infinite recursion when showing syntax warnings that happen in the first line of the source. Patch by Pablo Galindo

- gh-91054: Add `PyCode_AddWatcher()` and `PyCode_ClearWatcher()` APIs to register callbacks to receive notification on creation and destruction of code objects.

- gh-99729: Fix an issue that could cause frames to be visible to Python code as they are being torn down, possibly leading to memory corruption or hard crashes of the interpreter.

- gh-99708: Fix bug where compiler crashes on an if expression with an empty body block.

- gh-99578: Fix a reference bug in `_imp.create_builtin()` after the creation of the first sub-interpreter for modules `builtins` and `sys`. Patch by Victor Stinner.

- gh-99581: Fixed a bug that was causing a buffer overflow if the tokenizer copies a line missing the newline character from a file that is as long as the available tokenizer buffer. Patch by Pablo galindo

- gh-99553: Fix bug where an `ExceptionGroup` subclass can wrap a `BaseException`.

- gh-99547: Add a function to os.path to check if a path is a junction: isjunction. Add similar functionality to pathlib.Path as is_junction.

- gh-99370: Fix zip path for venv created from a non-installed python on POSIX platforms.

- gh-99377: Add audit events for thread creation and clear operations.

- gh-98686: Remove the `BINARY_OP_GENERIC` and `COMPARE_OP_GENERIC` “specializations”.

- gh-99298: Remove the remaining error paths for attribute specializations, and refuse to specialize attribute accesses on types that haven’t had `PyType_Ready()` called on them yet.

- gh-99127: Allow some features of `syslog` to the main interpreter only. Patch by Donghee Na.

- gh-91053: Optimizing interpreters and JIT compilers may need to invalidate internal metadata when functions are modified. This change adds the ability to provide a callback that will be invoked each time a function is created, modified, or destroyed.

- gh-90994: Improve error messages when there’s a syntax error with call arguments. The following three cases are covered: - No value is assigned to a named argument, eg `foo(a=)`. - A value is assigned to a star argument, eg `foo(*args=[0])`. - A value is assigned to a double-star keyword argument, eg `foo(**kwarg={'a': 0})`.

- bpo-45026: Optimize the `range` object iterator. It is now smaller, faster iteration of ranges containing large numbers. Smaller pickles, faster unpickling.

- bpo-31718: Raise `ValueError` instead of `SystemError` when methods of uninitialized `io.IncrementalNewlineDecoder` objects are called. Patch by Oren Milman.

- bpo-38031: Fix a possible assertion failure in `io.FileIO` when the opener returns an invalid file descriptor.

### Library

- gh-100001: Also escape s in the http.server BaseHTTPRequestHandler.log_message so that it is technically possible to parse the line and reconstruct what the original data was. Without this a xHH is ambiguious as to if it is a hex replacement we put in or the characters r”x” came through in the original request line.

- gh-99957: Add `frozen_default` parameter to `typing.dataclass_transform()`.

- gh-79033: Fix `asyncio.Server.wait_closed()` to actually do what the docs promise – wait for all existing connections to complete, after closing the server.

- gh-51524: Fix bug when calling trace.CoverageResults with valid infile.

- gh-99645: Fix a bug in handling class cleanups in `unittest.TestCase`. Now `addClassCleanup()` uses separate lists for different `TestCase` subclasses, and `doClassCleanups()` only cleans up the particular class.

- gh-99508: Fix `TypeError` in `Lib/importlib/_bootstrap_external.py` while calling `_imp.source_hash()`.

- gh-66285: Fix `asyncio` to not share event loop and signal wakeupfd in forked processes. Patch by Kumar Aditya.

- gh-97001: Release the GIL when calling termios APIs to avoid blocking threads.

- gh-92647: Use final status of an enum to determine lookup or creation branch of functional API.

- gh-99388: Add loop_factory parameter to `asyncio.run()` to allow specifying a custom event loop factory. Patch by Kumar Aditya.

- gh-99341: Fix `ast.increment_lineno()` to also cover `ast.TypeIgnore` when changing line numbers.

- gh-99382: Check the number of arguments in substitution in user generics containing a `TypeVarTuple` and one or more `TypeVar`.

- gh-99379: Fix substitution of `ParamSpec` followed by `TypeVarTuple` in generic aliases.

- gh-99344: Fix substitution of `TypeVarTuple` and `ParamSpec` together in user generics.

- gh-99284: Remove `_use_broken_old_ctypes_structure_semantics_` old untested and undocumented hack from `ctypes`.

- gh-99201: Fix `IndexError` when initializing the config variables on Windows if `HAVE_DYNAMIC_LOADING` is not set.

- gh-99240: Fix double-free bug in Argument Clinic `str_converter` by extracting memory clean up to a new `post_parsing` section.

- gh-64490: Fix refcount error when arguments are packed to tuple in Argument Clinic.

- gh-99029: `pathlib.PurePath.relative_to()` now treats naked Windows drive paths as relative. This brings its behaviour in line with other parts of pathlib.

- gh-98253: The implementation of the typing module is now more resilient to reference leaks in binary extension modules.

  Previously, a reference leak in a typed C API-based extension module could leak internals of the typing module, which could in turn introduce leaks in essentially any other package with typed function signatures. Although the typing package is not the original source of the problem, such non-local dependences exacerbate debugging of large-scale projects, and the implementation was therefore changed to reduce harm by providing better isolation.

- gh-98458: Fix infinite loop in unittest when a self-referencing chained exception is raised

- gh-93453: `asyncio.get_event_loop()` and many other `asyncio` functions like `asyncio.ensure_future()`, `asyncio.shield()` or `asyncio.gather()`, and also the `get_event_loop()` method of `asyncio.BaseDefaultEventLoopPolicy` now raise a `RuntimeError` if called when there is no running event loop and the current event loop was not set. Previously they implicitly created and set a new current event loop. `DeprecationWarning` is no longer emitted if there is no running event loop but the current event loop was set.

- gh-97966: On `uname_result`, restored expectation that `_fields` and `_asdict` would include all six properties including `processor`.

- gh-98248: Provide informative error messages in `struct.pack()` when its integral arguments are not in range.

- gh-98108: `zipfile.Path` is now pickleable if its initialization parameters were pickleable (e.g. for file system paths).

- gh-98098: Created packages from zipfile and test_zipfile modules, separating `zipfile.Path` functionality.

- gh-82836: Fix `is_private` properties in the `ipaddress` module. Previously non-private networks (0.0.0.0/0) would return `True` from this method; now they correctly return `False`.

- gh-96828: Add an `OP_ENABLE_KTLS` option for enabling the use of the kernel TLS (kTLS). Patch by Illia Volochii.

- gh-88863: To avoid apparent memory leaks when `asyncio.open_connection()` raises, break reference cycles generated by local exception and future instances (which has exception instance as its member var). Patch by Dong Uk, Kang.

- gh-91078: `TarFile.next()` now returns `None` when called on an empty tarfile.

- bpo-47220: Document the optional callback parameter of `WeakMethod`. Patch by Géry Ogam.

- bpo-44817: Ignore WinError 53 (ERROR_BAD_NETPATH), 65 (ERROR_NETWORK_ACCESS_DENIED) and 161 (ERROR_BAD_PATHNAME) when using ntpath.realpath().

- bpo-41260: Rename the fmt parameter of the pure Python implementation of `datetime.date.strftime()` to format.

- bpo-15999: All built-in functions now accept arguments of any type instead of just `bool` and `int` for boolean parameters.

### Documentation

- gh-99931: Use sphinxext-opengraph to generate OpenGraph metadata.

- gh-89682: Reworded docstring of the default `__contains__` to clarify that it returns a `bool`.

- gh-88330: Improved the description of what a resource is in importlib.resources docs.

- gh-92892: Document that calling variadic functions with ctypes requires special care on macOS/arm64 (and possibly other platforms).

- bpo-41825: Restructured the documentation for the `os.wait*` family of functions, and improved the docs for `os.waitid()` with more explanation of the possible argument constants.

### Tests

- gh-99892: Skip test_normalization() of test_unicodedata if it fails to download NormalizationTest.txt file from pythontest.net. Patch by Victor Stinner.

- gh-99934: Correct test_marsh on (32 bit) x86: test_deterministic sets was failing.

- gh-99741: We’ve implemented multi-phase init (PEP 489/630/687) for the internal (for testing) _xxsubinterpreters module.

- gh-99659: Optional big memory tests in `test_sqlite3` now catch the correct `sqlite.DataError` exception type in case of too large strings and/or blobs passed.

- gh-99593: Cover the Unicode C API with tests.

- gh-96002: Add functional test for Argument Clinic.

### Build

- gh-99086: Fix `-Wimplicit-int`, `-Wstrict-prototypes`, and `-Wimplicit-function-declaration` compiler warnings in configure checks.

- gh-99337: Fix a compilation issue with GCC 12 on macOS.

- gh-99289: Add a `COMPILEALL_OPTS` variable in Makefile to override `compileall` options (default: `-j0`) in `make install`. Also merged the `compileall` commands into a single command building .pyc files for the all optimization levels (0, 1, 2) at once. Patch by Victor Stinner.

- gh-98872: Fix a possible fd leak in `Programs/_freeze_module.c` introduced in Python 3.11.

- gh-88226: Always define `TARGET_*` labels in `Python/ceval.c`, even if `USE_COMPUTED_GOTOS` is disabled. This allows breakpoints to be set at those labels in (for instance) `gdb`.

### Windows

- gh-99345: Use faster initialization functions to detect install location for Windows Store package

- gh-98629: Fix initialization of `sys.version` and `sys._git` on Windows

- gh-99442: Fix handling in Python Launcher for Windows when `argv[0]` does not include a file extension.

- bpo-40882: Fix a memory leak in `multiprocessing.shared_memory.SharedMemory` on Windows.

### macOS

- gh-87235: On macOS `python3 /dev/fd/9 9</path/to/script.py` failed for any script longer than a couple of bytes.

- gh-98940: Fix `Mac/Extras.install.py` file filter bug.

### Tools/Demos

- gh-64490: Argument Clinic varargs bugfixes

  - Fix out-of-bounds error in `_PyArg_UnpackKeywordsWithVararg()`.

  - Fix incorrect check which allowed more than one varargs in clinic.py.

  - Fix miscalculation of `noptargs` in generated code.

  - Do not generate `noptargs` when there is a vararg argument and no optional argument.

### C API

- gh-98680: `PyBUF_*` constants were marked as part of Limited API of Python 3.11+. These were available in 3.11.0 with `Py_LIMITED_API` defined for 3.11, and are necessary to use the buffer API.

- gh-99612: Fix `PyUnicode_DecodeUTF8Stateful()` for ASCII-only data: `*consumed` was not set.

- gh-47146: The `structmember.h` header is deprecated. Its non-deprecated contents are now available just by including `Python.h`, with a `Py_` prefix added if it was missing. (Deprecated contents are `T_OBJECT`, `T_NONE`, and no-op flags.) Patch by Petr Viktorin, based on earlier work by Alexander Belopolsky and Matthias Braun.

## Python 3.12.0 alpha 2

Release date: 2022-11-14

### Security

- gh-98433: The IDNA codec decoder used on DNS hostnames by `socket` or `asyncio` related name resolution functions no longer involves a quadratic algorithm. This prevents a potential CPU denial of service if an out-of-spec excessive length hostname involving bidirectional characters were decoded. Some protocols such as `urllib` http `3xx` redirects potentially allow for an attacker to supply such a name.

  Individual labels within an IDNA encoded DNS name will now raise an error early during IDNA decoding if they are longer than 1024 unicode characters given that each decoded DNS label must be 63 or fewer characters and the entire decoded DNS name is limited to 255. Only an application presenting a hostname or label consisting primarily of RFC 3454 section 3.1 “Nothing” characters to be removed would run into of this new limit. See also RFC 5894 section 6 and RFC 3491.

- gh-98739: Update bundled libexpat to 2.5.0

### Core and Builtins

- gh-81057: The docs clearly say that `PyImport_Inittab`, `PyImport_AppendInittab()`, and `PyImport_ExtendInittab()` should not be used after `Py_Initialize()` has been called. We now enforce this for the two functions. Additionally, the runtime now uses an internal copy of `PyImport_Inittab`, to guard against modification.

- gh-99298: Fix an issue that could potentially cause incorrect error handling for some bytecode instructions.

- gh-99254: The compiler now removes all unused constants from code objects (except the first one, which may be a docstring).

- gh-99205: Fix an issue that prevented `PyThreadState` and `PyInterpreterState` memory from being freed properly.

- gh-81057: The 18 global C variables holding the state of the allocators have been moved to `_PyRuntimeState`. This is a strictly internal change with no change in behavior.

- gh-99181: Fix failure in `except*` with unhashable exceptions.

- gh-99204: Fix calculation of `sys._base_executable` when inside a POSIX virtual environment using copies of the python binary when the base installation does not provide the executable name used by the venv. Calculation will fall back to alternative names (“python<MAJOR>”, “python<MAJOR>.<MINOR>”).

- gh-96055: Update `faulthandler` to emit an error message with the proper unexpected signal number. Patch by Donghee Na.

- gh-99153: Fix location of `SyntaxError` for a `try` block with both `except` and `except*`.

- gh-98686: Merge the adaptive opcode logic into each instruction’s unquickened variant, and merge the logic in `EXTENDED_ARG_QUICK` into `EXTENDED_ARG`. With these changes, the quickening that happens at code object creation is now only responsible for initializing warmup counters and inserting superinstructions.

- gh-99103: Fix the error reporting positions of specialized traceback anchors when the source line contains Unicode characters.

- gh-99139: Improve the error suggestion for `NameError` exceptions for instances. Now if a `NameError` is raised in a method and the instance has an attribute that’s exactly equal to the name in the exception, the suggestion will include `self.<NAME>` instead of the closest match in the method scope. Patch by Pablo Galindo

- gh-98401: Octal escapes with value larger than `0o377` (ex: `"\477"`), deprecated in Python 3.11, now produce a `SyntaxWarning`, instead of `DeprecationWarning`. In a future Python version they will be eventually a `SyntaxError`. Patch by Victor Stinner.

- gh-98401: A backslash-character pair that is not a valid escape sequence now generates a `SyntaxWarning`, instead of `DeprecationWarning`. For example, `re.compile("\d+\.\d+")` now emits a `SyntaxWarning` (`"\d"` is an invalid escape sequence), use raw strings for regular expression: `re.compile(r"\d+\.\d+")`. In a future Python version, `SyntaxError` will eventually be raised, instead of `SyntaxWarning`. Patch by Victor Stinner.

- gh-96793: Handle StopIteration and StopAsyncIteration raised in generator or coroutines in the bytecode, rather than in wrapping C code.

- gh-98931: Improve the `SyntaxError` error message when the user types `import x from y` instead of `from y import x`. Patch by Pablo Galindo

- gh-98852: Fix subscription of type aliases containing bare generic types or types like `TypeVar`: for example `tuple[A, T][int]` and `tuple[TypeVar, T][int]`, where `A` is a generic type, and `T` is a type variable.

- gh-98925: Lower the recursion depth for marshal on WASI to support (in-development) wasmtime 2.0.

- gh-98783: Fix multiple crashes in debug mode when `str` subclasses are used instead of `str` itself.

- gh-98811: Use complete source locations to simplify detection of `__future__` imports which are not at the beginning of the file. Also corrects the offset in the exception raised in one case, which was off by one and impeded highlighting.

- gh-96793: Add specialization of `FOR_ITER` for generators. Saves multiple layers of dispatch and checking to get from the `FOR_ITER` instruction in the caller to the `RESUME` in the generator.

- gh-98762: Fix source locations of `match` sub-patterns.

- gh-98586: Added the methods `PyObject_Vectorcall()` and `PyObject_VectorcallMethod()` to the Limited API along with the auxiliary macro constant `PY_VECTORCALL_ARGUMENTS_OFFSET`.

  The availability of these functions enables more efficient PEP 590 vector calls from binary extension modules that avoid argument boxing/unboxing overheads.

- gh-99257: Fix an issue where member descriptors (such as those for `__slots__`) could behave incorrectly or crash instead of raising a `TypeError` when accessed via an instance of an invalid type.

- gh-93143: Rather than changing `co_code`, the interpreter will now display a `RuntimeWarning` and assign `None` to any fast locals that are left unbound after jumps or `del` statements executed while tracing.

- gh-96421: When calling into Python code from C code, through `PyEval_EvalFrameEx()` or a related C-API function, a shim frame in inserted into the call stack. This occurs in the `_PyEval_EvalFrameDefault()` function. The extra frame should be invisible to all Python and most C extensions, but out-of-process profilers and debuggers need to be aware of it. These shim frames can be detected by checking `frame->owner == FRAME_OWNED_BY_CSTACK`.

  Extensions implementing their own interpreters using PEP 523 need to be aware of this shim frame and the changes to the semantics of `RETURN_VALUE`, `YIELD_VALUE`, and `RETURN_GENERATOR`, which now clear the frame.

- gh-98415: Fix detection of MAC addresses for `uuid` on certain OSs. Patch by Chaim Sanders

- gh-98686: Quicken all code objects, and specialize adaptive bytecode instructions more aggressively.

- gh-92119: Print exception class name instead of its string representation when raising errors from `ctypes` calls.

- gh-91058: `ImportError` raised from failed `from <module> import <name>` now include suggestions for the value of `<name>` based on the available names in `<module>`. Patch by Pablo Galindo

- gh-96793: The `FOR_ITER` now leaves the iterator on the stack on termination of the loop. This is to assist specialization of loops for generators.

- gh-90716: Add _pylong.py module. It includes asymptotically faster algorithms that can be used for operations on integers with many digits. It is used by longobject.c to speed up some operations.

- gh-95389: Expose `ETH_P_ALL` and some of the ETHERTYPE_* constants in `socket`. Patch by Noam Cohen.

- gh-93696: Allow `pdb` to locate source for frozen modules in the standard library.

### Library

- gh-99418: Fix bug in `urllib.parse.urlparse()` that causes URL schemes that begin with a digit, a plus sign, or a minus sign to be parsed incorrectly.

- gh-94597: Deprecate `asyncio.AbstractChildWatcher` to be removed in Python 3.14. Patch by Kumar Aditya.

- gh-99305: Improve performance of `secrets.token_hex()`.

- gh-74044: Fixed bug where `inspect.signature()` reported incorrect arguments for decorated methods.

- gh-99275: Fix `SystemError` in `ctypes` when exception was not set during `__initsubclass__`.

- gh-99277: Remove older version of `_SSLProtocolTransport.get_write_buffer_limits` in `asyncio.sslproto`

- gh-99248: fix negative numbers failing in verify()

- gh-99155: Fix `statistics.NormalDist` pickle with `0` and `1` protocols.

- gh-93464: `enum.auto()` is now correctly activated when combined with other assignment values. E.g. `ONE = auto(), 'some text'` will now evaluate as `(1, 'some text')`.

- gh-99134: Update the bundled copy of pip to version 22.3.1.

- gh-92584: Remove the `distutils` package. It was deprecated in Python 3.10 by PEP 632 “Deprecate distutils module”. For projects still using `distutils` and cannot be updated to something else, the `setuptools` project can be installed: it still provides `distutils`. Patch by Victor Stinner.

- gh-98999: Now `_pyio` is consistent with `_io` in raising `ValueError` when executing methods over closed buffers.

- gh-83004: Clean up refleak on failed module initialisation in `_zoneinfo`

- gh-83004: Clean up refleaks on failed module initialisation in `_pickle`

- gh-83004: Clean up refleak on failed module initialisation in `_io`.

- gh-98897: Fix memory leak in `math.dist()` when both points don’t have the same dimension. Patch by Kumar Aditya.

- gh-98878: Use the frame bound builtins when offering a name suggestion in `traceback` to prevent crashing when `__builtins__` is not a dict.

- gh-98139: In `importlib._bootstrap`, enhance namespace package repr to `<module 'x' (namespace) from ['path']>`.

- gh-90352: Fix `_SelectorDatagramTransport` to inherit from `DatagramTransport` in `asyncio`. Patch by Kumar Aditya.

- gh-98793: Fix argument typechecks in `_overlapped.WSAConnect()` and `_overlapped.Overlapped.WSASendTo()` functions.

- gh-98744: Prevent crashing in `traceback` when retrieving the byte-offset for some source files that contain certain unicode characters.

- gh-98740: Fix internal error in the `re` module which in very rare circumstances prevented compilation of a regular expression containing a conditional expression without the “else” branch.

- gh-98703: Fix `asyncio.StreamWriter.drain()` to call `protocol.connection_lost` callback only once on Windows.

- gh-98624: Add a mutex to unittest.mock.NonCallableMock to protect concurrent access to mock attributes.

- gh-98658: The `array.array` class now supports subscripting, making it a generic type.

- gh-98284: Improved `TypeError` message for undefined abstract methods of a `abc.ABC` instance. The names of the missing methods are surrounded by single-quotes to highlight them.

- gh-96151: Allow `BUILTINS` to be a valid field name for frozen dataclasses.

- gh-98086: Make sure `patch.dict()` can be applied on async functions.

- gh-72719: Remove modules `asyncore` and `asynchat`, which were deprecated by PEP 594.

- gh-96192: Fix handling of `bytes` path-like objects in `os.ismount()`.

- gh-94172: `ftplib`: Remove the `FTP_TLS.ssl_version` class attribute: use the context parameter instead. Patch by Victor Stinner

- gh-94172: Remove the keyfile and certfile parameters from the `ftplib`, `imaplib`, `poplib` and `smtplib` modules, and the key_file, cert_file and check_hostname parameters from the `http.client` module, all deprecated since Python 3.6. Use the context parameter (ssl_context in `imaplib`) instead. Patch by Victor Stinner.

- gh-83638: Add the `autocommit` attribute to `sqlite3.Connection` and the autocommit parameter to `sqlite3.connect()` to control PEP 249-compliant transaction handling. Patch by Erlend E. Aasland.

- gh-92452: Fixed a race condition that could cause `sysconfig.get_config_var()` to incorrectly return `None` in multi-threaded programs.

- gh-91803: Fix an error when using a method of objects mocked with `unittest.mock.create_autospec()` after it was sealed with `unittest.mock.seal()` function.

- bpo-38523: `shutil.copytree()` now applies the ignore_dangling_symlinks argument recursively.

- bpo-40358: Add walk_up argument in `pathlib.PurePath.relative_to()`.

- bpo-36267: Fix IndexError in `argparse.ArgumentParser` when a `store_true` action is given an explicit argument.

### Documentation

- gh-98832: Changes wording of docstring for `pathlib.Path.iterdir()`.

- gh-97966: Update uname docs to clarify the special nature of the platform attribute and to indicate when it became late-bound.

### Tests

- gh-98903: The Python test suite now fails with exit code 4 if no tests ran. It should help detecting typos in test names and test methods.

- gh-98713: Fix a bug in the `typing` tests where a test relying on CPython-specific implementation details was not decorated with `@cpython_only` and was not skipped on other implementations.

- gh-87390: Add tests for star-unpacking with PEP 646, and some other miscellaneous PEP 646 tests.

- gh-96853: Added explicit coverage of `Py_Initialize` (and hence `Py_InitializeEx`) back to the embedding tests (all other embedding tests migrated to `Py_InitializeFromConfig` in Python 3.11)

- bpo-34272: Some C API tests were moved into the new Lib/test/test_capi/ directory.

### Build

- gh-99086: Fix `-Wimplicit-int` compiler warning in configure check for `PTHREAD_SCOPE_SYSTEM`.

- gh-99016: Fix build with `PYTHON_FOR_REGEN=python3.8`.

- gh-97731: Specify the full path to the source location for `make docclean` (needed for cross-builds).

- gh-98949: Drop unused build dependency on `readelf`.

- gh-98989: Use `python3.11`, if available, for regeneration and freezing.

- gh-98831: Add new tooling, in `Tools/cases_generator`, to generate the interpreter switch statement from a list of opcode definitions. This only affects adding, modifying or removing instruction definitions. The instruction definitions now live in `Python/bytecodes.c`, in the form of a custom DSL (under development). The tooling reads this file and writes `Python/generated_cases.c.h`, which is then included by `Python/ceval.c` to provide most of the cases of the main interpreter switch.

- gh-98817: Remove PCbuild/lib.pyproj: it’s not used for anything, is only a minor convenience for Visual Studio users (who probably mostly don’t even know about it), and it takes a lot of maintenance effort to keep updated.

- gh-98776: Fix `make regen-test-levenshtein` for out-of-tree builds.

- gh-98707: Don’t use vendored `libmpdec` headers if `--with-system-libmpdec` is passed to configure. Don’t use vendored `libexpat` headers if `--with-system-expat` is passed to configure.

### Windows

- gh-98689: Update Windows builds to zlib v1.2.13. v1.2.12 has CVE 2022-37434, but the vulnerable `inflateGetHeader` API is not used by Python.

- gh-98790: Assumes that a missing `DLLs` directory means that standard extension modules are in the executable’s directory.

- gh-98745: Update `py.exe` launcher to install 3.11 by default and 3.12 on request.

- gh-98692: Fix the Python Launcher for Windows ignoring unrecognized shebang lines instead of treating them as local paths

- gh-94328: Update Windows installer to use SQLite 3.39.4.

### macOS

- gh-94328: Update macOS installer to SQLite 3.39.4.

### C API

- gh-98724: The `Py_CLEAR`, `Py_SETREF` and `Py_XSETREF` macros now only evaluate their argument once. If the argument has side effects, these side effects are no longer duplicated. Patch by Victor Stinner.

- gh-98978: Fix use-after-free in `Py_SetPythonHome(NULL)`, `Py_SetProgramName(NULL)` and `_Py_SetProgramFullPath(NULL)` function calls. Issue reported by Benedikt Reinartz. Patch by Victor Stinner.

- gh-98410: Add `getbufferproc` and `releasebufferproc` to the stable API.

- gh-98610: Some configurable capabilities of sub-interpreters have changed. They always allow subprocesses (`subprocess`) now, whereas before subprocesses could be optionally disallowed for a sub-interpreter. Instead `os.exec()` can now be disallowed. Disallowing daemon threads is now supported. Disallowing all threads is still allowed, but is never done by default. Note that the optional restrictions are only available through `_Py_NewInterpreterFromConfig()`, which isn’t a public API. They do not affect the main interpreter, nor `Py_NewInterpreter()`.

- gh-98608: A `_PyInterpreterConfig` has been added and `_Py_NewInterpreter()` has been renamed to `_Py_NewInterpreterFromConfig()`. The “isolated_subinterpreters” argument is now a granular config that captures the previous behavior. Note that this is all “private” API.

- gh-96853: `Py_InitializeEx` now correctly calls `PyConfig_Clear` after initializing the interpreter (the omission didn’t cause a memory leak only because none of the dynamically allocated config fields are populated by the wrapper function)

- gh-91248: Add `PyFrame_GetVar()` and `PyFrame_GetVarString()` functions to get a frame variable by its name. Patch by Victor Stinner.

## Python 3.12.0 alpha 1

Release date: 2022-10-25

### Security

- gh-97616: Fix multiplying a list by an integer (`list *= int`): detect the integer overflow when the new allocated length is close to the maximum size. Issue reported by Jordan Limor. Patch by Victor Stinner.

- gh-97514: On Linux the `multiprocessing` module returns to using filesystem backed unix domain sockets for communication with the forkserver process instead of the Linux abstract socket namespace. Only code that chooses to use the “forkserver” start method is affected.

  Abstract sockets have no permissions and could allow any user on the system in the same network namespace (often the whole system) to inject code into the multiprocessing forkserver process. This was a potential privilege escalation. Filesystem based socket permissions restrict this to the forkserver process user as was the default in Python 3.8 and earlier.

  This prevents Linux CVE 2022-42919.

- gh-87389: `http.server`: Fix an open redirection vulnerability in the HTTP server when an URI path starts with `//`. Vulnerability discovered, and initial fix proposed, by Hamza Avvan.

- gh-79096: LWPCookieJar and MozillaCookieJar create files with file mode 600 instead of 644 (Microsoft Windows is not affected)

- gh-92888: Fix `memoryview` use after free when accessing the backing buffer in certain cases.

- gh-68966: The deprecated mailcap module now refuses to inject unsafe text (filenames, MIME types, parameters) into shell commands. Instead of using such text, it will warn and act as if a match was not found (or for test commands, as if the test failed).

### Core and Builtins

- gh-98374: Suppress ImportError for invalid query for help() command. Patch by Donghee Na.

- gh-98461: Fix source location in bytecode for list, set and dict comprehensions as well as generator expressions.

- gh-98354: Added unicode check for `name` attribute of `spec` argument passed in `_imp.create_builtin()` function.

- gh-98398: Fix source location of ‘assert’ bytecodes.

- gh-98390: Fix location of sub-expressions of boolean expressions, by reducing their scope to that of the sub-expression.

- gh-98254: Modules from the standard library are now potentially suggested as part of the error messages displayed by the interpreter when an `NameError` is raised to the top level. Patch by Pablo Galindo

- gh-97997: Add running column offset to the tokenizer state to avoid calculating AST column information with pointer arithmetic.

- gh-97973: Modify the tokenizer to return all necessary information the parser needs to set location information in the AST nodes, so that the parser does not have to calculate those doing pointer arithmetic.

- gh-96078: `os.sched_yield()` now release the GIL while calling sched_yield(2). Patch by Donghee Na.

- gh-97955: Migrate `zoneinfo` to Argument Clinic.

- gh-97912: The compiler now avoids quadratic behavior when finding which instructions should use the `LOAD_FAST_CHECK` opcode.

- gh-97002: Fix an issue where several frame objects could be backed by the same interpreter frame, possibly leading to corrupted memory and hard crashes of the interpreter.

- gh-97943: Bugfix: `PyFunction_GetAnnotations()` should return a borrowed reference. It was returning a new reference.

- gh-97922: The Garbage Collector now runs only on the eval breaker mechanism of the Python bytecode evaluation loop instead on object allocations. The GC can also run when `PyErr_CheckSignals()` is called so C extensions that need to run for a long time without executing any Python code also have a chance to execute the GC periodically.

- gh-65961: When `__package__` is different than `__spec__.parent`, raise a `DeprecationWarning` instead of `ImportWarning`.

  Also remove `importlib.util.set_package()` which was scheduled for removal.

- gh-97850: Long deprecated, `module_repr()` should now be completely eradicated.

- gh-86298: In cases where `warnings.warn_explicit()` consults the module’s loader, an `DeprecationWarning` is issued when `m.__loader__` differs from `m.__spec__.loader`.

- gh-97779: Ensure that all Python frame objects are backed by “complete” frames.

- gh-91052: Add API for subscribing to modification events on selected dictionaries.

- gh-97752: Fix possible data corruption or crashes when accessing the `f_back` member of newly-created generator or coroutine frames.

- gh-97591: Fixed a missing incref/decref pair in `Exception.__setstate__()`. Patch by Ofey Chan.

- gh-97670: Remove the `sys.getdxp()` function and the `Tools/scripts/analyze_dxp.py` script. DXP stands for “dynamic execution pairs”. They were related to `DYNAMIC_EXECUTION_PROFILE` and `DXPAIRS` macros which have been removed in Python 3.11. Python can now be built with `./configure --enable-pystats` to gather statistics on Python opcodes. Patch by Victor Stinner.

- gh-94526: Fix the Python path configuration used to initialized `sys.path` at Python startup. Paths are no longer encoded to UTF-8/strict to avoid encoding errors if it contains surrogate characters (bytes paths are decoded with the surrogateescape error handler). Patch by Victor Stinner.

- gh-96670: The parser now raises `SyntaxError` when parsing source code containing null bytes. Patch by Pablo Galindo

- gh-96975: Fix a crash occurring when `PyEval_GetFrame()` is called while the topmost Python frame is in a partially-initialized state.

- gh-96848: Fix command line parsing: reject `-X int_max_str_digits` option with no value (invalid) when the `PYTHONINTMAXSTRDIGITS` environment variable is set to a valid limit. Patch by Victor Stinner.

- gh-95921: Fix overly-broad source position information for chained comparisons used as branching conditions.

- gh-96821: Fix undefined behaviour in `audioop.c`.

- gh-96821: Fix undefined behaviour in `_testcapimodule.c`.

- gh-95778: When `ValueError` is raised if an integer is larger than the limit, mention the `sys.set_int_max_str_digits()` function in the error message. Patch by Victor Stinner.

- gh-96387: At Python exit, sometimes a thread holding the GIL can wait forever for a thread (usually a daemon thread) which requested to drop the GIL, whereas the thread already exited. To fix the race condition, the thread which requested the GIL drop now resets its request before exiting. Issue discovered and analyzed by Mingliang ZHAO. Patch by Victor Stinner.

- gh-96864: Fix a possible assertion failure, fatal error, or `SystemError` if a line tracing event raises an exception while opcode tracing is enabled.

- gh-95778: The `PyLong_FromString` function was refactored to make it more maintainable and extensible.

- gh-96678: Fix undefined behaviour in C code of null pointer arithmetic.

- gh-96754: Make sure that all frame objects created are created from valid interpreter frames. Prevents the possibility of invalid frames in backtraces and signal handlers.

- gh-90997: Improve the performance of reading and writing inline bytecode caches on some platforms.

- gh-96751: Remove dead code from `CALL_FUNCTION_EX` opcode.

- gh-90751: `memoryview` now supports half-floats. Patch by Donghee Na and Antoine Pitrou.

- gh-96678: Fix case of undefined behavior in ceval.c

- gh-64373: Convert `_functools` to argument clinic.

- gh-96641: Do not expose `KeyWrapper` in `_functools`.

- gh-96636: Ensure that tracing, `sys.setrace()`, is turned on immediately. In pre-release versions of 3.11, some tracing events might have been lost when turning on tracing in a `__del__` method or interrupt.

- gh-96572: Fix use after free in trace refs build mode. Patch by Kumar Aditya.

- gh-96611: When loading a file with invalid UTF-8 inside a multi-line string, a correct SyntaxError is emitted.

- gh-96612: Make sure that incomplete frames do not show up in tracemalloc traces.

- gh-90230: Fix compiler warnings and test failures when building with `--enable-pystats`.

- gh-96587: Correctly raise `SyntaxError` on exception groups (PEP 654) on python versions prior to 3.11

- gh-96569: Remove two cases of undefined behavior, by adding NULL checks.

- gh-96582: Fix possible `NULL` pointer dereference in `_PyThread_CurrentFrames`. Patch by Kumar Aditya.

- gh-91079: Separate Python recursion checking from C recursion checking which reduces the chance of C stack overflow and allows the recursion limit to be increased safely.

- gh-93911: Fix an issue that could prevent `LOAD_ATTR` from specializing properly when accessing properties.

- gh-96348: Emit a DeprecationWarning when `throw()`, `throw()` or `athrow()` are called with more than one argument.

- gh-95196: Disable incorrect pickling of the C implemented classmethod descriptors.

- gh-96364: Fix text signatures of `list.__getitem__` and `dict.__getitem__`.

- gh-96352: Fix `AttributeError` missing `name` and `obj` attributes in `object.__getattribute__()`. Patch by Philip Georgi.

- gh-93554: Change the jump opcodes so that all conditional jumps are forward jumps. Backward jumps are converted by the assembler into a conditional forward jump whose target is the fallthrough block (and with a reversed condition), followed by an unconditional backward jump. For example:

  `POP_JUMP_IF_TRUE BACKWARD_TARGET` becomes `POP_JUMP_IF_FALSE NEXT_BLOCK; JUMP BACKWARD_TARGET`.

  All the directed conditional jump opcodes were removed: `POP_JUMP_FORWARD_IF_TRUE`, `POP_JUMP_BACKWARD_IF_TRUE`, `POP_JUMP_FORWARD_IF_FALSE`, `POP_JUMP_BACKWARD_IF_FALSE`, `POP_JUMP_FORWARD_IF_NONE`, `POP_JUMP_BACKWARD_IF_NONE`, `POP_JUMP_FORWARD_IF_NOT_NONE`, `POP_JUMP_BACKWARD_IF_NOT_NONE`.

  The corresponding opcodes without direction are no longer pseudo-instructions, and they implement the forward conditional jumps.

- gh-96268: Loading a file with invalid UTF-8 will now report the broken character at the correct location.

- gh-96237: The internal field `_PyInterpreterFrame.f_func` is renamed to `_PyInterpreterFrame.f_funcobj` and may be any object. The `f_globals` and `f_builtin` fields may hold junk values.

  It is safest to treat the `_PyInterpreterFrame` struct as opaque.

- gh-96187: Fixed a bug that caused `_PyCode_GetExtra` to return garbage for negative indexes. Patch by Pablo Galindo

- gh-96143: Add a new `-X perf` Python command line option as well as `sys.activate_stack_trampoline()` and `sys.deactivate_stack_trampoline()` function in the `sys` module that allows to set/unset the interpreter in a way that the Linux `perf` profiler can detect Python calls. The new `sys.is_stack_trampoline_active()` function allows to query the state of the perf trampoline. Design by Pablo Galindo. Patch by Pablo Galindo and Christian Heimes with contributions from Gregory P. Smith [Google] and Mark Shannon.

- gh-96071: Fix a deadlock in `PyGILState_Ensure()` when allocating new thread state. Patch by Kumar Aditya.

- gh-96046: `PyType_Ready()` now initializes `ht_cached_keys` and performs additional checks to ensure that type objects are properly configured. This avoids crashes in 3rd party packages that don’t use regular API to create new types.

- gh-96005: On WASI `ENOTCAPABLE` is now mapped to `PermissionError`. The `errno` modules exposes the new error number. `getpath.py` now ignores `PermissionError` when it cannot open landmark files `pybuilddir.txt` and `pyenv.cfg`.

- gh-93678: Added test a harness for direct unit tests of the compiler’s optimization stage. The `_testinternalcapi.optimize_cfg()` function runs the optimiser on a sequence of instructions. The `CfgOptimizationTestCase` class in `test.support` has utilities for invoking the optimizer and checking the output.

- gh-95245: Reduces the size of a “simple” Python object from 8 to 6 words by moving the weakreflist pointer into the pre-header directly before the object’s dict/values pointer.

- gh-90997: Compile virtual `try`/`except` blocks to handle exceptions raised during `close()` or `throw()` calls through a suspended frame.

- gh-95977: Optimized calling `__get__()` with vectorcall. Patch by Kumar Aditya.

- gh-91210: Improve error message when a parameter without a default value follows one with a default value, and show the same message, even when the non-default/default sequence is preceded by positional-only parameters.

- gh-95922: Fixed bug where the compiler’s `eliminate_empty_basic_blocks` function ignores the last block of the code unit.

- gh-95818: Skip over incomplete frames in `PyThreadState_GetFrame()`.

- gh-95876: Fix format string in `_PyPegen_raise_error_known_location` that can lead to memory corruption on some 64bit systems. The function was building a tuple with `i` (int) instead of `n` (Py_ssize_t) for Py_ssize_t arguments.

- gh-95605: Fix misleading contents of error message when converting an all-whitespace string to `float`.

- gh-95150: Update code object hashing and equality to consider all debugging and exception handling tables. This fixes an issue where certain non-identical code objects could be “deduplicated” during compilation.

- gh-91146: Reduce allocation size of `list` from `str.split()` and `str.rsplit()`. Patch by Donghee Na and Inada Naoki.

- gh-87092: Create a ‘jump target label’ abstraction in the compiler so that the compiler’s codegen stage does not work directly with basic blocks. This prepares the code for changes to the underlying CFG generation mechanism.

- gh-95355: `_PyPegen_Parser_New` now properly detects token memory allocation errors. Patch by Honglin Zhu.

- gh-90081: Run Python code in tracer/profiler function at full speed. Fixes slowdown in earlier versions of 3.11.

- gh-95324: Emit a warning in debug mode if an object does not call `PyObject_GC_UnTrack()` before deallocation. Patch by Pablo Galindo.

- gh-95245: Merge managed dict and values pointer into a single tagged pointer to save one word in the pre-header.

- gh-93678: Add cfg_builder struct and refactor the relevant code so that a cfg can be constructed without an instance of the compiler struct.

- gh-95185: Prevented crashes in the AST constructor when compiling some absurdly long expressions like `"+0"*1000000`. `RecursionError` is now raised instead. Patch by Pablo Galindo

- gh-93351: `ast.AST` node positions are now validated when provided to `compile()` and other related functions. If invalid positions are detected, a `ValueError` will be raised.

- gh-94438: Fix an issue that caused extended opcode arguments and some conditional pops to be ignored when calculating valid jump targets for assignments to the `f_lineno` attribute of frame objects. In some cases, this could cause inconsistent internal state, resulting in a hard crash of the interpreter.

- gh-95060: Undocumented `PyCode_Addr2Location` function now properly returns when `addrq` argument is less than zero.

- gh-95113: Replace all `EXTENDED_ARG_QUICK` instructions with basic `EXTENDED_ARG` instructions in unquickened code. Consumers of non-adaptive bytecode should be able to handle extended arguments the same way they were handled in CPython 3.10 and older.

- gh-91409: Fix incorrect source location info caused by certain optimizations in the bytecode compiler.

- gh-95023: Implement `os.setns()` and `os.unshare()` for Linux. Patch by Noam Cohen.

- gh-94036: Fix incorrect source location info for some multi-line attribute accesses and method calls.

- gh-94938: Fix error detection in some builtin functions when keyword argument name is an instance of a str subclass with overloaded `__eq__` and `__hash__`. Previously it could cause SystemError or other undesired behavior.

- gh-94996: `ast.parse()` will no longer parse function definitions with positional-only params when passed `feature_version` less than `(3, 8)`. Patch by Shantanu Jain.

- gh-94739: Allow jumping within, out of, and across exception handlers in the debugger.

- gh-94949: `ast.parse()` will no longer parse parenthesized context managers when passed `feature_version` less than `(3, 9)`. Patch by Shantanu Jain.

- gh-94947: `ast.parse()` will no longer parse assignment expressions when passed `feature_version` less than `(3, 8)`. Patch by Shantanu Jain.

- gh-91256: Ensures the program name is known for help text during interpreter startup.

- gh-94869: Fix the column offsets for some expressions in multi-line f-strings `ast` nodes. Patch by Pablo Galindo.

- gh-94893: Fix an issue where frame object manipulations could corrupt inline bytecode caches.

- gh-94822: Fix an issue where lookups of metaclass descriptors may be ignored when an identically-named attribute also exists on the class itself.

- gh-91153: Fix an issue where a `bytearray` item assignment could crash if it’s resized by the new value’s `__index__()` method.

- gh-90699: Fix reference counting bug in `bool.__repr__()`. Patch by Kumar Aditya.

- gh-94694: Fix an issue that could cause code with multi-line method lookups to have misleading or incorrect column offset information. In some cases (when compiling a hand-built AST) this could have resulted in a hard crash of the interpreter.

- gh-93252: Fix an issue that caused internal frames to outlive failed Python function calls, possibly resulting in memory leaks or hard interpreter crashes.

- gh-94215: Fix an issue where exceptions raised by line-tracing events would cause frames to be left in an invalid state, possibly resulting in a hard crash of the interpreter.

- gh-92228: Disable the compiler’s inline-small-exit-blocks optimization for exit blocks that are associated with source code lines. This fixes a bug where the debugger cannot tell where an exception handler ends and the following code block begins.

- gh-94485: Line number of a module’s `RESUME` instruction is set to 0 as specified in PEP 626.

- gh-94438: Account for instructions that can push NULL to the stack when setting line number in a frame. Prevents some (unlikely) crashes.

- gh-91719: Reload `opcode` when raising `unknown opcode error` in the interpreter main loop, for C compilers to generate dispatching code independently.

- gh-94329: Compile and run code with unpacking of extremely large sequences (1000s of elements). Such code failed to compile. It now compiles and runs correctly.

- gh-94360: Fixed a tokenizer crash when reading encoded files with syntax errors from `stdin` with non utf-8 encoded text. Patch by Pablo Galindo

- gh-88116: Fix an issue when reading line numbers from code objects if the encoded line numbers are close to `INT_MIN`. Patch by Pablo Galindo

- gh-94262: Don’t create frame objects for incomplete frames. Prevents the creation of generators and closures from being observable to Python and C extensions, restoring the behavior of 3.10 and earlier.

- gh-94192: Fix error for dictionary literals with invalid expression as value.

- gh-87995: `types.MappingProxyType` instances are now hashable if the underlying mapping is hashable.

- gh-93883: Revise the display strategy of traceback enhanced error locations. The indicators are only shown when the location doesn’t span the whole line.

- gh-94163: Add `BINARY_SLICE` and `STORE_SLICE` instructions for more efficient handling and better specialization of slicing operations, where the slice is explicit in the source code.

- gh-94021: Fix unreachable code warning in `Python/specialize.c`.

- gh-93911: Specialize `LOAD_ATTR` for objects with custom `__getattribute__`.

- gh-93955: Improve performance of attribute lookups on objects with custom `__getattribute__` and `__getattr__`. Patch by Ken Jin.

- gh-93911: Specialize `LOAD_ATTR` for `property()` attributes.

- gh-93678: Refactor compiler optimisation code so that it no longer needs the `struct assembler` and `struct compiler` passed around. Instead, each function takes the CFG and other data that it actually needs. This will make it possible to test this code directly.

- gh-93841: When built with `-enable-pystats`, `sys._stats_on()`, `sys._stats_off()`, `sys._stats_clear()` and `sys._stats_dump()` functions have been added to enable gathering stats for parts of programs.

- gh-93516: Store offset of first traceable instruction in code object to avoid having to recompute it for each instruction when tracing.

- gh-93516: Lazily create a table mapping bytecode offsets to line numbers to speed up calculation of line numbers when tracing.

- gh-89828: `types.GenericAlias` no longer relays the `__class__` attribute. For example, `isinstance(list[int], type)` no longer returns `True`.

- gh-93678: Refactor the compiler to reduce boilerplate and repetition.

- gh-93671: Fix some exponential backtrace case happening with deeply nested sequence patterns in match statements. Patch by Pablo Galindo

- gh-93662: Make sure that the end column offsets are correct in multi-line method calls. Previously, the end column could precede the column offset.

- gh-93461: `importlib.invalidate_caches()` now drops entries from `sys.path_importer_cache` with a relative path as name. This solves a caching issue when a process changes its current working directory.

  `FileFinder` no longer inserts a dot in the path, e.g. `/egg/./spam` is now `/egg/spam`.

- gh-93621: Change order of bytecode instructions emitted for `with` and `async with` to reduce the number of entries in the exception table.

- gh-93533: Reduce the size of the inline cache for `LOAD_METHOD` by 2 bytes.

- gh-93444: Removed redundant fields from the compiler’s basicblock struct: `b_nofallthrough`, `b_exit`, `b_return`. They can be easily calculated from the opcode of the last instruction of the block.

- gh-93429: `LOAD_METHOD` instruction has been removed. It was merged back into `LOAD_ATTR`.

- gh-93418: Fixed an assert where an f-string has an equal sign ‘=’ following an expression, but there’s no trailing brace. For example, f”{i=”.

- gh-93382: Cache the result of `PyCode_GetCode()` function to restore the O(1) lookup of the `co_code` attribute.

- gh-93359: Ensure that custom `ast` nodes without explicit end positions can be compiled. Patch by Pablo Galindo.

- gh-93356: Code for exception handlers is emitted at the end of the code unit’s bytecode. This avoids one jump when no exception is raised.

- gh-93354: Use exponential backoff for specialization counters in the interpreter. Can reduce the number of failed specializations significantly and avoid slowdown for those parts of a program that are not suitable for specialization.

- gh-93283: Improve error message for invalid syntax of conversion character in f-string expressions.

- gh-93345: Fix a crash in substitution of a `TypeVar` in nested generic alias after `TypeVarTuple`.

- gh-93223: When a bytecode instruction jumps to an unconditional jump instruction, the first instruction can often be optimized to target the unconditional jump’s target directly. For tracing reasons, this would previously only occur if both instructions have the same line number. This also now occurs if the unconditional jump is artificial, i.e., if it has no associated line number.

- gh-84694: The `--experimental-isolated-subinterpreters` configure option and `EXPERIMENTAL_ISOLATED_SUBINTERPRETERS` macro have been removed.

- gh-91924: Fix `__lltrace__` debug feature if the stdout encoding is not UTF-8. Patch by Victor Stinner.

- gh-93040: Wraps unused parameters in `Objects/obmalloc.c` with `Py_UNUSED`.

- gh-93143: Avoid `NULL` checks for uninitialized local variables by determining at compile time which variables must be initialized.

- gh-93061: Backward jumps after `async for` loops are no longer given dubious line numbers.

- gh-93065: Fix contextvars HAMT implementation to handle iteration over deep trees.

  The bug was discovered and fixed by Eli Libman. See MagicStack/immutables#84 for more details.

- gh-93012: Added the new function `PyType_FromMetaclass()`, which generalizes the existing `PyType_FromModuleAndSpec()` using an additional metaclass argument. This is useful for language binding tools, where it can be used to intercept type-related operations like subclassing or static attribute access by specifying a metaclass with custom slots.

  Importantly, `PyType_FromMetaclass()` is available in the Limited API, which provides a path towards migrating more binding tools onto the Stable ABI.

- gh-93021: Fix the `__text_signature__` for `__get__()` methods implemented in C. Patch by Jelle Zijlstra.

- gh-89914: The operand of the `YIELD_VALUE` instruction is set to the stack depth. This is done to help frame handling on `yield` and may assist debuggers.

- gh-92955: Fix memory leak in code object’s lines and positions iterators as they were not finalized at exit. Patch by Kumar Aditya.

- gh-92930: Fixed a crash in `_pickle.c` from mutating collections during `__reduce__` or `persistent_id`.

- gh-90690: The PRECALL instruction has been removed. It offered only a small advantage for specialization and is not needed in the vast majority of cases.

- gh-92914: Always round the allocated size for lists up to the nearest even number.

- gh-92858: Improve error message for some suites with syntax error before ‘:’

- gh-90473: Decrease default recursion limit on WASI to address limited call stack size.

- gh-92804: Fix memory leak in `memoryview` iterator as it was not finalized at exit. Patch by Kumar Aditya.

- gh-92777: Specialize `LOAD_METHOD` for objects with lazy dictionaries. Patch by Ken Jin.

- gh-92658: Add support for connecting and binding to Hyper-V sockets on Windows Hyper-V hosts and guests.

- gh-92236: Remove spurious “LINE” event when starting a generator or coroutine, visible tracing functions implemented in C.

- gh-91102: `_warnings.warn_explicit()` is ported to Argument Clinic.

- gh-92619: Make the compiler duplicate an exit block only if none of its instructions have a lineno (previously only the first instruction in the block was checked, leading to unnecessarily duplicated blocks).

- gh-88750: The deprecated debug build only `PYTHONTHREADDEBUG` environment variable no longer does anything.

- gh-92261: Fix hang when trying to iterate over a `typing.Union`.

- gh-91432: Specialized the `FOR_ITER` opcode using the PEP 659 machinery

- gh-91399: Removed duplicate ‘{0, 0, 0, 0, 0, 0}’ entry in ‘Objects/unicodetype_db.h’.

- gh-91578: Updates the error message for abstract class.

- bpo-47091: Improve performance of repetition of `list` and `tuple` by using `memcpy` to copy data and performing the reference increments in one step.

- bpo-46142: Make `--help` output shorter by moving some info to the new `--help-env` and `--help-xoptions` command-line options. Also add `--help-all` option to print complete usage.

- bpo-42316: Document some places where an assignment expression needs parentheses.

### Library

- gh-89237: Fix hang on Windows in `subprocess.wait_closed()` in `asyncio` with `ProactorEventLoop`. Patch by Kumar Aditya.

- gh-97928: `tkinter.Text.count()` raises now an exception for options starting with “-” instead of silently ignoring them.

- gh-98393: The `os` module no longer accepts bytes-like paths, like `bytearray` and `memoryview` types: only the exact `bytes` type is accepted for bytes strings. Patch by Victor Stinner.

- gh-98363: Added itertools.batched() to batch data into lists of a given length with the last list possibly being shorter than the others.

- gh-98331: Update the bundled copies of pip and setuptools to versions 22.3 and 65.5.0 respectively.

- gh-98307: A `createSocket()` method was added to `SysLogHandler`.

- gh-96035: Fix bug in `urllib.parse.urlparse()` that causes certain port numbers containing whitespace, underscores, plus and minus signs, or non-ASCII digits to be incorrectly accepted.

- gh-98257: Make `sys.setprofile()` and `sys.settrace()` functions reentrant. They can no long fail with: `RuntimeError("Cannot install a trace function while another trace function is being installed")`. Patch by Victor Stinner.

- gh-98251: Allow `venv` to pass along `PYTHON*` variables to `ensurepip` and `pip` when they do not impact path resolution

- gh-94597: Deprecated `asyncio.AbstractEventLoopPolicy.get_child_watcher()` and `asyncio.AbstractEventLoopPolicy.set_child_watcher()` methods to be removed in Python 3.14. Patch by Kumar Aditya.

- gh-98178: On macOS, fix a crash in `syslog.syslog()` in multi-threaded applications. On macOS, the libc `syslog()` function is not thread-safe, so `syslog.syslog()` no longer releases the GIL to call it. Patch by Victor Stinner.

- gh-44098: Release the GIL when creating `mmap.mmap` objects on Unix.

- gh-87730: Wrap network errors consistently in urllib FTP support, so the test suite doesn’t fail when a network is available but the public internet is not reachable.

- gh-94597: The child watcher classes `MultiLoopChildWatcher`, `FastChildWatcher` and `SafeChildWatcher` are deprecated and will be removed in Python 3.14. Patch by Kumar Aditya.

- gh-98023: Change default child watcher to `PidfdChildWatcher` on Linux systems which supports it. Patch by Kumar Aditya.

- gh-90985: Earlier in 3.11 we deprecated `asyncio.Task.cancel("message")`. We realized we were too harsh, and have undeprecated it.

- gh-65961: Do not rely solely on `__cached__` on modules; code will also support `__spec__.cached`.

- gh-97646: Replace deprecated `application/javascript` with `text/javascript` in `mimetypes`. See RFC 9239. Patch by Noam Cohen.

- gh-97930: Apply changes from importlib_resources 5.8 and 5.9: `Traversable.joinpath` provides a concrete implementation. `as_file` now supports directories of resources.

- gh-97850: Remove deprecated `importlib.util.set_loader()` and `importlib.util.module_for_loader()` from `importlib.util`.

- gh-97837: Change deprecate warning message in `unittest` from

  `It is deprecated to return a value!=None`

  to

  `It is deprecated to return a value that is not None from a test case`

- gh-97825: Fixes `AttributeError` when `subprocess.check_output()` is used with argument `input=None` and either of the arguments encoding or errors are used.

- gh-97008: `NameError` and `AttributeError` spelling suggestions provided since gh-82711 are now also emitted by the pure Python `traceback` module. Tests for those suggestions now exercise both implementations to ensure they are equivalent. Patch by Carl Friedrich Bolz-Tereick and Łukasz Langa.

- gh-97799: `dataclass` now uses `inspect.get_annotations()` to examine the annotations on class objects.

- gh-97781: Removed deprecated interfaces in `importlib.metadata` (entry points accessed as dictionary, implicit dictionary construction of sequence of `EntryPoint` objects, mutablility of `EntryPoints` result, access of entry point by index). `entry_points` now has a simpler, more straightforward API (returning `EntryPoints`).

- gh-96827: Avoid spurious tracebacks from `asyncio` when default executor cleanup is delayed until after the event loop is closed (e.g. as the result of a keyboard interrupt).

- gh-95534: `gzip.GzipFile.read()` reads 10% faster.

- gh-97592: Avoid a crash in the C version of `asyncio.Future.remove_done_callback()` when an evil argument is passed.

- gh-97639: Remove `tokenize.NL` check from `tabnanny`.

- gh-97545: Make Semaphore run faster.

- gh-73588: Fix generation of the default name of `tkinter.Checkbutton`. Previously, checkbuttons in different parent widgets could have the same short name and share the same state if arguments “name” and “variable” are not specified. Now they are globally unique.

- gh-96865: fix Flag to use boundary CONFORM

  This restores previous Flag behavior of allowing flags with non-sequential values to be combined; e.g.

  class Skip(Flag): TWO = 2 EIGHT = 8

  Skip.TWO | Skip.EIGHT -> <Skip.TWO|EIGHT: 10>

- gh-97005: Update bundled libexpat to 2.4.9

- gh-85760: Fix race condition in `asyncio` where `process_exited()` called before the `pipe_data_received()` leading to inconsistent output. Patch by Kumar Aditya.

- gh-96704: Pass the correct `contextvars.Context` when a `asyncio` exception handler is called on behalf of a task or callback handle. This adds a new `Task` method, `get_context`, and also a new `Handle` method with the same name. If this method is not found on a task object (perhaps because it is a third-party library that does not yet provide this method), the context prevailing at the time the exception handler is called is used.

- gh-96819: Fixed check in `multiprocessing.resource_tracker` that guarantees that the length of a write to a pipe is not greater than `PIPE_BUF`.

- gh-95865: Reduce `urllib.parse.quote_from_bytes()` memory use on large values.

  Contributed by Dennis Sweeney.

- gh-96741: Corrected type annotation for dataclass attribute `pstats.FunctionProfile.ncalls` to be `str`.

- gh-96734: Update `unicodedata` database to Unicode 15.0.0.

- gh-96735: Fix undefined behaviour in `struct.unpack()`.

- gh-46412: Improve performance of `bool(db)` for large ndb/gdb databases. Previously this would call `len(db)` which would iterate over all keys – the answer (empty or not) is known after the first key.

- gh-96652: Fix the faulthandler implementation of `faulthandler.register(signal, chain=True)` if the `sigaction()` function is not available: don’t call the previous signal handler if it’s NULL. Patch by Victor Stinner.

- gh-68163: Correct conversion of `numbers.Rational`’s to `float`.

- gh-96538: Speed up `bisect.bisect()` functions by taking advantage of type-stability.

- gh-96465: Fraction hashes are now cached.

- gh-96079: In `typing`, fix missing field `name` and incorrect `__module__` in _AnnotatedAlias.

- gh-96415: Remove `types._cell_factory` from module namespace.

- gh-95987: Fix `repr` of `Any` subclasses.

- gh-96388: Work around missing socket functions in `socket`’s `__repr__`.

- gh-96385: Fix `TypeVarTuple.__typing_prepare_subst__`. `TypeError` was not raised when using more than one `TypeVarTuple`, like `[*T, *V]` in type alias substitutions.

- gh-96142: Add `match_args`, `kw_only`, `slots`, and `weakref_slot` to `_DataclassParams`.

- gh-96073: In `inspect`, fix overeager replacement of “`typing.`” in formatting annotations.

- gh-89258: Added a `getChildren()` method to `logging.Logger`, to get the immediate child loggers of a logger.

- gh-96346: Use double caching for compiled RE patterns.

- gh-96349: Fixed a minor performance regression in `threading.Event.__init__()`

- gh-90467: Fix `asyncio.streams.StreamReaderProtocol` to keep a strong reference to the created task, so that it’s not garbage collected

- gh-96172: Fix a bug in `unicodedata`: `east_asian_width` used to return the wrong value for unassigned characters; and for yet unassigned, but reserved characters.

- gh-96159: Fix a performance regression in logging TimedRotatingFileHandler. Only check for special files when the rollover time has passed.

- gh-96175: Fix unused `localName` parameter in the `Attr` class in `xml.dom.minidom`.

- gh-96145: Add AttrDict to JSON module for use with object_hook.

- gh-96052: Fix handling compiler warnings (SyntaxWarning and DeprecationWarning) in `codeop.compile_command()` when checking for incomplete input. Previously it emitted warnings and raised a SyntaxError. Now it always returns `None` for incomplete input without emitting any warnings.

- gh-96125: Fix incorrect condition that causes `sys.thread_info.name` to be wrong on pthread platforms.

- gh-96019: Fix a bug in the `makeunicodedata.py` script leading to about 13 KiB of space saving in the `unicodedata` module, specifically the character decomposition data.

- gh-95463: Remove an incompatible change from bpo-28080 that caused a regression that ignored the utf8 in `ZipInfo.flag_bits`. Patch by Pablo Galindo.

- gh-69142: Add `%:z` strftime format code (generates tzoffset with colons as separator), see strftime() and strptime() Behavior.

- gh-95899: Fix `asyncio.Runner` to call `asyncio.set_event_loop()` only once to avoid calling `attach_loop()` multiple times on child watchers. Patch by Kumar Aditya.

- gh-95736: Fix `unittest.IsolatedAsyncioTestCase` to set event loop before calling setup functions. Patch by Kumar Aditya.

- gh-95865: Speed up `urllib.parse.quote_from_bytes()` by replacing a list comprehension with `map()`.

- gh-95861: Add support for computing Spearman’s correlation coefficient to the existing statistics.correlation() function.

- gh-95804: Fix `logging` shutdown handler so it respects `MemoryHandler.flushOnClose`.

- gh-95704: When a task catches `asyncio.CancelledError` and raises some other error, the other error should generally not silently be suppressed.

- gh-95149: The `HTTPStatus` enum offers a couple of properties to indicate the HTTP status category e.g. `HTTPStatus.OK.is_success`.

- gh-95609: Update bundled pip to 22.2.2.

- gh-95289: Fix `asyncio.TaskGroup` to propagate exception when `asyncio.CancelledError` was replaced with another exception by a context manager. Patch by Kumar Aditya and Guido van Rossum.

- gh-94909: Fix incorrect joining of relative Windows paths with drives in `pathlib.PurePath` initializer.

- gh-95385: Faster `json.dumps()` when sorting of keys is not requested (default).

- gh-83901: Improve `Signature.bind` error message for missing keyword-only arguments.

- gh-95339: Update bundled pip to 22.2.1.

- gh-95045: Fix GC crash when deallocating `_lsprof.Profiler` by untracking it before calling any callbacks. Patch by Kumar Aditya.

- gh-95231: Fail gracefully if `EPERM` or `ENOSYS` is raised when loading `crypt` methods. This may happen when trying to load `MD5` on a Linux kernel with FIPS enabled.

- gh-95097: Fix `asyncio.run()` for `asyncio.Task` implementations without `uncancel()` method. Patch by Kumar Aditya.

- gh-95087: Fix IndexError in parsing invalid date in the `email` module.

- gh-95199: Upgrade bundled setuptools to 63.2.0.

- gh-95194: Upgrade bundled pip to 22.2.

- gh-93899: Fix check for existence of `os.EFD_CLOEXEC`, `os.EFD_NONBLOCK` and `os.EFD_SEMAPHORE` flags on older kernel versions where these flags are not present. Patch by Kumar Aditya.

- gh-95166: Fix `concurrent.futures.Executor.map()` to cancel the currently waiting on future on an error - e.g. TimeoutError or KeyboardInterrupt.

- gh-95132: Fix a `sqlite3` regression where `*args` and `**kwds` were incorrectly relayed from `connect()` to the `Connection` factory. The regression was introduced in 3.11a1 with PR 24421 (gh-85128). Patch by Erlend E. Aasland.

- gh-93157: Fix `fileinput` module didn’t support `errors` option when `inplace` is true.

- gh-91212: Fixed flickering of the turtle window when the tracer is turned off. Patch by Shin-myoung-serp.

- gh-95077: Add deprecation warning for enum `member.member` access (e.g. `Color.RED.BLUE`). Remove `EnumMeta.__getattr__`.

- gh-95109: Ensure that timeouts scheduled with `asyncio.Timeout` that have already expired are delivered promptly.

- gh-95105: `wsgiref.types.InputStream.__iter__()` should return `Iterator[bytes]`, not `Iterable[bytes]`. Patch by Shantanu Jain.

- gh-95066: Replaced assert with exception in `ast.parse()`, when `feature_version` has an invalid major version. Patch by Shantanu Jain.

- gh-77617: Add `sqlite3` command-line interface. Patch by Erlend Aasland.

- gh-95005: Replace _PyAccu with _PyUnicodeWriter in JSON encoder and StringIO and remove the _PyAccu implementation.

- gh-90085: Remove `-c/--clock` and `-t/--time` CLI options of `timeit`. The options had been deprecated since Python 3.3 and the functionality was removed in Python 3.7. Patch by Shantanu Jain.

- gh-94857: Fix refleak in `_io.TextIOWrapper.reconfigure`. Patch by Kumar Aditya.

- gh-94821: Fix binding of unix socket to empty address on Linux to use an available address from the abstract namespace, instead of “0”.

- gh-94736: Fix crash when deallocating an instance of a subclass of `_multiprocessing.SemLock`. Patch by Kumar Aditya.

- gh-81620: Add random.binomialvariate().

- gh-74116: Allow `asyncio.StreamWriter.drain()` to be awaited concurrently by multiple tasks. Patch by Kumar Aditya.

- gh-87822: When called with `capture_locals=True`, the `traceback` module functions swallow exceptions raised from calls to `repr()` on local variables of frames. This is in order to prioritize the original exception over rendering errors. An indication of the failure is printed in place of the missing value. (Patch by Simon-Martin Schroeder).

- gh-88050: Fix `asyncio` subprocess transport to kill process cleanly when process is blocked and avoid `RuntimeError` when loop is closed. Patch by Kumar Aditya.

- gh-94637: `SSLContext.set_default_verify_paths()` now releases the GIL around `SSL_CTX_set_default_verify_paths` call. The function call performs I/O and CPU intensive work.

- gh-94309: Deprecate aliases `typing.Hashable` and `typing.Sized`

- gh-92546: An undocumented `python -m pprint` benchmark is moved into `pprint` suite of pyperformance. Patch by Oleg Iarygin.

- gh-94607: Fix subclassing complex generics with type variables in `typing`. Previously an error message saying `Some type variables ... are not listed in Generic[...]` was shown. `typing` no longer populates `__parameters__` with the `__parameters__` of a Python class.

- gh-94619: Remove the long-deprecated `module_repr()` from `importlib`.

- gh-93910: The ability to access the other values of an enum on an enum (e.g. `Color.RED.BLUE`) has been restored in order to fix a performance regression.

- gh-93896: Fix `asyncio.run()` and `unittest.IsolatedAsyncioTestCase` to always the set event loop as it was done in Python 3.10 and earlier. Patch by Kumar Aditya.

- gh-94343: Allow setting the attributes of `reprlib.Repr` during object initialization

- gh-94382: Port static types of `_multiprocessing` module to heap types. Patch by Kumar Aditya.

- gh-78724: Fix crash in `struct.Struct` when it was not completely initialized by initializing it in `__new__()`. Patch by Kumar Aditya.

- gh-94510: Re-entrant calls to `sys.setprofile()` and `sys.settrace()` now raise `RuntimeError`. Patch by Pablo Galindo.

- gh-92336: Fix bug where `linecache.getline()` fails on bad files with `UnicodeDecodeError` or `SyntaxError`. It now returns an empty string as per the documentation.

- gh-94398: Once a `asyncio.TaskGroup` has started shutting down (i.e., at least one task has failed and the task group has started cancelling the remaining tasks), it should not be possible to add new tasks to the task group.

- gh-94383: `xml.etree`: Remove the `ElementTree.Element.copy()` method of the pure Python implementation, deprecated in Python 3.10, use the `copy.copy()` function instead. The C implementation of `xml.etree` has no `copy()` method, only a `__copy__()` method. Patch by Victor Stinner.

- gh-94379: `zipimport`: Remove `find_loader()` and `find_module()` methods, deprecated in Python 3.10: use the `find_spec()` method instead. See PEP 451 for the rationale. Patch by Victor Stinner.

- gh-94352: `shlex.split()`: Passing `None` for s argument now raises an exception, rather than reading `sys.stdin`. The feature was deprecated in Python 3.9. Patch by Victor Stinner.

- gh-94318: Strip trailing spaces in `pydoc` text output.

- gh-89988: Fix memory leak in `pickle.Pickler` when looking up `dispatch_table`. Patch by Kumar Aditya.

- gh-90016: Deprecate `sqlite3` default adapters and converters. Patch by Erlend E. Aasland.

- gh-94254: Fixed types of `struct` module to be immutable. Patch by Kumar Aditya.

- gh-93259: Now raise `ValueError` when `None` or an empty string are passed to `Distribution.from_name` (and other callers).

- gh-74696: `shutil.make_archive()` now passes the root_dir argument to custom archivers which support it.

- gh-94216: The `dis` module now has the opcodes for pseudo instructions (those which are used by the compiler during code generation but then removed or replaced by real opcodes before the final bytecode is emitted).

- gh-93096: Removed undocumented `python -m codecs`. Use `python -m unittest test.test_codecs.EncodedFileTest` instead.

- gh-94207: Made `_struct.Struct` GC-tracked in order to fix a reference leak in the `_struct` module.

- gh-93096: Removed undocumented `-t` argument of `python -m base64`. Use `python -m unittest test.test_base64.LegacyBase64TestCase.test_encodebytes` instead.

- gh-94226: Remove the `locale.format()` function, deprecated in Python 3.7: use `locale.format_string()` instead. Patch by Victor Stinner.

- gh-94199: Remove the `ssl.match_hostname()` function. The `ssl.match_hostname()` was deprecated in Python 3.7. OpenSSL performs hostname matching since Python 3.7, Python no longer uses the `ssl.match_hostname()` function. Patch by Victor Stinner.

- gh-94214: Document the `context` object used in the `venv.EnvBuilder` class, and add the new environment’s library path to it.

- gh-94199: Remove the `ssl.wrap_socket()` function, deprecated in Python 3.7: instead, create a `ssl.SSLContext` object and call its `ssl.SSLContext.wrap_socket` method. Any package that still uses `ssl.wrap_socket()` is broken and insecure. The function neither sends a SNI TLS extension nor validates server hostname. Code is subject to CWE 295 Improper Certificate Validation. Patch by Victor Stinner.

- gh-94199: Remove the `ssl.RAND_pseudo_bytes()` function, deprecated in Python 3.6: use `os.urandom()` or `ssl.RAND_bytes()` instead. Patch by Victor Stinner.

- gh-94199: `hashlib`: Remove the pure Python implementation of `hashlib.pbkdf2_hmac()`, deprecated in Python 3.10. Python 3.10 and newer requires OpenSSL 1.1.1 (PEP 644): this OpenSSL version provides a C implementation of `pbkdf2_hmac()` which is faster. Patch by Victor Stinner.

- gh-94196: `gzip`: Remove the `filename` attribute of `gzip.GzipFile`, deprecated since Python 2.6, use the `name` attribute instead. In write mode, the `filename` attribute added `'.gz'` file extension if it was not present. Patch by Victor Stinner.

- gh-94182: run the `asyncio.PidfdChildWatcher` on the running loop, this allows event loops to run subprocesses when there is no default event loop running on the main thread

- gh-94169: Remove `io.OpenWrapper` and `_pyio.OpenWrapper`, deprecated in Python 3.10: just use `open()` instead. The `open()` (`io.open()`) function is a built-in function. Since Python 3.10, `_pyio.open()` is also a static method. Patch by Victor Stinner.

- gh-91742: Fix `pdb` crash after jump caused by a null pointer dereference. Patch by Kumar Aditya.

- gh-94101: Manual instantiation of `ssl.SSLSession` objects is no longer allowed as it lead to misconfigured instances that crashed the interpreter when attributes where accessed on them.

- gh-84753: `inspect.iscoroutinefunction()`, `inspect.isgeneratorfunction()`, and `inspect.isasyncgenfunction()` now properly return `True` for duck-typed function-like objects like instances of `unittest.mock.AsyncMock`.

  This makes `inspect.iscoroutinefunction()` consistent with the behavior of `asyncio.iscoroutinefunction()`. Patch by Mehdi ABAAKOUK.

- gh-94028: Fix a regression in the `sqlite3` where statement objects were not properly cleared and reset after use in cursor iters. The regression was introduced by PR 27884 in Python 3.11a1. Patch by Erlend E. Aasland.

- gh-93973: Add keyword argument `all_errors` to `asyncio.create_connection` so that multiple connection errors can be raised as an `ExceptionGroup`.

- gh-93963: Officially deprecate from `importlib.abc` classes moved to `importlib.resources.abc`.

- gh-93858: Prevent error when activating venv in nested fish instances.

- gh-93820: Pickle `enum.Flag` by name.

- gh-93847: Fix repr of enum of generic aliases.

- gh-91404: Revert the `re` memory leak when a match is terminated by a signal or memory allocation failure as the implemented fix caused a major performance regression.

- gh-83499: Fix double closing of file description in `tempfile`.

- gh-93820: Fixed a regression when `copy.copy()`-ing `enum.Flag` with multiple flag members.

- gh-79512: Fixed names and `__module__` value of `weakref` classes `ReferenceType`, `ProxyType`, `CallableProxyType`. It makes them pickleable.

- gh-91389: Fix an issue where `dis` utilities could report missing or incorrect position information in the presence of `CACHE` entries.

- gh-93626: Set `__future__.annotations` to have a `None` mandatoryRelease to indicate that it is currently ‘TBD’.

- gh-90473: Emscripten and WASI have no home directory and cannot provide PEP 370 user site directory.

- gh-90494: `copy.copy()` and `copy.deepcopy()` now always raise a TypeError if `__reduce__()` returns a tuple with length 6 instead of silently ignore the 6th item or produce incorrect result.

- gh-90549: Fix a multiprocessing bug where a global named resource (such as a semaphore) could leak when a child process is spawned (as opposed to forked).

- gh-93521: Fixed a case where dataclasses would try to add `__weakref__` into the `__slots__` for a dataclass that specified `weakref_slot=True` when it was already defined in one of its bases. This resulted in a `TypeError` upon the new class being created.

- gh-79579: `sqlite3` now correctly detects DML queries with leading comments. Patch by Erlend E. Aasland.

- gh-93421: Update `sqlite3.Cursor.rowcount` when a DML statement has run to completion. This fixes the row count for SQL queries like `UPDATE ... RETURNING`. Patch by Erlend E. Aasland.

- gh-93475: Expose `FICLONE` and `FICLONERANGE` constants in `fcntl`. Patch by Illia Volochii.

- gh-93370: Deprecate `sqlite3.version` and `sqlite3.version_info`.

- gh-91810: Suppress writing an XML declaration in open files in `ElementTree.write()` with `encoding='unicode'` and `xml_declaration=None`.

- gh-91162: Support splitting of unpacked arbitrary-length tuple over `TypeVar` and `TypeVarTuple` parameters. For example:

  - `A[T, *Ts][*tuple[int, ...]]` -> `A[int, *tuple[int, ...]]`

  - `A[*Ts, T][*tuple[int, ...]]` -> `A[*tuple[int, ...], int]`

- gh-93353: Fix the `importlib.resources.as_file()` context manager to remove the temporary file if destroyed late during Python finalization: keep a local reference to the `os.remove()` function. Patch by Victor Stinner.

- gh-83658: Make `multiprocessing.Pool` raise an exception if `maxtasksperchild` is not `None` or a positive int.

- gh-93312: Add `os.PIDFD_NONBLOCK` flag to open a file descriptor for a process with `os.pidfd_open()` in non-blocking mode. Patch by Kumar Aditya.

- gh-88123: Implement `Enum.__contains__` that returns `True` or `False` to replace the deprecated behaviour that would sometimes raise a `TypeError`.

- gh-93297: Make asyncio task groups prevent child tasks from being GCed

- gh-85308: Changed `argparse.ArgumentParser` to use filesystem encoding and error handler instead of default text encoding to read arguments from file (e.g. `fromfile_prefix_chars` option). This change affects Windows; argument file should be encoded with UTF-8 instead of ANSI Codepage.

- gh-93156: Accessing the `pathlib.PurePath.parents` sequence of an absolute path using negative index values produced incorrect results.

- gh-93162: Add the ability for `logging.config.dictConfig()` to usefully configure `QueueHandler` and `QueueListener` as a pair, and add `logging.getHandlerByName()` and `logging.getHandlerNames()` APIs to allow access to handlers by name.

- gh-93243: The `smtpd` module was removed per the schedule in PEP 594.

- gh-92886: Replace `assert` statements with `raise AssertionError()` in `BaseHandler` so that the tested behaviour is maintained running with optimizations `(-O)`.

- gh-90155: Fix broken `asyncio.Semaphore` when acquire is cancelled.

- gh-90817: The `locale.resetlocale()` function is deprecated and will be removed in Python 3.13. Use `locale.setlocale(locale.LC_ALL, "")` instead. Patch by Victor Stinner.

- gh-91513: Added `taskName` attribute to `logging` module for use with `asyncio` tasks.

- gh-74696: `shutil.make_archive()` no longer temporarily changes the current working directory during creation of standard `.zip` or tar archives.

- gh-92728: The `re.template()` function and the corresponding `re.TEMPLATE` and `re.T` flags are restored after they were removed in 3.11.0b1, but they are now deprecated, so they might be removed from Python 3.13.

- gh-93033: Search in some strings (platform dependent i.e [U+0xFFFF, U+0x0100] on Windows or [U+0xFFFFFFFF, U+0x00010000] on Linux 64-bit) are now up to 10 times faster.

- gh-89973: Fix `re.error` raised in `fnmatch` if the pattern contains a character range with upper bound lower than lower bound (e.g. `[c-a]`). Now such ranges are interpreted as empty ranges.

- gh-93044: No longer convert the database argument of `sqlite3.connect()` to bytes before passing it to the factory.

- gh-93010: In a very special case, the email package tried to append the nonexistent `InvalidHeaderError` to the defect list. It should have been `InvalidHeaderDefect`.

- gh-92986: Fix `ast.unparse()` when `ImportFrom.level` is `None`

- gh-92932: Now `dis()` and `get_instructions()` handle operand values for instructions prefixed by `EXTENDED_ARG_QUICK`. Patch by Sam Gross and Donghee Na.

- gh-92675: Fix `venv.ensure_directories()` to accept `pathlib.Path` arguments in addition to `str` paths. Patch by David Foster.

- gh-87901: Removed the `encoding` argument from `os.popen()` that was added in 3.11b1.

- gh-91922: Fix function `sqlite.connect()` and the `sqlite.Connection` constructor on non-UTF-8 locales. Also, they now support bytes paths non-decodable with the current FS encoding.

- gh-92869: Added `c_time_t` to `ctypes`, which has the same size as the `time_t` type in C.

- gh-92839: Fixed crash resulting from calling bisect.insort() or bisect.insort_left() with the key argument not equal to `None`.

- gh-90473: `subprocess` now fails early on Emscripten and WASI platforms to work around missing `os.pipe()` on WASI.

- gh-89325: Removed many old deprecated `unittest` features: `TestCase` method aliases, undocumented and broken `TestCase` method `assertDictContainsSubset`, undocumented `TestLoader.loadTestsFromModule` parameter use_load_tests, and an underscored alias of the `TextTestResult` class.

- gh-92734: Allow multi-element reprs emitted by `reprlib` to be pretty-printed using configurable indentation.

- gh-92671: Fixed `ast.unparse()` for empty tuples in the assignment target context.

- gh-91581: `utcfromtimestamp()` no longer attempts to resolve `fold` in the pure Python implementation, since the fold is never 1 in UTC. In addition to being slightly faster in the common case, this also prevents some errors when the timestamp is close to `datetime.min`. Patch by Paul Ganssle.

- gh-86388: Removed randrange() functionality deprecated since Python 3.10. Formerly, randrange(10.0) losslessly converted to randrange(10). Now, it raises a TypeError. Also, the exception raised for non-integral values such as randrange(10.5) or randrange(‘10’) has been changed from ValueError to TypeError.

- gh-90385: Add `pathlib.Path.walk()` as an alternative to `os.walk()`.

- gh-92550: Fix `pathlib.Path.rglob()` for empty pattern.

- gh-92591: Allow `logging` filters to return a `logging.LogRecord` instance so that filters attached to `logging.Handler`s can enrich records without side effects on other handlers.

- gh-92445: Fix a bug in `argparse` where `nargs="*"` would raise an error instead of returning an empty list when 0 arguments were supplied if choice was also defined in `parser.add_argument`.

- gh-92547: Remove undocumented `sqlite3` features deprecated in Python 3.10:

  - `sqlite3.enable_shared_cache()`

  - `sqlite3.OptimizedUnicode`

  Patch by Erlend E. Aasland.

- gh-92530: Fix an issue that occurred after interrupting `threading.Condition.notify()`.

- gh-92531: The statistics.median_grouped() function now always return a float. Formerly, it did not convert the input type when for sequences of length one.

- gh-84131: The `pathlib.Path` deprecated method `link_to` has been removed. Use 3.10’s `hardlink_to()` method instead as its semantics are consistent with that of `symlink_to()`.

- gh-89336: Removed `configparser` module APIs: the `SafeConfigParser` class alias, the `ParsingError.filename` property and parameter, and the `ConfigParser.readfp` method, all of which were deprecated since Python 3.2.

- gh-92391: Add `__class_getitem__()` to `csv.DictReader` and `csv.DictWriter`, allowing them to be parameterized at runtime. Patch by Marc Mueller.

- gh-91968: Add `SO_RTABLE` and `SO_USER_COOKIE` constants to `socket`.

- gh-91810: `ElementTree` method `write()` and function `tostring()` now use the text file’s encoding (“UTF-8” if not available) instead of locale encoding in XML declaration when `encoding="unicode"` is specified.

- gh-81790: `os.path.splitdrive()` now understands DOS device paths with UNC links (beginning `\\?\UNC\`). Contributed by Barney Gale.

- gh-91760: Apply more strict rules for numerical group references and group names in regular expressions. Only sequence of ASCII digits is now accepted as a numerical reference. The group name in bytes patterns and replacement strings can now only contain ASCII letters and digits and underscore.

- gh-90622: Worker processes for `concurrent.futures.ProcessPoolExecutor` are no longer spawned on demand (a feature added in 3.9) when the multiprocessing context start method is `"fork"` as that can lead to deadlocks in the child processes due to a fork happening while threads are running.

- gh-91577: Move imports in `SharedMemory` methods to module level so that they can be executed late in python finalization.

- gh-91581: Remove an unhandled error case in the C implementation of calls to `datetime.fromtimestamp` with no time zone (i.e. getting a local time from an epoch timestamp). This should have no user-facing effect other than giving a possibly more accurate error message when called with timestamps that fall on 10000-01-01 in the local time. Patch by Paul Ganssle.

- gh-91539: Improve performance of `urllib.request.getproxies_environment` when there are many environment variables

- gh-91524: Speed up the regular expression substitution (functions `re.sub()` and `re.subn()` and corresponding `re.Pattern` methods) for replacement strings containing group references by 2–3 times.

- gh-91447: Fix findtext in the xml module to only give an empty string when the text attribute is set to `None`.

- gh-91456: Deprecate current default auto() behavior: In 3.13 the default will be for for auto() to always return the largest member value incremented by 1, and to raise if incompatible value types are used.

- bpo-47231: Fixed an issue with inconsistent trailing slashes in tarfile longname directories.

- bpo-39064: `zipfile.ZipFile` now raises `zipfile.BadZipFile` instead of `ValueError` when reading a corrupt zip file in which the central directory offset is negative.

- bpo-41287: Fix handling of the `doc` argument in subclasses of `property()`.

- gh-90005: `ctypes` dependency `libffi` is now detected with `pkg-config`.

- bpo-32547: The constructors for `DictWriter` and `DictReader` now coerce the `fieldnames` argument to a `list` if it is an iterator.

- bpo-35540: Fix `dataclasses.asdict()` crash when `collections.defaultdict` is present in the attributes.

- bpo-47063: Add an index_pages parameter to support using non-default index page names.

- bpo-47025: Drop support for `bytes` on `sys.path`.

- bpo-46951: Order the contents of zipapp archives, to make builds more reproducible.

- bpo-42777: Implement `pathlib.Path.is_mount()` for Windows paths.

- bpo-46755: In `QueueHandler`, clear `stack_info` from `LogRecord` to prevent stack trace from being written twice.

- bpo-45393: Fix the formatting for `await x` and `not x` in the operator precedence table when using the `help()` system.

- bpo-46642: Improve error message when trying to subclass an instance of `typing.TypeVar`, `typing.ParamSpec`, `typing.TypeVarTuple`, etc. Based on patch by Gregory Beauregard.

- bpo-46364: Restrict use of sockets instead of pipes for stdin of subprocesses created by `asyncio` to AIX platform only.

- bpo-28249: Set `doctest.DocTest.lineno` to `None` when an object does not have `__doc__`.

- bpo-46197: Fix `ensurepip` environment isolation for subprocess running `pip`.

- bpo-45924: Fix `asyncio` incorrect traceback when future’s exception is raised multiple times. Patch by Kumar Aditya.

- bpo-45046: Add support of context managers in `unittest`: methods `enterContext()` and `enterClassContext()` of class `TestCase`, method `enterAsyncContext()` of class `IsolatedAsyncioTestCase` and function `unittest.enterModuleContext()`.

- bpo-44173: Enable fast seeking of uncompressed unencrypted `zipfile.ZipExtFile`

- bpo-42627: Fix incorrect parsing of Windows registry proxy settings

- bpo-42047: Add `threading.get_native_id()` support for DragonFly BSD. Patch by David Carlier.

- bpo-14243: The `tempfile.NamedTemporaryFile` function has a new optional parameter delete_on_close

- bpo-41246: Give the same callback function for when the overlapped operation is done to the functions `recv`, `recv_into`, `recvfrom`, `sendto`, `send` and `sendfile` inside `IocpProactor`.

- bpo-39264: Fixed `collections.UserDict.get()` to not call `__missing__()` when a value is not found. This matches the behavior of `dict`. Patch by Bar Harel.

- bpo-38693: `importlib` now uses f-strings internally instead of `str.format`.

- bpo-38267: Add timeout parameter to `asyncio.loop.shutdown_default_executor()`. The default value is `None`, which means the executor will be given an unlimited amount of time. When called from `asyncio.Runner` or `asyncio.run()`, the default timeout is 5 minutes.

- bpo-34828: `sqlite3.Connection.iterdump()` now handles databases that use `AUTOINCREMENT` in one or more tables.

- bpo-32990: Support reading wave files with the `WAVE_FORMAT_EXTENSIBLE` format in the `wave` module.

- bpo-26253: Allow adjustable compression level for tarfile streams in `tarfile.open()`.

### Documentation

- gh-85525: Remove extra row

- gh-86404: Deprecated tools `make suspicious` and `rstlint.py` are now removed. They have been replaced by sphinx-lint.

- gh-97741: Fix `!` in c domain ref target syntax via a `conf.py` patch, so it works as intended to disable ref target resolution.

- gh-96432: Fraction literals now support whitespace around the forward slash, `Fraction('2 / 3')`.

- gh-96098: Improve discoverability of the higher level concurrent.futures module by providing clearer links from the lower level threading and multiprocessing modules.

- gh-95957: What’s New 3.11 now has instructions for how to provide compiler and linker flags for Tcl/Tk and OpenSSL on RHEL 7 and CentOS 7.

- gh-95588: Clarified the conflicting advice given in the `ast` documentation about `ast.literal_eval()` being “safe” for use on untrusted input while at the same time warning that it can crash the process. The latter statement is true and is deemed unfixable without a large amount of work unsuitable for a bugfix. So we keep the warning and no longer claim that `literal_eval` is safe.

- gh-91207: Fix stylesheet not working in Windows CHM htmlhelp docs and add warning that they are deprecated. Contributed by C.A.M. Gerlach.

- gh-95454: Replaced incorrectly written true/false values in documentation. Patch by Robert O’Shea

- gh-95451: Update library documentation with availability information on WebAssembly platforms `wasm32-emscripten` and `wasm32-wasi`.

- gh-95415: Use consistent syntax for platform availability. The directive now supports a content body and emits a warning when it encounters an unknown platform.

- gh-94321: Document the PEP 246 style protocol type `sqlite3.PrepareProtocol`.

- gh-86128: Document a limitation in ThreadPoolExecutor where its exit handler is executed before any handlers in atexit.

- gh-61162: Clarify `sqlite3` behavior when How to use the connection context manager.

- gh-87260: Align `sqlite3` argument specs with the actual implementation.

- gh-86986: The minimum Sphinx version required to build the documentation is now 3.2.

- gh-88831: Augmented documentation of asyncio.create_task(). Clarified the need to keep strong references to tasks and added a code snippet detailing how to do this.

- gh-86438: Clarify that `-W` and `PYTHONWARNINGS` are matched literally and case-insensitively, rather than as regular expressions, in `warnings`.

- gh-93031: Update tutorial introduction output to use 3.10+ SyntaxError invalid range.

- gh-92240: Added release dates for “What’s New in Python 3.X” for 3.0, 3.1, 3.2, 3.8 and 3.10

- bpo-47161: Document that `pathlib.PurePath` does not collapse initial double slashes because they denote UNC paths.

- bpo-40838: Document that `inspect.getdoc()`, `inspect.getmodule()`, and `inspect.getsourcefile()` might return `None`.

- bpo-43689: The `Differ` documentation now also mentions other whitespace characters, which make it harder to understand the diff output.

- bpo-38056: Overhaul the Error Handlers documentation in `codecs`.

- bpo-13553: Document tkinter.Tk args.

### Tests

- gh-95027: On Windows, when the Python test suite is run with the `-jN` option, the ANSI code page is now used as the encoding for the stdout temporary file, rather than using UTF-8 which can lead to decoding errors. Patch by Victor Stinner.

- gh-96624: Fixed the failure of repeated runs of `test.test_unittest` caused by side effects in `test_dotted_but_module_not_loaded`.

- gh-95243: Mitigate the inherent race condition from using find_unused_port() in testSockName() by trying to find an unused port a few times before failing. Patch by Ross Burton.

- gh-95573: Lib/test/test_asyncio/test_ssl.py exposed a bug in the macOS kernel where intense concurrent load on non-blocking sockets occasionally causes `errno.ENOBUFS` (“No buffer space available”) to be emitted. FB11063974 filed with Apple, in the mean time as a workaround buffer size used in tests on macOS is decreased to avoid intermittent failures. Patch by Fantix King.

- gh-95280: Fix problem with `test_ssl` `test_get_ciphers` on systems that require perfect forward secrecy (PFS) ciphers.

- gh-95212: Make multiprocessing test case `test_shared_memory_recreate` parallel-safe.

- gh-95218: Move tests for importlib.resources into test_importlib.resources.

- gh-93963: Updated tests to use preferred location for `importlib.resources` ABCs.

- gh-94675: Add a regression test for `re` exponentional slowdown when using rjsmin.

- gh-91330: Added more tests for `dataclasses` to cover behavior with data descriptor-based fields.

- gh-94208: `test_ssl` is now checking for supported TLS version and protocols in more tests.

- gh-94315: Tests now check for DAC override capability instead of relying on `os.geteuid()`.

- gh-54781: Rename test_tk to test_tkinter, and rename test_ttk_guionly to test_ttk. Patch by Victor Stinner.

- gh-93839: Move `Lib/ctypes/test/` to `Lib/test/test_ctypes/`. Patch by Victor Stinner.

- gh-93951: In test_bdb.StateTestCase.test_skip, avoid including auxiliary importers.

- gh-93957: Provide nicer error reporting from subprocesses in test_venv.EnsurePipTest.test_with_pip.

- gh-93884: Add test cases for `PyNumber_ToBase()` that take a large number or a non-int object as parameter.

- gh-93852: test_asyncio, test_logging, test_socket and test_socketserver now create AF_UNIX domains in the current directory to no longer fail with `OSError("AF_UNIX path too long")` if the temporary directory (the `TMPDIR` environment variable) is too long. Patch by Victor Stinner.

- gh-93353: regrtest now checks if a test leaks temporary files or directories if run with -jN option. Patch by Victor Stinner.

- gh-84461: `run_tests.py` now handles cross compiling env vars correctly and pass `HOSTRUNNER` to regression tests.

- gh-93616: `test_modulefinder` now creates a temporary directory in `ModuleFinderTest.setUp()` instead of module scope.

- gh-93575: Fix issue with test_unicode test_raiseMemError. The test case now use `test.support.calcobjsize` to calculate size of PyUnicode structs. `sys.getsizeof()` may return different size when string has UTF-8 memory.

- gh-90473: WASI does not have a `chmod(2)` syscall. `os.chmod()` is now a dummy function on WASI. Skip all tests that depend on working `os.chmod()`.

- gh-90473: Skip tests on WASI that require symlinks with absolute paths.

- gh-57539: Increase calendar test coverage for `calendar.LocaleTextCalendar.formatweekday()`.

- gh-90473: Skip symlink tests on WASI. wasmtime uses `openat2(2)` with `RESOLVE_BENEATH` flag, which prevents symlinks with absolute paths.

- gh-89858: Fix `test_embed` for out-of-tree builds. Patch by Kumar Aditya.

- gh-92886: Fixing tests that fail when running with optimizations (`-O`) in `test_imaplib.py`.

- gh-92886: Fixing tests that fail when running with optimizations (`-O`) in `test_zipimport.py`

- gh-92886: Fixing tests that fail when running with optimizations (`-O`) in `test_py_compile.py`

- gh-92886: Fixing tests that fail when running with optimizations (`-O`) in `test_sys_settrace.py`.

- gh-92886: Fixing tests that fail when running with optimizations (`-O`) in `_test_multiprocessing.py`

- gh-92670: Skip `test_shutil.TestCopy.test_copyfile_nonexistent_dir` test on AIX as the test uses a trailing slash to force the OS consider the path as a directory, but on AIX the trailing slash has no effect and is considered as a file.

- gh-92514: Remove unused `test.support.BasicTestRunner`. Patch by Jelle Zijlstra.

- bpo-47016: Create a GitHub Actions workflow for verifying bundled pip and setuptools. Patch by Illia Volochii and Adam Turner.

### Build

- gh-96761: Fix the build process of clang compiler for _bootstrap_python if LTO optimization is applied. Patch by Matthias Görgens and Donghee Na.

- gh-96883: `wasm32-emscripten` builds for browsers now include `concurrent.futures` for `asyncio` and `unittest.mock`.

- gh-85936: CPython now uses the ThinLTO option as the default policy if the Clang compiler accepts the flag. Patch by Donghee Na.

- gh-96729: Ensure that Windows releases built with `Tools\msi\buildrelease.bat` are upgradable to and from official Python releases.

- gh-96269: Shared module targets now depend on new `MODULE_DEPS` variable, which includes `EXPORTSYMS`. This fixes a build order issue on unsupported AIX platform.

- gh-84461: `wasm32-emscripten` platform no longer builds `resource` module, `getresuid()`, `getresgid()`, and their setters. The APIs are stubs and not functional.

- gh-95973: Add a new `--with-dsymutil` configure option to link debug information in macOS. Patch by Pablo Galindo.

- gh-90536: Use the BOLT post-link optimizer to improve performance, particularly on medium-to-large applications.

- gh-93744: Remove the `configure --with-cxx-main` build option: it didn’t work for many years. Remove the `MAINCC` variable from `configure` and `Makefile`. Patch by Victor Stinner.

- gh-94801: Fix a regression in `configure` script that caused some header checks to ignore custom `CPPFLAGS`. The regression was introduced in gh-94802.

- gh-95145: wasm32-wasi builds no longer depend on WASIX’s pthread stubs. Python now has its own stubbed pthread API.

- gh-95174: Python now detects missing `dup` function in WASI and works around some missing `errno`, `select`, and `socket` constants.

- gh-95174: Python now skips missing `socket` functions and methods on WASI. WASI can only create sockets from existing fd / accept and has no netdb.

- gh-95085: Platforms `wasm32-unknown-emscripten` and `wasm32-unknown-wasi` have been promoted to PEP 11 tier 3 platform support.

- gh-94847: Fixed `_decimal` module build issue on GCC when compiling with LTO and pydebug. Debug builds no longer force inlining of functions.

- gh-94841: Fix the possible performance regression of `PyObject_Free()` compiled with MSVC version 1932.

- gh-94801: `configure` now uses custom flags like `ZLIB_CFLAGS` and `ZLIB_LIBS` when searching for headers and libraries.

- gh-94773: `deepfreeze.py` now supports code object with frozensets that contain incompatible, unsortable types.

- gh-94682: Build and test with OpenSSL 1.1.1q

- gh-90005: Dependencies of `readline` and `curses` module are now detected in `configure` script with `pkg-config`. Only `ncurses` / `ncursesw` are detected automatically. The old `curses` library is not configured automatically. Workaround for missing `termcap` or `tinfo` library has been removed.

- gh-90005: Fix building `_ctypes` extension without `pkg-config`.

- gh-90005: `_dbm` module dependencies are now detected by configure.

- gh-94404: `makesetup` now works around an issue with sed on macOS and uses correct CFLAGS for object files that end up in a shared extension. Module CFLAGS are used before PY_STDMODULE_CFLAGS to avoid clashes with system headers.

- gh-93939: C extension modules are now built by `configure` and `make` instead of `distutils` and `setup.py`.

- gh-93939: The `2to3`, `idle`, and `pydoc` scripts are now generated and installed by `Makefile` instead of `setup.py`.

- gh-94280: Updated pegen regeneration script on Windows to find and use Python 3.9 or higher. Prior to this, pegen regeneration already required 3.9 or higher, but the script may have used lower versions of Python.

- gh-93584: Address race condition in `Makefile` when installing a PGO build. All `test` and `install` targets now depend on `all` target.

- gh-93491: `configure` now detects and reports PEP 11 support tiers.

- gh-69093: Fix `Modules/Setup.stdlib.in` rule for `_sqlite3` extension.

- gh-93207: `va_start()` with two parameters, like `va_start(args, format),` is now required to build Python. `va_start()` is no longer called with a single parameter. Patch by Kumar Aditya.

- gh-93202: Python now always use the `%zu` and `%zd` printf formats to format a `size_t` or `Py_ssize_t` number. Building Python 3.12 requires a C11 compiler, so these printf formats are now always supported. Patch by Victor Stinner.

- gh-90473: Disable pymalloc and increase stack size on `wasm32-wasi`.

- bpo-34449: Drop invalid compiler switch `-fPIC` for HP aCC on HP-UX. Patch by Michael Osipov.

### Windows

- gh-98360: Fixes `multiprocessing` spawning child processes on Windows from a virtual environment to ensure that child processes that also use `multiprocessing` to spawn more children will recognize that they are in a virtual environment.

- gh-98414: Fix `py.exe` launcher handling of `-V:<company>/` option when default preferences have been set in environment variables or configuration files.

- gh-97728: Fix possible crashes caused by the use of uninitialized variables when pass invalid arguments in `os.system()` on Windows and in Windows-specific modules (like `winreg`).

- gh-90989: Made Python Launcher for Windows install per-user by default (unless an all users install already exists), and clarify some text in the installer.

- gh-97649: The `Tools` directory is no longer installed on Windows

- gh-96965: Update libffi to 3.4.3

- gh-96577: Fixes a potential buffer overrun in `msilib`.

- gh-96559: Fixes the Windows launcher not using the compatible interpretation of default tags found in configuration files when no tag was passed to the command.

- gh-94781: Fix `pcbuild.proj` to clean previous instances of output files in `Python\deepfreeze` and `Python\frozen_modules` directories on Windows. Patch by Charlie Zhao.

- gh-89545: Updates `platform` code getting the Windows version to use native Windows Management Instrumentation (WMI) queries to determine OS version, type, and architecture.

- gh-95733: Make certain requirements of the Windows Store package optional to allow installing on earlier updates of Windows.

- gh-95656: Enable the `enable_load_extension()` `sqlite3` API.

- gh-95587: Fixes some issues where the Windows installer would incorrectly detect certain features of an existing install when upgrading.

- gh-94399: Restores the behaviour of Python Launcher for Windows for `/usr/bin/env` shebang lines, which will now search `PATH` for an executable matching the given command. If none is found, the usual search process is used.

- gh-95445: Fixes the unsuccessful removal of the HTML document directory when uninstalling with Windows msi.

- gh-95359: Fix Python Launcher for Windows handling of `py.ini` commands (it was incorrectly expecting a `py_` prefix on keys) and crashes when reading per-user configuration file.

- gh-95285: Fix Python Launcher for Windows handling of command lines where it is only passed a short executable name.

- gh-90844: Allow virtual environments to correctly launch when they have spaces in the path.

- gh-94772: Fix incorrect handling of shebang lines in py.exe launcher

- gh-94018: `zipfile` will now remove trailing spaces from path components when extracting files on Windows.

- gh-93824: Drag and drop of files onto Python files in Windows Explorer has been enabled for Windows ARM64.

- gh-43414: `os.get_terminal_size()` now attempts to read the size from any provided handle, rather than only supporting file descriptors 0, 1 and 2.

- gh-92817: Ensures that `py.exe` will prefer an active virtual environment over default tags specified with environment variables or through a `py.ini` file.

- gh-92984: Explicitly disable incremental linking for non-Debug builds

- gh-92841: `asyncio` no longer throws `RuntimeError: Event loop is closed` on interpreter exit after asynchronous socket activity. Patch by Oleg Iarygin.

- bpo-46907: Update Windows installer to use SQLite 3.38.4.

- gh-91061: Accept os.PathLike for the argument to winsound.PlaySound

- bpo-42658: Support native Windows case-insensitive path comparisons by using `LCMapStringEx` instead of `str.lower()` in `ntpath.normcase()`. Add `LCMapStringEx` to the `_winapi` module.

- bpo-38704: Prevent installation on unsupported Windows versions.

### macOS

- gh-97897: The macOS 13 SDK includes support for the `mkfifoat` and `mknodat` system calls. Using the `dir_fd` option with either `os.mkfifo()` or `os.mknod()` could result in a segfault if cpython is built with the macOS 13 SDK but run on an earlier version of macOS. Prevent this by adding runtime support for detection of these system calls (“weaklinking”) as is done for other newer syscalls on macOS.

### IDLE

- gh-97527: Fix a bug in the previous bugfix that caused IDLE to not start when run with 3.10.8, 3.12.0a1, and at least Microsoft Python 3.10.2288.0 installed without the Lib/test package. 3.11.0 was never affected.

- gh-65802: Document handling of extensions in Save As dialogs.

- gh-95191: Include prompts when saving Shell (interactive input and output).

- gh-95511: Fix the Shell context menu copy-with-prompts bug of copying an extra line when one selects whole lines.

- gh-95471: In the Edit menu, move `Select All` and add a new separator.

- gh-95411: Enable using IDLE’s module browser with .pyw files.

- gh-89610: Add .pyi as a recognized extension for IDLE on macOS. This allows opening stub files by double clicking on them in the Finder.

### Tools/Demos

- gh-68686: Remove ptags and eptags scripts.

- gh-97681: Remove the `Tools/demo/` directory which contained old demo scripts. A copy can be found in the old-demos project. Patch by Victor Stinner.

- gh-97669: Remove outdated example scripts of the `Tools/scripts/` directory. A copy can be found in the old-demos project. Patch by Victor Stinner.

- gh-95853: The `wasm_build.py` script now pre-builds Emscripten ports, checks for broken EMSDK versions, and warns about pkg-config env vars.

- gh-95853: The new tool `Tools/wasm/wasm_builder.py` automates configure, compile, and test steps for building CPython on WebAssembly platforms.

- gh-95731: Fix handling of module docstrings in `Tools/i18n/pygettext.py`.

- gh-93939: Add script `Tools/scripts/check_modules.py` to check and validate builtin and shared extension modules. The script also handles `Modules/Setup` and will eventually replace `setup.py`.

- gh-94538: Fix Argument Clinic output to custom file destinations. Patch by Erlend E. Aasland.

- gh-94430: Allow parameters named `module` and `self` with custom C names in Argument Clinic. Patch by Erlend E. Aasland

- gh-86087: The `Tools/scripts/parseentities.py` script used to parse HTML4 entities has been removed.

### C API

- gh-98393: The `PyUnicode_FSDecoder()` function no longer accepts bytes-like paths, like `bytearray` and `memoryview` types: only the exact `bytes` type is accepted for bytes strings. Patch by Victor Stinner.

- gh-91051: Add `PyType_Watch()` and related APIs to allow callbacks on `PyType_Modified()`.

- gh-95756: Lazily create and cache `co_` attributes for better performance for code getters.

- gh-96512: Configuration for the integer string conversion length limitation now lives in the PyConfig C API struct.

- gh-95589: Extensions classes that set `tp_dictoffset` and `tp_weaklistoffset` lose the support for multiple inheritance, but are now safe. Extension classes should use `Py_TPFLAGS_MANAGED_DICT` and `Py_TPFLAGS_MANAGED_WEAKREF` instead.

- gh-95781: An unrecognized format character in `PyUnicode_FromFormat()` and `PyUnicode_FromFormatV()` now sets a `SystemError`. In previous versions it caused all the rest of the format string to be copied as-is to the result string, and any extra arguments discarded.

- gh-92678: Restore the 3.10 behavior for multiple inheritance of C extension classes that store their dictionary at the end of the struct.

- gh-92678: Support C extensions using managed dictionaries by setting the `Py_TPFLAGS_MANAGED_DICT` flag.

- gh-93274: API for implementing vectorcall (`Py_TPFLAGS_HAVE_VECTORCALL`, `PyVectorcall_NARGS()` and `PyVectorcall_Call()`) was added to the limited API and stable ABI.

- gh-95504: Fix sign placement when specifying width or precision in `PyUnicode_FromFormat()` and `PyUnicode_FromFormatV()`. Patch by Philip Georgi.

- gh-93012: The `Py_TPFLAGS_HAVE_VECTORCALL` flag is now removed from a class when the class’s `__call__()` method is reassigned. This makes vectorcall safe to use with mutable types (i.e. heap types without the `immutable` flag). Mutable types that do not override `tp_call` now inherit the `Py_TPFLAGS_HAVE_VECTORCALL` flag.

- gh-95388: Creating `immutable types` with mutable bases is deprecated and is planned to be disabled in Python 3.14.

- gh-92678: Adds unstable C-API functions `_PyObject_VisitManagedDict` and `_PyObject_ClearManagedDict` to allow C extensions to allow the VM to manage their object’s dictionaries.

- gh-94936: Added `PyCode_GetVarnames()`, `PyCode_GetCellvars()` and `PyCode_GetFreevars()` for accessing `co_varnames`, `co_cellvars` and `co_freevars` respectively via the C API.

- gh-94930: Fix `SystemError` raised when `PyArg_ParseTupleAndKeywords()` is used with `#` in `(...)` but without `PY_SSIZE_T_CLEAN` defined.

- gh-94731: Python again uses C-style casts for most casting operations when compiled with C++. This may trigger compiler warnings, if they are enabled with e.g. `-Wold-style-cast` or `-Wzero-as-null-pointer-constant` options for `g++`.

- gh-93937: The following frame functions and type are now directly available with `#include <Python.h>`, it’s no longer needed to add `#include <frameobject.h>`:

  - `PyFrame_Check()`

  - `PyFrame_GetBack()`

  - `PyFrame_GetBuiltins()`

  - `PyFrame_GetGenerator()`

  - `PyFrame_GetGlobals()`

  - `PyFrame_GetLasti()`

  - `PyFrame_GetLocals()`

  - `PyFrame_Type`

  Patch by Victor Stinner.

- gh-91321: Fix the compatibility of the Python C API with C++ older than C++11. Patch by Victor Stinner.

- gh-91731: Avoid defining the `static_assert` when compiling with C++ 11, where this is a keyword and redefining it can lead to undefined behavior. Patch by Pablo Galindo

- gh-89546: `PyType_FromMetaclass()` (and other `PyType_From*` functions) now check that offsets and the base class’s `tp_basicsize` fit in the new class’s `tp_basicsize`.

- gh-93503: Add two new public functions to the public C-API, `PyEval_SetProfileAllThreads()` and `PyEval_SetTraceAllThreads()`, that allow to set tracing and profiling functions in all running threads in addition to the calling one. Also, two analogous functions to the `threading` module (`threading.setprofile_all_threads()` and `threading.settrace_all_threads()`) that allow to do the same from Python. Patch by Pablo Galindo

- gh-93442: Add C++ overloads for _Py_CAST_impl() to handle 0/NULL. This will allow C++ extensions that pass 0 or NULL to macros using _Py_CAST() to continue to compile.

- gh-93466: Slot IDs in PyType_Spec may not be repeated. The documentation was updated to mention this. For some cases of repeated slots, PyType_FromSpec and related functions will now raise an exception.

- gh-92898: Fix C++ compiler warnings when casting function arguments to `PyObject*`. Patch by Serge Guelton.

- gh-93103: Deprecate global configuration variables, like `Py_IgnoreEnvironmentFlag`, in the documentation: the `Py_InitializeFromConfig()` API should be instead. Patch by Victor Stinner.

- gh-77782: Deprecate global configuration variable like `Py_IgnoreEnvironmentFlag`: the `Py_InitializeFromConfig()` API should be instead. Patch by Victor Stinner.

- gh-92913: Ensures changes to `PyConfig.module_search_paths` are ignored unless `PyConfig.module_search_paths_set` is set

- gh-92781: Avoid mixing declarations and code in the C API to fix the compiler warning: “ISO C90 forbids mixed declarations and code” [-Werror=declaration-after-statement]. Patch by Victor Stinner.

- gh-92651: Remove the `token.h` header file. There was never any public tokenizer C API. The `token.h` header file was only designed to be used by Python internals. Patch by Victor Stinner.

- gh-92536: Remove legacy Unicode APIs based on `Py_UNICODE*`.

- gh-85858: Remove the `PyUnicode_InternImmortal()` function and the `SSTATE_INTERNED_IMMORTAL` macro. Patch by Victor Stinner.

- gh-92193: Add new function `PyFunction_SetVectorcall()` to the C API which sets the vectorcall field of a given `PyFunctionObject`.

  Warning: extensions using this API must preserve the behavior of the unaltered function!

- gh-59121: Fixed an assert that prevented `PyRun_InteractiveOne` from providing tracebacks when parsing from the provided FD.

- bpo-45383: The `PyType_FromSpec()` API will now find and use a metaclass based on the provided bases. An error will be raised if there is a metaclass conflict.

## Python 3.11.0 beta 1

Release date: 2022-05-06

### Security

- gh-57684: Add the `-P` command line option and the `PYTHONSAFEPATH` environment variable to not prepend a potentially unsafe path to `sys.path`. Patch by Victor Stinner.

### Core and Builtins

- gh-89519: Chaining classmethod descriptors (introduced in bpo-19072) is deprecated. It can no longer be used to wrap other descriptors such as property(). The core design of this feature was flawed, and it caused a number of downstream problems.

- gh-92345: `pymain_run_python()` now imports `readline` and `rlcompleter` before sys.path is extended to include the current working directory of an interactive interpreter. Non-interactive interpreters are not affected.

- bpo-43857: Improve the `AttributeError` message when deleting a missing attribute. Patch by Géry Ogam.

- gh-92245: Make sure that PEP 523 is respected in all cases. In 3.11a7, specialization may have prevented Python-to-Python calls respecting PEP 523.

- gh-92203: Add a closure keyword-only parameter to `exec()`. It can only be specified when exec-ing a code object that uses free variables. When specified, it must be a tuple, with exactly the number of cell variables referenced by the code object. closure has a default value of `None`, and it must be `None` if the code object doesn’t refer to any free variables.

- gh-91173: Disable frozen modules in debug builds. Patch by Kumar Aditya.

- gh-92114: Improve error message when subscript a type with `__class_getitem__` set to `None`.

- gh-92112: Fix crash triggered by an evil custom `mro()` on a metaclass.

- gh-92063: The `PRECALL_METHOD_DESCRIPTOR_FAST_WITH_KEYWORDS` instruction now ensures methods are called only on objects of the correct type.

- gh-92031: Deoptimize statically allocated code objects during `Py_FINALIZE()` so that future `_PyCode_Quicken` calls always start with unquickened code.

- gh-92036: Fix a crash in subinterpreters related to the garbage collector. When a subinterpreter is deleted, untrack all objects tracked by its GC. To prevent a crash in deallocator functions expecting objects to be tracked by the GC, leak a strong reference to these objects on purpose, so they are never deleted and their deallocator functions are not called. Patch by Victor Stinner.

- gh-92032: The interpreter can now autocomplete soft keywords, as of now `match`, `case`, and `_` (wildcard pattern) from PEP 634.

- gh-87999: The warning emitted by the Python parser for a numeric literal immediately followed by keyword has been changed from deprecation warning to syntax warning.

- gh-91869: Fix an issue where specialized opcodes with extended arguments could produce incorrect tracing output or lead to assertion failures.

- gh-91603: Speed up `types.UnionType` instantiation. Based on patch provided by Yurii Karabas.

- gh-89373: If Python is built in debug mode, Python now ensures that deallocator functions leave the current exception unchanged. Patch by Victor Stinner.

- gh-91632: Fix a minor memory leak at exit: release the memory of the `generic_alias_iterator` type. Patch by Donghee Na.

- gh-81548: Octal escapes with value larger than `0o377` now produce a `DeprecationWarning`. In a future Python version they will be a `SyntaxWarning` and eventually a `SyntaxError`.

- bpo-43950: Use a single compact table for line starts, ends and column offsets. Reduces memory consumption for location info by half

- gh-91102: Use Argument Clinic for `EncodingMap`. Patch by Oleg Iarygin.

- gh-91636: Fixed a crash in a garbage-collection edge-case, in which a `PyFunction_Type.tp_clear` function could leave a python function object in an inconsistent state.

- gh-91603: Speed up `isinstance()` and `issubclass()` checks for `types.UnionType`. Patch by Yurii Karabas.

- gh-91625: Fixed a bug in which adaptive opcodes ignored any preceding `EXTENDED_ARG`s on specialization failure.

- gh-78607: The LLTRACE special build now looks for the name `__lltrace__` defined in module globals, rather than the name `__ltrace__`, which had been introduced as a typo.

- gh-91576: Speed up iteration of ascii strings by 50%. Patch by Kumar Aditya.

- gh-89279: Improve interpreter performance on Windows by inlining a few specific macros.

- gh-91502: Add a new `_PyFrame_IsEntryFrame()` API function, to check if a `PyFrameObject` is an entry frame. Patch by Pablo Galindo.

- gh-91266: Refactor the `bytearray` strip methods `strip`, `lstrip` and `rstrip` to use a common implementation.

- gh-91479: Replaced the `__note__` field of `BaseException` (added in an earlier version of 3.11) with the final design of PEP 678. Namely, `BaseException` gets an `add_note()` method, and its `__notes__` field is created when necessary.

- gh-46055: Speed up right shift of negative integers, by removing unnecessary creation of temporaries. Original patch by Xinhang Xu, reworked by Mark Dickinson.

- gh-91462: Make the interpreter’s low-level tracing (lltrace) feature output more readable by displaying opcode names (rather than just numbers), and by displaying stack contents before each opcode.

- gh-89455: Fixed an uninitialized bool value in the traceback printing code path that was introduced by the initial bpo-45292 exception groups work.

- gh-91421: Fix a potential integer overflow in _Py_DecodeUTF8Ex.

- gh-91428: Add `static const char *const _PyOpcode_OpName[256] = {...};` to `opcode.h` for debug builds to assist in debugging the Python interpreter. It is now more convenient to make various forms of debugging output more human-readable by including opcode names rather than just the corresponding decimal digits.

- bpo-47120: Make `POP_JUMP_IF_TRUE`, `POP_JUMP_IF_FALSE`, `POP_JUMP_IF_NONE` and `POP_JUMP_IF_NOT_NONE` virtual, mapping to new relative jump opcodes.

- bpo-45317: Add internal documentation explaining design of new (for 3.11) frame stack.

- bpo-47197: ctypes used to mishandle `void` return types, so that for instance a function declared like `ctypes.CFUNCTYPE(None, ctypes.c_int)` would be called with signature `int f(int)` instead of `void f(int)`. Wasm targets require function pointers to be called with the correct signatures so this led to crashes. The problem is now fixed.

- bpo-47120: Make opcodes `JUMP_IF_TRUE_OR_POP` and `JUMP_IF_FALSE_OR_POP` relative rather than absolute.

- bpo-47177: Replace the `f_lasti` member of the internal `_PyInterpreterFrame` structure with a `prev_instr` pointer, which reduces overhead in the main interpreter loop. The `f_lasti` attribute of Python-layer frame objects is preserved for backward-compatibility.

- bpo-46961: Integer mod/remainder operations, including the three-argument form of `pow()`, now consistently return ints from the global small integer cache when applicable.

- bpo-46962: Classes and functions that unconditionally declared their docstrings ignoring the `--without-doc-strings` compilation flag no longer do so.

  The classes affected are `ctypes.UnionType`, `pickle.PickleBuffer`, `testcapi.RecursingInfinitelyError`, and `types.GenericAlias`.

  The functions affected are 24 methods in `ctypes`.

  Patch by Oleg Iarygin.

- bpo-46942: Use Argument Clinic for the `types.MethodType` constructor. Patch by Oleg Iarygin.

- bpo-46764: Fix wrapping bound methods with @classmethod

- bpo-43464: Optimize `set.intersection()` for non-set arguments.

- bpo-46721: Optimize `set.issuperset()` for non-set argument.

- bpo-46509: Add type-specialized versions of the `Py_DECREF()`, and use them for `float`, `int`, `str`, `bool`, and `None` to avoid pointer-chasing at runtime where types are known at C compile time.

- bpo-46045: Do not use POSIX semaphores on NetBSD

- bpo-36819: Fix crashes in built-in encoders with error handlers that return position less or equal than the starting position of non-encodable characters.

- bpo-34093: `marshal.dumps()` uses `FLAG_REF` for all interned strings. This makes output more deterministic and helps reproducible build.

- bpo-26579: Added `object.__getstate__` which provides the default implementation of the `__getstate__()` method.

  Copying and pickling instances of subclasses of builtin types bytearray, set, frozenset, collections.OrderedDict, collections.deque, weakref.WeakSet, and datetime.tzinfo now copies and pickles instance attributes implemented as slots.

### Library

- gh-87901: Add the encoding parameter to `os.popen()`.

- gh-90997: Fix an issue where `dis` utilities may interpret populated inline cache entries as valid instructions.

- gh-92332: Deprecate `typing.Text` (removal of the class is currently not planned). Patch by Alex Waygood.

- gh-78157: Deprecate nested classes in enum definitions becoming members – in 3.13 they will be normal classes; add `member` and `nonmember` functions to allow control over results now.

- gh-92356: Fixed a performance regression in ctypes function calls.

- gh-90997: Show the actual named values stored in inline caches when `show_caches=True` is passed to `dis` utilities.

- gh-92301: Prefer `close_range()` to iterating over procfs for file descriptor closing in `subprocess` for better performance.

- gh-67248: Sort the miscellaneous topics in Cmd.do_help()

- gh-92210: Port `socket.__init__` to Argument Clinic. Patch by Cinder.

- gh-80010: Add support for generalized ISO 8601 parsing to `datetime.datetime.fromisoformat()`, `datetime.date.fromisoformat()` and `datetime.time.fromisoformat()`. Patch by Paul Ganssle.

- gh-92118: Fix a 3.11 regression in `contextmanager()`, which caused it to propagate exceptions with incorrect tracebacks.

- gh-90887: Adding `COPYFILE_STAT`, `COPYFILE_ACL` and `COPYFILE_XATTR` constants for `os.fcopyfile()` available in macOs.

- gh-91215: For `@dataclass`, add weakref_slot. The new parameter defaults to `False`. If true, and if `slots=True`, add a slot named `"__weakref__"`, which will allow instances to be weakref’d. Contributed by Eric V. Smith

- gh-85984: New function os.login_tty() for Unix.

- gh-92128: Add `__class_getitem__()` to `logging.LoggerAdapter` and `logging.StreamHandler`, allowing them to be parameterized at runtime. Patch by Alex Waygood.

- gh-92049: Forbid pickling constants `re._constants.SUCCESS` etc. Previously, pickling did not fail, but the result could not be unpickled.

- gh-92062: `inspect.Parameter` now raises `ValueError` if `name` is a keyword, in addition to the existing check that it is an identifier.

- gh-87390: Add an `__unpacked__` attribute to `types.GenericAlias`. Patch by Jelle Zijlstra.

- gh-88089: Add support for generic `typing.NamedTuple`.

- gh-91996: New http.HTTPMethod enum to represent all the available HTTP request methods in a convenient way

- gh-91984: Modified test strings in test_argparse.py to not contain trailing spaces before end of line.

- gh-91952: Add `encoding="locale"` support to `TextIOWrapper.reconfigure()`.

- gh-91954: Add encoding and errors arguments to `subprocess.getoutput()` and `subprocess.getstatusoutput()`.

- bpo-47029: Always close the read end of the pipe used by `multiprocessing.Queue` after the last write of buffered data to the write end of the pipe to avoid `BrokenPipeError` at garbage collection and at `multiprocessing.Queue.close()` calls. Patch by Géry Ogam.

- gh-91928: Add `datetime.UTC` alias for `datetime.timezone.utc`.

  Patch by Kabir Kwatra.

- gh-68966: The `mailcap` module is now deprecated and will be removed in Python 3.13. See PEP 594 for the rationale and the `mimetypes` module for an alternative. Patch by Victor Stinner.

- gh-91401: Provide a way to disable `subprocess` use of `vfork()` just in case it is ever needed and document the existing mechanism for `posix_spawn()`.

- gh-64783: Fix `signal.NSIG` value on FreeBSD to accept signal numbers greater than 32, like `signal.SIGRTMIN` and `signal.SIGRTMAX`. Patch by Victor Stinner.

- gh-91910: Add missing f prefix to f-strings in error messages from the `multiprocessing` and `asyncio` modules.

- gh-91860: Add `typing.dataclass_transform()`, implementing PEP 681. Patch by Jelle Zijlstra.

- gh-91832: Add `required` attribute to `argparse.Action` repr output.

- gh-91827: In the `tkinter` module add method `info_patchlevel()` which returns the exact version of the Tcl library as a named tuple similar to `sys.version_info`.

- gh-84461: Add `--enable-wasm-pthreads` to enable pthreads support for WASM builds. `Emscripten/node` no longer has threading enabled by default. Include additional file systems.

- gh-91821: Fix unstable `test_from_tuple` test in `test_decimal.py`.

- gh-91217: Deprecate the xdrlib module.

- gh-91217: Deprecate the uu module.

- gh-91760: More strict rules will be applied for numerical group references and group names in regular expressions. For now, a deprecation warning is emitted for group references and group names which will be errors in future Python versions.

- gh-84461: Add provisional `sys._emscripten_info` named tuple with build-time and run-time information about Emscripten platform.

- gh-90623: `signal.raise_signal()` and `os.kill()` now check immediately for pending signals. Patch by Victor Stinner.

- gh-91734: Fix OSS audio support on Solaris.

- gh-90633: Include the passed value in the exception thrown by `typing.assert_never()`. Patch by Jelle Zijlstra.

- gh-91700: Compilation of regular expression containing a conditional expression `(?(group)...)` now raises an appropriate `re.error` if the group number refers to not defined group. Previously an internal RuntimeError was raised.

- gh-91231: Add an optional keyword shutdown_timeout parameter to the `multiprocessing.BaseManager` constructor. Kill the process if terminate() takes longer than the timeout. Patch by Victor Stinner.

- gh-91621: Fix `typing.get_type_hints()` for `collections.abc.Callable`. Patch by Shantanu Jain.

- gh-90568: Parsing `\N` escapes of Unicode Named Character Sequences in a `regular expression` raises now `re.error` instead of `TypeError`.

- gh-91670: Remove deprecated `SO` config variable in `sysconfig`.

- gh-91217: Deprecate the telnetlib module.

- gh-91217: Deprecate the sunau module.

- gh-91217: Deprecate the spwd module.

- gh-91217: Deprecate the sndhdr module, as well as inline needed functionality for `email.mime.MIMEAudio`.

- gh-91616: `re` module, fix `fullmatch()` mismatch when using Atomic Grouping or Possessive Quantifiers.

- gh-91217: Deprecate the ‘pipes’ module.

- gh-91217: Deprecate the ossaudiodev module.

- bpo-47256: `re` module, limit the maximum capturing group to 1,073,741,823 in 64-bit build, this increases the depth of backtracking.

- gh-91217: Deprecate the nis module.

- gh-91595: Fix the comparison of character and integer inside `Tools.gdb.libpython.write_repr()`. Patch by Yu Liu.

- gh-74166: Add option to raise all errors from `create_connection()` in an `ExceptionGroup` when it fails to create a connection. The default remains to raise only the last error that had occurred when multiple addresses were tried.

- gh-91487: Optimize asyncio UDP speed, over 100 times faster when transferring a large file.

- gh-91575: Update case-insensitive matching in the `re` module to the latest Unicode version.

- gh-90622: In `concurrent.futures.process.ProcessPoolExecutor` disallow the “fork” multiprocessing start method when the new `max_tasks_per_child` feature is used as the mix of threads+fork can hang the child processes. Default to using the safe “spawn” start method in that circumstance if no `mp_context` was supplied.

- gh-89022: In `sqlite3`, `SQLITE_MISUSE` result codes are now mapped to `InterfaceError` instead of `ProgrammingError`. Also, more accurate exceptions are raised when binding parameters fail. Patch by Erlend E. Aasland.

- gh-91526: Stop calling `os.device_encoding(file.fileno())` in `TextIOWrapper`. It was complex, never documented, and didn’t work for most cases. (Patch by Inada Naoki.)

- gh-88116: Change the frame-related functions in the `inspect` module to return a regular object (that is backwards compatible with the old tuple-like interface) that include the extended PEP 657 position information (end line number, column and end column). The affected functions are: `inspect.getframeinfo()`, `inspect.getouterframes()`, `inspect.getinnerframes()`, `inspect.stack()` and `inspect.trace()`. Patch by Pablo Galindo.

- gh-69093: Add indexing and slicing support to `sqlite3.Blob`. Patch by Aviv Palivoda and Erlend E. Aasland.

- gh-69093: Add context manager support to `sqlite3.Blob`. Patch by Aviv Palivoda and Erlend E. Aasland.

- gh-91217: Deprecate nntplib.

- gh-91217: Deprecate msilib.

- gh-91404: Improve the performance of `re` matching by using computed gotos (or “threaded code”) on supported platforms and removing expensive pointer indirections.

- gh-91217: Deprecate the imghdr module.

- gh-91217: Deprecate the crypt module.

- gh-91276: Make space for longer opcodes in `dis` output.

- bpo-47000: Make `TextIOWrapper` uses locale encoding when `encoding="locale"` is specified even in UTF-8 mode.

- gh-91230: `warnings.catch_warnings()` now accepts arguments for `warnings.simplefilter()`, providing a more concise way to locally ignore warnings or convert them to errors.

- gh-91217: Deprecate the chunk module.

- gh-91498: Add the `TCP_CONNECTION_INFO` option (available on macOS) to `socket`.

- bpo-47260: Fix `os.closerange()` potentially being a no-op in a Linux seccomp sandbox.

- bpo-47087: Implement `typing.Required` and `typing.NotRequired` (PEP 655). Patch by David Foster and Jelle Zijlstra.

- bpo-47061: Deprecate cgi and cgitb.

- bpo-47061: Deprecate audioop.

- bpo-47000: Add `locale.getencoding()` to get the current locale encoding. It is similar to `locale.getpreferredencoding(False)` but ignores the Python UTF-8 Mode.

- bpo-42012: Add `wsgiref.types`, containing WSGI-specific types for static type checking.

- bpo-47227: Suppress expression chaining for more `re` parsing errors.

- bpo-47211: Remove undocumented and never working function `re.template()` and flag `re.TEMPLATE`. This was later reverted in 3.11.0b2 and deprecated instead.

- bpo-47135: `decimal.localcontext()` now accepts context attributes via keyword arguments

- bpo-43323: Fix errors in the `email` module if the charset itself contains undecodable/unencodable characters.

- bpo-46841: Disassembly of quickened code.

- bpo-46681: Forward gzip.compress() compresslevel to zlib.

- bpo-45100: Add `typing.get_overloads()` and `typing.clear_overloads()`. Patch by Jelle Zijlstra.

- bpo-44807: `typing.Protocol` no longer silently replaces `__init__()` methods defined on subclasses. Patch by Adrian Garcia Badaracco.

- bpo-46787: Fix `concurrent.futures.ProcessPoolExecutor` exception memory leak

- bpo-46720: Add support for path-like objects to `multiprocessing.set_executable()` for Windows to be on a par with Unix-like systems. Patch by Géry Ogam.

- bpo-46696: Add `SO_INCOMING_CPU` constant to `socket`.

- bpo-46053: Fix OSS audio support on NetBSD.

- bpo-45639: `image/avif` and `image/webp` were added to `mimetypes`.

- bpo-46285: Add command-line option `-p`/`--protocol` to module `http.server` which specifies the HTTP version to which the server is conformant (HTTP/1.1 conformant servers can now be run from the command-line interface of module `http.server`). Patch by Géry Ogam.

- bpo-44791: Accept ellipsis as the last argument of `typing.Concatenate`.

- bpo-46547: Remove variables leaking into `pydoc.Helper` class namespace.

- bpo-46415: Fix ipaddress.ip_{address,interface,network} raising TypeError instead of ValueError if given invalid tuple as address parameter.

- bpo-46075: `CookieJar` with `DefaultCookiePolicy` now can process cookies from localhost with domain=localhost explicitly specified in Set-Cookie header.

- bpo-45995: Add a “z” option to the string formatting specification that coerces negative zero floating-point values to positive zero after rounding to the format precision. Contributed by John Belmonte.

- bpo-26175: Fully implement the `io.BufferedIOBase` or `io.TextIOBase` interface for `tempfile.SpooledTemporaryFile` objects. This lets them work correctly with higher-level layers (like compression modules). Patch by Carey Metcalfe.

- bpo-45138: Fix a regression in the `sqlite3` trace callback where bound parameters were not expanded in the passed statement string. The regression was introduced in Python 3.10 by bpo-40318. Patch by Erlend E. Aasland.

- bpo-44863: Allow `TypedDict` subclasses to also include `Generic` as a base class in class based syntax. Thereby allowing the user to define a generic `TypedDict`, just like a user-defined generic but with `TypedDict` semantics.

- bpo-44587: Fix BooleanOptionalAction to not automatically add a default string. If a default string is desired, use a formatter to add it.

- bpo-43827: All positional-or-keyword parameters to `ABCMeta.__new__` are now positional-only to avoid conflicts with keyword arguments to be passed to `__init_subclass__()`.

- bpo-43218: Prevent creation of a venv whose path contains the PATH separator. This could affect the usage of the activate script. Patch by Dustin Rodrigues.

- bpo-38435: Add a `process_group` parameter to `subprocess.Popen` to help move more things off of the unsafe `preexec_fn` parameter.

- bpo-42066: Fix cookies getting sorted in `CookieJar.__iter__()` which is an extra behavior and not mentioned in RFC 2965 or Netscape cookie protocol. Now the cookies in `CookieJar` follows the order of the `Set-Cookie` header. Patch by Iman Kermani.

- bpo-40617: Add `create_window_function()` to `sqlite3.Connection` for creating aggregate window functions. Patch by Erlend E. Aasland.

- bpo-40676: Convert `csv` to use Argument Clinic for `csv.field_size_limit()`, `csv.get_dialect()`, `csv.unregister_dialect()` and `csv.list_dialects()`.

- bpo-39716: Raise an `ArgumentError` when the same subparser name is added twice to an `argparse.ArgumentParser`. This is consistent with the (default) behavior when the same option string is added twice to an `ArgumentParser`.

- bpo-36073: Raise `ProgrammingError` instead of segfaulting on recursive usage of cursors in `sqlite3` converters. Patch by Sergey Fedoseev.

- bpo-34975: Adds a `start_tls()` method to `StreamWriter`, which upgrades the connection with TLS using the given `SSLContext`.

- bpo-22276: `Path` methods `glob()` and `rglob()` return only directories if pattern ends with a pathname components separator (`/` or `sep`). Patch by Eisuke Kawashima.

- bpo-24905: Add `blobopen()` to `sqlite3.Connection`. `sqlite3.Blob` allows incremental I/O operations on blobs. Patch by Aviv Palivoda and Erlend E. Aasland.

### Documentation

- gh-91888: Add a new `gh` role to the documentation to link to GitHub issues.

- gh-91783: Document security issues concerning the use of the function `shutil.unpack_archive()`

- gh-91547: Remove “Undocumented modules” page.

- gh-91298: In `importlib.resources.abc`, refined the documentation of the Traversable Protocol, applying changes from importlib_resources 5.7.1.

- bpo-44347: Clarify the meaning of dirs_exist_ok, a kwarg of `shutil.copytree()`.

- bpo-36329: Remove ‘make -C Doc serve’ in favour of ‘make -C Doc htmlview’

- bpo-47189: Add a What’s New in Python 3.11 entry for the Faster CPython project. Documentation by Ken Jin and Kumar Aditya.

- bpo-38668: Update the introduction to documentation for `os.path` to remove warnings that became irrelevant after the implementations of PEP 383 and PEP 529.

- bpo-47115: The documentation now lists which members of C structs are part of the Limited API/Stable ABI.

- bpo-46962: All docstrings in code snippets are now wrapped into `PyDoc_STR` to follow the guideline of PEP 7’s Documentation Strings paragraph. Patch by Oleg Iarygin.

- bpo-26792: Improve the docstrings of `runpy.run_module()` and `runpy.run_path()`. Original patch by Andrew Brezovsky.

### Tests

- gh-92169: Use `warnings_helper.import_deprecated()` to import deprecated modules uniformly in tests. Patch by Hugo van Kemenade.

- gh-84461: When multiprocessing is enabled, libregrtest can now use a Python executable other than `sys.executable` via the `--python` flag.

- gh-91904: Fix initialization of `PYTHONREGRTEST_UNICODE_GUARD` which prevented running regression tests on non-UTF-8 locale.

- gh-91752: Added @requires_zlib to test.test_tools.test_freeze.TestFreeze.

- gh-91607: Fix `test_concurrent_futures` to test the correct multiprocessing start method context in several cases where the test logic mixed this up.

- bpo-40280: Threading tests are now skipped on WASM targets without pthread support.

- bpo-47109: Test for `ctypes.macholib.dyld`, `ctypes.macholib.dylib`, and `ctypes.macholib.framework` are brought from manual pre-`unittest` times to `ctypes.test` location and structure. Patch by Oleg Iarygin.

- bpo-29890: Add tests for `ipaddress.IPv4Interface` and `ipaddress.IPv6Interface` construction with tuple arguments. Original patch and tests by louisom.

### Build

- gh-89452: gdbm-compat is now preferred over ndbm if both are available on the system. This allows avoiding the problematic ndbm.h on macOS.

- gh-91731: Python is now built with `-std=c11` compiler option, rather than `-std=c99`. Patch by Victor Stinner.

- bpo-47152: Add script and make target for generating `sre_constants.h`.

- bpo-47103: Windows `PGInstrument` builds now copy a required DLL into the output directory, making it easier to run the profile stage of a PGO build.

### Windows

- bpo-46907: Update Windows installer to use SQLite 3.38.3.

- bpo-47239: Fixed –list and –list-paths output for Python Launcher for Windows when used in an active virtual environment.

- bpo-46907: Update Windows installer to use SQLite 3.38.2.

- bpo-46785: Fix race condition between `os.stat()` and unlinking a file on Windows, by using errors codes returned by `FindFirstFileW()` when appropriate in `win32_xstat_impl`.

- bpo-40859: Update Windows build to use xz-5.2.5

### macOS

- bpo-46907: Update macOS installer to SQLite 3.38.4.

### Tools/Demos

- gh-91583: Fix regression in the code generated by Argument Clinic for functions with the `defining_class` parameter.

- gh-91575: Add script `Tools/scripts/generate_re_casefix.py` and the make target `regen-re` for generating additional data for case-insensitive matching according to the current Unicode version.

- gh-91551: Remove the ancient Pynche color editor. It has moved to https://gitlab.com/warsaw/pynche

### C API

- gh-88279: Deprecate the C functions: `PySys_SetArgv()`, `PySys_SetArgvEx()`, `PySys_SetPath()`. Patch by Victor Stinner.

- gh-92154: Added the `PyCode_GetCode()` function. This function does the equivalent of the Python code `getattr(code_object, 'co_code')`.

- gh-92173: Fix the `closure` argument to `PyEval_EvalCodeEx()`.

- gh-91320: Fix C++ compiler warnings about “old-style cast” (`g++ -Wold-style-cast`) in the Python C API. Use C++ `reinterpret_cast<>` and `static_cast<>` casts when the Python C API is used in C++. Patch by Victor Stinner.

- gh-80527: Mark functions as deprecated by PEP 623: `PyUnicode_AS_DATA()`, `PyUnicode_AS_UNICODE()`, `PyUnicode_GET_DATA_SIZE()`, `PyUnicode_GET_SIZE()`. Patch by Victor Stinner.

- gh-91768: `Py_REFCNT()`, `Py_TYPE()`, `Py_SIZE()` and `Py_IS_TYPE()` functions argument type is now `PyObject*`, rather than `const PyObject*`. Patch by Victor Stinner.

- gh-91020: Add `PyBytes_Type.tp_alloc` to initialize `PyBytesObject.ob_shash` for bytes subclasses.

- bpo-40421: Add `PyFrame_GetLasti` C-API function to access frame object’s `f_lasti` attribute safely from C code.

- bpo-35134: Remove the `Include/code.h` header file. C extensions should only include the main `<Python.h>` header file. Patch by Victor Stinner.

- bpo-47169: `PyOS_CheckStack()` is now exported in the Stable ABI on Windows.

- bpo-47169: `PyThread_get_thread_native_id()` is excluded from the stable ABI on platforms where it doesn’t exist (like Solaris).

- bpo-46343: Added `PyErr_GetHandledException()` and `PyErr_SetHandledException()` as simpler alternatives to `PyErr_GetExcInfo()` and `PyErr_SetExcInfo()`.

  They are included in the stable ABI.

## Python 3.11.0 alpha 7

Release date: 2022-04-05

### Core and Builtins

- bpo-47212: Raise `IndentationError` instead of `SyntaxError` for a bare `except` with no following indent. Improve `SyntaxError` locations for an un-parenthesized generator used as arguments. Patch by Matthieu Dartiailh.

- bpo-47186: Replace `JUMP_IF_NOT_EG_MATCH` by `CHECK_EG_MATCH` + jump.

- bpo-47176: Emscripten builds cannot handle signals in the usual way due to platform limitations. Python can now handle signals. To use, set Module.Py_EmscriptenSignalBuffer to be a single byte SharedArrayBuffer and set Py_EMSCRIPTEN_SIGNAL_HANDLING to 1. Writing a number into the SharedArrayBuffer will cause the corresponding signal to be raised into the Python thread.

- bpo-47186: Replace `JUMP_IF_NOT_EXC_MATCH` by `CHECK_EXC_MATCH` + jump.

- bpo-47120: Replace the absolute jump opcode `JUMP_NO_INTERRUPT` by the relative `JUMP_BACKWARD_NO_INTERRUPT`.

- bpo-46841: Avoid unnecessary allocations when comparing code objects.

- bpo-47182: Fix a crash when using a named unicode character like `"\N{digit nine}"` after the main interpreter has been initialized a second time.

- bpo-47162: WebAssembly cannot deal with bad function pointer casts (different count or types of arguments). Python can now use call trampolines to mitigate the problem. Define `PY_CALL_TRAMPOLINE` to enable call trampolines.

- bpo-46775: Some Windows system error codes(>= 10000) are now mapped into the correct errno and may now raise a subclass of `OSError`. Patch by Donghee Na.

- bpo-47129: Improve error messages in f-string syntax errors concerning empty expressions.

- bpo-47117: Fix a crash if we fail to decode characters in interactive mode if the tokenizer buffers are uninitialized. Patch by Pablo Galindo.

- bpo-47127: Speed up calls to c functions with keyword arguments by 25% with specialization. Patch by Kumar Aditya.

- bpo-47120: Replaced `JUMP_ABSOLUTE` by the relative jump `JUMP_BACKWARD`.

- bpo-42197: `PyFrame_FastToLocalsWithError()` and `PyFrame_LocalsToFast()` are no longer called during profiling nor tracing. C code can access the `f_locals` attribute of `PyFrameObject` by calling `PyFrame_GetLocals()`.

- bpo-47070: Improve performance of `array_inplace_repeat` by reducing the number of invocations of `memcpy`. Refactor the `repeat` and inplace `repeat` methods of `array`, `bytes`, `bytearray` and `unicodeobject` to use the common `_PyBytes_Repeat`.

- bpo-47053: Reduce de-optimization in the specialized `BINARY_OP_INPLACE_ADD_UNICODE` opcode.

- bpo-47045: Remove the `f_state` field from the _PyInterpreterFrame struct. Add the `owner` field to the _PyInterpreterFrame struct to make ownership explicit to simplify clearing and deallocing frames and generators.

- bpo-46968: Check for the existence of the “sys/auxv.h” header in `faulthandler` to avoid compilation problems in systems where this header doesn’t exist. Patch by Pablo Galindo

- bpo-46329: Use low bit of `LOAD_GLOBAL` to indicate whether to push a `NULL` before the global. Helps streamline the call sequence a bit.

- bpo-46841: Quicken bytecode in-place by storing it as part of the corresponding `PyCodeObject`.

- bpo-47012: Speed up iteration of `bytes` and `bytearray` by 30%. Patch by Kumar Aditya.

- bpo-47009: Improved the performance of `list.append()` and list comprehensions by optimizing for the common case, where no resize is needed. Patch by Dennis Sweeney.

- bpo-47005: Improve performance of `bytearray_repeat` and `bytearray_irepeat` by reducing the number of invocations of `memcpy`.

- bpo-46829: Deprecate passing a message into `asyncio.Future.cancel()` and `asyncio.Task.cancel()`

- bpo-46993: Speed up `bytearray` creation from `list` and `tuple` by 40%. Patch by Kumar Aditya.

- bpo-39829: Removed the `__len__()` call when initializing a list and moved initializing to `list_extend`. Patch by Jeremiah Pascual.

- bpo-46944: Speed up throwing exception in generator with `METH_FASTCALL` calling convention. Patch by Kumar Aditya.

- bpo-46841: Modify `STORE_SUBSCR` to use an inline cache entry (rather than its oparg) as an adaptive counter.

- bpo-46841: Use inline caching for `PRECALL` and `CALL`, and remove the internal machinery for managing the (now unused) non-inline caches.

- bpo-46881: Statically allocate and initialize the latin1 characters.

- bpo-46838: Improve syntax errors for incorrect function definitions. Patch by Pablo Galindo

- bpo-43721: Fix docstrings of `getter`, `setter`, and `deleter` to clarify that they create a new copy of the property.

- bpo-43224: Make grammar changes required for PEP 646.

### Library

- bpo-47208: Allow vendors to override `CTYPES_MAX_ARGCOUNT`.

- bpo-23689: `re` module: fix memory leak when a match is terminated by a signal or memory allocation failure. Patch by Ma Lin.

- bpo-47167: Allow overriding a future compliance check in `asyncio.Task`.

- bpo-47151: When subprocess tries to use vfork, it now falls back to fork if vfork returns an error. This allows use in situations where vfork isn’t allowed by the OS kernel.

- bpo-47152: Convert the `re` module into a package. Deprecate modules `sre_compile`, `sre_constants` and `sre_parse`.

- bpo-4833: Add `ZipFile.mkdir()`

- bpo-27929: Fix `asyncio.loop.sock_connect()` to only resolve names for `socket.AF_INET` or `socket.AF_INET6` families. Resolution may not make sense for other families, like `socket.AF_BLUETOOTH` and `socket.AF_UNIX`.

- bpo-14265: Adds the fully qualified test name to unittest output

- bpo-47061: Deprecate the aifc module.

- bpo-39622: Handle Ctrl+C in asyncio programs to interrupt the main task.

- bpo-47101: `hashlib.algorithms_available` now lists only algorithms that are provided by activated crypto providers on OpenSSL 3.0. Legacy algorithms are not listed unless the legacy provider has been loaded into the default OSSL context.

- bpo-47099: All `URLError` exception messages raised in `urllib.request.URLopener` now contain a colon between `ftp error` and the rest of the message. Previously, `open_ftp()` missed the colon. Patch by Oleg Iarygin.

- bpo-47099: Exception chaining is changed from `Exception.with_traceback()`/`sys.exc_info()` to PEP 3134. Patch by Oleg Iarygin.

- bpo-47095: `hashlib`’s internal `_blake2` module now prefers `libb2` from https://www.blake2.net/ over Python’s vendored copy of blake2.

- bpo-47098: The Keccak Code Package for `hashlib`’s internal `_sha3` module has been replaced with tiny_sha3. The module is used as fallback when Python is built without OpenSSL.

- bpo-47088: Implement `typing.LiteralString`, part of PEP 675. Patch by Jelle Zijlstra.

- bpo-42885: Optimize `re.search()`, `re.split()`, `re.findall()`, `re.finditer()` and `re.sub()` for regular expressions starting with `\A` or `^`.

- bpo-23691: Protect the `re.finditer()` iterator from re-entering.

- bpo-47067: Optimize calling `GenericAlias` objects by using PEP 590 `vectorcall` and by replacing `PyObject_SetAttrString` with `PyObject_SetAttr`.

- bpo-28080: Add the metadata_encoding parameter in the `zipfile.ZipFile` constructor and the `--metadata-encoding` option in the `zipfile` CLI to allow reading zipfiles using non-standard codecs to encode the filenames within the archive.

- bpo-47000: Make `io.text_encoding()` returns “utf-8” when UTF-8 mode is enabled.

- bpo-42369: Fix thread safety of `zipfile._SharedFile.tell()` to avoid a “zipfile.BadZipFile: Bad CRC-32 for file” exception when reading a `ZipFile` from multiple threads.

- bpo-38256: Fix `binascii.crc32()` when it is compiled to use zlib’c crc32 to work properly on inputs 4+GiB in length instead of returning the wrong result. The workaround prior to this was to always feed the function data in increments smaller than 4GiB or to just call the zlib module function.

  We also have `binascii.crc32()` release the GIL when computing on larger inputs as `zlib.crc32()` and `hashlib` do.

  This also boosts performance on Windows as it now uses the zlib crc32 implementation for `binascii.crc32()` for a 2-3x speedup.

  That the stdlib has a crc32 API in two modules is a known historical oddity. This moves us closer to a single implementation behind them.

- bpo-47066: Global inline flags (e.g. `(?i)`) can now only be used at the start of the regular expressions. Using them not at the start of expression was deprecated since Python 3.6.

- bpo-39394: A warning about inline flags not at the start of the regular expression now contains the position of the flag.

- bpo-433030: Add support of atomic grouping (`(?>...)`) and possessive quantifiers (`*+`, `++`, `?+`, `{m,n}+`) in `regular expressions`.

- bpo-47062: Implement `asyncio.Runner` context manager.

- bpo-46382: `dataclass()` `slots=True` now correctly omits slots already defined in base classes. Patch by Arie Bovenberg.

- bpo-47057: Use FASTCALL convention for `FutureIter.throw()`

- bpo-47061: Deprecate the various modules listed by PEP 594:

  aifc, asynchat, asyncore, audioop, cgi, cgitb, chunk, crypt, imghdr, msilib, nntplib, nis, ossaudiodev, pipes, smtpd, sndhdr, spwd, sunau, telnetlib, uu, xdrlib

- bpo-34790: Remove passing coroutine objects to `asyncio.wait()`.

- bpo-47039: Normalize `repr()` of asyncio future and task objects.

- bpo-2604: Fix bug where doctests using globals would fail when run multiple times.

- bpo-45150: Add `hashlib.file_digest()` helper for efficient hashing of file object.

- bpo-34861: Made cumtime the default sorting key for cProfile

- bpo-45997: Fix `asyncio.Semaphore` re-aquiring FIFO order.

- bpo-47022: The `asynchat`, `asyncore` and `smtpd` modules have been deprecated since at least Python 3.6. Their documentation and deprecation warnings and have now been updated to note they will removed in Python 3.12 (PEP 594).

- bpo-43253: Fix a crash when closing transports where the underlying socket handle is already invalid on the Proactor event loop.

- bpo-40280: `select.select()` now passes `NULL` to `select` for each empty fdset.

- bpo-47004: Apply bugfixes from importlib_metadata 4.11.3, including bugfix for EntryPoint.extras, which was returning match objects and not the extras strings.

- bpo-46998: Allow subclassing of `typing.Any`. Patch by Shantanu Jain.

- bpo-46995: Deprecate missing `asyncio.Task.set_name()` for third-party task implementations, schedule making it mandatory in Python 3.13.

- bpo-46994: Accept explicit contextvars.Context in `asyncio.create_task()` and `asyncio.loop.create_task()`.

- bpo-46981: `typing.get_args(typing.Tuple[()])` now returns `()` instead of `((),)`.

- bpo-46968: Add `os.sysconf_names['SC_MINSIGSTKSZ']`.

- bpo-46985: Upgrade pip wheel bundled with ensurepip (pip 22.0.4)

- bpo-46968: `faulthandler`: On Linux 5.14 and newer, dynamically determine size of signal handler stack size CPython allocates using `getauxval(AT_MINSIGSTKSZ)`. This changes allows for Python extension’s request to Linux kernel to use AMX_TILE instruction set on Sapphire Rapids Xeon processor to succeed, unblocking use of the ISA in frameworks.

- bpo-46917: The `math.nan` value is now always available. Patch by Victor Stinner.

- bpo-46955: Expose `asyncio.base_events.Server` as `asyncio.Server`. Patch by Stefan Zabka.

- bpo-23325: The `signal` module no longer assumes that `SIG_IGN` and `SIG_DFL` are small int singletons.

- bpo-46932: Update bundled libexpat to 2.4.7

- bpo-46933: The `pwd` module is now optional. `os.path.expanduser()` returns the path when the `pwd` module is not available.

- bpo-40059: PEP 680, the `tomllib` module. Adds support for parsing TOML.

- bpo-464471: `asyncio.timeout()` and `asyncio.timeout_at()` context managers added. Patch by Tin Tvrtković and Andrew Svetlov.

- bpo-46805: Added raw datagram socket functions for asyncio: `sock_sendto()`, `sock_recvfrom()` and `sock_recvfrom_into()`.

- bpo-46644: No longer require valid typeforms to be callable. This allows `typing.Annotated` to wrap `typing.ParamSpecArgs` and `dataclasses.InitVar`. Patch by Gregory Beauregard.

- bpo-46581: Brings `ParamSpec` propagation for `GenericAlias` in line with `Concatenate` (and others).

- bpo-45413: Define posix_venv and nt_venv sysconfig installation schemes to be used for bootstrapping new virtual environments. Add venv sysconfig installation scheme to get the appropriate one of the above. The schemes are identical to the pre-existing posix_prefix and nt install schemes. The `venv` module now uses the venv scheme to create new virtual environments instead of hardcoding the paths depending only on the platform. Downstream Python distributors customizing the posix_prefix or nt install scheme in a way that is not compatible with the install scheme used in virtual environments are encouraged not to customize the venv schemes. When Python itself runs in a virtual environment, `sysconfig.get_default_scheme()` and `sysconfig.get_preferred_scheme()` with `key="prefix"` returns venv.

- bpo-43224: Implement support for PEP 646 in typing.py.

- bpo-43224: Allow unpacking types.GenericAlias objects, e.g. `*tuple[int, str]`.

- bpo-46557: Warnings captured by the logging module are now logged without a format string to prevent systems that group logs by the msg argument from grouping captured warnings together.

- bpo-41370: `typing.get_type_hints()` now supports evaluating strings as forward references in PEP 585 generic aliases.

- bpo-46607: Add `DeprecationWarning` to `LegacyInterpolation`, deprecated in the docstring since Python 3.2. Will be removed in Python 3.13. Use `BasicInterpolation` or `ExtendedInterpolation` instead.

- bpo-26120: `pydoc` now excludes __future__ imports from the module’s data items.

- bpo-46480: Add `typing.assert_type()`. Patch by Jelle Zijlstra.

- bpo-46421: Fix a unittest issue where if the command was invoked as `python -m unittest` and the filename(s) began with a dot (.), a `ValueError` is returned.

- bpo-46245: Add optional parameter dir_fd in `shutil.rmtree()`.

- bpo-22859: `usageExit()` is marked deprecated, to be removed in 3.13.

- bpo-46170: Improve the error message when you try to subclass an instance of `typing.NewType`.

- bpo-40296: Fix supporting generic aliases in `pydoc`.

- bpo-20392: Fix inconsistency with uppercase file extensions in `MimeTypes.guess_type()`. Patch by Kumar Aditya.

- bpo-46030: Add `LOCAL_CREDS`, `LOCAL_CREDS_PERSISTENT` and `SCM_CREDS2` FreeBSD constants to the socket module.

- bpo-44439: Fix `.write()` method of a member file in `ZipFile`, when the input data is an object that supports the buffer protocol, the file length may be wrong.

- bpo-45171: Fix handling of the `stacklevel` argument to logging functions in the `logging` module so that it is consistent across all logging functions and, as advertised, similar to the `stacklevel` argument used in `warn()`.

- bpo-24959: Fix bug where `unittest` sometimes drops frames from tracebacks of exceptions raised in tests.

- bpo-44859: Raise more accurate and PEP 249 compatible exceptions in `sqlite3`.

  - Raise `InterfaceError` instead of `ProgrammingError` for `SQLITE_MISUSE` errors.

  - Don’t overwrite `BufferError` with `ValueError` when conversion to BLOB fails.

  - Raise `ProgrammingError` instead of `Warning` if user tries to `execute()` more than one SQL statement.

  - Raise `ProgrammingError` instead of `ValueError` if an SQL query contains null characters.

- bpo-44493: Add missing terminated NUL in sockaddr_un’s length

  This was potentially observable when using non-abstract AF_UNIX datagram sockets to processes written in another programming language.

- bpo-41930: Add `serialize()` and `deserialize()` support to `sqlite3`. Patch by Erlend E. Aasland.

- bpo-33178: Added `ctypes.BigEndianUnion` and `ctypes.LittleEndianUnion` classes, as originally documented in the library docs but not yet implemented.

- bpo-43352: Add an Barrier object in synchronization primitives of asyncio Lib in order to be consistent with Barrier from threading and multiprocessing libs*

- bpo-35859: `re` module, fix a few bugs about capturing group. In rare cases, capturing group gets an incorrect string. Patch by Ma Lin.

### Documentation

- bpo-45099: Document internal `asyncio` API.

- bpo-47126: Update PEP URLs to PEP 676’s new canonical form.

- bpo-47040: Clarified the old Python versions compatibility note of `binascii.crc32()` / `zlib.adler32()` / `zlib.crc32()` functions.

- bpo-46033: Clarify `for` statement execution in its doc.

- bpo-45790: Adjust inaccurate phrasing in Defining Extension Types: Tutorial about the `ob_base` field and the macros used to access its contents.

- bpo-42340: Document that in some circumstances `KeyboardInterrupt` may cause the code to enter an inconsistent state. Provided a sample workaround to avoid it if needed.

- bpo-41233: Link the errnos referenced in `Doc/library/exceptions.rst` to their respective section in `Doc/library/errno.rst`, and vice versa. Previously this was only done for EINTR and InterruptedError. Patch by Yan “yyyyyyyan” Orestes.

### Tests

- bpo-47205: Skip test for `sched_getaffinity()` and `sched_setaffinity()` error case on FreeBSD.

- bpo-46126: Restore ‘descriptions’ when running tests internally.

- bpo-47104: Rewrite `asyncio.to_thread()` tests to use `unittest.IsolatedAsyncioTestCase`.

- bpo-40280: The test suite is now passing on the Emscripten platform. All fork, socket, and subprocess-based tests are skipped.

- bpo-47037: Skip `strftime("%4Y")` feature test on Windows. It can cause an assertion error in debug builds.

- bpo-46587: Skip tests if platform’s `strftime` does not support non-portable glibc extensions.

- bpo-47015: A test case for `os.sendfile()` is converted from deprecated `asyncore` (see PEP 594) to `asyncio`. Patch by Oleg Iarygin.

### Build

- bpo-40280: Add configure option `--enable-wasm-dynamic-linking` to enable `dlopen` and MAIN_MODULE / SIDE_MODULE on `wasm32-emscripten`.

- bpo-46023: `makesetup` now detects and skips all duplicated module definitions. The first entry wins.

- bpo-40280: Add SOABI `wasm32-emscripten` for Emscripten and `wasm32-wasi` for WASI on 32bit WASM as well as `wasm64` counter parts.

- bpo-47032: Ensure Windows install builds fail correctly with a non-zero exit code when part of the build fails.

- bpo-47024: Update OpenSSL to 1.1.1n for macOS installers and all Windows builds.

- bpo-46996: The `tkinter` package now requires Tcl/Tk version 8.5.12 or newer.

- bpo-46973: Add `regen-configure` make target to regenerate configure script with Christian’s container image `quay.io/tiran/cpython_autoconf:269`.

- bpo-46917: Building Python now requires support of IEEE 754 floating-point numbers. Patch by Victor Stinner.

- bpo-45774: `configure` now verifies that all SQLite C APIs needed for the `sqlite3` extension module are found.

### Windows

- bpo-47194: Update `zlib` to v1.2.12 to resolve CVE 2018-25032.

- bpo-47171: Enables installing the `py.exe` launcher on Windows ARM64.

- bpo-46566: Upgraded Python Launcher for Windows to support a new `-V:company/tag` argument for full PEP 514 support and to detect ARM64 installs. The `-64` suffix on arguments is deprecated, but still selects any non-32-bit install. Setting `PYLAUNCHER_ALLOW_INSTALL` and specifying a version that is not installed will attempt to install the requested version from the Microsoft Store.

- bpo-47086: The installer for Windows now includes documentation as loose HTML files rather than a single compiled `.chm` file.

- bpo-46907: Update Windows installer to use SQLite 3.38.1.

- bpo-44549: Update bzip2 to 1.0.8 in Windows builds to mitigate CVE 2016-3189 and CVE 2019-12900.

- bpo-46948: Prevent CVE 2022-26488 by ensuring the Add to PATH option in the Windows installer uses the correct path when being repaired.

### macOS

- bpo-46890: Fix a regression in the setting of `sys._base_executable` in framework builds, and thereby fix a regression in `venv` virtual environments with such builds.

- bpo-46907: Update macOS installer to SQLite 3.38.1.

### Tools/Demos

- bpo-40280: Replace Emscripten’s limited shell with Katie Bell’s browser-ui REPL from python-wasm project.

### C API

- bpo-40421: Add `PyFrame_GetBuiltins`, `PyFrame_GetGenerator` and `PyFrame_GetGlobals` C-API functions to access frame object attributes safely from C code.

- bpo-46850: Move the private `_PyFrameEvalFunction` type, and private `_PyInterpreterState_GetEvalFrameFunc()` and `_PyInterpreterState_SetEvalFrameFunc()` functions to the internal C API. The `_PyFrameEvalFunction` callback function type now uses the `_PyInterpreterFrame` type which is part of the internal C API. Patch by Victor Stinner.

- bpo-46850: Move the private undocumented `_PyEval_EvalFrameDefault()` function to the internal C API. The function now uses the `_PyInterpreterFrame` type which is part of the internal C API. Patch by Victor Stinner.

- bpo-46850: Remove the private undocumented function `_PyEval_CallTracing()` from the C API. Call the public `sys.call_tracing()` function instead. Patch by Victor Stinner.

- bpo-46850: Remove the private undocumented function `_PyEval_GetCoroutineOriginTrackingDepth()` from the C API. Call the public `sys.get_coroutine_origin_tracking_depth()` function instead. Patch by Victor Stinner.

- bpo-46850: Remove the following private undocumented functions from the C API:

  - `_PyEval_GetAsyncGenFirstiter()`

  - `_PyEval_GetAsyncGenFinalizer()`

  - `_PyEval_SetAsyncGenFirstiter()`

  - `_PyEval_SetAsyncGenFinalizer()`

  Call the public `sys.get_asyncgen_hooks()` and `sys.set_asyncgen_hooks()` functions instead. Patch by Victor Stinner.

- bpo-46987: Remove private functions `_PySys_GetObjectId()` and `_PySys_SetObjectId()`. Patch by Donghee Na.

- bpo-46906: Add new functions to pack and unpack C double (serialize and deserialize): `PyFloat_Pack2()`, `PyFloat_Pack4()`, `PyFloat_Pack8()`, `PyFloat_Unpack2()`, `PyFloat_Unpack4()` and `PyFloat_Unpack8()`. Patch by Victor Stinner.

## Python 3.11.0 alpha 6

Release date: 2022-03-07

### Core and Builtins

- bpo-46940: Avoid overriding `AttributeError` metadata information for nested attribute access calls. Patch by Pablo Galindo.

- bpo-46927: Include the type’s name in the error message for subscripting non-generic types.

- bpo-46921: Support vectorcall for `super()`. Patch by Ken Jin.

- bpo-46841: Fix incorrect handling of inline cache entries when specializing `BINARY_OP`.

- bpo-46841: Use an oparg to simplify the construction of helpful error messages in `GET_AWAITABLE`.

- bpo-46903: Make sure that str subclasses can be used as attribute names for instances with virtual dictionaries. Fixes regression in 3.11alpha

- bpo-46841: Add more detailed specialization failure stats for `COMPARE_OP` followed by `EXTENDED_ARG`.

- bpo-46891: Fix bug introduced during 3.11alpha where subclasses of `types.ModuleType` with `__slots__` were not initialized correctly, resulting in an interpreter crash.

- bpo-46841: Use inline caching for `LOAD_ATTR`, `LOAD_METHOD`, and `STORE_ATTR`.

- bpo-46841: Use inline cache for `BINARY_SUBSCR`.

- bpo-46841: Use inline caching for `COMPARE_OP`.

- bpo-46864: Deprecate `PyBytesObject.ob_shash`. It will be removed in Python 3.13.

- bpo-46841: Use inline caching for `UNPACK_SEQUENCE`.

- bpo-46845: Reduces dict size by removing hash value from hash table when all inserted keys are Unicode. For example, `sys.getsizeof(dict.fromkeys("abcdefg"))` becomes 272 bytes from 352 bytes on 64bit platform.

- bpo-46841: Use inline cache for `LOAD_GLOBAL`.

- bpo-46852: Rename the private undocumented `float.__set_format__()` method to `float.__setformat__()` to fix a typo introduced in Python 3.7. The method is only used by test_float. Patch by Victor Stinner.

- bpo-46852: Remove the undocumented private `float.__set_format__()` method, previously known as `float.__setformat__()` in Python 3.7. Its docstring said: “You probably don’t want to use this function. It exists mainly to be used in Python’s test suite.” Patch by Victor Stinner.

- bpo-40116: Fix regression that dict.update(other) may don’t respect iterate order of other when other is key sharing dict.

- bpo-46712: Share global string identifiers in deep-frozen modules.

- bpo-46430: Fix memory leak in interned strings of deep-frozen modules.

- bpo-46841: Store `BINARY_OP` caches inline using a new `CACHE` instruction.

- bpo-45107: Specialize `LOAD_METHOD` for instances with a dict.

- bpo-44337: Reduce the memory usage of specialized `LOAD_ATTR` and `STORE_ATTR` instructions.

- bpo-46729: Add number of sub-exceptions to `BaseException.__str__()`.

- bpo-45885: Don’t un-adapt `COMPARE_OP` when collecting specialization stats.

- bpo-46329: Fix specialization stats gathering for `PRECALL` instructions.

- bpo-46794: Bump up the libexpat version into 2.4.6

- bpo-46823: Implement a specialized combined opcode `LOAD_FAST__LOAD_ATTR_INSTANCE_VALUE`. Patch by Dennis Sweeney.

- bpo-46820: Fix parsing a numeric literal immediately (without spaces) followed by “not in” keywords, like in `1not in x`. Now the parser only emits a warning, not a syntax error.

- bpo-46329: Move `KW_NAMES` before `PRECALL` instruction in call sequence. Change `operand` of `CALL` to match `PRECALL` for easier specialization.

- bpo-46808: Remove the `NEXT_BLOCK` macro from compile.c, and make the compiler automatically generate implicit blocks when they are needed.

- bpo-46329: Add `PUSH_NULL` instruction. This is used as a prefix when evaluating a callable, so that the stack has the same shape for methods and other calls. `PRECALL_FUNCTION` and `PRECALL_METHOD` are merged into a single `PRECALL` instruction.

  There is no change in semantics.

- bpo-46762: Fix an assert failure in debug builds when a ‘<’, ‘>’, or ‘=’ is the last character in an f-string that’s missing a closing right brace.

- bpo-46730: Message of AttributeError caused by getting, setting or deleting a property without the corresponding function now mentions that the attribute is in fact a property and also specifies type of the class that it belongs to.

- bpo-46724: Make sure that all backwards jumps use the `JUMP_ABSOLUTE` instruction, rather than `JUMP_FORWARD` with an argument of `(2**32)+offset`.

- bpo-46732: Correct the docstring for the `__bool__()` method. Patch by Jelle Zijlstra.

- bpo-46072: Add more detailed specialization failure statistics for `BINARY_OP`.

- bpo-46707: Avoid potential exponential backtracking when producing some syntax errors involving lots of brackets. Patch by Pablo Galindo.

- bpo-46323: `ctypes` now allocates memory on the stack instead of on the heap to pass arguments while calling a Python callback function. Patch by Donghee Na.

- bpo-45923: Add a quickened form of `RESUME` that skips quickening checks.

- bpo-46702: Specialize `UNPACK_SEQUENCE` for `tuple` and `list` unpackings.

- bpo-46072: Opcode pair stats are now gathered with `--enable-pystats`. Defining `DYNAMIC_EXECUTION_PROFILE` or `DXPAIRS` no longer has any effect.

- bpo-46675: Allow more than 16 items in a split dict before it is combined. The limit is now 254.

- bpo-40479: Add a missing call to `va_end()` in `Modules/_hashopenssl.c`.

- bpo-46323: Use `PyObject_Vectorcall()` while calling ctypes callback function. Patch by Donghee Na.

- bpo-46615: When iterating over sets internally in `setobject.c`, acquire strong references to the resulting items from the set. This prevents crashes in corner-cases of various set operations where the set gets mutated.

- bpo-45828: The bytecode compiler now attempts to apply runtime stack manipulations at compile-time (whenever it is feasible to do so).

- bpo-30496: Fixed a minor portability issue in the implementation of `PyLong_FromLong()`, and added a fast path for single-digit integers to `PyLong_FromLongLong()`.

### Library

- bpo-25707: Fixed a file leak in `xml.etree.ElementTree.iterparse()` when the iterator is not exhausted. Patch by Jacob Walls.

- bpo-46877: Export `unittest.doModuleCleanups()` in `unittest`. Patch by Kumar Aditya.

- bpo-46848: For performance, use the optimized string-searching implementations from `find()` and `rfind()` for `find()` and `rfind()`.

- bpo-46736: `SimpleHTTPRequestHandler` now uses HTML5 grammar. Patch by Donghee Na.

- bpo-44886: Inherit asyncio proactor datagram transport from `asyncio.DatagramTransport`.

- bpo-46827: Support UDP sockets in `asyncio.loop.sock_connect()` for selector-based event loops. Patch by Thomas Grainger.

- bpo-46811: Make test suite support Expat >=2.4.5

- bpo-46252: Raise `TypeError` if `ssl.SSLSocket` is passed to transport-based APIs.

- bpo-46784: Fix libexpat symbols collisions with user dynamically loaded or statically linked libexpat in embedded Python.

- bpo-46786: The HTML serialisation in xml.etree.ElementTree now writes `embed`, `source`, `track` and `wbr` as empty tags, as defined in HTML 5.

- bpo-39327: `shutil.rmtree()` can now work with VirtualBox shared folders when running from the guest operating-system.

- bpo-45390: Propagate `asyncio.CancelledError` message from inner task to outer awaiter.

- bpo-46756: Fix a bug in `urllib.request.HTTPPasswordMgr.find_user_password()` and `urllib.request.HTTPPasswordMgrWithPriorAuth.is_authenticated()` which allowed to bypass authorization. For example, access to URI `example.org/foobar` was allowed if the user was authorized for URI `example.org/foo`.

- bpo-46737: `random.gauss()` and `random.normalvariate()` now have default arguments.

- bpo-46752: Add task groups to asyncio (structured concurrency, inspired by Trio’s nurseries). This also introduces a change to task cancellation, where a cancelled task can’t be cancelled again until it calls .uncancel().

- bpo-46724: Fix `dis` behavior on negative jump offsets.

- bpo-46333: The `__repr__()` method of `typing.ForwardRef` now includes the `module` parameter of `typing.ForwardRef` when it is set.

- bpo-46643: In `typing.get_type_hints()`, support evaluating stringified `ParamSpecArgs` and `ParamSpecKwargs` annotations. Patch by Gregory Beauregard.

- bpo-45863: When the `tarfile` module creates a pax format archive, it will put an integer representation of timestamps in the ustar header (if possible) for the benefit of older unarchivers, in addition to the existing full-precision timestamps in the pax extended header.

- bpo-46066: Deprecate kwargs-based syntax for `typing.TypedDict` definitions. It had confusing semantics when specifying totality, and was largely unused. Patch by Jingchen Ye.

- bpo-46676: Make `typing.ParamSpec` args and kwargs equal to themselves. Patch by Gregory Beauregard.

- bpo-46323: `ctypes.CFUNCTYPE()` and `ctypes.WINFUNCTYPE()` now fail to create the type if its `_argtypes_` member contains too many arguments. Previously, the error was only raised when calling a function. Patch by Victor Stinner.

- bpo-46672: Fix `NameError` in `asyncio.gather()` when initial type check fails.

- bpo-46659: The `calendar.LocaleTextCalendar` and `calendar.LocaleHTMLCalendar` classes now use `locale.getlocale()`, instead of using `locale.getdefaultlocale()`, if no locale is specified. Patch by Victor Stinner.

- bpo-46659: The `locale.getdefaultlocale()` function is deprecated and will be removed in Python 3.13. Use `locale.setlocale()`, `locale.getpreferredencoding(False)` and `locale.getlocale()` functions instead. Patch by Victor Stinner.

- bpo-46655: In `typing.get_type_hints()`, support evaluating bare stringified `TypeAlias` annotations. Patch by Gregory Beauregard.

- bpo-45948: Fixed a discrepancy in the C implementation of the `xml.etree.ElementTree` module. Now, instantiating an `xml.etree.ElementTree.XMLParser` with a `target=None` keyword provides a default `xml.etree.ElementTree.TreeBuilder` target as the Python implementation does.

- bpo-46626: Expose Linux’s `IP_BIND_ADDRESS_NO_PORT` option in `socket`.

- bpo-46521: Fix a bug in the `codeop` module that was incorrectly identifying invalid code involving string quotes as valid code.

- bpo-46571: Improve `typing.no_type_check()`.

  Now it does not modify external classes and functions. We also now correctly mark classmethods as not to be type checked.

- bpo-46400: expat: Update libexpat from 2.4.1 to 2.4.4

- bpo-46556: Deprecate undocumented support for using a `pathlib.Path` object as a context manager.

- bpo-46534: Implement PEP 673 `typing.Self`. Patch by James Hilton-Balfe.

- bpo-46522: Make various module `__getattr__` AttributeErrors more closely match a typical AttributeError

- bpo-46475: Add `typing.Never` and `typing.assert_never()`. Patch by Jelle Zijlstra.

- bpo-46333: The `__eq__()` and `__hash__()` methods of `typing.ForwardRef` now honor the `module` parameter of `typing.ForwardRef`. Forward references from different modules are now differentiated.

- bpo-46246: Add missing `__slots__` to `importlib.metadata.DeprecatedList`. Patch by Arie Bovenberg.

- bpo-46232: The `ssl` module now handles certificates with bit strings in DN correctly.

- bpo-46195: `typing.get_type_hints()` no longer adds `Optional` to parameters with `None` as a default. This aligns to changes to PEP 484 in https://github.com/python/peps/pull/689

- bpo-31369: Add `RegexFlag` to `re.__all__` and documented it. Add `NOFLAG` to indicate no flags being set.

- bpo-45898: `ctypes` no longer defines `ffi_type_*` symbols in `cfield.c`. The symbols have been provided by libffi for over a decade.

- bpo-44953: Calling `operator.itemgetter` objects and `operator.attrgetter` objects is now faster due to use of the vectorcall calling convention.

- bpo-44289: Fix an issue with `is_tarfile()` method when using fileobj argument: position in the fileobj was advanced forward which made it unreadable with `tarfile.TarFile.open()`.

- bpo-44011: Reimplement SSL/TLS support in asyncio, borrow the implementation from uvloop library.

- bpo-41086: Make the `configparser.ConfigParser` constructor raise `TypeError` if the `interpolation` parameter is not of type `configparser.Interpolation`

- bpo-29418: Implement `inspect.ismethodwrapper()` and fix `inspect.isroutine()` for cases where methodwrapper is given. Patch by Hakan Çelik.

- bpo-14156: argparse.FileType now supports an argument of ‘-’ in binary mode, returning the .buffer attribute of sys.stdin/sys.stdout as appropriate. Modes including ‘x’ and ‘a’ are treated equivalently to ‘w’ when argument is ‘-’. Patch contributed by Josh Rosenberg

### Documentation

- bpo-42238: `Doc/tools/rstlint.py` has moved to its own repository and is now packaged on PyPI as `sphinx-lint`.

### Tests

- bpo-46913: Fix test_faulthandler.test_sigfpe() if Python is built with undefined behavior sanitizer (UBSAN): disable UBSAN on the faulthandler_sigfpe() function. Patch by Victor Stinner.

- bpo-46760: Remove bytecode offsets from expected values in test.test_dis module. Reduces the obstacles to modifying the VM or compiler.

- bpo-46708: Prevent default asyncio event loop policy modification warning after `test_asyncio` execution.

- bpo-46678: The function `make_legacy_pyc` in `Lib/test/support/import_helper.py` no longer fails when `PYTHONPYCACHEPREFIX` is set to a directory on a different device from where tempfiles are stored.

- bpo-46623: Skip test_pair() and test_speech128() of test_zlib on s390x since they fail if zlib uses the s390x hardware accelerator. Patch by Victor Stinner.

### Build

- bpo-46860: Respect `--with-suffix` when building on case-insensitive file systems.

- bpo-46656: Building Python now requires a C11 compiler. Optional C11 features are not required. Patch by Victor Stinner.

- bpo-46656: Building Python now requires support for floating-point Not-a-Number (NaN): remove the `Py_NO_NAN` macro. Patch by Victor Stinner.

- bpo-46640: Building Python now requires a C99 `<math.h>` header file providing a `NAN` constant, or the `__builtin_nan()` built-in function. Patch by Victor Stinner.

- bpo-46608: Exclude marshalled-frozen data if deep-freezing to save 300 KB disk space. This includes adding a new `is_package` field to `_frozen`. Patch by Kumar Aditya.

- bpo-40280: Fix wasm32-emscripten test failures and platform issues. - Disable syscalls that are not supported or don’t work, e.g. wait, getrusage, prlimit, mkfifo, mknod, setres[gu]id, setgroups. - Use fd_count to count open fds. - Add more checks for subprocess and fork. - Add workarounds for missing _multiprocessing and failing socket.accept(). - Enable bzip2. - Disable large file support. - Disable signal.alarm.

- bpo-46430: Intern strings in deep-frozen modules. Patch by Kumar Aditya.

### Windows

- bpo-46744: The default all users install directory for ARM64 is now under the native `Program Files` folder, rather than `Program Files (Arm)` which is intended for ARM (32-bit) files.

- bpo-46567: Adds Tcl and Tk support for Windows ARM64. This also adds IDLE to the installation.

- bpo-46638: Ensures registry virtualization is consistently disabled. For 3.10 and earlier, it remains enabled (some registry writes are protected), while for 3.11 and later it is disabled (registry modifications affect all applications).

### IDLE

- bpo-46630: Make query dialogs on Windows start with a cursor in the entry box.

- bpo-45447: Apply IDLE syntax highlighting to `.pyi` files. Patch by Alex Waygood and Terry Jan Reedy.

### C API

- bpo-46748: Python’s public headers no longer import `<stdbool.h>`, leaving code that embeds/extends Python free to define `bool`, `true` and `false`.

- bpo-46836: Move the `PyFrameObject` type definition (`struct _frame`) to the internal C API `pycore_frame.h` header file. Patch by Victor Stinner.

- bpo-45459: Rename `Include/buffer.h` header file to `Include/pybuffer.h` to avoid conflicts with projects having an existing `buffer.h` header file. Patch by Victor Stinner.

- bpo-45412: Remove the `HAVE_PY_SET_53BIT_PRECISION` macro (moved to the internal C API). Patch by Victor Stinner.

- bpo-46613: Added function `PyType_GetModuleByDef()`, which allows access to module state when a method’s defining class is not available.

## Python 3.11.0 alpha 5

Release date: 2022-02-03

### Core and Builtins

- bpo-45773: Remove two invalid “peephole” optimizations from the bytecode compiler.

- bpo-46564: Do not create frame objects when creating `super` object. Patch by Kumar Aditya.

- bpo-45885: Added more fined-grained specialization failure stats regarding the `COMPARE_OP` bytecode.

- bpo-44977: The delegation of `int()` to `__trunc__()` is now deprecated. Calling `int(a)` when `type(a)` implements `__trunc__()` but not `__int__()` or `__index__()` now raises a `DeprecationWarning`.

- bpo-46458: Reorder code emitted by the compiler for a `try`-`except` block so that the `else` block’s code immediately follows the `try` body (without a jump). This is more optimal for the happy path.

- bpo-46527: Allow passing `iterable` as a keyword argument to `enumerate()` again. Patch by Jelle Zijlstra.

- bpo-46528: Replace several stack manipulation instructions (`DUP_TOP`, `DUP_TOP_TWO`, `ROT_TWO`, `ROT_THREE`, `ROT_FOUR`, and `ROT_N`) with new `COPY` and `SWAP` instructions.

- bpo-46329: Use two or three bytecodes to implement most calls.

  Calls without named arguments are implemented as a sequence of two instructions: `PRECALL; CALL`. Calls with named arguments are implemented as a sequence of three instructions: `PRECALL; KW_NAMES; CALL`. There are two different `PRECALL` instructions: `PRECALL_FUNTION` and `PRECALL_METHOD`. The latter pairs with `LOAD_METHOD`.

  This partition into pre-call and call allows better specialization, and thus better performance ultimately.

  There is no change in semantics.

- bpo-46503: Fix an assert when parsing some invalid N escape sequences in f-strings.

- bpo-46431: Improve error message on invalid calls to `BaseExceptionGroup.__new__()`.

- bpo-46476: Fix memory leak in code objects generated by deepfreeze. Patch by Kumar Aditya.

- bpo-46481: Speed up calls to `weakref.ref.__call__()` by using the PEP 590 `vectorcall` calling convention. Patch by Donghee Na.

- bpo-46417: Fix a race condition on setting a type `__bases__` attribute: the internal function `add_subclass()` now gets the `PyTypeObject.tp_subclasses` member after calling `PyWeakref_NewRef()` which can trigger a garbage collection which can indirectly modify `PyTypeObject.tp_subclasses`. Patch by Victor Stinner.

- bpo-46417: `python -X showrefcount` now shows the total reference count after clearing and destroyed the main Python interpreter. Previously, it was shown before. Patch by Victor Stinner.

- bpo-43683: Add ASYNC_GEN_WRAP opcode to wrap the value to be yielded in async generators. Removes the need to special case async generators in the `YIELD_VALUE` instruction.

- bpo-46407: Optimize some modulo operations in `Objects/longobject.c`. Patch by Jeremiah Vivian.

- bpo-46409: Add new `RETURN_GENERATOR` bytecode to make generators. Simplifies calling Python functions in the VM, as they no longer any need to special case generator functions.

  Also add `JUMP_NO_INTERRUPT` bytecode that acts like `JUMP_ABSOLUTE`, but does not check for interrupts.

- bpo-46406: The integer division `//` implementation has been optimized to better let the compiler understand its constraints. It can be 20% faster on the amd64 platform when dividing an int by a value smaller than `2**30`.

- bpo-46383: Fix invalid signature of `_zoneinfo`’s `module_free` function to resolve a crash on wasm32-emscripten platform.

- bpo-46361: Ensure that “small” integers created by `int.from_bytes()` and `decimal.Decimal` are properly cached.

- bpo-46161: Fix the class building error when the arguments are constants and CALL_FUNCTION_EX is used.

- bpo-46028: Fixes calculation of `sys._base_executable` when inside a virtual environment that uses symlinks with different binary names than the base environment provides.

- bpo-46091: Correctly calculate indentation levels for lines with whitespace character that are ended by line continuation characters. Patch by Pablo Galindo

- bpo-30512: Add CAN Socket support for NetBSD.

- bpo-46045: Do not use POSIX semaphores on NetBSD

- bpo-44024: Improve the `TypeError` message for non-string second arguments passed to the built-in functions `getattr()` and `hasattr()`. Patch by Géry Ogam.

### Library

- bpo-46624: Restore support for non-integer arguments of `random.randrange()` and `random.randint()`.

- bpo-46591: Make the IDLE doc URL on the About IDLE dialog clickable.

- bpo-46565: Remove loop variables that are leaking into modules’ namespaces.

- bpo-46553: In `typing.get_type_hints()`, support evaluating bare stringified `ClassVar` annotations. Patch by Gregory Beauregard.

- bpo-46544: Don’t leak `x` & `uspace` intermediate vars in `textwrap.TextWrapper`.

- bpo-46487: Add the `get_write_buffer_limits` method to `asyncio.transports.WriteTransport` and to the SSL transport.

- bpo-45173: Note the configparser deprecations will be removed in Python 3.12.

- bpo-45162: The deprecated `unittest` APIs removed in 3.11a1 have been temporarily restored to be removed in 3.12 while cleanups in external projects go in.

- bpo-46539: In `typing.get_type_hints()`, support evaluating stringified `ClassVar` and `Final` annotations inside `Annotated`. Patch by Gregory Beauregard.

- bpo-46510: Add missing test for `types.TracebackType` and `types.FrameType`. Calculate them directly from the caught exception without calling `sys.exc_info()`.

- bpo-46491: Allow `typing.Annotated` to wrap `typing.Final` and `typing.ClassVar`. Patch by Gregory Beauregard.

- bpo-46483: Remove `__class_getitem__()` from `pathlib.PurePath` as this class was not supposed to be generic.

- bpo-46436: Fix command-line option `-d`/`--directory` in module `http.server` which is ignored when combined with command-line option `--cgi`. Patch by Géry Ogam.

- bpo-41403: Make `mock.patch()` raise a `TypeError` with a relevant error message on invalid arg. Previously it allowed a cryptic `AttributeError` to escape.

- bpo-46474: In `importlib.metadata.EntryPoint.pattern`, avoid potential REDoS by limiting ambiguity in consecutive whitespace.

- bpo-46474: Removed private method from `importlib.metadata.Path`. Sync with importlib_metadata 4.10.0.

- bpo-46470: Remove unused branch from `typing._remove_dups_flatten`

- bpo-46469: `asyncio` generic classes now return `types.GenericAlias` in `__class_getitem__` instead of the same class.

- bpo-41906: Support passing filter instances in the `filters` values of `handlers` and `loggers` in the dictionary passed to `logging.config.dictConfig()`.

- bpo-46422: Use `dis.Positions` in `dis.Instruction` instead of a regular `tuple`.

- bpo-46434: `pdb` now gracefully handles `help` when `__doc__` is missing, for example when run with pregenerated optimized `.pyc` files.

- bpo-43869: Python uses the same time Epoch on all platforms. Add an explicit unit test to ensure that it’s the case. Patch by Victor Stinner.

- bpo-46414: Add `typing.reveal_type()`. Patch by Jelle Zijlstra.

- bpo-40280: `subprocess` now imports Windows-specific imports when `msvcrt` module is available, and POSIX-specific imports on all other platforms. This gives a clean exception when `_posixsubprocess` is not available (e.g. Emscripten browser target).

- bpo-40066: `IntEnum`, `IntFlag`, and `StrEnum` use the mixed-in type for their `str()` and `format()` output.

- bpo-46316: Optimize `pathlib.Path.iterdir()` by removing an unnecessary check for special entries.

- bpo-29688: Document `pathlib.Path.absolute()` (which has always existed).

- bpo-43012: The pathlib module’s obsolete and internal `_Accessor` class has been removed to prepare the terrain for upcoming enhancements to the module.

- bpo-46258: Speed up `math.isqrt()` for small positive integers by replacing two division steps with a lookup table.

- bpo-46242: Improve error message when creating a new `enum.Enum` type subclassing an existing `Enum` with `_member_names_` using `enum.Enum.__call__()`.

- bpo-43118: Fix a bug in `inspect.signature()` that was causing it to fail on some subclasses of classes with a `__text_signature__` referencing module globals. Patch by Weipeng Hong.

- bpo-26552: Fixed case where failing `asyncio.ensure_future()` did not close the coroutine. Patch by Kumar Aditya.

- bpo-21987: Fix an issue with `tarfile.TarFile.getmember()` getting a directory name with a trailing slash.

- bpo-46124: Update `zoneinfo` to rely on importlib.resources traversable API.

- bpo-46103: Now `inspect.getmembers()` only gets `__bases__` attribute from class type. Patch by Weipeng Hong.

- bpo-46080: Fix exception in argparse help text generation if a `argparse.BooleanOptionalAction` argument’s default is `argparse.SUPPRESS` and it has `help` specified. Patch by Felix Fontein.

- bpo-44791: Fix substitution of `ParamSpec` in `Concatenate` with different parameter expressions. Substitution with a list of types returns now a tuple of types. Substitution with `Concatenate` returns now a `Concatenate` with concatenated lists of arguments.

### Documentation

- bpo-46463: Fixes `escape4chm.py` script used when building the CHM documentation file

### Tests

- bpo-43478: Mocks can no longer be provided as the specs for other Mocks. As a result, an already-mocked object cannot be passed to `mock.Mock()`. This can uncover bugs in tests since these Mock-derived Mocks will always pass certain tests (e.g. isinstance) and builtin assert functions (e.g. assert_called_once_with) will unconditionally pass.

- bpo-46616: Ensures `test_importlib.test_windows` cleans up registry keys after completion.

- bpo-44359: test_ftplib now silently ignores socket errors to prevent logging unhandled threading exceptions. Patch by Victor Stinner.

- bpo-46600: Fix test_gdb.test_pycfunction() for Python built with `clang -Og`. Tolerate inlined functions in the gdb traceback. Patch by Victor Stinner.

- bpo-46542: Fix a Python crash in test_lib2to3 when using Python built in debug mode: limit the recursion limit. Patch by Victor Stinner.

- bpo-46576: test_peg_generator now disables compiler optimization when testing compilation of its own C extensions to significantly speed up the testing on non-debug builds of CPython.

- bpo-46542: Fix `test_json` tests checking for `RecursionError`: modify these tests to use `support.infinite_recursion()`. Patch by Victor Stinner.

- bpo-13886: Skip test_builtin PTY tests on non-ASCII characters if the readline module is loaded. The readline module changes input() behavior, but test_builtin is not intended to test the readline module. Patch by Victor Stinner.

- bpo-40280: Add `test.support.requires_fork()` decorators to mark tests that require a working `os.fork()`.

- bpo-40280: Add `test.support.requires_subprocess()` decorator to mark tests which require working `subprocess` module or `os.spawn*`. The wasm32-emscripten platform has no support for processes.

- bpo-46126: Disable ‘descriptions’ when running tests internally.

### Build

- bpo-46602: Tidied up configure.ac so that conftest.c is truncated rather than appended. This assists in the case where the ‘rm’ of conftest.c fails to happen between tests. Downstream issues such as a clobbered SOABI can result.

- bpo-46600: Fix the test checking if the C compiler supports `-Og` option in the `./configure` script to also use `-Og` on clang which supports it. Patch by Victor Stinner.

- bpo-38472: Fix GCC detection in setup.py when cross-compiling. The C compiler is now run with LC_ALL=C. Previously, the detection failed with a German locale.

- bpo-46513: configure no longer uses `AC_C_CHAR_UNSIGNED` macro and `pyconfig.h` no longer defines reserved symbol `__CHAR_UNSIGNED__`.

- bpo-46471: Use global singletons for single byte bytes objects in deepfreeze.

- bpo-46443: Deepfreeze now uses cached small integers as it saves some space for common small integers.

- bpo-46429: Merge all deep-frozen files into one for space savings. Patch by Kumar Aditya.

- bpo-45569: The build now defaults to using 30-bit digits for Python integers. Previously either 15-bit or 30-bit digits would be selected, depending on the platform. 15-bit digits may still be selected using the `--enable-big-digits=15` option to the `configure` script, or by defining `PYLONG_BITS_IN_DIGIT` in `pyconfig.h`.

- bpo-45925: Update Windows installer to use SQLite 3.37.2.

- bpo-43112: Detect musl libc as a separate SOABI (tagged as `linux-musl`).

### Windows

- bpo-33125: The traditional EXE/MSI based installer for Windows is now available for ARM64

- bpo-46362: os.path.abspath(“C:CON”) is now fixed to return “\.CON”, not the same path. The regression was true of all legacy DOS devices such as COM1, LPT1, or NUL.

- bpo-44934: The installer now offers a command-line only option to add the installation directory to the end of `PATH` instead of at the start.

### macOS

- bpo-45925: Update macOS installer to SQLite 3.37.2.

### IDLE

- bpo-45296: Clarify close, quit, and exit in IDLE. In the File menu, ‘Close’ and ‘Exit’ are now ‘Close Window’ (the current one) and ‘Exit’ is now ‘Exit IDLE’ (by closing all windows). In Shell, ‘quit()’ and ‘exit()’ mean ‘close Shell’. If there are no other windows, this also exits IDLE.

### C API

- bpo-40170: Remove the `PyHeapType_GET_MEMBERS()` macro. It was exposed in the public C API by mistake, it must only be used by Python internally. Use the `PyTypeObject.tp_members` member instead. Patch by Victor Stinner.

- bpo-40170: Move _Py_GetAllocatedBlocks() and _PyObject_DebugMallocStats() private functions to the internal C API. Patch by Victor Stinner.

- bpo-46433: The internal function _PyType_GetModuleByDef now correctly handles inheritance patterns involving static types.

- bpo-45459: `Py_buffer` and various `Py_buffer` related functions are now part of the limited API and stable ABI.

- bpo-14916: Fixed bug in the tokenizer that prevented `PyRun_InteractiveOne` from parsing from the provided FD.

## Python 3.11.0 alpha 4

Release date: 2022-01-13

### Core and Builtins

- bpo-46070: `Py_EndInterpreter()` now explicitly untracks all objects currently tracked by the GC. Previously, if an object was used later by another interpreter, calling `PyObject_GC_UnTrack()` on the object crashed if the previous or the next object of the `PyGC_Head` structure became a dangling pointer. Patch by Victor Stinner.

- bpo-46347: Fix memory leak in PyEval_EvalCodeEx.

- bpo-46339: Fix a crash in the parser when retrieving the error text for multi-line f-strings expressions that do not start in the first line of the string. Patch by Pablo Galindo

- bpo-46331: Do not set line number of instruction storing doc-string. Fixes regression introduced in 3.11 alpha.

- bpo-46314: Remove spurious “call” event when creating a lambda function that was accidentally introduced in 3.11a4.

- bpo-46289: ASDL declaration of `FormattedValue` has changed to reflect `conversion` field is not optional.

- bpo-46297: Fixed an interpreter crash on bootup with multiple PythonPaths set in the Windows registry. Patch by Derzsi Dániel.

- bpo-46237: Fix the line number of tokenizer errors inside f-strings. Patch by Pablo Galindo.

- bpo-46263: We always expect the “use_frozen_modules” config to be set, now that getpath.c was rewritten in pure Python and the logic improved.

- bpo-46006: Fix a regression when a type method like `__init__()` is modified in a subinterpreter. Fix a regression in `_PyUnicode_EqualToASCIIId()` and type `update_slot()`. Revert the change which made the Unicode dictionary of interned strings compatible with subinterpreters: the internal interned dictionary is shared again by all interpreters. Patch by Victor Stinner.

- bpo-45923: Add RESUME opcode. This is a logical no-op. It is emitted by the compiler anywhere a Python function can be entered. It is used by the interpreter to perform tracing and optimizer checks.

- bpo-46208: Fix the regression of os.path.normpath(“A/../../B”) not returning expected “../B” but “B”.

- bpo-46240: Correct the error message for unclosed parentheses when the tokenizer doesn’t reach the end of the source when the error is reported. Patch by Pablo Galindo

- bpo-46009: Remove the `GEN_START` opcode.

- bpo-46235: Certain sequence multiplication operations like `[0] * 1_000` are now faster due to reference-counting optimizations. Patch by Dennis Sweeney.

- bpo-46221: `PREP_RERAISE_STAR` no longer pushes `lasti` to the stack.

- bpo-46202: Remove `POP_EXCEPT_AND_RERAISE` and replace it by an equivalent sequence of other opcodes.

- bpo-46085: Fix iterator cache mechanism of `OrderedDict`.

- bpo-46055: Speed up shifting operation involving integers less than `PyLong_BASE`. Patch by Xinhang Xu.

- bpo-46110: Add a maximum recursion check to the PEG parser to avoid stack overflow. Patch by Pablo Galindo

- bpo-46107: Fix bug where `ExceptionGroup.split()` and `ExceptionGroup.subgroup()` did not copy the exception group’s `__note__` field to the parts.

- bpo-45711: The interpreter state’s representation of handled exceptions (a.k.a exc_info, or _PyErr_StackItem) now has only the `exc_value` field, `exc_type` and `exc_traceback` have been removed as their values can be derived from `exc_value`.

- bpo-44525: Replace the four call bytecode instructions which one pre-call instruction and two call instructions.

  Removes `CALL_FUNCTION`, `CALL_FUNCTION_KW`, `CALL_METHOD` and `CALL_METHOD_KW`.

  Adds `CALL_NO_KW` and `CALL_KW` call instructions, and `PRECALL_METHOD` prefix for pairing with `LOAD_METHOD`.

- bpo-46039: Remove the `YIELD_FROM` instruction and replace it with the `SEND` instruction which performs the same operation, but without the loop.

- bpo-45635: The code called from `_PyErr_Display()` was refactored to improve error handling. It now exits immediately upon an unrecoverable error.

- bpo-46054: Fix parser error when parsing non-utf8 characters in source files. Patch by Pablo Galindo.

- bpo-46042: Improve the location of the caret in `SyntaxError` exceptions emitted by the symbol table. Patch by Pablo Galindo.

- bpo-46049: Ensure `._pth` files work as intended on platforms other than Windows.

- bpo-46048: Fixes parsing of `._pth` files on startup so that single-character paths are correctly read.

- bpo-37971: Fix a bug where the line numbers given in a traceback when a decorator application raised an exception were wrong.

- bpo-46031: Add `POP_JUMP_IF_NOT_NONE` and `POP_JUMP_IF_NONE` opcodes to speed up conditional jumps.

- bpo-45654: Deepfreeze `runpy`, patch by Kumar Aditya.

- bpo-46025: Fix a crash in the `atexit` module involving functions that unregister themselves before raising exceptions. Patch by Pablo Galindo.

- bpo-46000: Improve compatibility of the `curses` module with NetBSD curses.

- bpo-44525: Specialize the CALL_FUNCTION instruction for calls to builtin types with a single argument. Speeds up `range(x)`, `list(x)`, and specifically `type(obj)`.

- bpo-42918: Fix bug where the built-in `compile()` function did not always raise a `SyntaxError` when passed multiple statements in ‘single’ mode. Patch by Weipeng Hong.

- bpo-45953: The main interpreter in _PyRuntimeState.interpreters is now statically allocated (as part of _PyRuntime). Likewise for the initial thread state of each interpreter. This means less allocation during runtime init, as well as better memory locality for these key state objects.

- bpo-45292: Complete the PEP 654 implementation: add `except*`.

- bpo-43413: Revert changes in `set.__init__`. Subclass of `set` needs to define a `__init__()` method if it defines a `__new__()` method with additional keyword parameters.

- bpo-43931: Added the `Py_Version` constant which bears the same value as `PY_VERSION_HEX`. Patch by Gabriele N. Tornetta.

### Library

- bpo-46342: The `@typing.final` decorator now sets the `__final__` attribute on the decorated object to allow runtime introspection. Patch by Jelle Zijlstra.

- bpo-46328: Added the `sys.exception()` method which returns the active exception instance.

- bpo-46307: Add `string.Template.is_valid()` and `string.Template.get_identifiers()` methods.

- bpo-46306: Assume that `types.CodeType` always has `types.CodeType.co_firstlineno` in `doctest`.

- bpo-40479: Fix `hashlib` usedforsecurity option to work correctly with OpenSSL 3.0.0 in FIPS mode.

- bpo-46070: Fix possible segfault when importing the `asyncio` module from different sub-interpreters in parallel. Patch by Erlend E. Aasland.

- bpo-46244: Removed `__slots__` from `typing.ParamSpec` and `typing.TypeVar`. They served no purpose. Patch by Arie Bovenberg.

- bpo-46278: Reflect `context` argument in `AbstractEventLoop.call_*()` methods. Loop implementations already support it.

- bpo-46269: Remove special-casing of `__new__` in `enum.Enum.__dir__()`.

- bpo-46266: Improve day constants in `calendar`.

  Now all constants (`MONDAY` … `SUNDAY`) are documented, tested, and added to `__all__`.

- bpo-46257: Optimized the mean, variance, and stdev functions in the statistics module. If the input is an iterator, it is consumed in a single pass rather than eating memory by conversion to a list. The single pass algorithm is about twice as fast as the previous two pass code.

- bpo-41011: Added two new variables to pyvenv.cfg which is generated by `venv` module: executable for the executable and command for the command line used to create the environment.

- bpo-46239: Improve error message when importing `asyncio.windows_events` on non-Windows.

- bpo-46238: Reuse `_winapi` constants in `asyncio.windows_events`.

- bpo-46222: Adding `SF_NOCACHE` sendfile constant for FreeBSD for the posixmodule.

- bpo-37295: Add fast path for `0 <= k <= n <= 67` for `math.comb()`.

- bpo-46176: Adding the `MAP_STACK` constant for the mmap module.

- bpo-43424: Deprecate `webbrowser.MacOSXOSAScript._name` and use `name` instead.

- bpo-45321: Added missing error codes to module `xml.parsers.expat.errors`.

- bpo-46125: Refactor tests to test traversable API directly. Includes changes from importlib 5.4.0.

- bpo-46118: Moved importlib.resources and its related functionality to a package.

- bpo-37578: Add include_hidden parameter to `glob()` and `iglob()` to match hidden files and directories when using special characters like `*`, `**`, `?` and `[]`.

- bpo-20369: `concurrent.futures.wait()` no longer blocks forever when given duplicate Futures. Patch by Kumar Aditya.

- bpo-46105: Honor spec when generating requirement specs with urls and extras (importlib_metadata 4.8.3).

- bpo-44893: EntryPoint objects are no longer tuples. Recommended means to access is by attribute (‘.name’, ‘.group’) or accessor (‘.load()’). Access by index is deprecated and will raise deprecation warning.

- bpo-22815: Print unexpected successes together with failures and errors in summary in `unittest.TextTestResult`.

- bpo-22047: Calling `add_argument_group()` on an argument group is deprecated. Calling `add_argument_group()` or `add_mutually_exclusive_group()` on a mutually exclusive group is deprecated.

  These features were never supported and do not always work correctly. The functions exist on the API by accident through inheritance and will be removed in the future.

- bpo-26952: `argparse` raises `ValueError` with clear message when trying to render usage for an empty mutually exclusive group. Previously it raised a cryptic `IndexError`.

- bpo-45615: Functions in the `traceback` module raise `TypeError` rather than `AttributeError` when an exception argument is not of type `BaseException`.

- bpo-16594: Add allow allow_reuse_port flag in socketserver.

- bpo-27718: Fix help for the `signal` module. Some functions (e.g. `signal()` and `getsignal()`) were omitted.

- bpo-46032: The `registry()` method of `functools.singledispatch()` functions checks now the first argument or the first parameter annotation and raises a TypeError if it is not supported. Previously unsupported “types” were ignored (e.g. `typing.List[int]`) or caused an error at calling time (e.g. `list[int]`).

- bpo-46014: Add ability to use `typing.Union` and `types.UnionType` as dispatch argument to `functools.singledispatch`. Patch provided by Yurii Karabas.

- bpo-27062: Add `__all__` to `inspect`, patch by Kumar Aditya.

- bpo-46018: Ensure that `math.expm1()` does not raise on underflow.

- bpo-46016: Adding `F_DUP2FD` and `F_DUP2FD_CLOEXEC` constants from FreeBSD into the `fcntl` module.

- bpo-45755: `typing` generic aliases now reveal the class attributes of the original generic class when passed to `dir()`. This was the behavior up to Python 3.6, but was changed in 3.7-3.9.

- bpo-45874: The empty query string, consisting of no query arguments, is now handled correctly in `urllib.parse.parse_qsl`. This caused problems before when strict parsing was enabled.

- bpo-44674: Change how dataclasses disallows mutable default values. It used to use a list of known types (list, dict, set). Now it disallows unhashable objects to be defaults. It’s using unhashability as a proxy for mutability. Patch by Eric V. Smith, idea by Raymond Hettinger.

- bpo-23882: Remove namespace package (PEP 420) support from unittest discovery. It was introduced in Python 3.4 but has been broken since Python 3.7.

- bpo-25066: Added a `__repr__()` method to `multiprocessing.Event` objects, patch by Kumar Aditya.

- bpo-45643: Added `signal.SIGSTKFLT` on platforms where this signal is defined.

- bpo-44092: Fetch across rollback no longer raises `InterfaceError`. Instead we leave it to the SQLite library to handle these cases. Patch by Erlend E. Aasland.

- bpo-42413: Replace `concurrent.futures.TimeoutError` and `asyncio.TimeoutError` with builtin `TimeoutError`, keep these names as deprecated aliases.

### Documentation

- bpo-46196: Document method `cmd.Cmd.columnize()`.

- bpo-46120: State that `|` is preferred for readability over `Union` in the `typing` docs.

- bpo-46109: Extracted `importlib.resources` and `importlib.resources.abc` documentation into separate files.

- bpo-19737: Update the documentation for the `globals()` function.

### Tests

- bpo-46296: Add a test case for `enum` with `_use_args_ == True` and `_member_type_ == object`.

- bpo-46205: Fix hang in runtest_mp due to race condition

- bpo-46263: Fix test_capi on FreeBSD 14-dev: instruct jemalloc to not fill freed memory with junk byte.

- bpo-46262: Cover `ValueError` path in tests for `enum.Flag._missing_()`.

- bpo-46150: Now `fakename` in `test_pathlib.PosixPathTest.test_expanduser` is checked to be non-existent.

- bpo-46129: Rewrite `asyncio.locks` tests with `unittest.IsolatedAsyncioTestCase` usage.

- bpo-23819: Fixed `asyncio` tests in python optimized mode. Patch by Kumar Aditya.

- bpo-46114: Fix test case for OpenSSL 3.0.1 version. OpenSSL 3.0 uses `0xMNN00PP0L`.

### Build

- bpo-44133: When Python is configured with `--without-static-libpython`, the Python static library (libpython.a) is no longer built. Patch by Victor Stinner.

- bpo-44133: When Python is built without `--enable-shared`, the `python` program is now linked to object files, rather than being linked to the Python static library (libpython.a), to make sure that all symbols are exported. Previously, the linker omitted some symbols like the `Py_FrozenMain()` function. Patch by Victor Stinner.

- bpo-40280: The `configure` script has a new option `--with-emscripten-target` to select browser or node as Emscripten build target.

- bpo-46315: Added and fixed `#ifdef HAVE_FEATURE` checks for functionality that is not available on WASI platform.

- bpo-45723: Fixed a regression in `configure` check for `select.epoll()`.

- bpo-46263: `configure` no longer sets `MULTIARCH` on FreeBSD platforms.

- bpo-46106: Updated OpenSSL to 1.1.1m in Windows builds, macOS installer builds, and CI. Patch by Kumar Aditya.

- bpo-46088: Automatically detect or install bootstrap Python runtime when building from Visual Studio.

- bpo-46072: Add a –with-pystats configure option to turn on internal statistics gathering.

- bpo-40280: A new directory `Tools/wasm` contains WebAssembly-related helpers like `config.site` override for wasm32-emscripten, wasm assets generator to bundle the stdlib, and a README.

- bpo-46023: makesetup no longer builds extensions that have been marked as disabled. This allows users to disable modules in `Modules/Setup.local`.

- bpo-45949: Use pure Python `freeze_module` for all but importlib bootstrap files. `--with-freeze-module` configure option is no longer needed for cross builds.

### Windows

- bpo-46217: Removed parameter that is unsupported on Windows 8.1 and early Windows 10 and may have caused build or runtime failures.

### macOS

- bpo-40477: The Python Launcher app for macOS now properly launches scripts and, if necessary, the Terminal app when running on recent macOS releases.

### C API

- bpo-46236: Fix a bug in `PyFunction_GetAnnotations()` that caused it to return a `tuple` instead of a `dict`.

- bpo-46140: `PyBuffer_GetPointer()`, `PyBuffer_FromContiguous()`, `PyBuffer_ToContiguous()` and `PyMemoryView_FromBuffer()` now take buffer info by `const Py_buffer *` instead of `Py_buffer *`, as they do not need mutability. `PyBuffer_FromContiguous()` also now takes the source buffer as `const void *`, and similarly `PyBuffer_GetPointer()` takes the strides as `const Py_ssize_t *`.

- bpo-45855: Document that the no_block argument to `PyCapsule_Import()` is a no-op now.

- bpo-45855: Replaced deprecated usage of `PyImport_ImportModuleNoBlock()` with `PyImport_ImportModule()` in stdlib modules. Patch by Kumar Aditya.

- bpo-46007: The `PyUnicode_CHECK_INTERNED()` macro has been excluded from the limited C API. It was never usable there, because it used internal structures which are not available in the limited C API. Patch by Victor Stinner.

## Python 3.11.0 alpha 3

Release date: 2021-12-08

### Core and Builtins

- bpo-46009: Restore behavior from 3.9 and earlier when sending non-None to newly started generator. In 3.9 this did not affect the state of the generator. In 3.10.0 and 3.10.1 `gen_func().send(0)` is equivalent to `gen_func().throw(TypeError(...)` which exhausts the generator. In 3.10.2 onward, the behavior has been reverted to that of 3.9.

- bpo-46004: Fix the `SyntaxError` location for errors involving for loops with invalid targets. Patch by Pablo Galindo

- bpo-45711: `_PyErr_ChainStackItem()` no longer normalizes `exc_info` (including setting the traceback on the exception instance) because `exc_info` is always normalized.

- bpo-45607: The `__note__` field was added to `BaseException`. It is `None` by default but can be set to a string which is added to the exception’s traceback.

- bpo-45947: Place pointers to dict and values immediately before GC header. This reduces number of dependent memory loads to access either dict or values from 3 to 1.

- bpo-45915: `is_valid_fd` now uses faster `fcntl(fd, F_GETFD)` on Linux, macOS, and Windows.

- bpo-44530: Reverts a change to the `code.__new__` audit event from an earlier prerelease.

- bpo-42268: Fail the configure step if the selected compiler doesn’t support memory sanitizer. Patch by Pablo Galindo

- bpo-45711: The three values of `exc_info` are now always consistent with each other. In particular, the `type` and `traceback` fields are now derived from the exception instance. This impacts the return values of `sys.exc_info()` and `PyErr_GetExcInfo()` if the exception instance is modified while the exception is handled, as well as `PyErr_SetExcInfo()`, which now ignores the `type` and `traceback` arguments provided to it.

- bpo-45727: Refine the custom syntax error that suggests that a comma may be missing to trigger only when the expressions are detected between parentheses or brackets. Patch by Pablo Galindo

- bpo-45885: Specialized the `COMPARE_OP` opcode using the PEP 659 machinery.

- bpo-45786: Allocate space for the interpreter frame in the frame object, to avoid an additional allocation when the frame object outlives the frame activation.

- bpo-45614: Fix `traceback` display for exceptions with invalid module name.

- bpo-45813: Fix crash when calling coro.cr_frame.clear() after coroutine has been freed.

- bpo-45811: Improve the tokenizer errors when encountering invisible control characters in the parser. Patch by Pablo Galindo

- bpo-45848: Allow the parser to obtain error lines directly from encoded files. Patch by Pablo Galindo

- bpo-45709: Restore behavior from 3.10 when tracing an exception raised within a with statement.

- bpo-44525: Adds new `COPY_FREE_VARS` opcode, to make copying of free variables from function to frame explicit. Helps optimization of calls to Python function.

- bpo-45829: Specialize `BINARY_SUBSCR` for classes with a `__getitem__` method implemented in Python

- bpo-45826: Fixed a crash when calling `.with_traceback(None)` on `NameError`. This occurs internally in `unittest.TestCase.assertRaises()`.

- bpo-45822: Fixed a bug in the parser that was causing it to not respect PEP 263 coding cookies when no flags are provided. Patch by Pablo Galindo

- bpo-45820: Fix a segfault when the parser fails without reading any input. Patch by Pablo Galindo

- bpo-45636: Simplify the implementation of `BINARY_OP` by indexing into an array of function pointers (rather than switching on the oparg).

- bpo-42540: Fix crash when `os.fork()` is called with an active non-default memory allocator.

- bpo-45738: Fix computation of error location for invalid continuation characters in the parser. Patch by Pablo Galindo.

- bpo-45636: Remove an existing “fast path” for old-style string formatting, since it no longer appears to have any measurable impact.

- bpo-45753: Make recursion checks a bit more efficient by tracking amount of calls left before overflow.

- bpo-45773: Fix a compiler hang when attempting to optimize certain jump patterns.

- bpo-45764: The parser now gives a better error message when leaving out the opening parenthesis `(` after a `def`-statement:

      >>> def f:
        File "<stdin>", line 1
          def f:
               ^
      SyntaxError: expected '('

- bpo-45609: Specialized the `STORE_SUBSCR` opcode using the PEP 659 machinery.

- bpo-45636: Replace all numeric `BINARY_*` and `INPLACE_*` instructions with a single `BINARY_OP` implementation.

- bpo-45582: Path calculation (known as `getpath`) has been reimplemented as a frozen Python module. This should have no visible impact, but may affect calculation of all paths referenced in `sys` and `sysconfig`.

- bpo-45450: Improve the syntax error message for parenthesized arguments. Patch by Pablo Galindo.

### Library

- bpo-27946: Fix possible crash when getting an attribute of `xml.etree.ElementTree.Element` simultaneously with replacing the `attrib` dict.

- bpo-45711: Make `asyncio` normalize exceptions as soon as they are captured with `PyErr_Fetch()`, and before they are stored as an exc_info triplet. This brings `asyncio` in line with the rest of the codebase, where an exc_info triplet is always normalized.

- bpo-23819: Replaced asserts with exceptions in asyncio, patch by Kumar Aditya.

- bpo-13236: `unittest.TextTestResult` and `unittest.TextTestRunner` flush now the output stream more often.

- bpo-45917: Added `math.exp2()`:, which returns 2 raised to the power of x.

- bpo-37658: Fix issue when on certain conditions `asyncio.wait_for()` may allow a coroutine to complete successfully, but fail to return the result, potentially causing memory leaks or other issues.

- bpo-45876: Improve the accuracy of stdev() and pstdev() in the statistics module. When the inputs are floats or fractions, the output is a correctly rounded float

- bpo-44649: Handle dataclass(slots=True) with a field that has default a default value, but for which init=False.

- bpo-45803: Added missing kw_only parameter to dataclasses.make_dataclass().

- bpo-45837: The `turtle.RawTurtle.settiltangle()` is deprecated since Python 3.1, it now emits a deprecation warning and will be removed in Python 3.13.

  Use `turtle.RawTurtle.tiltangle()` instead.

  `turtle.RawTurtle.tiltangle()` was earlier incorrectly marked as deprecated, its docstring has been corrected.

  Patch by Hugo van Kemenade.

- bpo-45831: `faulthandler` can now write ASCII-only strings (like filenames and function names) with a single write() syscall when dumping a traceback. It reduces the risk of getting an unreadable dump when two threads or two processes dump a traceback to the same file (like stderr) at the same time. Patch by Victor Stinner.

- bpo-45828: `sqlite` C callbacks now use unraisable exceptions if callback tracebacks are enabled. Patch by Erlend E. Aasland.

- bpo-41735: Fix thread lock in `zlib.Decompress.flush()` method before `PyObject_GetBuffer`.

- bpo-45235: Reverted an argparse bugfix that caused regression in the handling of default arguments for subparsers. This prevented leaf level arguments from taking precedence over root level arguments.

- bpo-45754: Fix a regression in Python 3.11a1 and 3.11a2 where `sqlite3` incorrectly would use `SQLITE_LIMIT_LENGTH` when checking SQL statement lengths. Now, `SQLITE_LIMIT_SQL_LENGTH` is used. Patch by Erlend E. Aasland.

- bpo-45766: Added proportional option to `statistics.linear_regression()`.

- bpo-45765: In importlib.metadata, fix distribution discovery for an empty path.

- bpo-45757: Fix bug where `dis` produced an incorrect oparg when `EXTENDED_ARG` is followed by an opcode that does not use its argument.

- bpo-45644: In-place JSON file formatting using `python3 -m json.tool infile infile` now works correctly, previously it left the file empty. Patch by Chris Wesseling.

- bpo-45703: When a namespace package is imported before another module from the same namespace is created/installed in a different `sys.path` location while the program is running, calling the `importlib.invalidate_caches()` function will now also guarantee the new module is noticed.

- bpo-45535: Improve output of `dir()` with Enums.

- bpo-45664: Fix `types.resolve_bases()` and `types.new_class()` for `types.GenericAlias` instance as a base.

- bpo-45663: Fix `dataclasses.is_dataclass()` for dataclasses which are subclasses of `types.GenericAlias`.

- bpo-45662: Fix the repr of `dataclasses.InitVar` with a type alias to the built-in class, e.g. `InitVar[list[int]]`.

- bpo-43137: Launch GNOME web browsers via gio tool instead of obsolete gvfs-open

- bpo-45429: On Windows, `time.sleep()` now uses a waitable timer which supports high-resolution timers. Patch by Donghee Na and Eryk Sun.

- bpo-37295: Optimize `math.comb()` and `math.perm()`.

- bpo-45514: Deprecated legacy functions in `importlib.resources`.

- bpo-45507: Add tests for truncated/missing trailers in gzip.decompress implementation.

- bpo-45359: Implement PEP 585 for `graphlib.TopologicalSorter`.

- bpo-44733: Add `max_tasks_per_child` to `concurrent.futures.ProcessPoolExecutor`. This allows users to specify the maximum number of tasks a single process should execute before the process needs to be restarted.

- bpo-28806: Improve netrc library. netrc file no longer needs to contain all tokens. And if the login name is anonymous, security check is no longer need.

- bpo-43498: Avoid a possible “RuntimeError: dictionary changed size during iteration” when adjusting the process count of `ProcessPoolExecutor`.

- bpo-42158: Add MIME types for N-quads, N-triples, Notation3 and TriG to `mimetypes`.

- bpo-30533: Add `inspect.getmembers_static()` , it return all members without triggering dynamic lookup via the descriptor protocol. Patch by Weipeng Hong.

### Documentation

- bpo-42238: `make -C Doc suspicious` will be removed soon in favor of `make -C Doc check`, mark it as deprecated.

- bpo-45840: Improve cross-references in the documentation for the data model.

- bpo-45640: Properly marked-up grammar tokens in the documentation are now clickable and take you to the definition of a given piece of grammar. Patch by Arthur Milchior.

- bpo-45788: Link doc for sys.prefix to sysconfig doc on installation paths.

- bpo-45772: `socket.socket` documentation is corrected to a class from a function.

- bpo-45392: Update the docstring of the `type` built-in to remove a redundant line and to mention keyword arguments for the constructor.

- bpo-45250: Update the documentation to note that CPython does not consistently require iterators to define `__iter__`.

- bpo-25381: In the extending chapter of the extending doc, update a paragraph about the global variables containing exception information.

- bpo-43905: Expanded `astuple()` and `asdict()` docs, warning about deepcopy being applied and providing a workaround.

### Tests

- bpo-45695: Out-of-tree builds with a read-only source directory are now tested by CI.

- bpo-19460: Add new Test for `Lib/email/mime/nonmultipart.py::MIMENonMultipart`.

- bpo-45835: Fix race condition in test_queue tests with multiple “feeder” threads.

- bpo-45783: The test for the freeze tool now handles file moves and deletions.

- bpo-45745: Remove the `--findleaks` command line option of regrtest: use the `--fail-env-changed` option instead. Since Python 3.7, it was a deprecated alias to the `--fail-env-changed` option.

- bpo-45701: Add tests with `tuple` type with `functools.lru_cache()` to `test_functools`.

### Build

- bpo-44035: CI now verifies that autoconf files have been regenerated with a current and unpatched autoconf package.

- bpo-45950: The build system now uses a _bootstrap_python interpreter for freezing and deepfreezing again. To speed up build process the build tools _bootstrap_python and _freeze_module are no longer build with LTO.

- bpo-45881: The configure script now accepts `--with-build-python` and `--with-freeze-module` options to make cross compiling easier.

- bpo-40280: Emscripten platform now uses `.wasm` suffix by default.

- bpo-40280: Disable unusable core extension modules on WASM/Emscripten targets.

- bpo-40280: `configure` now checks for socket `shutdown` function. The check makes it possible to disable `SYS_shutdown` with `ac_cv_func_shutdown=no` in CONFIG_SITE.

- bpo-40280: `configure` now checks for functions `fork1, getegid, geteuid, getgid, getppid, getuid, opendir, pipe, system, wait, ttyname`.

- bpo-33393: Update `config.guess` to 2021-06-03 and `config.sub` to 2021-08-14. `Makefile` now has an `update-config` target to make updating more convenient.

- bpo-45866: `make regen-all` now produces the same output when run from a directory other than the source tree: when building Python out of the source tree. pegen now strips directory of the “generated by pygen from <FILENAME>” header Patch by Victor Stinner.

- bpo-40280: `configure` now accepts machine `wasm32` or `wasm64` and OS `wasi` or `emscripten` for cross building, e.g. `wasm32-unknown-emscripten`, `wasm32-wasi`, or `wasm32-unknown-wasi`.

- bpo-41498: Python now compiles on platforms without `sigset_t`. Several functions in `signal` are not available when `sigset_t` is missing.

  Based on patch by Roman Yurchak for pyodide.

- bpo-45881: `setup.py` now uses `CC` from environment first to discover multiarch and cross compile paths.

- bpo-45886: The `_freeze_module` program path can now be overridden on the command line, e.g. `make FREEZE_MODULE=../x86_64/Program/_freeze_module`.

- bpo-45873: Get rid of the `_bootstrap_python` build step. The deepfreeze.py script is now run using `$(PYTHON_FOR_REGEN)` which can be Python 3.7 or newer (on Windows, 3.8 or newer).

- bpo-45847: Port builtin hashlib extensions to `PY_STDLIB_MOD` macro and `addext()`.

- bpo-45723: Add `autoconf` helpers for saving and restoring environment variables:

  - `SAVE_ENV`: Save `$CFLAGS`, `$LDFLAGS`, `$LIBS`, and `$CPPFLAGS`.

  - `RESTORE_ENV`: Restore `$CFLAGS`, `$LDFLAGS`, `$LIBS`, and `$CPPFLAGS`.

  - `WITH_SAVE_ENV([SCRIPT])`: Run `SCRIPT` wrapped with `SAVE_ENV` and `RESTORE_ENV`.

  Patch by Erlend E. Aasland.

- bpo-45573: Mandatory core modules, that are required to bootstrap Python, are now in `Modules/Setup.bootstrap`.

- bpo-45573: `configure` now creates `Modules/Setup.stdlib` with conditionally enabled/disabled extension module lines. The file is not used, yet.

- bpo-45573: `configure` now uses a unified format to set state, compiler flags, and linker flags in Makefile. The new macro `PY_STDLIB_MOD` sets three variables that are consumed by `Modules/Setup` and `setup.py`.

- bpo-45816: Python now supports building with Visual Studio 2022 (MSVC v143, VS Version 17.0). Patch by Jeremiah Vivian.

- bpo-45800: Settings for `pyexpat` C extension are now detected by `configure`. The bundled `expat` library is built in `Makefile`.

- bpo-45798: Settings for `decimal` internal C extension are now detected by `configure`. The bundled `libmpdec` library is built in `Makefile`.

- bpo-45723: configure has a new option `--with-pkg-config` to disable or require pkg-config.

- bpo-45774: The build dependencies for `sqlite3` are now detected by `configure` and `pkg-config`. Patch by Erlend E. Aasland.

- bpo-45763: The build dependencies for `zlib`, `bz2`, and `lzma` are now detected by `configure`.

- bpo-45747: gdbm and dbm build dependencies are now detected by `configure`.

- bpo-45743: On macOS, the build system no longer passes `search_paths_first` to the linker. The flag has been the default since Xcode 4 / macOS 10.6.

- bpo-45723: `configure.ac` is now compatible with autoconf 2.71. Deprecated checks `STDC_HEADERS` and `AC_HEADER_TIME` have been removed.

- bpo-45723: `configure` now prints a warning when pkg-config is missing.

- bpo-45731: `configure --enable-loadable-sqlite-extensions` is now handled by new `PY_SQLITE_ENABLE_LOAD_EXTENSION` macro instead of logic in setup.py.

- bpo-45723: configure.ac now uses custom helper macros and `AC_CACHE_CHECK` to simplify and speed up configure runs.

- bpo-45696: Skip the marshal step for frozen modules by generating C code that produces a set of ready-to-use code objects. This speeds up startup time by another 10% or more.

- bpo-45561: Run smelly.py tool from $(srcdir).

### Windows

- bpo-46105: Fixed calculation of `sys.path` in a venv on Windows.

- bpo-45901: When installed through the Microsoft Store and set as the default app for `*.py` files, command line arguments will now be passed to Python when invoking a script without explicitly launching Python (that is, `script.py args` rather than `python script.py args`).

- bpo-45616: Fix Python Launcher’s ability to distinguish between versions 3.1 and 3.10 when either one is explicitly requested. Previously, 3.1 would be used if 3.10 was requested but not installed, and 3.10 would be used if 3.1 was requested but 3.10 was installed.

- bpo-45850: Implement changes to build with deep-frozen modules on Windows. Note that we now require Python 3.10 as the “bootstrap” or “host” Python.

- bpo-45732: Updates bundled Tcl/Tk to 8.6.12.

- bpo-45720: Internal reference to `shlwapi.dll` was dropped to help improve startup time. This DLL will no longer be loaded at the start of every Python process.

### macOS

- bpo-45732: Update python.org macOS installer to use Tcl/Tk 8.6.12.

### C API

- bpo-39026: Fix Python.h to build C extensions with Xcode: remove a relative include from `Include/cpython/pystate.h`.

## Python 3.11.0 alpha 2

Release date: 2021-11-05

### Core and Builtins

- bpo-45716: Improve the `SyntaxError` message when using `True`, `None` or `False` as keywords in a function call. Patch by Pablo Galindo.

- bpo-45688: `sys.stdlib_module_names` now contains the macOS-specific module `_scproxy`.

- bpo-45379: Clarify `ImportError` message when we try to explicitly import a frozen module but frozen modules are disabled.

- bpo-44525: Specialize simple calls to Python functions (no starargs, keyword dict, or closure)

- bpo-45530: Cases of sorting using tuples as keys may now be significantly faster in some cases. Patch by Tim Peters.

  The order of the result may differ from earlier releases if the tuple elements don’t define a total ordering (see Value comparisons for information on total ordering). It’s generally true that the result of sorting simply isn’t well-defined in the absence of a total ordering on list elements.

- bpo-45526: In obmalloc, set ADDRESS_BITS to not ignore any bits (ignored 16 before). That is safer in the case that the kernel gives user-space virtual addresses that span a range greater than 48 bits.

- bpo-30570: Fixed a crash in `issubclass()` from infinite recursion when searching pathological `__bases__` tuples.

- bpo-45521: Fix a bug in the obmalloc radix tree code. On 64-bit machines, the bug causes the tree to hold 46-bits of virtual addresses, rather than the intended 48-bits.

- bpo-45494: Fix parser crash when reporting errors involving invalid continuation characters. Patch by Pablo Galindo.

- bpo-45445: Python now fails to initialize if it finds an invalid `-X` option in the command line. Patch by Pablo Galindo.

- bpo-45340: Object attributes are held in an array instead of a dictionary. An object’s dictionary are created lazily, only when needed. Reduces the memory consumption of a typical Python object by about 30%. Patch by Mark Shannon.

- bpo-45408: Fix a crash in the parser when reporting tokenizer errors that occur at the same time unclosed parentheses are detected. Patch by Pablo Galindo.

- bpo-29410: Add SipHash13 for string hash algorithm and use it by default.

- bpo-45385: Fix reference leak from descr_check. Patch by Donghee Na.

- bpo-45367: Specialized the `BINARY_MULTIPLY` opcode to `BINARY_MULTIPLY_INT` and `BINARY_MULTIPLY_FLOAT` using the PEP 659 machinery.

- bpo-21736: Frozen stdlib modules now have `__file__` to the .py file they would otherwise be loaded from, if possible. For packages, `__path__` now has the correct entry instead of being an empty list, which allows unfrozen submodules to be imported. These are set only if the stdlib directory is known when the runtime is initialized. Note that the file at `__file__` is not guaranteed to exist. None of this affects non-stdlib frozen modules nor, for now, frozen modules imported using `PyImport_ImportFrozenModule()`. Also, at the moment `co_filename` is not updated for the module.

- bpo-45020: For frozen stdlib modules, record the original module name as `module.__spec__.loader_state.origname`. If the value is different than `module.__spec__.name` then the module was defined as an alias in Tools/scripts/freeze_modules.py. If it is `None` then the module comes from a source file outside the stdlib.

- bpo-45324: In FrozenImporter.find_spec(), we now preserve the information needed in exec_module() to load the module. This change mostly impacts internal details, rather than changing the importer’s behavior.

- bpo-45292: Implement PEP 654. Add `ExceptionGroup` and `BaseExceptionGroup`. Update traceback display code.

- bpo-40116: Change to the implementation of split dictionaries. Classes where the instances differ either in the exact set of attributes, or in the order in which those attributes are set, can still share keys. This should have no observable effect on users of Python or the C-API. Patch by Mark Shannon.

- bpo-44050: Extensions that indicate they use global state (by setting `m_size` to -1) can again be used in multiple interpreters. This reverts to behavior of Python 3.8.

- bpo-44525: Setup initial specialization infrastructure for the `CALL_FUNCTION` opcode. Implemented initial specializations for C function calls:

  - `CALL_FUNCTION_BUILTIN_O` for `METH_O` flag.

  - `CALL_FUNCTION_BUILTIN_FAST` for `METH_FASTCALL` flag without keywords.

  - `CALL_FUNCTION_LEN` for `len(o)`.

  - `CALL_FUNCTION_ISINSTANCE` for `isinstance(o, t)`.

- bpo-44511: Improve the generated bytecode for class and mapping patterns.

- bpo-43706: Speed up calls to `enumerate()` by using the PEP 590 `vectorcall` calling convention. Patch by Donghee Na.

### Library

- bpo-45679: Fix caching of multi-value `typing.Literal`. `Literal[True, 2]` is no longer equal to `Literal[1, 2]`.

- bpo-42064: Convert `sqlite3` to multi-phase initialisation (PEP 489). Patches by Erlend E. Aasland.

- bpo-45438: Fix typing.Signature string representation for generic builtin types.

- bpo-45613: `sqlite3` now sets `sqlite3.threadsafety` based on the default threading mode the underlying SQLite library has been compiled with. Patch by Erlend E. Aasland.

- bpo-45574: Fix warning about `print_escape` being unused.

- bpo-45581: `sqlite3.connect()` now correctly raises `MemoryError` if the underlying SQLite API signals memory error. Patch by Erlend E. Aasland.

- bpo-45557: `pprint.pprint()` now handles underscore_numbers correctly. Previously it was always setting it to `False`.

- bpo-44019: Add `operator.call()` to `operator.__all__`. Patch by Kreusada.

- bpo-42174: `shutil.get_terminal_size()` now falls back to sane values if the column or line count are 0.

- bpo-35673: Improve the introspectability of the `__loader__` attribute for namespace packages. `importlib.machinery.NamespaceLoader` is now public, and implements the `importlib.abc.InspectLoader` interface. `_NamespaceLoader` is kept for backward compatibility.

- bpo-45515: Add references to `zoneinfo` in the `datetime` documentation, mostly replacing outdated references to `dateutil.tz`. Change by Paul Ganssle.

- bpo-45475: Reverted optimization of iterating `gzip.GzipFile`, `bz2.BZ2File`, and `lzma.LZMAFile` (see bpo-43787) because it caused regression when user iterate them without having reference of them. Patch by Inada Naoki.

- bpo-45489: Update `ForwardRef` to support `|` operator. Patch by Donghee Na.

- bpo-42222: Removed deprecated support for float arguments in randrange().

- bpo-45428: Fix a regression in py_compile when reading filenames from standard input.

- bpo-45467: Fix incremental decoder and stream reader in the “raw-unicode-escape” codec. Previously they failed if the escape sequence was split.

- bpo-45461: Fix incremental decoder and stream reader in the “unicode-escape” codec. Previously they failed if the escape sequence was split.

- bpo-45239: Fixed `email.utils.parsedate_tz()` crashing with `UnboundLocalError` on certain invalid input instead of returning `None`. Patch by Ben Hoyt.

- bpo-45417: Fix quadratic behaviour in the enum module: Creation of enum classes with a lot of entries was quadratic.

- bpo-45249: Fix the behaviour of `traceback.print_exc()` when displaying the caret when the `end_offset` in the exception is set to 0. Patch by Pablo Galindo

- bpo-45416: Fix use of `asyncio.Condition` with explicit `asyncio.Lock` objects, which was a regression due to removal of explicit loop arguments. Patch by Joongi Kim.

- bpo-20028: Empty escapechar/quotechar is not allowed when initializing `csv.Dialect`. Patch by Vajrasky Kok and Donghee Na.

- bpo-44904: Fix bug in the `doctest` module that caused it to fail if a docstring included an example with a `classmethod` `property`. Patch by Alex Waygood.

- bpo-45406: Make `inspect.getmodule()` catch `FileNotFoundError` raised by `inspect.getabsfile()`, and return `None` to indicate that the module could not be determined.

- bpo-45411: Add extensions for files containing subtitles - .srt & .vtt - to the mimetypes.py module.

- bpo-10716: Migrated pydoc to HTML5 (without changing the look of it). Side effect is to update xmlrpc’s `ServerHTMLDoc` which now uses the CSS too. cgitb now relies less on pydoc (as it can’t use the CSS file).

- bpo-27580: Add support of null characters in `csv`.

- bpo-45262: Prevent use-after-free in asyncio. Make sure the cached running loop holder gets cleared on dealloc to prevent use-after-free in get_running_loop

- bpo-45386: Make `xmlrpc.client` more robust to C runtimes where the underlying C `strftime` function results in a `ValueError` when testing for year formatting options.

- bpo-20028: Improve error message of `csv.Dialect` when initializing. Patch by Vajrasky Kok and Donghee Na.

- bpo-45343: Update bundled pip to 21.2.4 and setuptools to 58.1.0

- bpo-45328: Fixed `http.client.HTTPConnection` to work properly in OSs that don’t support the `TCP_NODELAY` socket option.

- bpo-45243: Add `setlimit()` and `getlimit()` to `sqlite3.Connection` for setting and getting SQLite limits by connection basis. Patch by Erlend E. Aasland.

- bpo-45320: Removed from the `inspect` module:

  - the `getargspec` function, deprecated since Python 3.0;

      use `inspect.signature()` or `inspect.getfullargspec()` instead.

  - the `formatargspec` function, deprecated since Python 3.5; use the `inspect.signature()` function and `Signature` object directly.

  - the undocumented `Signature.from_builtin` and `Signature.from_function` functions, deprecated since Python 3.5; use the `Signature.from_callable()` method instead.

  Patch by Hugo van Kemenade.

- bpo-45192: Fix the `tempfile._infer_return_type` function so that the `dir` argument of the `tempfile` functions accepts an object implementing the `os.PathLike` protocol.

  Patch by Kyungmin Lee.

- bpo-45160: When tracing a tkinter variable used by a ttk OptionMenu, callbacks are no longer made twice.

- bpo-25625: Added non parallel-safe `chdir()` context manager to change the current working directory and then restore it on exit. Simple wrapper around `chdir()`.

- bpo-24139: Add support for SQLite extended result codes in `sqlite3.Error`. Patch by Erlend E. Aasland.

- bpo-24444: Fixed an error raised in `argparse` help display when help for an option is set to 1+ blank spaces or when choices arg is an empty container.

- bpo-44547: Implement `Fraction.__int__`, so that a `fractions.Fraction` instance `f` passes an `isinstance(f, typing.SupportsInt)` check.

- bpo-40321: Adds support for HTTP 308 redirects to `urllib`. See RFC 7538 for details. Patch by Jochem Schulenklopper.

- bpo-41374: Ensure that `socket.TCP_*` constants are exposed on Cygwin 3.1.6 and greater.

- bpo-35970: Add help flag to the base64 module’s command line interface. Patch contributed by Robert Kuska.

### Documentation

- bpo-45726: Improve documentation for `functools.singledispatch()` and `functools.singledispatchmethod`.

- bpo-45680: Amend the docs on `GenericAlias` objects to clarify that non-container classes can also implement `__class_getitem__`. Patch contributed by Alex Waygood.

- bpo-45618: Update Sphinx version used to build the documentation to 4.2.0. Patch by Maciej Olko.

- bpo-45655: Add a new “relevant PEPs” section to the top of the documentation for the `typing` module. Patch by Alex Waygood.

- bpo-45604: Add `level` argument to `multiprocessing.log_to_stderr` function docs.

- bpo-45516: Add protocol description to the `importlib.abc.TraversableResources` documentation.

- bpo-45464: Mention in the documentation of Built-in Exceptions that inheriting from multiple exception types in a single subclass is not recommended due to possible memory layout incompatibility.

- bpo-45449: Add note about PEP 585 in `collections.abc`.

- bpo-45516: Add protocol description to the `importlib.abc.Traversable` documentation.

- bpo-20692: Add Programming FAQ entry explaining that int literal attribute access requires either a space after or parentheses around the literal.

### Tests

- bpo-45678: Add tests for scenarios in which `functools.singledispatchmethod` is stacked on top of a method that has already been wrapped by two other decorators. Patch by Alex Waygood.

- bpo-45578: Add tests for `dis.distb()`

- bpo-45678: Add tests to ensure that `functools.singledispatchmethod` correctly wraps the attributes of the target function.

- bpo-45668: PGO tests now pass when Python is built without test extension modules.

- bpo-45577: Add subtests for all `pickle` protocols in `test_zoneinfo`.

- bpo-45566: Fix `test_frozen_pickle` in `test_dataclasses` to check all `pickle` versions.

- bpo-43592: `test.libregrtest` now raises the soft resource limit for the maximum number of file descriptors when the default is too low for our test suite as was often the case on macOS.

- bpo-39679: Add more test cases for `@functools.singledispatchmethod` when combined with `@classmethod` or `@staticmethod`.

- bpo-45410: When libregrtest spawns a worker process, stderr is now written into stdout to keep messages order. Use a single pipe for stdout and stderr, rather than two pipes. Previously, messages were out of order which made analysis of buildbot logs harder Patch by Victor Stinner.

- bpo-45402: Fix test_tools.test_sundry() when Python is built out of tree: fix how the freeze_modules.py tool locates the _freeze_module program. Patch by Victor Stinner.

- bpo-45403: Fix test_sys.test_stdlib_dir() when Python is built outside the source tree: compare normalized paths. Patch by Victor Stinner.

- bpo-45400: Fix test_name_error_suggestions_do_not_trigger_for_too_many_locals() of test_exceptions if a directory name contains “a1” (like “Python-3.11.0a1”): use a stricter regular expression. Patch by Victor Stinner.

- bpo-10572: Rename `sqlite3` tests from `test_sqlite` to `test_sqlite3`, and relocate them to `Lib/test/test_sqlite3`. Patch by Erlend E. Aasland.

### Build

- bpo-43158: `setup.py` now uses values from configure script to build the `_uuid` extension module. Configure now detects util-linux’s `libuuid`, too.

- bpo-45666: Fix warning of `swprintf` and `%s` usage in `_testembed.c`

- bpo-45548: `Modules/Setup` and `Modules/makesetup` have been improved. The `Setup` file now contains working rules for all extensions. Outdated comments have been removed. Rules defined by `makesetup` track dependencies correctly.

- bpo-45548: The `math` and `cmath` implementation now require a C99 compatible `libm` and no longer ship with workarounds for missing acosh, asinh, atanh, expm1, and log1p functions.

- bpo-45595: `setup.py` and `makesetup` now track build dependencies on all Python header files and module specific header files.

- bpo-45571: `Modules/Setup` now use `PY_CFLAGS_NODIST` instead of `PY_CFLAGS` to compile shared modules.

- bpo-45570: `pyexpat` and `_elementtree` no longer define obsolete macros `HAVE_EXPAT_CONFIG_H` and `USE_PYEXPAT_CAPI`. `XML_POOR_ENTROPY` is now defined in `expat_config.h`.

- bpo-43974: `setup.py` no longer defines `Py_BUILD_CORE_MODULE`. Instead every module, that uses the internal API, defines the macro.

- bpo-45548: Fill in missing entries in Modules/Setup.

- bpo-45532: Update `sys.version` to use `main` as fallback information. Patch by Jeong YunWon.

- bpo-45536: The `configure` script now checks whether OpenSSL headers and libraries provide required APIs. Most common APIs are verified. The check detects outdated or missing OpenSSL. Failures do not stop configure.

- bpo-45221: Fixed regression in handling of `LDFLAGS` and `CPPFLAGS` options where `argparse.parse_known_args()` could interpret an option as one of the built-in command line argument, for example `-h` for help.

- bpo-45440: Building Python now requires a C99 `<math.h>` header file providing the following functions: `copysign()`, `hypot()`, `isfinite()`, `isinf()`, `isnan()`, `round()`. Patch by Victor Stinner.

- bpo-45405: Prevent `internal configure error` when running `configure` with recent versions of non-Apple clang. Patch by David Bohman.

- bpo-45433: Avoid linking libpython with libcrypt.

### Windows

- bpo-43652: Update Tcl/Tk to 8.6.11, actually this time. The previous update incorrectly included 8.6.10.

- bpo-45337: venv now warns when the created environment may need to be accessed at a different path, due to redirections, links or junctions. It also now correctly installs or upgrades components when the alternate path is required.

- bpo-43851: Build SQLite `SQLITE_OMIT_AUTOINIT` on Windows. Patch by Erlend E. Aasland.

### macOS

- bpo-44828: Avoid tkinter file dialog failure on macOS 12 Monterey when using the Tk 8.6.11 provided by python.org macOS installers. Patch by Marc Culler of the Tk project.

### IDLE

- bpo-45495: Add context keywords ‘case’ and ‘match’ to completions list.

### C API

- bpo-29103: `PyType_FromSpec*` now copies the class name from the spec to a buffer owned by the class, so the original can be safely deallocated. Patch by Petr Viktorin.

- bpo-45522: The internal freelists for frame, float, list, dict, async generators, and context objects can now be disabled.

- bpo-35134: Exclude `PyWeakref_GET_OBJECT()` from the limited C API. It never worked since the `PyWeakReference` structure is opaque in the limited C API.

- bpo-35081: Move the `interpreteridobject.h` header file from `Include/` to `Include/internal/`. It only provides private functions. Patch by Victor Stinner.

- bpo-35134: The non-limited API files `cellobject.h`, `classobject.h`, `context.h`, `funcobject.h`, `genobject.h` and `longintrepr.h` have been moved to the `Include/cpython` directory. Moreover, the `eval.h` header file was removed. These files must not be included directly, as they are already included in `Python.h`: Include Files. If they have been included directly, consider including `Python.h` instead. Patch by Victor Stinner.

- bpo-45474: The following items are no longer available when `Py_LIMITED_API` is defined:

  - `PyMarshal_WriteLongToFile()`

  - `PyMarshal_WriteObjectToFile()`

  - `PyMarshal_ReadObjectFromString()`

  - `PyMarshal_WriteObjectToString()`

  - the `Py_MARSHAL_VERSION` macro

  These are not part of the limited API.

  Patch by Victor Stinner.

- bpo-45434: Remove the `pystrhex.h` header file. It only contains private functions. C extensions should only include the main `<Python.h>` header file. Patch by Victor Stinner.

- bpo-45440: Remove the `Py_FORCE_DOUBLE()` macro. It was used by the `Py_IS_INFINITY()` macro. Patch by Victor Stinner.

- bpo-45434: `<Python.h>` no longer includes the header files `<stdlib.h>`, `<stdio.h>`, `<errno.h>` and `<string.h>` when the `Py_LIMITED_API` macro is set to `0x030b0000` (Python 3.11) or higher. C extensions should explicitly include the header files after `#include <Python.h>`. Patch by Victor Stinner.

- bpo-41123: Remove `Py_UNICODE_COPY()` and `Py_UNICODE_FILL()` macros, deprecated since Python 3.3. Use `PyUnicode_CopyCharacters()` or `memcpy()` (`wchar_t*` string), and `PyUnicode_Fill()` functions instead. Patch by Victor Stinner.

- bpo-45412: Remove the following math macros using the `errno` variable:

  - `Py_ADJUST_ERANGE1()`

  - `Py_ADJUST_ERANGE2()`

  - `Py_OVERFLOWED()`

  - `Py_SET_ERANGE_IF_OVERFLOW()`

  - `Py_SET_ERRNO_ON_MATH_ERROR()`

  Patch by Victor Stinner.

- bpo-45395: Custom frozen modules (the array set to `PyImport_FrozenModules`) are now treated as additions, rather than replacing all the default frozen modules. Frozen stdlib modules can still be disabled by setting the “code” field of the custom array entry to NULL.

- bpo-43760: Add new `PyThreadState_EnterTracing()`, and `PyThreadState_LeaveTracing()` functions to the limited C API to suspend and resume tracing and profiling. Patch by Victor Stinner.

- bpo-44220: `PyStructSequence_UnnamedField` is added to the Stable ABI.

## Python 3.11.0 alpha 1

Release date: 2021-10-05

### Security

- bpo-42278: Replaced usage of `tempfile.mktemp()` with `TemporaryDirectory` to avoid a potential race condition.

- bpo-44600: Fix incorrect line numbers while tracing some failed patterns in match statements. Patch by Charles Burkland.

- bpo-41180: Add auditing events to the `marshal` module, and stop raising `code.__init__` events for every unmarshalled code object. Directly instantiated code objects will continue to raise an event, and audit event handlers should inspect or collect the raw marshal data. This reduces a significant performance overhead when loading from `.pyc` files.

- bpo-44394: Update the vendored copy of libexpat to 2.4.1 (from 2.2.8) to get the fix for the CVE 2013-0340 “Billion Laughs” vulnerability. This copy is most used on Windows and macOS.

- bpo-43124: Made the internal `putcmd` function in `smtplib` sanitize input for presence of `\r` and `\n` characters to avoid (unlikely) command injection.

- bpo-44022: `http.client` now avoids infinitely reading potential HTTP headers after a `100 Continue` status response from the server.

### Core and Builtins

- bpo-43760: The number of hardware branches per instruction dispatch is reduced from two to one by adding a special instruction for tracing. Patch by Mark Shannon.

- bpo-45061: Add a deallocator to the bool type to detect refcount bugs in C extensions which call Py_DECREF(Py_True) or Py_DECREF(Py_False) by mistake. Detect also refcount bugs when the empty tuple singleton or the Unicode empty string singleton is destroyed by mistake. Patch by Victor Stinner.

- bpo-24076: sum() was further optimised for summing up single digit integers.

- bpo-45190: Update Unicode databases to Unicode 14.0.0.

- bpo-45167: Fix deepcopying of `types.GenericAlias` objects.

- bpo-45155: `int.to_bytes()` and `int.from_bytes()` now take a default value of `"big"` for the `byteorder` argument. `int.to_bytes()` also takes a default value of `1` for the `length` argument.

- bpo-44219: Release the GIL while performing `isatty` system calls on arbitrary file descriptors. In particular, this affects `os.isatty()`, `os.device_encoding()` and `io.TextIOWrapper`. By extension, `io.open()` in text mode is also affected. This change solves a deadlock in `os.isatty()`. Patch by Vincent Michel in bpo-44219.

- bpo-44959: Added fallback to extension modules with ‘.sl’ suffix on HP-UX

- bpo-45121: Fix issue where `Protocol.__init__` raises `RecursionError` when it’s called directly or via `super()`. Patch provided by Yurii Karabas.

- bpo-44348: The deallocator function of the `BaseException` type now uses the trashcan mechanism to prevent stack overflow. For example, when a `RecursionError` instance is raised, it can be linked to another RecursionError through the `__context__` attribute or the `__traceback__` attribute, and then a chain of exceptions is created. When the chain is destroyed, nested deallocator function calls can crash with a stack overflow if the chain is too long compared to the available stack memory. Patch by Victor Stinner.

- bpo-45123: Fix PyAiter_Check to only check for the __anext__ presence (not for __aiter__). Rename PyAiter_Check to PyAIter_Check, PyObject_GetAiter -> PyObject_GetAIter.

- bpo-1514420: Interpreter no longer attempts to open files with names in angle brackets (like “<string>” or “<stdin>”) when formatting an exception.

- bpo-41031: Match C and Python code formatting of unprintable exceptions and exceptions in the `__main__` module.

- bpo-37330: `open()`, `io.open()`, `codecs.open()` and `fileinput.FileInput` no longer accept `'U'` (“universal newline”) in the file mode. This flag was deprecated since Python 3.3. Patch by Victor Stinner.

- bpo-45083: When the interpreter renders an exception, its name now has a complete qualname. Previously only the class name was concatenated to the module name, which sometimes resulted in an incorrect full name being displayed.

  (This issue impacted only the C code exception rendering, the `traceback` module was using qualname already).

- bpo-34561: List sorting now uses the merge-ordering strategy from Munro and Wild’s `powersort()`. Unlike the former strategy, this is provably near-optimal in the entropy of the distribution of run lengths. Most uses of `list.sort()` probably won’t see a significant time difference, but may see significant improvements in cases where the former strategy was exceptionally poor. However, as these are all fast linear-time approximations to a problem that’s inherently at best quadratic-time to solve truly optimally, it’s also possible to contrive cases where the former strategy did better.

- bpo-45056: Compiler now removes trailing unused constants from co_consts.

- bpo-45020: Add a new command line option, “-X frozen_modules=[on|off]” to opt out of (or into) using optional frozen modules. This defaults to “on” (or “off” if it’s running out of the source tree).

- bpo-45012: In `posix`, release GIL during `stat()`, `lstat()`, and `fstatat()` syscalls made by `os.DirEntry.stat()`. Patch by Stanisław Skonieczny.

- bpo-45018: Fixed pickling of range iterators that iterated for over `2**32` times.

- bpo-45000: A `SyntaxError` is now raised when trying to delete `__debug__`. Patch by Donghee Na.

- bpo-44963: Implement `send()` and `throw()` methods for `anext_awaitable` objects. Patch by Pablo Galindo.

- bpo-44962: Fix a race in WeakKeyDictionary, WeakValueDictionary and WeakSet when two threads attempt to commit the last pending removal. This fixes asyncio.create_task and fixes a data loss in asyncio.run where shutdown_asyncgens is not run

- bpo-24234: Implement the `__bytes__()` special method on the `bytes` type, so a bytes object `b` passes an `isinstance(b, typing.SupportsBytes)` check.

- bpo-24234: Implement the `__complex__()` special method on the `complex` type, so a complex number `z` passes an `isinstance(z, typing.SupportsComplex)` check.

- bpo-44954: Fixed a corner case bug where the result of `float.fromhex('0x.8p-1074')` was rounded the wrong way.

- bpo-44947: Refine the syntax error for trailing commas in import statements. Patch by Pablo Galindo.

- bpo-44945: Specialize the BINARY_ADD instruction using the PEP 659 machinery. Adds five new instructions:

  - BINARY_ADD_ADAPTIVE

  - BINARY_ADD_FLOAT

  - BINARY_ADD_INT

  - BINARY_ADD_UNICODE

  - BINARY_ADD_UNICODE_INPLACE_FAST

- bpo-44929: Fix some edge cases of `enum.Flag` string representation in the REPL. Patch by Pablo Galindo.

- bpo-44914: Class version tags are no longer recycled.

  This means that a version tag serves as a unique identifier for the state of a class. We rely on this for effective specialization of the LOAD_ATTR and other instructions.

- bpo-44698: Restore behaviour of complex exponentiation with integer-valued exponent of type `float` or `complex`.

- bpo-44895: A debug variable `PYTHONDUMPREFSFILE` is added for creating a dump file which is generated by `--with-trace-refs`. Patch by Donghee Na.

- bpo-44900: Add five superinstructions for PEP 659 quickening:

  - LOAD_FAST LOAD_FAST

  - STORE_FAST LOAD_FAST

  - LOAD_FAST LOAD_CONST

  - LOAD_CONST LOAD_FAST

  - STORE_FAST STORE_FAST

- bpo-44889: Initial implementation of adaptive specialization of `LOAD_METHOD`. The following specialized forms were added:

  - `LOAD_METHOD_CACHED`

  - `LOAD_METHOD_MODULE`

  - `LOAD_METHOD_CLASS`

- bpo-44890: Specialization stats are always collected in debug builds.

- bpo-44885: Correct the ast locations of f-strings with format specs and repeated expressions. Patch by Pablo Galindo

- bpo-44878: Remove the loop from the bytecode interpreter. All instructions end with a DISPATCH macro, so the loop is now redundant.

- bpo-44878: Remove switch statement for interpreter loop when using computed gotos. This makes sure that we only have one dispatch table in the interpreter.

- bpo-44874: Deprecate the old trashcan macros (`Py_TRASHCAN_SAFE_BEGIN`/`Py_TRASHCAN_SAFE_END`). They should be replaced by the new macros `Py_TRASHCAN_BEGIN` and `Py_TRASHCAN_END`.

- bpo-44872: Use new trashcan macros (Py_TRASHCAN_BEGIN/END) in frameobject.c instead of the old ones (Py_TRASHCAN_SAFE_BEGIN/END).

- bpo-33930: Fix segmentation fault with deep recursion when cleaning method objects. Patch by Augusto Goulart and Pablo Galindo.

- bpo-25782: Fix bug where `PyErr_SetObject` hangs when the current exception has a cycle in its context chain.

- bpo-44856: Fix reference leaks in the error paths of `update_bases()` and `__build_class__`. Patch by Pablo Galindo.

- bpo-44826: Initial implementation of adaptive specialization of STORE_ATTR

  Three specialized forms of STORE_ATTR are added:

  - STORE_ATTR_SLOT

  - STORE_ATTR_SPLIT_KEYS

  - STORE_ATTR_WITH_HINT

- bpo-44838: Fixed a bug that was causing the parser to raise an incorrect custom `SyntaxError` for invalid ‘if’ expressions. Patch by Pablo Galindo.

- bpo-44821: Create instance dictionaries (__dict__) eagerly, to improve regularity of object layout and assist specialization.

- bpo-44792: Improve syntax errors for if expressions. Patch by Miguel Brito

- bpo-34013: Generalize the invalid legacy statement custom error message (like the one generated when “print” is called without parentheses) to include more generic expressions. Patch by Pablo Galindo

- bpo-44732: Rename `types.Union` to `types.UnionType`.

- bpo-44725: Expose specialization stats in python via `_opcode.get_specialization_stats()`.

- bpo-44717: Improve AttributeError on circular imports of submodules.

- bpo-44698: Fix undefined behaviour in complex object exponentiation.

- bpo-44653: Support `typing` types in parameter substitution in the union type.

- bpo-44676: Add ability to serialise `types.Union` objects. Patch provided by Yurii Karabas.

- bpo-44633: Parameter substitution of the union type with wrong types now raises `TypeError` instead of returning `NotImplemented`.

- bpo-44661: Update `property_descr_set` to use vectorcall if possible. Patch by Donghee Na.

- bpo-44662: Add `__module__` to `types.Union`. This also fixes `types.Union` issues with `typing.Annotated`. Patch provided by Yurii Karabas.

- bpo-44655: Include the name of the type in unset __slots__ attribute errors. Patch by Pablo Galindo

- bpo-44655: Don’t include a missing attribute with the same name as the failing one when offering suggestions for missing attributes. Patch by Pablo Galindo

- bpo-44646: Fix the hash of the union type: it no longer depends on the order of arguments.

- bpo-44636: Collapse union of equal types. E.g. the result of `int | int` is now `int`. Fix comparison of the union type with non-hashable objects. E.g. `int | str == {}` no longer raises a TypeError.

- bpo-44611: On Windows, `os.urandom()`: uses BCryptGenRandom API instead of CryptGenRandom API which is deprecated from Microsoft Windows API. Patch by Donghee Na.

- bpo-44635: Convert `None` to `type(None)` in the union type constructor.

- bpo-26280: Implement adaptive specialization for BINARY_SUBSCR

  Three specialized forms of BINARY_SUBSCR are added:

  - BINARY_SUBSCR_LIST_INT

  - BINARY_SUBSCR_TUPLE_INT

  - BINARY_SUBSCR_DICT

- bpo-44589: Mapping patterns in `match` statements with two or more equal literal keys will now raise a `SyntaxError` at compile-time.

- bpo-44606: Fix `__instancecheck__` and `__subclasscheck__` for the union type.

- bpo-42073: The `@classmethod` decorator can now wrap other classmethod-like descriptors.

- bpo-41972: Tuned the string-searching algorithm of fastsearch.h to have a shorter inner loop for most cases.

- bpo-44590: All necessary data for executing a Python function (local variables, stack, etc) is now kept in a per-thread stack. Frame objects are lazily allocated on demand. This increases performance by about 7% on the standard benchmark suite. Introspection and debugging are unaffected as frame objects are always available when needed. Patch by Mark Shannon.

- bpo-44584: The threading debug (`PYTHONTHREADDEBUG` environment variable) is deprecated in Python 3.10 and will be removed in Python 3.12. This feature requires a debug build of Python. Patch by Victor Stinner.

- bpo-43895: An obsolete internal cache of shared object file handles added in 1995 that attempted, but did not guarantee, that a .so would not be dlopen’ed twice to work around flaws in mid-1990s posix-ish operating systems has been removed from dynload_shlib.c.

- bpo-44490: `typing` now searches for type parameters in `types.Union` objects. `get_type_hints` will also properly resolve annotations with nested `types.Union` objects. Patch provided by Yurii Karabas.

- bpo-43950: Code objects can now provide the column information for instructions when available. This is levaraged during traceback printing to show the expressions responsible for errors.

  Contributed by Pablo Galindo, Batuhan Taskaya and Ammar Askar as part of PEP 657.

- bpo-44562: Remove uses of `PyObject_GC_Del()` in error path when initializing `types.GenericAlias`.

- bpo-41486: Fix a memory consumption and copying performance regression in earlier 3.10 beta releases if someone used an output buffer larger than 4GiB with zlib.decompress on input data that expands that large.

- bpo-43908: Heap types with the `Py_TPFLAGS_IMMUTABLETYPE` flag can now inherit the PEP 590 vectorcall protocol. Previously, this was only possible for static types. Patch by Erlend E. Aasland.

- bpo-44553: Implement GC methods for `types.Union` to break reference cycles and prevent memory leaks.

- bpo-44490: Add `__parameters__` attribute and `__getitem__` operator to `types.Union`. Patch provided by Yurii Karabas.

- bpo-44523: Remove the pass-through for `hash()` of `weakref.proxy` objects to prevent unintended consequences when the original referred object dies while the proxy is part of a hashable object. Patch by Pablo Galindo.

- bpo-44483: Fix a crash in `types.Union` objects when creating a union of an object with bad `__module__` field.

- bpo-44486: Modules will always have a dictionary, even when created by `types.ModuleType.__new__()`

- bpo-44472: Fix ltrace functionality when exceptions are raised. Patch by Pablo Galindo

- bpo-12022: A `TypeError` is now raised instead of an `AttributeError` in `with` and `async with` statements for objects which do not support the context manager or asynchronous context manager protocols correspondingly.

- bpo-44297: Make sure that the line number is set when entering a comprehension scope. This ensures that backtraces including generator expressions show the correct line number.

- bpo-44456: Improve the syntax error when mixing positional and keyword patterns. Patch by Pablo Galindo.

- bpo-44409: Fix error location information for tokenizer errors raised on initialization of the tokenizer. Patch by Pablo Galindo.

- bpo-44396: Fix a possible crash in the tokenizer when raising syntax errors for unclosed strings. Patch by Pablo Galindo.

- bpo-44376: Exact integer exponentiation (like `i**2` or `pow(i, 2)`) with a small exponent is much faster, due to reducing overhead in such cases.

- bpo-44313: Directly imported objects and modules (through import and from import statements) don’t generate `LOAD_METHOD`/`CALL_METHOD` for directly accessed objects on their namespace. They now use the regular `LOAD_ATTR`/`CALL_FUNCTION`.

- bpo-44338: Implement adaptive specialization for LOAD_GLOBAL

  Two specialized forms of LOAD_GLOBAL are added:

  - LOAD_GLOBAL_MODULE

  - LOAD_GLOBAL_BUILTIN

- bpo-44368: Improve syntax errors for invalid “as” targets. Patch by Pablo Galindo

- bpo-44349: Fix an edge case when displaying text from files with encoding in syntax errors. Patch by Pablo Galindo.

- bpo-44337: Initial implementation of adaptive specialization of LOAD_ATTR

  Four specialized forms of LOAD_ATTR are added:

  - LOAD_ATTR_SLOT

  - LOAD_ATTR_SPLIT_KEYS

  - LOAD_ATTR_WITH_HINT

  - LOAD_ATTR_MODULE

- bpo-44335: Fix a regression when identifying incorrect characters in syntax errors. Patch by Pablo Galindo

- bpo-43693: Computation of the offsets of cell variables is done in the compiler instead of at runtime. This reduces the overhead of handling cell and free variables, especially in the case where a variable is both an argument and cell variable.

- bpo-44317: Improve tokenizer error with improved locations. Patch by Pablo Galindo.

- bpo-44304: Fix a crash in the `sqlite3` module that happened when the garbage collector clears `sqlite.Statement` objects. Patch by Pablo Galindo

- bpo-44305: Improve error message for `try` blocks without `except` or `finally` blocks. Patch by Pablo Galindo.

- bpo-43413: Constructors of subclasses of some builtin classes (e.g. `tuple`, `list`, `frozenset`) no longer accept arbitrary keyword arguments. [reverted in 3.11a4] Subclass of `set` can now define a `__new__()` method with additional keyword parameters without overriding also `__init__()`.

- bpo-43667: Improve Unicode support in non-UTF locales on Oracle Solaris. This issue does not affect other Solaris systems.

- bpo-43693: A new opcode MAKE_CELL has been added that effectively moves some of the work done on function entry into the compiler and into the eval loop. In addition to creating the required cell objects, the new opcode converts relevant arguments (and other locals) to cell variables on function entry.

- bpo-44232: Fix a regression in `type()` when a metaclass raises an exception. The C function `type_new()` must properly report the exception when a metaclass constructor raises an exception and the winner class is not the metaclass. Patch by Victor Stinner.

- bpo-44201: Avoid side effects of checking for specialized syntax errors in the REPL that was causing it to ask for extra tokens after a syntax error had been detected. Patch by Pablo Galindo

- bpo-43693: `PyCodeObject` gained `co_fastlocalnames` and `co_fastlocalkinds` as the authoritative source of fast locals info. Marshaled code objects have changed accordingly.

- bpo-44184: Fix a crash at Python exit when a deallocator function removes the last strong reference to a heap type. Patch by Victor Stinner.

- bpo-44187: Implement quickening in the interpreter. This offers no advantages as yet, but is an enabler of future optimizations. See PEP 659 for full explanation.

- bpo-44180: The parser doesn’t report generic syntax errors that happen in a position further away that the one it reached in the first pass. Patch by Pablo Galindo

- bpo-44168: Fix error message in the parser involving keyword arguments with invalid expressions. Patch by Pablo Galindo

- bpo-44156: String caches in `compile.c` are now subinterpreter compatible.

- bpo-44143: Fixed a crash in the parser that manifest when raising tokenizer errors when an existing exception was present. Patch by Pablo Galindo.

- bpo-44032: Move ‘fast’ locals and other variables from the frame object to a per-thread datastack.

- bpo-44114: Fix incorrect dictkeys_reversed and dictitems_reversed function signatures in C code, which broke webassembly builds.

- bpo-44110: Improve `str.__getitem__()` error message

- bpo-26110: Add `CALL_METHOD_KW` opcode to speed up method calls with keyword arguments. Idea originated from PyPy. A side effect is executing `CALL_METHOD` is now branchless in the evaluation loop.

- bpo-28307: Compiler now optimizes simple C-style formatting with literal format containing only format codes %s, %r and %a by converting them to f-string expressions.

- bpo-43149: Correct the syntax error message regarding multiple exception types to not refer to “exception groups”. Patch by Pablo Galindo

- bpo-43822: The parser will prioritize tokenizer errors over custom syntax errors when raising exceptions. Patch by Pablo Galindo.

- bpo-40222: “Zero cost” exception handling.

  - Uses a lookup table to determine how to handle exceptions.

  - Removes SETUP_FINALLY and POP_TOP block instructions, eliminating the runtime overhead of try statements.

  - Reduces the size of the frame object by about 60%.

  Patch by Mark Shannon

- bpo-43918: Document the signature and `default` argument in the docstring of the new `anext` builtin.

- bpo-43833: Emit a deprecation warning if the numeric literal is immediately followed by one of keywords: and, else, for, if, in, is, or. Raise a syntax error with more informative message if it is immediately followed by other keyword or identifier.

- bpo-43879: Add native_thread_id to PyThreadState. Patch by Gabriele N. Tornetta.

- bpo-43693: Compute cell offsets relative to locals in compiler. Allows the interpreter to treats locals and cells a single array, which is slightly more efficient. Also make the LOAD_CLOSURE opcode an alias for LOAD_FAST. Preserving LOAD_CLOSURE helps keep bytecode a bit more readable.

- bpo-17792: More accurate error messages for access of unbound locals or free vars.

- bpo-28146: Fix a confusing error message in `str.format()`.

- bpo-11105: When compiling `ast.AST` objects with recursive references through `compile()`, the interpreter doesn’t crash anymore instead it raises a `RecursionError`.

- bpo-39091: Fix crash when using passing a non-exception to a generator’s `throw()` method. Patch by Noah Oxer

- bpo-33346: Asynchronous comprehensions are now allowed inside comprehensions in asynchronous functions. Outer comprehensions implicitly become asynchronous.

### Library

- bpo-45371: Fix clang rpath issue in `distutils`. The UnixCCompiler now uses correct clang option to add a runtime library directory (rpath) to a shared library.

- bpo-45329: Fix freed memory access in `pyexpat.xmlparser` when building it with an installed expat library <= 2.2.0.

- bpo-41710: On Unix, if the `sem_clockwait()` function is available in the C library (glibc 2.30 and newer), the `threading.Lock.acquire()` method now uses the monotonic clock (`time.CLOCK_MONOTONIC`) for the timeout, rather than using the system clock (`time.CLOCK_REALTIME`), to not be affected by system clock changes. Patch by Victor Stinner.

- bpo-1596321: Fix the `threading._shutdown()` function when the `threading` module was imported first from a thread different than the main thread: no longer log an error at Python exit.

- bpo-45274: Fix a race condition in the `Thread.join()` method of the `threading` module. If the function is interrupted by a signal and the signal handler raises an exception, make sure that the thread remains in a consistent state to prevent a deadlock. Patch by Victor Stinner.

- bpo-21302: In Unix operating systems, `time.sleep()` now uses the `nanosleep()` function, if `clock_nanosleep()` is not available but `nanosleep()` is available. `nanosleep()` allows to sleep with nanosecond precision.

- bpo-21302: On Windows, `time.sleep()` now uses a waitable timer which has a resolution of 100 nanoseconds (10-7 seconds). Previously, it had a resolution of 1 millisecond (10-3 seconds). Patch by Benjamin Szőke and Victor Stinner.

- bpo-45238: Fix `unittest.IsolatedAsyncioTestCase.debug()`: it runs now asynchronous methods and callbacks.

- bpo-36674: `unittest.TestCase.debug()` raises now a `unittest.SkipTest` if the class or the test method are decorated with the skipping decorator.

- bpo-45235: Fix an issue where argparse would not preserve values in a provided namespace when using a subparser with defaults.

- bpo-45183: Have zipimport.zipimporter.find_spec() not raise an exception when the underlying zip file has been deleted and the internal cache has been reset via invalidate_cache().

- bpo-45234: Fixed a regression in `copyfile()`, `copy()`, `copy2()` raising `FileNotFoundError` when source is a directory, which should raise `IsADirectoryError`

- bpo-45228: Fix stack buffer overflow in parsing J1939 network address.

- bpo-45225: use map function instead of genexpr in capwords.

- bpo-42135: Fix typo: `importlib.find_loader` is really slated for removal in Python 3.12 not 3.10, like the others in PR 25169.

  Patch by Hugo van Kemenade.

- bpo-20524: Improves error messages on `.format()` operation for `str`, `float`, `int`, and `complex`. New format now shows the problematic pattern and the object type.

- bpo-45168: Change `dis.dis()` output to omit op arg values that cannot be resolved due to `co_consts`, `co_names` etc not being provided. Previously the oparg itself was repeated in the value field, which is not useful and can be confusing.

- bpo-21302: In Unix operating systems, `time.sleep()` now uses the `clock_nanosleep()` function, if available, which allows to sleep for an interval specified with nanosecond precision.

- bpo-45173: Remove from the `configparser` module: the `SafeConfigParser` class, the `filename` property of the `ParsingError` class, the `readfp()` method of the `ConfigParser` class, deprecated since Python 3.2.

  Patch by Hugo van Kemenade.

- bpo-44987: Pure ASCII strings are now normalized in constant time by `unicodedata.normalize()`. Patch by Donghee Na.

- bpo-35474: Calling `mimetypes.guess_all_extensions()` with `strict=False` no longer affects the result of the following call with `strict=True`. Also, mutating the returned list no longer affects the global state.

- bpo-45166: `typing.get_type_hints()` now works with `Final` wrapped in `ForwardRef`.

- bpo-45162: Remove many old deprecated `unittest` features:

  - “`fail*`” and “`assert*`” aliases of `TestCase` methods.

  - Broken from start `TestCase` method `assertDictContainsSubset()`.

  - Ignored `<unittest.TestLoader.loadTestsFromModule> TestLoader.loadTestsFromModule()` parameter use_load_tests.

  - Old alias `_TextTestResult` of `TextTestResult`.

- bpo-38371: Remove the deprecated `split()` method of `_tkinter.TkappType`. Patch by Erlend E. Aasland.

- bpo-20499: Improve the speed and accuracy of statistics.pvariance().

- bpo-45132: Remove `__getitem__()` methods of `xml.dom.pulldom.DOMEventStream`, `wsgiref.util.FileWrapper` and `fileinput.FileInput`, deprecated since Python 3.9.

  Patch by Hugo van Kemenade.

- bpo-45129: Due to significant security concerns, the reuse_address parameter of `asyncio.loop.create_datagram_endpoint()`, disabled in Python 3.9, is now entirely removed. This is because of the behavior of the socket option `SO_REUSEADDR` in UDP.

  Patch by Hugo van Kemenade.

- bpo-45124: The `bdist_msi` command, deprecated in Python 3.9, is now removed.

  Use `bdist_wheel` (wheel packages) instead.

  Patch by Hugo van Kemenade.

- bpo-30856: `unittest.TestResult` methods `addFailure()`, `addError()`, `addSkip()` and `addSubTest()` are now called immediately after raising an exception in test or finishing a subtest. Previously they were called only after finishing the test clean up.

- bpo-45034: Changes how error is formatted for `struct.pack` with `'H'` and `'h'` modes and too large / small numbers. Now it shows the actual numeric limits, while previously it was showing arithmetic expressions.

- bpo-25894: `unittest` now always reports skipped and failed subtests separately: separate characters in default mode and separate lines in verbose mode. Also the test description is now output for errors in test method, class and module cleanups.

- bpo-45081: Fix issue when dataclasses that inherit from `typing.Protocol` subclasses have wrong `__init__`. Patch provided by Yurii Karabas.

- bpo-45085: The `binhex` module, deprecated in Python 3.9, is now removed. The following `binascii` functions, deprecated in Python 3.9, are now also removed:

  - `a2b_hqx()`, `b2a_hqx()`;

  - `rlecode_hqx()`, `rledecode_hqx()`.

  The `binascii.crc_hqx()` function remains available.

  Patch by Victor Stinner.

- bpo-40360: The `lib2to3` package is now deprecated and may not be able to parse Python 3.10 or newer. See the PEP 617 (New PEG parser for CPython). Patch by Victor Stinner.

- bpo-45075: Rename `traceback.StackSummary.format_frame()` to `traceback.StackSummary.format_frame_summary()`. This method was added for 3.11 so it was not released yet.

  Updated code and docs to better distinguish frame and FrameSummary.

- bpo-31299: Add option to completely drop frames from a traceback by returning `None` from a `format_frame()` override.

- bpo-41620: `run()` now always return a `TestResult` instance. Previously it returned `None` if the test class or method was decorated with a skipping decorator.

- bpo-45021: Fix a potential deadlock at shutdown of forked children when using `concurrent.futures` module

- bpo-43913: Fix bugs in cleaning up classes and modules in `unittest`:

  - Functions registered with `addModuleCleanup()` were not called unless the user defines `tearDownModule()` in their test module.

  - Functions registered with `addClassCleanup()` were not called if `tearDownClass` is set to `None`.

  - Buffering in `TestResult` did not work with functions registered with `addClassCleanup()` and `addModuleCleanup()`.

  - Errors in functions registered with `addClassCleanup()` and `addModuleCleanup()` were not handled correctly in buffered and debug modes.

  - Errors in `setUpModule()` and functions registered with `addModuleCleanup()` were reported in wrong order.

  - And several lesser bugs.

- bpo-45030: Fix integer overflow in pickling and copying the range iterator.

- bpo-45001: Made email date parsing more robust against malformed input, namely a whitespace-only `Date:` header. Patch by Wouter Bolsterlee.

- bpo-45010: Remove support of special method `__div__` in `unittest.mock`. It is not used in Python 3.

- bpo-39218: Improve accuracy of variance calculations by using `x*x` instead of `x**2`.

- bpo-43613: Improve the speed of `gzip.compress()` and `gzip.decompress()` by compressing and decompressing at once in memory instead of in a streamed fashion.

- bpo-37596: Ensure that `set` and `frozenset` objects are always `marshalled` reproducibly.

- bpo-44019: A new function `operator.call` has been added, such that `operator.call(obj, *args, **kwargs) == obj(*args, **kwargs)`.

- bpo-42255: `webbrowser.MacOSX` is deprecated and will be removed in Python 3.13. It is untested and undocumented and also not used by webbrowser itself. Patch by Donghee Na.

- bpo-44955: Method `stopTestRun()` is now always called in pair with method `startTestRun()` for `TestResult` objects implicitly created in `run()`. Previously it was not called for test methods and classes decorated with a skipping decorator.

- bpo-39039: tarfile.open raises `ReadError` when a zlib error occurs during file extraction.

- bpo-44935: `subprocess` on Solaris now also uses `os.posix_spawn()` for better performance.

- bpo-44911: `IsolatedAsyncioTestCase` will no longer throw an exception while cancelling leaked tasks. Patch by Bar Harel.

- bpo-41322: Added `DeprecationWarning` for tests and async tests that return a value!=None (as this may indicate an improperly written test, for example a test written as a generator function).

- bpo-44524: Make exception message more useful when subclass from typing special form alias. Patch provided by Yurii Karabas.

- bpo-38956: `argparse.BooleanOptionalAction`’s default value is no longer printed twice when used with `argparse.ArgumentDefaultsHelpFormatter`.

- bpo-44860: Fix the `posix_user` scheme in `sysconfig` to not depend on `sys.platlibdir`.

- bpo-44859: Improve error handling in `sqlite3` and raise more accurate exceptions.

  - `MemoryError` is now raised instead of `sqlite3.Warning` when memory is not enough for encoding a statement to UTF-8 in `Connection.__call__()` and `Cursor.execute()`.

  - `UnicodEncodeError` is now raised instead of `sqlite3.Warning` when the statement contains surrogate characters in `Connection.__call__()` and `Cursor.execute()`.

  - `TypeError` is now raised instead of `ValueError` for non-string script argument in `Cursor.executescript()`.

  - `ValueError` is now raised for script containing the null character instead of truncating it in `Cursor.executescript()`.

  - Correctly handle exceptions raised when getting boolean value of the result of the progress handler.

  - Add many tests covering different corner cases.

- bpo-44581: Upgrade bundled pip to 21.2.3 and setuptools to 57.4.0

- bpo-44849: Fix the `os.set_inheritable()` function on FreeBSD 14 for file descriptor opened with the `O_PATH` flag: ignore the `EBADF` error on `ioctl()`, fallback on the `fcntl()` implementation. Patch by Victor Stinner.

- bpo-44605: The @functools.total_ordering() decorator now works with metaclasses.

- bpo-44524: Fixed an issue wherein the `__name__` and `__qualname__` attributes of subscribed specialforms could be `None`.

- bpo-44839: `MemoryError` raised in user-defined functions will now produce a `MemoryError` in `sqlite3`. `OverflowError` will now be converted to `DataError`. Previously `OperationalError` was produced in these cases.

- bpo-44822: `sqlite3` user-defined functions and aggregators returning `strings` with embedded NUL characters are no longer truncated. Patch by Erlend E. Aasland.

- bpo-44801: Ensure that the `ParamSpec` variable in Callable can only be substituted with a parameters expression (a list of types, an ellipsis, ParamSpec or Concatenate).

- bpo-44806: Non-protocol subclasses of `typing.Protocol` ignore now the `__init__` method inherited from protocol base classes.

- bpo-27275: `collections.OrderedDict.popitem()` and `collections.OrderedDict.pop()` no longer call `__getitem__` and `__delitem__` methods of the OrderedDict subclasses.

- bpo-44793: Fix checking the number of arguments when subscribe a generic type with `ParamSpec` parameter.

- bpo-44784: In importlib.metadata tests, override warnings behavior under expected DeprecationWarnings (importlib_metadata 4.6.3).

- bpo-44667: The `tokenize.tokenize()` doesn’t incorrectly generate a `NEWLINE` token if the source doesn’t end with a new line character but the last line is a comment, as the function is already generating a `NL` token. Patch by Pablo Galindo

- bpo-44771: Added `importlib.simple` module implementing adapters from a low-level resources reader interface to a `TraversableResources` interface. Legacy API (`path`, `contents`, …) is now supported entirely by the `.files()` API with a compatibility shim supplied for resource loaders without that functionality. Feature parity with `importlib_resources` 5.2.

- bpo-44752: `rcompleter` does not call `getattr()` on `property` objects to avoid the side-effect of evaluating the corresponding method.

- bpo-44747: Refactor usage of `sys._getframe` in `typing` module. Patch provided by Yurii Karabas.

- bpo-42378: Fixes the issue with log file being overwritten when `logging.FileHandler` is used in `atexit` with filemode set to `'w'`. Note this will cause the message in atexit not being logged if the log stream is already closed due to shutdown of logging.

- bpo-44720: `weakref.proxy` objects referencing non-iterators now raise `TypeError` rather than dereferencing the null `tp_iternext` slot and crashing.

- bpo-44704: The implementation of `collections.abc.Set._hash()` now matches that of `frozenset.__hash__()`.

- bpo-44666: Fixed issue in `compileall.compile_file()` when `sys.stdout` is redirected. Patch by Stefan Hölzl.

- bpo-44688: `sqlite3.Connection.create_collation()` now accepts non-ASCII collation names. Patch by Erlend E. Aasland.

- bpo-44690: Adopt binacii.a2b_base64’s strict mode in base64.b64decode.

- bpo-42854: Fixed a bug in the `_ssl` module that was throwing `OverflowError` when using `_ssl._SSLSocket.write()` and `_ssl._SSLSocket.read()` for a big value of the `len` parameter. Patch by Pablo Galindo.

- bpo-44686: Replace `unittest.mock._importer` with `pkgutil.resolve_name`.

- bpo-44353: Make `NewType.__call__` faster by implementing it in C. Patch provided by Yurii Karabas.

- bpo-44682: Change the `pdb` commands directive to disallow setting commands for an invalid breakpoint and to display an appropriate error.

- bpo-44353: Refactor `typing.NewType` from function into callable class. Patch provided by Yurii Karabas.

- bpo-44678: Added a separate error message for discontinuous padding in binascii.a2b_base64 strict mode.

- bpo-44524: Add missing `__name__` and `__qualname__` attributes to `typing` module classes. Patch provided by Yurii Karabas.

- bpo-40897: Give priority to using the current class constructor in `inspect.signature()`. Patch by Weipeng Hong.

- bpo-44638: Add a reference to the zipp project and hint as to how to use it.

- bpo-44648: Fixed wrong error being thrown by `inspect.getsource()` when examining a class in the interactive session. Instead of `TypeError`, it should be `OSError` with appropriate error message.

- bpo-44608: Fix memory leak in `_tkinter._flatten()` if it is called with a sequence or set, but not list or tuple.

- bpo-44594: Fix an edge case of `ExitStack` and `AsyncExitStack` exception chaining. They will now match `with` block behavior when `__context__` is explicitly set to `None` when the exception is in flight.

- bpo-42799: In `fnmatch`, the cache size for compiled regex patterns (`functools.lru_cache()`) was bumped up from 256 to 32768, affecting functions: `fnmatch.fnmatch()`, `fnmatch.fnmatchcase()`, `fnmatch.filter()`.

- bpo-41928: Update `shutil.copyfile()` to raise `FileNotFoundError` instead of confusing `IsADirectoryError` when a path ending with a `os.path.sep` does not exist; `shutil.copy()` and `shutil.copy2()` are also affected.

- bpo-44569: Added the `StackSummary.format_frame()` function in `traceback`. This allows users to customize the way individual lines are formatted in tracebacks without re-implementing logic to handle recursive tracebacks.

- bpo-44566: handle StopIteration subclass raised from @contextlib.contextmanager generator

- bpo-44558: Make the implementation consistency of `indexOf()` between C and Python versions. Patch by Donghee Na.

- bpo-41249: Fixes `TypedDict` to work with `typing.get_type_hints()` and postponed evaluation of annotations across modules.

- bpo-44554: Refactor argument processing in `pdb.main()` to simplify detection of errors in input loading and clarify behavior around module or script invocation.

- bpo-34798: Break up paragraph about `pprint.PrettyPrinter` construction parameters to make it easier to read.

- bpo-44539: Added support for recognizing JPEG files without JFIF or Exif markers.

- bpo-44461: Fix bug with `pdb`’s handling of import error due to a package which does not have a `__main__` module

- bpo-43625: Fix a bug in the detection of CSV file headers by `csv.Sniffer.has_header()` and improve documentation of same.

- bpo-44516: Update vendored pip to 21.1.3

- bpo-42892: Fixed an exception thrown while parsing a malformed multipart email by `email.message.EmailMessage`.

- bpo-44468: `typing.get_type_hints()` now finds annotations in classes and base classes with unexpected `__module__`. Previously, it skipped those MRO elements.

- bpo-44491: Allow clearing the `sqlite3` authorizer callback by passing `None` to `set_authorizer()`. Patch by Erlend E. Aasland.

- bpo-43977: Set the proper `Py_TPFLAGS_MAPPING` and `Py_TPFLAGS_SEQUENCE` flags for subclasses created before a parent has been registered as a `collections.abc.Mapping` or `collections.abc.Sequence`.

- bpo-44482: Fix very unlikely resource leak in `glob` in alternate Python implementations.

- bpo-44466: The `faulthandler` module now detects if a fatal error occurs during a garbage collector collection. Patch by Victor Stinner.

- bpo-44471: A `TypeError` is now raised instead of an `AttributeError` in `contextlib.ExitStack.enter_context()` and `contextlib.AsyncExitStack.enter_async_context()` for objects which do not support the context manager or asynchronous context manager protocols correspondingly.

- bpo-44404: `tkinter`’s `after()` method now supports callables without the `__name__` attribute.

- bpo-41546: Make `pprint` (like the builtin `print`) not attempt to write to `stdout` when it is `None`.

- bpo-44458: `BUFFER_BLOCK_SIZE` is now declared static, to avoid linking collisions when bz2, lmza or zlib are statically linked.

- bpo-44464: Remove exception for flake8 in deprecated importlib.metadata interfaces. Sync with importlib_metadata 4.6.

- bpo-44446: Take into account that `lineno` might be `None` in `traceback.FrameSummary`.

- bpo-44439: Fix in `bz2.BZ2File.write()` / `lzma.LZMAFile.write()` methods, when the input data is an object that supports the buffer protocol, the file length may be wrong.

- bpo-44434: _thread.start_new_thread() no longer calls PyThread_exit_thread() explicitly at the thread exit, the call was redundant. On Linux with the glibc, pthread_exit() aborts the whole process if dlopen() fails to open libgcc_s.so file (ex: EMFILE error). Patch by Victor Stinner.

- bpo-42972: The _thread.RLock type now fully implement the GC protocol: add a traverse function and the `Py_TPFLAGS_HAVE_GC` flag. Patch by Victor Stinner.

- bpo-44422: The `threading.enumerate()` function now uses a reentrant lock to prevent a hang on reentrant call. Patch by Victor Stinner.

- bpo-38291: Importing typing.io or typing.re now prints a `DeprecationWarning`.

- bpo-37880: argparse actions store_const and append_const each receive a default value of `None` when the `const` kwarg is not provided. Previously, this raised a `TypeError`.

- bpo-44389: Fix deprecation of `ssl.OP_NO_TLSv1_3`

- bpo-27827: `pathlib.PureWindowsPath.is_reserved()` now identifies a greater range of reserved filenames, including those with trailing spaces or colons.

- bpo-44395: Fix `as_string()` to pass unixfrom properly. Patch by Donghee Na.

- bpo-34266: Handle exceptions from parsing the arg of `pdb`’s run/restart command.

- bpo-44362: Improve `ssl` module’s deprecation messages, error reporting, and documentation for deprecations.

- bpo-44342: [Enum] Change pickling from by-value to by-name.

- bpo-44356: [Enum] Allow multiple data-type mixins if they are all the same.

- bpo-44351: Restore back `parse_makefile()` in `distutils.sysconfig` because it behaves differently than the similar implementation in `sysconfig`.

- bpo-35800: `smtpd.MailmanProxy` is now removed as it is unusable without an external module, `mailman`. Patch by Donghee Na.

- bpo-44357: Added a function that returns cube root of the given number `math.cbrt()`

- bpo-44339: Change `math.pow(±0.0, -math.inf)` to return `inf` instead of raising `ValueError`. This brings the special-case handling of `math.pow` into compliance with the IEEE 754 standard.

- bpo-44242: Remove missing flag check from Enum creation and move into a `verify` decorator.

- bpo-44246: In `importlib.metadata`, restore compatibility in the result from `Distribution.entry_points` (`EntryPoints`) to honor expectations in older implementations and issuing deprecation warnings for these cases: A. `EntryPoints` objects are once again mutable, allowing for `sort()` and other list-based mutation operations. Avoid deprecation warnings by casting to a mutable sequence (e.g. `list(dist.entry_points).sort()`). B. `EntryPoints` results once again allow for access by index. To avoid deprecation warnings, cast the result to a Sequence first (e.g. `tuple(dist.entry_points)[0]`).

- bpo-44246: In importlib.metadata.entry_points, de-duplication of distributions no longer requires loading the full metadata for PathDistribution objects, improving entry point loading performance by ~10x.

- bpo-43858: Added a function that returns a copy of a dict of logging levels: `logging.getLevelNamesMapping()`

- bpo-44260: The `random.Random` constructor no longer reads system entropy without need.

- bpo-44254: On Mac, give turtledemo button text a color that works on both light or dark background. Programmers cannot control the latter.

- bpo-44258: Support PEP 515 for Fraction’s initialization from string.

- bpo-44235: Remove deprecated functions in the `gettext`. Patch by Donghee Na.

- bpo-38693: Prefer f-strings to `.format` in importlib.resources.

- bpo-33693: Importlib.metadata now prefers f-strings to .format.

- bpo-44241: Incorporate minor tweaks from importlib_metadata 4.1: SimplePath protocol, support for Metadata 2.2.

- bpo-43216: Remove the `@asyncio.coroutine` decorator enabling legacy generator-based coroutines to be compatible with async/await code; remove `asyncio.coroutines.CoroWrapper` used for wrapping legacy coroutine objects in the debug mode. The decorator has been deprecated since Python 3.8 and the removal was initially scheduled for Python 3.10. Patch by Illia Volochii.

- bpo-44210: Make importlib.metadata._meta.PackageMetadata public.

- bpo-43643: Declare readers.MultiplexedPath.name as a property per the spec.

- bpo-27334: The `sqlite3` context manager now performs a rollback (thus releasing the database lock) if commit failed. Patch by Luca Citi and Erlend E. Aasland.

- bpo-4928: Documented existing behavior on POSIX: NamedTemporaryFiles are not deleted when creating process is killed with SIGKILL

- bpo-44154: Optimize `fractions.Fraction` pickling for large components.

- bpo-33433: For IPv4 mapped IPv6 addresses (RFC 4291 Section 2.5.5.2), the `ipaddress.IPv6Address.is_private` check is deferred to the mapped IPv4 address. This solves a bug where public mapped IPv4 addresses were considered private by the IPv6 check.

- bpo-44150: Add optional weights argument to statistics.fmean().

- bpo-44142: `ast.unparse()` will now drop the redundant parentheses when tuples used as assignment targets (e.g in for loops).

- bpo-44145: `hmac` computations were not releasing the GIL while calling the OpenSSL `HMAC_Update` C API (a new feature in 3.9). This unintentionally prevented parallel computation as other `hashlib` algorithms support.

- bpo-44095: `zipfile.Path` now supports `zipfile.Path.stem`, `zipfile.Path.suffixes`, and `zipfile.Path.suffix` attributes.

- bpo-44077: It’s now possible to receive the type of service (ToS), a.k.a. differentiated services (DS), a.k.a. differentiated services code point (DSCP) and explicit congestion notification (ECN) IP header fields with `socket.IP_RECVTOS`.

- bpo-37788: Fix a reference leak when a Thread object is never joined.

- bpo-38908: Subclasses of `typing.Protocol` which only have data variables declared will now raise a `TypeError` when checked with `isinstance` unless they are decorated with `runtime_checkable()`. Previously, these checks passed silently. Patch provided by Yurii Karabas.

- bpo-44098: `typing.ParamSpec` will no longer be found in the `__parameters__` of most `typing` generics except in valid use locations specified by PEP 612. This prevents incorrect usage like `typing.List[P][int]`. This change means incorrect usage which may have passed silently in 3.10 beta 1 and earlier will now error.

- bpo-44089: Allow subclassing `csv.Error` in 3.10 (it was allowed in 3.9 and earlier but was disallowed in early versions of 3.10).

- bpo-44081: `ast.unparse()` now doesn’t use redundant spaces to separate `lambda` and the `:` if there are no parameters.

- bpo-44061: Fix regression in previous release when calling `pkgutil.iter_modules()` with a list of `pathlib.Path` objects

- bpo-44059: Register the SerenityOS Browser in the `webbrowser` module.

- bpo-36515: The `hashlib` module no longer does unaligned memory accesses when compiled for ARM platforms.

- bpo-40465: Remove random module features deprecated in Python 3.9.

- bpo-44018: random.seed() no longer mutates bytearray inputs.

- bpo-38352: Add `IO`, `BinaryIO`, `TextIO`, `Match`, and `Pattern` to `typing.__all__`. Patch by Jelle Zijlstra.

- bpo-44002: `urllib.parse` now uses `functool.lru_cache()` for its internal URL splitting and quoting caches instead of rolling its own like its the ’90s.

  The undocumented internal `urllib.parse` `Quoted` class API is now deprecated, for removal in 3.14.

- bpo-43972: When `http.server.SimpleHTTPRequestHandler` sends a `301 (Moved Permanently)` for a directory path not ending with `/`, add a `Content-Length: 0` header. This improves the behavior for certain clients.

- bpo-28528: Fix a bug in `pdb` where `checkline()` raises `AttributeError` if it is called after `reset()`.

- bpo-43853: Improved string handling for `sqlite3` user-defined functions and aggregates:

  - It is now possible to pass strings with embedded null characters to UDFs

  - Conversion failures now correctly raise `MemoryError`

  Patch by Erlend E. Aasland.

- bpo-43666: AIX: `Lib/_aix_support.get_platform()` may fail in an AIX WPAR. The fileset bos.rte appears to have a builddate in both LPAR and WPAR so this fileset is queried rather than bos.mp64. To prevent a similar situation (no builddate in ODM) a value (9988) sufficient for completing a build is provided. Patch by M Felt.

- bpo-43650: Fix `MemoryError` in `shutil.unpack_archive()` which fails inside `shutil._unpack_zipfile()` on large files. Patch by Igor Bolshakov.

- bpo-43612: `zlib.compress()` now accepts a wbits parameter which allows users to compress data as a raw deflate block without zlib headers and trailers in one go. Previously this required instantiating a `zlib.compressobj`. It also provides a faster alternative to `gzip.compress` when wbits=31 is used.

- bpo-43392: `importlib._bootstrap._find_and_load()` now implements a two-step check to avoid locking when modules have been already imported and are ready. This improves performance of repeated calls to `importlib.import_module()` and `importlib.__import__()`.

- bpo-43318: Fix a bug where `pdb` does not always echo cleared breakpoints.

- bpo-43234: Prohibit passing non-`concurrent.futures.ThreadPoolExecutor` executors to `loop.set_default_executor()` following a deprecation in Python 3.8. Patch by Illia Volochii.

- bpo-43232: Prohibit previously deprecated potentially disruptive operations on `asyncio.trsock.TransportSocket`. Patch by Illia Volochii.

- bpo-30077: Added support for Apple’s aifc/sowt pseudo-compression

- bpo-42971: Add definition of `errno.EQFULL` for platforms that define this constant (such as macOS).

- bpo-43086: Added a new optional `strict_mode` parameter to binascii.a2b_base64. When `scrict_mode` is set to `True`, the a2b_base64 function will accept only valid base64 content. More details about what “valid base64 content” is, can be found in the function’s documentation.

- bpo-43024: Improve the help signature of `traceback.print_exception()`, `traceback.format_exception()` and `traceback.format_exception_only()`.

- bpo-33809: Add the `traceback.TracebackException.print()` method which prints the formatted exception information.

- bpo-42862: `sqlite3` now utilizes `functools.lru_cache()` to implement the connection statement cache. As a small optimisation, the default statement cache size has been increased from 100 to 128. Patch by Erlend E. Aasland.

- bpo-41818: Soumendra Ganguly: add termios.tcgetwinsize(), termios.tcsetwinsize().

- bpo-40497: `subprocess.check_output()` now raises `ValueError` when the invalid keyword argument check is passed by user code. Previously such use would fail later with a `TypeError`. Patch by Rémi Lapeyre.

- bpo-37449: `ensurepip` now uses `importlib.resources.files()` traversable APIs

- bpo-40956: Use Argument Clinic in `sqlite3`. Patches by Erlend E. Aasland.

- bpo-41730: `DeprecationWarning` is now raised when importing `tkinter.tix`, which has been deprecated in documentation since Python 3.6.

- bpo-20684: Remove unused `_signature_get_bound_param` function from `inspect` - by Anthony Sottile.

- bpo-41402: Fix `email.message.EmailMessage.set_content()` when called with binary data and `7bit` content transfer encoding.

- bpo-32695: The compresslevel and preset keyword arguments of `tarfile.open()` are now both documented and tested.

- bpo-41137: Use utf-8 encoding while reading .pdbrc files. Patch by Srinivas Reddy Thatiparthy

- bpo-24391: Improved reprs of `threading` synchronization objects: `Semaphore`, `BoundedSemaphore`, `Event` and `Barrier`.

- bpo-5846: Deprecated the following `unittest` functions, scheduled for removal in Python 3.13:

  - `findTestCases()`

  - `makeSuite()`

  - `getTestCaseNames()`

  Use `TestLoader` methods instead:

  - `unittest.TestLoader.loadTestsFromModule()`

  - `unittest.TestLoader.loadTestsFromTestCase()`

  - `unittest.TestLoader.getTestCaseNames()`

  Patch by Erlend E. Aasland.

- bpo-40563: Support pathlike objects on dbm/shelve. Patch by Hakan Çelik and Henry-Joseph Audéoud.

- bpo-34990: Fixed a Y2k38 bug in the compileall module where it would fail to compile files with a modification time after the year 2038.

- bpo-39549: Whereas the code for reprlib.Repr had previously used a hardcoded string value of ‘…’, this PR updates it to use of a “fillvalue” attribute, whose value defaults to ‘…’ and can be reset in either individual reprlib.Repr instances or in subclasses thereof.

- bpo-37022: `pdb` now displays exceptions from `repr()` with its `p` and `pp` commands.

- bpo-38840: Fix `test___all__` on platforms lacking a shared memory implementation.

- bpo-39359: Add one missing check that the password is a bytes object for an encrypted zipfile.

- bpo-38741: `configparser`: using ‘]’ inside a section header will no longer cut the section name short at the ‘]’

- bpo-38415: Added missing behavior to `contextlib.asynccontextmanager()` to match `contextlib.contextmanager()` so decorated functions can themselves be decorators.

- bpo-30256: Pass multiprocessing BaseProxy argument `manager_owned` through AutoProxy.

- bpo-27513: `email.utils.getaddresses()` now accepts `email.header.Header` objects along with string values. Patch by Zackery Spytz.

- bpo-16379: Add SQLite error code and name to `sqlite3` exceptions. Patch by Aviv Palivoda, Daniel Shahaf, and Erlend E. Aasland.

- bpo-26228: pty.spawn no longer hangs on FreeBSD, macOS, and Solaris.

- bpo-33349: lib2to3 now recognizes async generators everywhere.

- bpo-29298: Fix `TypeError` when required subparsers without `dest` do not receive arguments. Patch by Anthony Sottile.

### Documentation

- bpo-45216: Remove extra documentation listing methods in `difflib`. It was rendering twice in pydoc and was outdated in some places.

- bpo-45024: `collections.abc` documentation has been expanded to explicitly cover how instance and subclass checks work, with additional doctest examples and an exhaustive list of ABCs which test membership purely by presence of the right special methods. Patch by Raymond Hettinger.

- bpo-44957: Promote PEP 604 union syntax by using it where possible. Also, mention `X | Y` more prominently in section about `Union` and mention `X | None` at all in section about `Optional`.

- bpo-16580: Added code equivalents for the `int.to_bytes()` and `int.from_bytes()` methods, as well as tests ensuring that these code equivalents are valid.

- bpo-44903: Removed the `othergui.rst` file, any references to it, and the list of GUI frameworks in the FAQ. In their place I’ve added links to the Python Wiki page on GUI frameworks.

- bpo-33479: Tkinter documentation has been greatly expanded with new “Architecture” and “Threading model” sections.

- bpo-36700: `base64` RFC references were updated to point to RFC 4648; a section was added to point users to the new “security considerations” section of the RFC.

- bpo-44740: Replaced occurrences of uppercase “Web” and “Internet” with lowercase versions per the 2016 revised Associated Press Style Book.

- bpo-44693: Update the definition of __future__ in the glossary by replacing the confusing word “pseudo-module” with a more accurate description.

- bpo-35183: Add typical examples to os.path.splitext docs

- bpo-30511: Clarify that `shutil.make_archive()` is not thread-safe due to reliance on changing the current working directory.

- bpo-44561: Update of three expired hyperlinks in Doc/distributing/index.rst: “Project structure”, “Building and packaging the project”, and “Uploading the project to the Python Packaging Index”.

- bpo-44651: Delete entry “coercion” in Doc/glossary.rst for its outdated definition.

- bpo-42958: Updated the docstring and docs of `filecmp.cmp()` to be more accurate and less confusing especially in respect to shallow arg.

- bpo-44631: Refactored the `repr()` code of the `_Environ` (os module).

- bpo-44613: importlib.metadata is no longer provisional.

- bpo-44558: Match the docstring and python implementation of `countOf()` to the behavior of its c implementation.

- bpo-44544: List all kwargs for `textwrap.wrap()`, `textwrap.fill()`, and `textwrap.shorten()`. Now, there are nav links to attributes of `TextWrap`, which makes navigation much easier while minimizing duplication in the documentation.

- bpo-38062: Clarify that atexit uses equality comparisons internally.

- bpo-40620: Convert examples in tutorial controlflow.rst section 4.3 to be interpreter-demo style.

- bpo-43066: Added a warning to `zipfile` docs: filename arg with a leading slash may cause archive to be un-openable on Windows systems.

- bpo-39452: Rewrote `Doc/library/__main__.rst`. Broadened scope of the document to explicitly discuss and differentiate between `__main__.py` in packages versus the `__name__ == '__main__'` expression (and the idioms that surround it).

- bpo-13814: In the Design FAQ, answer “Why don’t generators support the with statement?”

- bpo-27752: Documentation of csv.Dialect is more descriptive.

- bpo-44453: Fix documentation for the return type of `sysconfig.get_path()`.

- bpo-44392: Added a new section in the C API documentation for types used in type hinting. Documented `Py_GenericAlias` and `Py_GenericAliasType`.

- bpo-38291: Mark `typing.io` and `typing.re` as deprecated since Python 3.8 in the documentation. They were never properly supported by type checkers.

- bpo-44322: Document that SyntaxError args have a details tuple and that details are adjusted for errors in f-string field replacement expressions.

- bpo-42392: Document the deprecation and removal of the `loop` parameter for many functions and classes in `asyncio`.

- bpo-44195: Corrected references to `TraversableResources` in docs. There is no `TraversableReader`.

- bpo-41963: Document that `ConfigParser` strips off comments when reading configuration files.

- bpo-44072: Correct where in the numeric ABC hierarchy `**` support is added, i.e., in numbers.Complex, not numbers.Integral.

- bpo-43558: Add the remark to `dataclasses` documentation that the `__init__()` of any base class has to be called in `__post_init__()`, along with a code example.

- bpo-44025: Clarify when ‘_’ in match statements is a keyword, and when not.

- bpo-41706: Fix docs about how methods like `__add__` are invoked when evaluating operator expressions.

- bpo-41621: Document that `collections.defaultdict` parameter `default_factory` defaults to `None` and is positional-only.

- bpo-41576: document BaseException in favor of bare except

- bpo-21760: The description for __file__ fixed. Patch by Furkan Onder

- bpo-39498: Add a “Security Considerations” index which links to standard library modules that have explicitly documented security considerations.

- bpo-33479: Remove the unqualified claim that tkinter is threadsafe. It has not been true for several years and likely never was. An explanation of what is true may be added later, after more discussion, and possibly after patching _tkinter.c,

### Tests

- bpo-40173: Fix `test.support.import_helper.import_fresh_module()`.

- bpo-45280: Add a test case for empty `typing.NamedTuple`.

- bpo-45269: Cover case when invalid `markers` type is supplied to `c_make_encoder`.

- bpo-45128: Fix `test_multiprocessing_fork` failure due to `test_logging` and `sys.modules` manipulation.

- bpo-45209: Fix `UserWarning: resource_tracker` warning in `_test_multiprocessing._TestSharedMemory.test_shared_memory_cleaned_after_process_termination`

- bpo-45185: Enables `TestEnumerations` test cases in `test_ssl` suite.

- bpo-45195: Fix test_readline.test_nonascii(): sometimes, the newline character is not written at the end, so don’t expect it in the output. Patch by Victor Stinner.

- bpo-45156: Fixes infinite loop on `unittest.mock.seal()` of mocks created by `create_autospec()`.

- bpo-45125: Improves pickling tests and docs of `SharedMemory` and `SharableList` objects.

- bpo-44860: Update `test_sysconfig.test_user_similar()` for the posix_user scheme: `platlib` doesn’t use `sys.platlibdir`. Patch by Victor Stinner.

- bpo-45052: `WithProcessesTestSharedMemory.test_shared_memory_basics` test was ignored, because `self.assertEqual(sms.size, sms2.size)` line was failing. It is now removed and test is unskipped.

  The main motivation for this line to be removed from the test is that the `size` of `SharedMemory` is not ever guaranteed to be the same. It is decided by the platform.

- bpo-44895: libregrtest now clears the type cache later to reduce the risk of false alarm when checking for reference leaks. Previously, the type cache was cleared too early and libregrtest raised a false alarm about reference leaks under very specific conditions. Patch by Irit Katriel and Victor Stinner.

- bpo-45042: Fixes that test classes decorated with `@hashlib_helper.requires_hashdigest` were skipped all the time.

- bpo-25130: Add calls of `gc.collect()` in tests to support PyPy.

- bpo-45011: Made tests relying on the `_asyncio` C extension module optional to allow running on alternative Python implementations. Patch by Serhiy Storchaka.

- bpo-44949: Fix auto history tests of test_readline: sometimes, the newline character is not written at the end, so don’t expect it in the output.

- bpo-44891: Tests were added to clarify `id()` is preserved when `obj * 1` is used on `str` and `bytes` objects. Patch by Nikita Sobolev.

- bpo-44852: Add ability to wholesale silence DeprecationWarnings while running the regression test suite.

- bpo-40928: Notify users running test_decimal regression tests on macOS of potential harmless “malloc can’t allocate region” messages spewed by test_decimal.

- bpo-44734: Fixed floating-point precision issue in turtle tests.

- bpo-44708: Regression tests, when run with -w, are now re-running only the affected test methods instead of re-running the entire test file.

- bpo-42095: Added interop tests for Apple plists: generate plist files with Python plistlib and parse with Apple plutil; and the other way round.

- bpo-44647: Added a permanent Unicode-valued environment variable to regression tests to ensure they handle this use case in the future. If your test environment breaks because of that, report a bug to us, and temporarily set PYTHONREGRTEST_UNICODE_GUARD=0 in your test environment.

- bpo-44515: Adjust recently added contextlib tests to avoid assuming the use of a refcounted GC

- bpo-44287: Fix asyncio test_popen() of test_windows_utils by using a longer timeout. Use military grade battle-tested `test.support.SHORT_TIMEOUT` timeout rather than a hardcoded timeout of 10 seconds: it’s 30 seconds by default, but it is made longer on slow buildbots. Patch by Victor Stinner.

- bpo-44451: Reset `DeprecationWarning` filters in `test.test_importlib.test_metadata_api.APITests.test_entry_points_by_index` to avoid `StopIteration` error if `DeprecationWarnings` are ignored.

- bpo-44363: Account for address sanitizer in test_capi. test_capi now passes when run GCC address sanitizer.

- bpo-44364: Add non integral tests for `math.sqrt()` function.

- bpo-43921: Fix test_ssl.test_wrong_cert_tls13(): use `suppress_ragged_eofs=False`, since `read()` can raise `ssl.SSLEOFError` on Windows. Patch by Victor Stinner.

- bpo-43921: Fix test_pha_required_nocert() of test_ssl: catch two more EOF cases (when the `recv()` method returns an empty string). Patch by Victor Stinner.

- bpo-44131: Add test_frozenmain to test_embed to test the `Py_FrozenMain()` C function. Patch by Victor Stinner.

- bpo-31904: Ignore error string case in test_file_not_exists().

- bpo-42083: Add test to check that `PyStructSequence_NewType` accepts a `PyStructSequence_Desc` with `doc` field set to `NULL`.

- bpo-35753: Fix crash in doctest when doctest parses modules that include unwrappable functions by skipping those functions.

- bpo-30256: Add test for nested queues when using `multiprocessing` shared objects `AutoProxy[Queue]` inside `ListProxy` and `DictProxy`

### Build

- bpo-45220: Avoid building with the Windows 11 SDK previews automatically. This may be overridden by setting the `DefaultWindowsSDKVersion` environment variable before building.

- bpo-45020: Freeze stdlib modules that are imported during startup. This provides significant performance improvements to startup. If necessary, use the previously added “-X frozen_modules=off” commandline option to force importing the source modules.

- bpo-45188: Windows builds now regenerate frozen modules as the first part of the build. Previously the regeneration was later in the build, which would require it to be restarted if any modules had changed.

- bpo-45163: Fixes Haiku platform build.

- bpo-45067: The ncurses function extended_color_content was introduced in 2017

  (https://invisible-island.net/ncurses/NEWS.html#index-t20170401). The

  ncurses-devel package in CentOS 7 had a older version ncurses resulted in compilation error. For compiling ncurses with extended color support, we verify the version of the ncurses library >= 20170401.

- bpo-45019: Generate lines in relevant files for frozen modules. Up until now each of the files had to be edited manually. This change makes it easier to add to and modify the frozen modules.

- bpo-44340: Add support for building with clang thin lto via –with-lto=thin/full. Patch by Donghee Na and Brett Holman.

- bpo-44535: Enable building using a Visual Studio 2022 install on Windows.

- bpo-43298: Improved error message when building without a Windows SDK installed.

- bpo-44381: The Windows build now accepts `EnableControlFlowGuard` set to `guard` to enable CFG.

- bpo-41282: Fix broken `make install` that caused standard library extension modules to be unnecessarily and incorrectly rebuilt during the install phase of cpython.

### Windows

- bpo-45375: Fixes an assertion failure due to searching for the standard library in unnormalised paths.

- bpo-45022: Update Windows release to include libffi 3.4.2

- bpo-45007: Update to OpenSSL 1.1.1l in Windows build

- bpo-44848: Upgrade Windows installer to use SQLite 3.36.0.

- bpo-44572: Avoid consuming standard input in the `platform` module

- bpo-44582: Accelerate speed of `mimetypes` initialization using a native implementation of the registry scan.

- bpo-41299: Fix 16 milliseconds jitter when using timeouts in `threading`, such as with `threading.Lock.acquire()` or `threading.Condition.wait()`.

- bpo-42686: Build `sqlite3` with math functions enabled. Patch by Erlend E. Aasland.

- bpo-40263: This is a follow-on bug from https://bugs.python.org/issue26903. Once that is applied we run into an off-by-one assertion problem. The assert was not correct.

### macOS

- bpo-45007: Update macOS installer builds to use OpenSSL 1.1.1l.

- bpo-34602: When building CPython on macOS with `./configure --with-undefined-behavior-sanitizer --with-pydebug`, the stack size is now quadrupled to allow for the entire test suite to pass.

- bpo-44848: Update macOS installer to use SQLite 3.36.0.

- bpo-44689: `ctypes.util.find_library()` now works correctly on macOS 11 Big Sur even if Python is built on an older version of macOS. Previously, when built on older macOS systems, `find_library` was not able to find macOS system libraries when running on Big Sur due to changes in how system libraries are stored.

- bpo-41972: The framework build’s user header path in sysconfig is changed to add a ‘pythonX.Y’ component to match distutils’s behavior.

- bpo-43109: Allow –with-lto configure option to work with Apple-supplied Xcode or Command Line Tools.

- bpo-34932: Add socket.TCP_KEEPALIVE support for macOS. Patch by Shane Harvey.

### IDLE

- bpo-45296: On Windows, change exit/quit message to suggest Ctrl-D, which works, instead of <Ctrl-Z Return>, which does not work in IDLE.

- bpo-45193: Make completion boxes appear on Ubuntu again.

- bpo-40128: Mostly fix completions on macOS when not using tcl/tk 8.6.11 (as with 3.9). The added update_idletask call should be harmless and possibly helpful otherwise.

- bpo-33962: Move the indent space setting from the Font tab to the new Windows tab. Patch by Mark Roseman and Terry Jan Reedy.

- bpo-40468: Split the settings dialog General tab into Windows and Shell/ED tabs. Move help sources, which extend the Help menu, to the Extensions tab. Make space for new options and shorten the dialog. The latter makes the dialog better fit small screens.

- bpo-41611: Avoid uncaught exceptions in `AutoCompleteWindow.winconfig_event()`.

- bpo-41611: Fix IDLE sometimes freezing upon tab-completion on macOS.

- bpo-44010: Highlight the new match statement’s soft keywords: `match`, `case`, and `_`. However, this highlighting is not perfect and will be incorrect in some rare cases, including some `_`-s in `case` patterns.

- bpo-44026: Include interpreter’s typo fix suggestions in message line for NameErrors and AttributeErrors. Patch by E. Paine.

### Tools/Demos

- bpo-44786: Fix a warning in regular expression in the c-analyzer script.

- bpo-44967: pydoc now returns a non-zero status code when a module cannot be found.

- bpo-44978: Allow the Argument Clinic tool to handle `__complex__` special methods.

- bpo-43425: Removed the ‘test2to3’ demo project that demonstrated using lib2to3 to support Python 2.x and Python 3.x from a single source in a distutils package. Patch by Donghee Na

- bpo-44074: Make patchcheck automatically detect the correct base branch name (previously it was hardcoded to ‘master’)

- bpo-20291: Added support for variadic positional parameters in Argument Clinic.

### C API

- bpo-41710: The PyThread_acquire_lock_timed() function now clamps the timeout if it is too large, rather than aborting the process. Patch by Victor Stinner.

- bpo-44687: `BufferedReader.peek()` no longer raises `ValueError` when the entire file has already been buffered.

- bpo-45116: Add the `Py_ALWAYS_INLINE` macro to ask the compiler to always inline a static inline function. The compiler can ignore it and decides to not inline the function. Patch by Victor Stinner.

- bpo-45094: Add the `Py_NO_INLINE` macro to disable inlining on a function. Patch by Victor Stinner.

- bpo-45061: Add a deallocator to the `bool` type to detect refcount bugs in C extensions which call `Py_DECREF(Py_True);` or `Py_DECREF(Py_False);` by mistake. Patch by Victor Stinner.

- bpo-42035: Add a new `PyType_GetQualName()` function to get type’s qualified name.

- bpo-41103: Reverts removal of the old buffer protocol because they are part of stable ABI.

- bpo-44751: Remove `crypt.h` include from the public `Python.h` header.

- bpo-42747: The `Py_TPFLAGS_HAVE_VERSION_TAG` type flag now does nothing. The `Py_TPFLAGS_HAVE_AM_SEND` flag (which was added in 3.10) is removed. Both were unnecessary because it is not possible to have type objects with the relevant fields missing.

- bpo-44530: Added the `co_qualname` to the `PyCodeObject` structure to propagate the qualified name from the compiler to code objects.

  Patch by Gabriele N. Tornetta

- bpo-44441: `Py_RunMain()` now resets `PyImport_Inittab` to its initial value at exit. It must be possible to call `PyImport_AppendInittab()` or `PyImport_ExtendInittab()` at each Python initialization. Patch by Victor Stinner.

- bpo-39947: Remove 4 private trashcan C API functions which were only kept for the backward compatibility of the stable ABI with Python 3.8 and older, since the trashcan API was not usable with the limited C API on Python 3.8 and older. The trashcan API was excluded from the limited C API in Python 3.9.

  Removed functions:

  - _PyTrash_deposit_object()

  - _PyTrash_destroy_chain()

  - _PyTrash_thread_deposit_object()

  - _PyTrash_thread_destroy_chain()

  The trashcan C API was never usable with the limited C API, since old trashcan macros accessed directly `PyThreadState` members like `_tstate->trash_delete_nesting`, whereas the `PyThreadState` structure is opaque in the limited C API.

  Exclude also the `PyTrash_UNWIND_LEVEL` constant from the C API.

  Patch by Victor Stinner.

- bpo-40939: Removed documentation for the removed `PyParser_*` C API.

- bpo-43795: The list in Contents of Limited API now shows the public name `PyFrameObject` rather than `_frame`. The non-existing entry `_node` no longer appears in the list.

- bpo-44378: `Py_IS_TYPE()` no longer uses `Py_TYPE()` to avoid a compiler warning: no longer cast `const PyObject*` to `PyObject*`. Patch by Victor Stinner.

- bpo-39573: Convert the `Py_TYPE()` and `Py_SIZE()` macros to static inline functions. The `Py_SET_TYPE()` and `Py_SET_SIZE()` functions must now be used to set an object type and size. Patch by Victor Stinner.

- bpo-44263: The `PyType_Ready()` function now raises an error if a type is defined with the `Py_TPFLAGS_HAVE_GC` flag set but has no traverse function (`PyTypeObject.tp_traverse`). Patch by Victor Stinner.

- bpo-43795: The undocumented function `Py_FrozenMain()` is removed from the Limited API.

- bpo-44113: Deprecate the following functions to configure the Python initialization:

  - `PySys_AddWarnOptionUnicode()`

  - `PySys_AddWarnOption()`

  - `PySys_AddXOption()`

  - `PySys_HasWarnOptions()`

  - `Py_SetPath()`

  - `Py_SetProgramName()`

  - `Py_SetPythonHome()`

  - `Py_SetStandardStreamEncoding()`

  - `_Py_SetProgramFullPath()`

  Use the new `PyConfig` API of the Python Initialization Configuration instead (PEP 587).

- bpo-44094: Remove `PyErr_SetFromErrnoWithUnicodeFilename()`, `PyErr_SetFromWindowsErrWithUnicodeFilename()`, and `PyErr_SetExcFromWindowsErrWithUnicodeFilename()`. They are not documented and have been deprecated since Python 3.3.

- bpo-43795: `PyCodec_Unregister()` is now properly exported as a function in the Windows Stable ABI DLL.

- bpo-44029: Remove deprecated `Py_UNICODE` APIs: `PyUnicode_Encode`, `PyUnicode_EncodeUTF7`, `PyUnicode_EncodeUTF8`, `PyUnicode_EncodeUTF16`, `PyUnicode_EncodeUTF32`, `PyUnicode_EncodeLatin1`, `PyUnicode_EncodeMBCS`, `PyUnicode_EncodeDecimal`, `PyUnicode_EncodeRawUnicodeEscape`, `PyUnicode_EncodeCharmap`, `PyUnicode_EncodeUnicodeEscape`, `PyUnicode_TransformDecimalToASCII`, `PyUnicode_TranslateCharmap`, `PyUnicodeEncodeError_Create`, `PyUnicodeTranslateError_Create`. See PEP 393 and PEP 624 for reference.

- bpo-42035: Add a new `PyType_GetName()` function to get type’s short name.

## Python 3.10.0 beta 1

Release date: 2021-05-03

### Security

- bpo-43434: Creating `sqlite3.Connection` objects now also produces `sqlite3.connect` and `sqlite3.connect/handle` auditing events. Previously these events were only produced by `sqlite3.connect()` calls. Patch by Erlend E. Aasland.

- bpo-43998: The `ssl` module sets more secure cipher suites defaults. Ciphers without forward secrecy and with SHA-1 MAC are disabled by default. Security level 2 prohibits weak RSA, DH, and ECC keys with less than 112 bits of security. `SSLContext` defaults to minimum protocol version TLS 1.2. Settings are based on Hynek Schlawack’s research.

- bpo-43882: The presence of newline or tab characters in parts of a URL could allow some forms of attacks.

  Following the controlling specification for URLs defined by WHATWG `urllib.parse()` now removes ASCII newlines and tabs from URLs, preventing such attacks.

- bpo-43472: Ensures interpreter-level audit hooks receive the `cpython.PyInterpreterState_New` event when called through the `_xxsubinterpreters` module.

- bpo-43362: Fix invalid free in _sha3 module. The issue was introduced in 3.10.0a1. Python 3.9 and earlier are not affected.

- bpo-43762: Add audit events for `sqlite3.connect/handle()`, `sqlite3.Connection.enable_load_extension()`, and `sqlite3.Connection.load_extension()`. Patch by Erlend E. Aasland.

- bpo-43756: Add new audit event `glob.glob/2` to incorporate the new root_dir and dir_fd arguments added to `glob.glob()` and `glob.iglob()`.

- bpo-36384: `ipaddress` module no longer accepts any leading zeros in IPv4 address strings. Leading zeros are ambiguous and interpreted as octal notation by some libraries. For example the legacy function `socket.inet_aton()` treats leading zeros as octal notation. glibc implementation of modern `inet_pton()` does not accept any leading zeros. For a while the `ipaddress` module used to accept ambiguous leading zeros.

- bpo-43075: Fix Regular Expression Denial of Service (ReDoS) vulnerability in `urllib.request.AbstractBasicAuthHandler`. The ReDoS-vulnerable regex has quadratic worst-case complexity and it allows cause a denial of service when identifying crafted invalid RFCs. This ReDoS issue is on the client side and needs remote attackers to control the HTTP server.

- bpo-42800: Audit hooks are now fired for frame.f_code, traceback.tb_frame, and generator code/frame attribute access.

- bpo-37363: Add audit events to the `http.client` module.

### Core and Builtins

- bpo-43977: Prevent classes being both a sequence and a mapping when pattern matching.

- bpo-43977: Use `tp_flags` on the class object to determine if the subject is a sequence or mapping when pattern matching. Avoids the need to import `collections.abc` when pattern matching.

- bpo-43892: Restore proper validation of complex literal value patterns when parsing `match` blocks.

- bpo-43933: Set frame.f_lineno to the line number of the ‘with’ kweyword when executing the call to `__exit__`.

- bpo-43933: If the current position in a frame has no line number then set the f_lineno attribute to None, instead of -1, to conform to PEP 626. This should not normally be possible, but might occur in some unusual circumstances.

- bpo-43963: Importing the `_signal` module in a subinterpreter has no longer side effects.

- bpo-42739: The internal representation of line number tables is changed to not use sentinels, and an explicit length parameter is added to the out of process API function `PyLineTable_InitAddressRange`. This makes the handling of line number tables more robust in some circumstances.

- bpo-43908: Make `re` types immutable. Patch by Erlend E. Aasland.

- bpo-43908: Make the `array.array` type immutable. Patch by Erlend E. Aasland.

- bpo-43901: Change class and module objects to lazy-create empty annotations dicts on demand. The annotations dicts are stored in the object’s __dict__ for backwards compatibility.

- bpo-43892: Match patterns now use new dedicated AST nodes (`MatchValue`, `MatchSingleton`, `MatchSequence`, `MatchStar`, `MatchMapping`, `MatchClass`) rather than reusing expression AST nodes. `MatchAs` and `MatchOr` are now defined as pattern nodes rather than as expression nodes. Patch by Nick Coghlan.

- bpo-42725: Usage of `await`/`yield`/`yield from` and named expressions within an annotation is now forbidden when PEP 563 is activated.

- bpo-43754: When performing structural pattern matching (PEP 634), captured names are now left unbound until the entire pattern has matched successfully.

- bpo-42737: Annotations for complex targets (everything beside simple names) no longer cause any runtime effects with `from __future__ import annotations`.

- bpo-43914: `SyntaxError` exceptions raised by the interpreter will highlight the full error range of the expression that consistutes the syntax error itself, instead of just where the problem is detected. Patch by Pablo Galindo.

- bpo-38605: Revert making `from __future__ import annotations` the default. This follows the Steering Council decision to postpone PEP 563 changes to at least Python 3.11. See the original email for more information regarding the decision: https://mail.python.org/archives/list/python-dev@python.org/thread/CLVXXPQ2T2LQ5MP2Y53VVQFCXYWQJHKZ/. Patch by Pablo Galindo.

- bpo-43475: Hashes of NaN values now depend on object identity. Formerly, they always hashed to 0 even though NaN values are not equal to one another. Having the same hash for unequal values caused pile-ups in hash tables.

- bpo-43859: Improve the error message for `IndentationError` exceptions. Patch by Pablo Galindo

- bpo-41323: Constant tuple folding in bytecode optimizer now reuses tuple in constant table.

- bpo-43846: Data stack usage is much reduced for large literal and call expressions.

- bpo-38530: When printing `NameError` raised by the interpreter, `PyErr_Display()` will offer suggestions of similar variable names in the function that the exception was raised from. Patch by Pablo Galindo

- bpo-43823: Improve syntax errors for invalid dictionary literals. Patch by Pablo Galindo.

- bpo-43822: Improve syntax errors in the parser for missing commas between expressions. Patch by Pablo Galindo.

- bpo-43798: `ast.alias` nodes now include source location metadata attributes e.g. lineno, col_offset.

- bpo-43797: Improve `SyntaxError` error messages for invalid comparisons. Patch by Pablo Galindo.

- bpo-43760: Move the flag for checking whether tracing is enabled to the C stack, from the heap. Should speed up dispatch in the interpreter.

- bpo-43682: Static methods (`@staticmethod`) and class methods (`@classmethod`) now inherit the method attributes (`__module__`, `__name__`, `__qualname__`, `__doc__`, `__annotations__`) and have a new `__wrapped__` attribute. Patch by Victor Stinner.

- bpo-43751: Fixed a bug where `anext(ait, default)` would erroneously return None.

- bpo-42128: `__match_args__` is no longer allowed to be a list.

- bpo-43683: Add GEN_START opcode. Marks start of generator, including async, or coroutine and handles sending values to a newly created generator or coroutine.

- bpo-43105: Importlib now resolves relative paths when creating module spec objects from file locations.

- bpo-43682: Static methods (`@staticmethod`) are now callable as regular functions. Patch by Victor Stinner.

- bpo-42609: Prevented crashes in the AST validator and optimizer when compiling some absurdly long expressions like `"+0"*1000000`. `RecursionError` is now raised instead.

- bpo-38530: When printing `AttributeError`, `PyErr_Display()` will offer suggestions of similar attribute names in the object that the exception was raised from. Patch by Pablo Galindo

### Library

- bpo-44015: In @dataclass(), raise a TypeError if KW_ONLY is specified more than once.

- bpo-25478: Added a total() method to collections.Counter() to compute the sum of the counts.

- bpo-43733: Change `netrc.netrc` to use UTF-8 encoding before using locale encoding.

- bpo-43979: Removed an unnecessary list comprehension before looping from `urllib.parse.parse_qsl()`. Patch by Christoph Zwerschke and Donghee Na.

- bpo-43993: Update bundled pip to 21.1.1.

- bpo-43957: [Enum] Deprecate `TypeError` when non-member is used in a containment check; In 3.12 `True` or `False` will be returned instead, and containment will return `True` if the value is either a member of that enum or one of its members’ value.

- bpo-42904: For backwards compatibility with previous minor versions of Python, if `typing.get_type_hints()` receives no namespace dictionary arguments, `typing.get_type_hints()` will search through the global then local namespaces during evaluation of stringized type annotations (string forward references) inside a class.

- bpo-43945: [Enum] Deprecate non-standard mixin format() behavior: in 3.12 the enum member, not the member’s value, will be used for format() calls.

- bpo-41139: Deprecate undocumented `cgi.log()` API.

- bpo-43937: Fixed the `turtle` module working with non-default root window.

- bpo-43930: Update bundled pip to 21.1 and setuptools to 56.0.0

- bpo-43907: Fix a bug in the pure-Python pickle implementation when using protocol 5, where bytearray instances that occur several time in the pickled object graph would incorrectly unpickle into repeated copies of the bytearray object.

- bpo-43926: In `importlib.metadata`, provide a uniform interface to `Description`, allow for any field to be encoded with multiline values, remove continuation lines from multiline values, and add a `.json` property for easy access to the PEP 566 JSON-compatible form. Sync with `importlib_metadata 4.0`.

- bpo-43920: OpenSSL 3.0.0: `load_verify_locations()` now returns a consistent error message when cadata contains no valid certificate.

- bpo-43607: `urllib` can now convert Windows paths with `\\?\` prefixes into URL paths.

- bpo-43817: Add `inspect.get_annotations()`, which safely computes the annotations defined on an object. It works around the quirks of accessing the annotations from various types of objects, and makes very few assumptions about the object passed in. `inspect.get_annotations()` can also correctly un-stringize stringized annotations.

  `inspect.signature()`, `inspect.from_callable()`, and `inspect.from_function()` now call `inspect.get_annotations()` to retrieve annotations. This means `inspect.signature()` and `inspect.from_callable()` can now un-stringize stringized annotations, too.

- bpo-43284: platform.win32_ver derives the windows version from sys.getwindowsversion().platform_version which in turn derives the version from kernel32.dll (which can be of a different version than Windows itself). Therefore change the platform.win32_ver to determine the version using the platform module’s _syscmd_ver private function to return an accurate version.

- bpo-42854: The `ssl` module now uses `SSL_read_ex` and `SSL_write_ex` internally. The functions support reading and writing of data larger than 2 GB. Writing zero-length data no longer fails with a protocol violation error.

- bpo-42333: Port `_ssl` extension module to multiphase initialization.

- bpo-43880: `ssl` now raises DeprecationWarning for OP_NO_SSL/TLS* options, old TLS versions, old protocols, and other features that have been deprecated since Python 3.6, 3.7, or OpenSSL 1.1.0.

- bpo-41559: PEP 612 is now implemented purely in Python; builtin `types.GenericAlias` objects no longer include `typing.ParamSpec` in `__parameters__` (with the exception of `collections.abc.Callable`‘s `GenericAlias`). This means previously invalid uses of `ParamSpec` (such as `list[P]`) which worked in earlier versions of Python 3.10 alpha, will now raise `TypeError` during substitution.

- bpo-43867: The `multiprocessing` `Server` class now explicitly catches `SystemExit` and closes the client connection in this case. It happens when the `Server.serve_client()` method reaches the end of file (EOF).

- bpo-40443: Remove unused imports: pyclbr no longer uses copy, and typing no longer uses ast. Patch by Victor Stinner.

- bpo-43820: Remove an unneeded copy of the namespace passed to dataclasses.make_dataclass().

- bpo-43787: Add `__iter__()` method to `bz2.BZ2File`, `gzip.GzipFile`, and `lzma.LZMAFile`. It makes iterating them about 2x faster. Patch by Inada Naoki.

- bpo-43680: Deprecate io.OpenWrapper and _pyio.OpenWrapper: use io.open and _pyio.open instead. Until Python 3.9, _pyio.open was not a static method and builtins.open was set to OpenWrapper to not become a bound method when set to a class variable. _io.open is a built-in function whereas _pyio.open is a Python function. In Python 3.10, _pyio.open() is now a static method, and builtins.open() is now io.open().

- bpo-43680: The Python `_pyio.open()` function becomes a static method to behave as `io.open()` built-in function: don’t become a bound method when stored as a class variable. It becomes possible since static methods are now callable in Python 3.10. Moreover, `_pyio.OpenWrapper()` becomes a simple alias to `_pyio.open()`. Patch by Victor Stinner.

- bpo-41515: Fix `KeyError` raised in `typing.get_type_hints()` due to synthetic modules that don’t appear in `sys.modules`.

- bpo-43776: When `subprocess.Popen` args are provided as a string or as `pathlib.Path`, the Popen instance repr now shows the right thing.

- bpo-42248: [Enum] ensure exceptions raised in `_missing__` are released

- bpo-43744: fix issue with enum member name matching the start of a private variable name

- bpo-43772: Fixed the return value of `TypeVar.__ror__`. Patch by Jelle Zijlstra.

- bpo-43764: Add match_args parameter to @dataclass decorator to allow suppression of __match_args__ generation.

- bpo-43799: OpenSSL 3.0.0: define `OPENSSL_API_COMPAT` 1.1.1 to suppress deprecation warnings. Python requires OpenSSL 1.1.1 APIs.

- bpo-43478: Mocks can no longer be used as the specs for other Mocks. As a result, an already-mocked object cannot have an attribute mocked using `autospec=True` or be the subject of a `create_autospec(...)` call. This can uncover bugs in tests since these Mock-derived Mocks will always pass certain tests (e.g. `isinstance()`) and builtin assert functions (e.g. assert_called_once_with) will unconditionally pass.

- bpo-43794: Add `ssl.OP_IGNORE_UNEXPECTED_EOF` constants (OpenSSL 3.0.0)

- bpo-43785: Improve `bz2.BZ2File` performance by removing the RLock from BZ2File. This makes BZ2File thread unsafe in the face of multiple simultaneous readers or writers, just like its equivalent classes in `gzip` and `lzma` have always been. Patch by Inada Naoki.

- bpo-43789: OpenSSL 3.0.0: Don’t call the password callback function a second time when first call has signaled an error condition.

- bpo-43788: The header files for `ssl` error codes are now OpenSSL version-specific. Exceptions will now show correct reason and library codes. The `make_ssl_data.py` script has been rewritten to use OpenSSL’s text file with error codes.

- bpo-43766: Implement PEP 647 in the `typing` module by adding `TypeGuard`.

- bpo-25264: `os.path.realpath()` now accepts a strict keyword-only argument. When set to `True`, `OSError` is raised if a path doesn’t exist or a symlink loop is encountered.

- bpo-43780: In `importlib.metadata`, incorporate changes from importlib_metadata 3.10: Add mtime-based caching during distribution discovery. Flagged use of dict result from `entry_points()` as deprecated.

- gh-47383: The `P.args` and `P.kwargs` attributes of `typing.ParamSpec` are now instances of the new classes `typing.ParamSpecArgs` and `typing.ParamSpecKwargs`, which enables a more useful `repr()`. Patch by Jelle Zijlstra.

- bpo-43731: Add an `encoding` parameter `logging.fileConfig()`.

- bpo-43712: Add `encoding` and `errors` parameters to `fileinput.input()` and `fileinput.FileInput`.

- bpo-38659: A `simple_enum` decorator is added to the `enum` module to convert a normal class into an Enum. `test_simple_enum` added to test simple enums against a corresponding normal Enum. Standard library modules updated to use `simple_enum`.

- bpo-43764: Fix an issue where `__match_args__` generation could fail for some `dataclasses`.

- bpo-43752: Fix `sqlite3` regression for zero-sized blobs with converters, where `b""` was returned instead of `None`. The regression was introduced by PR 24723. Patch by Erlend E. Aasland.

- bpo-43655: `tkinter` dialog windows are now recognized as dialogs by window managers on macOS and X Window.

- bpo-43723: The following `threading` methods are now deprecated and should be replaced:

  - `currentThread` => `threading.current_thread()`

  - `activeCount` => `threading.active_count()`

  - `Condition.notifyAll` => `threading.Condition.notify_all()`

  - `Event.isSet` => `threading.Event.is_set()`

  - `Thread.setName` => `threading.Thread.name`

  - `thread.getName` => `threading.Thread.name`

  - `Thread.isDaemon` => `threading.Thread.daemon`

  - `Thread.setDaemon` => `threading.Thread.daemon`

  Patch by Jelle Zijlstra.

- bpo-2135: Deprecate find_module() and find_loader() implementations in importlib and zipimport.

- bpo-43534: `turtle.textinput()` and `turtle.numinput()` create now a transient window working on behalf of the canvas window.

- bpo-43532: Add the ability to specify keyword-only fields to dataclasses. These fields will become keyword-only arguments to the generated __init__.

- bpo-43522: Fix problem with `hostname_checks_common_name`. OpenSSL does not copy hostflags from struct SSL_CTX to struct SSL.

- bpo-8978: Improve error message for `tarfile.open()` when `lzma` / `bz2` are unavailable. Patch by Anthony Sottile.

- bpo-42967: Allow `bytes` `separator` argument in `urllib.parse.parse_qs` and `urllib.parse.parse_qsl` when parsing `str` query strings. Previously, this raised a `TypeError`.

- bpo-43296: Improve `sqlite3` error handling: `sqlite3_value_blob()` errors that set `SQLITE_NOMEM` now raise `MemoryError`. Patch by Erlend E. Aasland.

- bpo-43312: New functions `sysconfig.get_preferred_scheme()` and `sysconfig.get_default_scheme()` are added to query a platform for its preferred “user”, “home”, and “prefix” (default) scheme names.

- bpo-43265: Improve `sqlite3.Connection.backup()` error handling. The error message for non-existent target database names is now `unknown database <database name>` instead of `SQL logic error`. Patch by Erlend E. Aasland.

- bpo-41282: Install schemes in `distutils.command.install` are now loaded from `sysconfig`.

- bpo-41282: `distutils.sysconfig` has been merged to `sysconfig`.

- bpo-43176: Fixed processing of a dataclass that inherits from a frozen dataclass with no fields. It is now correctly detected as an error.

- bpo-43080: `pprint` now has support for `dataclasses.dataclass`. Patch by Lewis Gaul.

- bpo-39950: Add `pathlib.Path.hardlink_to()` method that supersedes `link_to()`. The new method has the same argument order as `symlink_to()`.

- bpo-42904: `typing.get_type_hints()` now checks the local namespace of a class when evaluating PEP 563 annotations inside said class.

- bpo-42269: Add `slots` parameter to `dataclasses.dataclass` decorator to automatically generate `__slots__` for class. Patch provided by Yurii Karabas.

- bpo-39529: Deprecated use of `asyncio.get_event_loop()` without running event loop. Emit deprecation warning for `asyncio` functions which implicitly create a `Future` or `Task` objects if there is no running event loop and no explicit loop argument is passed: `ensure_future()`, `wrap_future()`, `gather()`, `shield()`, `as_completed()` and constructors of `Future`, `Task`, `StreamReader`, `StreamReaderProtocol`.

- bpo-18369: Certificate and PrivateKey classes were added to the ssl module. Certificates and keys can now be loaded from memory buffer, too.

- bpo-41486: Use a new output buffer management code for `bz2` / `lzma` / `zlib` modules, and add `.readall()` function to `_compression.DecompressReader` class. These bring some performance improvements. Patch by Ma Lin.

- bpo-31870: The `ssl.get_server_certificate()` function now has a timeout parameter.

- bpo-41735: Fix thread locks in zlib module may go wrong in rare case. Patch by Ma Lin.

- bpo-36470: Fix dataclasses with `InitVar`s and `replace()`. Patch by Claudiu Popa.

- bpo-40849: Expose X509_V_FLAG_PARTIAL_CHAIN ssl flag

- bpo-35114: `ssl.RAND_status()` now returns a boolean value (as documented) instead of `1` or `0`.

- bpo-39906: `pathlib.Path.stat()` and `chmod()` now accept a follow_symlinks keyword-only argument for consistency with corresponding functions in the `os` module.

- bpo-39899: `os.path.expanduser()` now refuses to guess Windows home directories if the basename of current user’s home directory does not match their username.

  `pathlib.Path.expanduser()` and `home()` now consistently raise `RuntimeError` exception when a home directory cannot be resolved. Previously a `KeyError` exception could be raised on Windows when the `"USERNAME"` environment variable was unset.

- bpo-36076: Added SNI support to `ssl.get_server_certificate()`.

- bpo-38490: Covariance, Pearson’s correlation, and simple linear regression functionality was added to statistics module. Patch by Tymoteusz Wołodźko.

- bpo-33731: Provide a locale.localize() function, which converts a normalized number string into a locale format.

- bpo-32745: Fix a regression in the handling of ctypes’ `ctypes.c_wchar_p` type: embedded null characters would cause a `ValueError` to be raised. Patch by Zackery Spytz.

### Documentation

- bpo-43987: Add “Annotations Best Practices” document as a new HOWTO.

- bpo-43977: Document the new `Py_TPFLAGS_MAPPING` and `Py_TPFLAGS_SEQUENCE` type flags.

- bpo-43959: The documentation on the PyContextVar C-API was clarified.

- bpo-43938: Update dataclasses documentation to express that FrozenInstanceError is derived from AttributeError.

- bpo-43778: Fix the Sphinx glossary_search extension: create the _static/ sub-directory if it doesn’t exist.

- bpo-43755: Update documentation to reflect that unparenthesized lambda expressions can no longer be the expression part in an `if` clause in comprehensions and generator expressions since Python 3.9.

- bpo-43739: Fixing the example code in Doc/extending/extending.rst to declare and initialize the pmodule variable to be of the right type.

### Tests

- bpo-43961: Fix test_logging.test_namer_rotator_inheritance() on Windows: use `os.replace()` rather than `os.rename()`. Patch by Victor Stinner.

- bpo-43842: Fix a race condition in the SMTP test of test_logging. Don’t close a file descriptor (socket) from a different thread while asyncore.loop() is polling the file descriptor. Patch by Victor Stinner.

- bpo-43843: `test.libregrtest` now marks a test as ENV_CHANGED (altered the execution environment) if a thread raises an exception but does not catch it. It sets a hook on `threading.excepthook()`. Use `--fail-env-changed` option to mark the test as failed. Patch by Victor Stinner.

- bpo-43811: Tests multiple OpenSSL versions on GitHub Actions. Use ccache to speed up testing.

- bpo-43791: OpenSSL 3.0.0: Disable testing of legacy protocols TLS 1.0 and 1.1. Tests are failing with TLSV1_ALERT_INTERNAL_ERROR.

### Build

- bpo-43567: Improved generated code refresh (AST/tokens/opcodes/keywords) on Windows.

- bpo-43669: Implement PEP 644. Python now requires OpenSSL 1.1.1 or newer.

### Windows

- bpo-35306: Adds additional arguments to `os.startfile()` function.

- bpo-43538: Avoid raising errors from `pathlib.Path.exists()` when passed an invalid filename.

- bpo-38822: Fixed `os.stat()` failing on inaccessible directories with a trailing slash, rather than falling back to the parent directory’s metadata. This implicitly affected `os.path.exists()` and `os.path.isdir()`.

- bpo-26227: Fixed decoding of host names in `socket.gethostbyaddr()` and `socket.gethostbyname_ex()`.

- bpo-40432: Updated pegen regeneration script on Windows to find and use Python 3.8 or higher. Prior to this, pegen regeneration already required 3.8 or higher, but the script may have used lower versions of Python.

- bpo-43745: Actually updates Windows release to OpenSSL 1.1.1k. Earlier releases were mislabelled and actually included 1.1.1i again.

- bpo-43652: Update Tcl and Tk to 8.6.11 in Windows installer.

- bpo-43492: Upgrade Windows installer to use SQLite 3.35.5.

- bpo-30555: Fix `WindowsConsoleIO` errors in the presence of fd redirection. Patch by Segev Finer.

### macOS

- bpo-42119: Fix check for macOS SDK paths when building Python. Narrow search to match contents of SDKs, namely only files in `/System/Library`, `/System/IOSSupport`, and `/usr` other than `/usr/local`. Previously, anything under `/System` was assumed to be in an SDK which causes problems with the new file system layout in 10.15+ where user file systems may appear to be mounted under `/System`. Paths in `/Library` were also incorrectly treated as SDK locations.

- bpo-43568: Drop support for MACOSX_DEPLOYMENT_TARGET < 10.3

- bpo-44009: Provide “python3.x-intel64” executable to allow reliably forcing macOS universal2 framework builds to run under Rosetta 2 Intel-64 emulation on Apple Silicon Macs. This can be useful for testing or when universal2 wheels are not yet available.

- bpo-43851: Build SQLite with `SQLITE_OMIT_AUTOINIT` on macOS. Patch by Erlend E. Aasland.

- bpo-43492: Update macOS installer to use SQLite 3.35.4.

- bpo-42235: `Mac/BuildScript/build-installer.py` will now use “–enable-optimizations” and `--with-lto` when building on macOS 10.15 or later.

### IDLE

- bpo-37903: Add mouse actions to the shell sidebar. Left click and optional drag selects one or more lines, as with the editor line number sidebar. Right click after selecting raises a context menu with ‘copy with prompts’. This zips together prompts from the sidebar with lines from the selected text.

- bpo-43981: Fix reference leak in test_sidebar and test_squeezer. Patches by Terry Jan Reedy and Pablo Galindo

- bpo-37892: Indent IDLE Shell input with spaces instead of tabs

- bpo-43655: IDLE dialog windows are now recognized as dialogs by window managers on macOS and X Window.

- bpo-37903: IDLE’s shell now shows prompts in a separate side-bar.

### C API

- bpo-43916: Add a new `Py_TPFLAGS_DISALLOW_INSTANTIATION` type flag to disallow creating type instances. Patch by Victor Stinner.

- bpo-43774: Remove the now unused `PYMALLOC_DEBUG` macro. Debug hooks on memory allocators are now installed by default if Python is built in debug mode (if `Py_DEBUG` macro is defined). Moreover, they can now be used on Python build in release mode (ex: using `PYTHONMALLOC=debug` environment variable).

- bpo-43962: _PyInterpreterState_IDIncref() now calls _PyInterpreterState_IDInitref() and always increments id_refcount. Previously, calling _xxsubinterpreters.get_current() could create an id_refcount inconsistency when a _xxsubinterpreters.InterpreterID object was deallocated. Patch by Victor Stinner.

- bpo-28254: Add new C-API functions to control the state of the garbage collector: `PyGC_Enable()`, `PyGC_Disable()`, `PyGC_IsEnabled()`, corresponding to the functions in the `gc` module.

- bpo-43908: Introduce `Py_TPFLAGS_IMMUTABLETYPE` flag for immutable type objects, and modify `PyType_Ready()` to set it for static types. Patch by Erlend E. Aasland.

- bpo-43795: `PyMem_Calloc()` is now available in the limited C API (`Py_LIMITED_API`).

- bpo-43868: `PyOS_ReadlineFunctionPointer()` is no longer exported by limited C API headers and by `python3.dll` on Windows. Like any function that takes `FILE*`, it is not part of the stable ABI.

- bpo-43795: Stable ABI and limited API definitions are generated from a central manifest (PEP 652).

- bpo-43753: Add the `Py_Is(x, y)` function to test if the x object is the y object, the same as `x is y` in Python. Add also the `Py_IsNone()`, `Py_IsTrue()`, `Py_IsFalse()` functions to test if an object is, respectively, the `None` singleton, the `True` singleton or the `False` singleton. Patch by Victor Stinner.

## Python 3.10.0 alpha 7

Release date: 2021-04-05

### Security

- bpo-42988: CVE 2021-3426: Remove the `getfile` feature of the `pydoc` module which could be abused to read arbitrary files on the disk (directory traversal vulnerability). Moreover, even source code of Python modules can contain sensitive data like passwords. Vulnerability reported by David Schwörer.

- bpo-43285: `ftplib` no longer trusts the IP address value returned from the server in response to the PASV command by default. This prevents a malicious FTP server from using the response to probe IPv4 address and port combinations on the client network.

  Code that requires the former vulnerable behavior may set a `trust_server_pasv_ipv4_address` attribute on their `ftplib.FTP` instances to `True` to re-enable it.

- bpo-43439: Add audit hooks for `gc.get_objects()`, `gc.get_referrers()` and `gc.get_referents()`. Patch by Pablo Galindo.

### Core and Builtins

- bpo-27129: Update CPython bytecode magic number.

- bpo-43672: Raise ImportWarning when calling find_loader().

- bpo-43660: Fix crash that happens when replacing `sys.stderr` with a callable that can remove the object while an exception is being printed. Patch by Pablo Galindo.

- bpo-27129: The bytecode interpreter uses instruction, rather byte, offsets internally. This reduces the number of EXTENDED_ARG instructions needed and streamlines instruction dispatch a bit.

- bpo-40645: Fix reference leak in the `_hashopenssl` extension. Patch by Pablo Galindo.

- bpo-42134: Calls to find_module() by the import system now raise ImportWarning.

- bpo-41064: Improve the syntax error for invalid usage of double starred elements (‘**’) in f-strings. Patch by Pablo Galindo.

- bpo-43575: Speed up calls to `map()` by using the PEP 590 `vectorcall` calling convention. Patch by Donghee Na.

- bpo-42137: The import system now prefers using `__spec__` for `ModuleType.__repr__` over `module_repr()`.

- bpo-43452: Added micro-optimizations to `_PyType_Lookup()` to improve cache lookup performance in the common case of cache hits.

- bpo-43555: Report the column offset for `SyntaxError` for invalid line continuation characters. Patch by Pablo Galindo.

- bpo-43517: Fix misdetection of circular imports when using `from pkg.mod import attr`, which caused false positives in non-trivial multi-threaded code.

- bpo-43497: Emit SyntaxWarnings for assertions with tuple constants, this is a regression introduced in python3.7

- bpo-39316: Tracing now has correct line numbers for attribute accesses when the attribute is on a different line from the object. Improves debugging and profiling for multi-line method chains.

- bpo-35883: Python no longer fails at startup with a fatal error if a command line argument contains an invalid Unicode character. The `Py_DecodeLocale()` function now escapes byte sequences which would be decoded as Unicode characters outside the [U+0000; U+10ffff] range.

- bpo-43410: Fix a bug that was causing the parser to crash when emitting syntax errors when reading input from stdin. Patch by Pablo Galindo

- bpo-43406: Fix a possible race condition where `PyErr_CheckSignals` tries to execute a non-Python signal handler.

- bpo-42128: Add `__match_args__` to struct sequence objects. Patch by Pablo Galindo.

- bpo-43390: CPython now sets the `SA_ONSTACK` flag in `PyOS_setsig` for the VM’s default signal handlers. This is friendlier to other in-process code that an extension module or embedding use could pull in (such as Golang’s cgo) where tiny thread stacks are the norm and `sigaltstack()` has been used to provide for signal handlers. This is a no-op change for the vast majority of processes that don’t use sigaltstack.

- bpo-43287: Speed up calls to `filter()` by using the PEP 590 `vectorcall` calling convention. Patch by Donghee Na.

- bpo-37448: Add a radix tree based memory map to track in-use obmalloc arenas. Use to replace the old implementation of address_in_range(). The radix tree approach makes it easy to increase pool sizes beyond the OS page size. Boosting the pool and arena size allows obmalloc to handle a significantly higher percentage of requests from its ultra-fast paths.

  It also has the advantage of eliminating the memory unsanitary behavior of the previous address_in_range(). The old address_in_range() was marked with the annotations _Py_NO_SANITIZE_ADDRESS, _Py_NO_SANITIZE_THREAD, and _Py_NO_SANITIZE_MEMORY. Those annotations are no longer needed.

  To disable the radix tree map, set a preprocessor flag as follows: `-DWITH_PYMALLOC_RADIX_TREE=0`.

  Co-authored-by: Tim Peters <tim.peters@gmail.com>

- bpo-29988: Only handle asynchronous exceptions and requests to drop the GIL when returning from a call or on the back edges of loops. Makes sure that `__exit__()` is always called in with statements, even for interrupts.

### Library

- bpo-43720: Document various stdlib deprecations in imp, pkgutil, and importlib.util for removal in Python 3.12.

- bpo-43433: `xmlrpc.client.ServerProxy` no longer ignores query and fragment in the URL of the server.

- bpo-31956: The `index()` method of `array.array` now has optional start and stop parameters.

- bpo-40066: Enum: adjust `repr()` to show only enum and member name (not value, nor angle brackets) and `str()` to show only member name. Update and improve documentation to match.

- bpo-42136: Deprecate all module_repr() methods found in importlib as their use is being phased out by Python 3.12.

- bpo-35930: Raising an exception raised in a “future” instance will create reference cycles.

- bpo-41369: Finish updating the vendored libmpdec to version 2.5.1. Patch by Stefan Krah.

- bpo-43422: Revert the _decimal C API which was added in bpo-41324.

- bpo-43577: Fix deadlock when using `ssl.SSLContext` debug callback with `ssl.SSLContext.sni_callback()`.

- bpo-43571: It’s now possible to create MPTCP sockets with IPPROTO_MPTCP

- bpo-43542: `image/heic` and `image/heif` were added to `mimetypes`.

- bpo-40645: The `hmac` module now uses OpenSSL’s HMAC implementation when digestmod argument is a hash name or builtin hash function.

- bpo-43510: Implement PEP 597: Add `EncodingWarning` warning, `-X warn_default_encoding` option, `PYTHONWARNDEFAULTENCODING` environment variable and `encoding="locale"` argument value.

- bpo-43521: `ast.unparse` can now render NaNs and empty sets.

- bpo-42914: `pprint.pprint()` gains a new boolean `underscore_numbers` optional argument to emit integers with thousands separated by an underscore character for improved readability (for example `1_000_000` instead of `1000000`).

- bpo-41361: `rotate()` calls are now slightly faster due to faster argument parsing.

- bpo-43423: `subprocess.communicate()` no longer raises an IndexError when there is an empty stdout or stderr IO buffer during a timeout on Windows.

- bpo-27820: Fixed long-standing bug of smtplib.SMTP where doing AUTH LOGIN with initial_response_ok=False will fail.

  The cause is that SMTP.auth_login _always_ returns a password if provided with a challenge string, thus non-compliant with the standard for AUTH LOGIN.

  Also fixes bug with the test for smtpd.

- bpo-43445: Add frozen modules to `sys.stdlib_module_names`. For example, add `"_frozen_importlib"` and `"_frozen_importlib_external"` names.

- bpo-43245: Add keyword arguments support to `ChainMap.new_child()`.

- bpo-29982: Add optional parameter ignore_cleanup_errors to `tempfile.TemporaryDirectory()` and allow multiple `cleanup()` attempts. Contributed by C.A.M. Gerlach.

- bpo-43428: Include changes from importlib_metadata 3.7:

  Performance enhancements to distribution discovery.

  `entry_points` only returns unique distributions.

  Introduces new `EntryPoints` object for containing a set of entry points with convenience methods for selecting entry points by group or name. `entry_points` now returns this object if selection parameters are supplied but continues to return a dict object for compatibility. Users are encouraged to rely on the selection interface. The dict object result is likely to be deprecated in the future.

  Added packages_distributions function to return a mapping of packages to the distributions that provide them.

- bpo-43332: Improves the networking efficiency of `http.client` when using a proxy via `set_tunnel()`. Fewer small send calls are made during connection setup.

- bpo-43420: Improve performance of `fractions.Fraction` arithmetics for large components. Contributed by Sergey B. Kirpichev.

- bpo-43356: Allow passing a signal number to `_thread.interrupt_main()`.

- bpo-43399: Fix `ElementTree.extend` not working on iterators when using the Python implementation

- bpo-43369: Improve `sqlite3` error handling: If `sqlite3_column_text()` and `sqlite3_column_blob()` set `SQLITE_NOMEM`, `MemoryError` is now raised. Patch by Erlend E. Aasland.

- bpo-43368: Fix a regression introduced in PR 24562, where an empty bytestring was fetched as `None` instead of `b''` in `sqlite3`. Patch by Mariusz Felisiak.

- bpo-41282: Fixed stacklevel of `DeprecationWarning` emitted from `import distutils`.

- bpo-42129: `importlib.resources` now honors namespace packages, merging resources from each location in the namespace as introduced in `importlib_resources` 3.2 and including incidental changes through 5.0.3.

- bpo-43295: `datetime.datetime.strptime()` now raises `ValueError` instead of `IndexError` when matching `'z'` with the `%z` format specifier.

- bpo-43125: Return empty string if base64mime.body_encode receive empty bytes

- bpo-43084: `curses.window.enclose()` returns now `True` or `False` (as was documented) instead of `1` or `0`.

- bpo-42994: Add MIME types for opus, AAC, 3gpp and 3gpp2

- bpo-14678: Add an invalidate_caches() method to the zipimport.zipimporter class to support importlib.invalidate_caches(). Patch by Desmond Cheong.

- bpo-42782: Fail fast in `shutil.move()` to avoid creating destination directories on failure.

- bpo-40066: Enum’s `repr()` and `str()` have changed: `repr()` is now EnumClass.MemberName and `str()` is MemberName. Additionally, stdlib Enum’s whose contents are available as module attributes, such as `RegexFlag.IGNORECASE`, have their `repr()` as module.name, e.g. `re.IGNORECASE`.

- bpo-26053: Fixed bug where the `pdb` interactive run command echoed the args from the shell command line, even if those have been overridden at the pdb prompt.

- bpo-24160: Fixed bug where breakpoints did not persist across multiple debugger sessions in `pdb`’s interactive mode.

- bpo-40701: When the `tempfile.tempdir` global variable is set to a value of type bytes, it is now handled consistently. Previously exceptions could be raised from some tempfile APIs when the directory did not already exist in this situation. Also ensures that the `tempfile.gettempdir()` and `tempfile.gettempdirb()` functions always return `str` and `bytes` respectively.

- bpo-39342: Expose `X509_V_FLAG_ALLOW_PROXY_CERTS` as `VERIFY_ALLOW_PROXY_CERTS` to allow proxy certificate validation as explained in https://docs.openssl.org/1.1.1/man7/proxy-certificates/.

- bpo-31861: Add builtins.aiter and builtins.anext. Patch by Joshua Bronson (@jab), Daniel Pope (@lordmauve), and Justin Wang (@justin39).

### Documentation

- bpo-43199: Answer “Why is there no goto?” in the Design and History FAQ.

- bpo-43407: Clarified that a result from `time.monotonic()`, `time.perf_counter()`, `time.process_time()`, or `time.thread_time()` can be compared with the result from any following call to the same function - not just the next immediate call.

- bpo-43354: Fix type documentation for `Fault.faultCode`; the type has to be `int` instead of `str`.

- bpo-41933: Clarified wording of s * n in the Common Sequence Operations

### Tests

- bpo-37945: Fix test_getsetlocale_issue1813() of test_locale: skip the test if `setlocale()` fails. Patch by Victor Stinner.

- bpo-41561: Add workaround for Ubuntu’s custom OpenSSL security level policy.

### Build

- bpo-43179: Introduce and correctly use ALIGNOF_X in place of SIZEOF_X for alignment-related code in optimized string routines. Patch by Jessica Clarke.

- bpo-43631: Update macOS, Windows, and CI to OpenSSL 1.1.1k.

- bpo-43617: Improve configure.ac: Check for presence of autoconf-archive package and remove our copies of M4 macros.

- bpo-43466: The `configure` script now supports `--with-openssl-rpath` option.

- bpo-43372: Use `_freeze_importlib` to generate code for the `__hello__` module. This approach ensures the code matches the interpreter version. Previously, PYTHON_FOR_REGEN was used to generate the code, which might be wrong. The marshal format for code objects has changed with bpo-42246, commit 877df851. Update the code and the expected code sizes in ctypes test_frozentable.

### Windows

- bpo-43440: Build `sqlite3` with the `R*Tree` module enabled. Patch by Erlend E. Aasland.

### IDLE

- bpo-42225: Document that IDLE can fail on Unix either from misconfigured IP masquerade rules or failure displaying complex colored (non-ascii) characters.

### C API

- bpo-43688: The limited C API is now supported if Python is built in debug mode (if the `Py_DEBUG` macro is defined). In the limited C API, the `Py_INCREF()` and `Py_DECREF()` functions are now implemented as opaque function calls, rather than accessing directly the `PyObject.ob_refcnt` member, if Python is built in debug mode and the `Py_LIMITED_API` macro targets Python 3.10 or newer. It became possible to support the limited C API in debug mode because the `PyObject` structure is the same in release and debug mode since Python 3.8 (see bpo-36465).

  The limited C API is still not supported in the `--with-trace-refs` special build (`Py_TRACE_REFS` macro).

  Patch by Victor Stinner.

- bpo-43244: Remove the `pyarena.h` header file with functions:

  - `PyArena_New()`

  - `PyArena_Free()`

  - `PyArena_Malloc()`

  - `PyArena_AddPyObject()`

  These functions were undocumented, excluded from the limited C API, and were only used internally by the compiler. Patch by Victor Stinner.

- bpo-43244: Remove the compiler and parser functions using `struct _mod` type, because the public AST C API was removed:

  - `PyAST_Compile()`

  - `PyAST_CompileEx()`

  - `PyAST_CompileObject()`

  - `PyFuture_FromAST()`

  - `PyFuture_FromASTObject()`

  - `PyParser_ASTFromFile()`

  - `PyParser_ASTFromFileObject()`

  - `PyParser_ASTFromFilename()`

  - `PyParser_ASTFromString()`

  - `PyParser_ASTFromStringObject()`

  These functions were undocumented and excluded from the limited C API. Patch by Victor Stinner.

- bpo-43244: Remove `ast.h`, `asdl.h`, and `Python-ast.h` header files. These functions were undocumented and excluded from the limited C API. Most names defined by these header files were not prefixed by `Py` and so could create names conflicts. For example, `Python-ast.h` defined a `Yield` macro which was conflict with the `Yield` name used by the Windows `<winbase.h>` header. Use the Python `ast` module instead. Patch by Victor Stinner.

- bpo-43541: Fix a `PyEval_EvalCodeEx()` regression: fix reference counting on builtins. Patch by Victor Stinner.

- bpo-43244: Remove the `symtable.h` header file and the undocumented functions:

  - `PyST_GetScope()`

  - `PySymtable_Build()`

  - `PySymtable_BuildObject()`

  - `PySymtable_Free()`

  - `Py_SymtableString()`

  - `Py_SymtableStringObject()`

  The `Py_SymtableString()` function was part the stable ABI by mistake but it could not be used, because the `symtable.h` header file was excluded from the limited C API.

  The Python `symtable` module remains available and is unchanged.

  Patch by Victor Stinner.

- bpo-43244: Remove the `PyAST_Validate()` function. It is no longer possible to build a AST object (`mod_ty` type) with the public C API. The function was already excluded from the limited C API (PEP 384). Patch by Victor Stinner.

## Python 3.10.0 alpha 6

Release date: 2021-03-01

### Security

- bpo-42967: Fix web cache poisoning vulnerability by defaulting the query args separator to `&`, and allowing the user to choose a custom separator.

### Core and Builtins

- bpo-43321: Fix `SystemError` raised when `PyArg_Parse*()` is used with `#` but without `PY_SSIZE_T_CLEAN` defined.

- bpo-36346: `PyArg_Parse*()` functions now emits `DeprecationWarning` when `u` or `Z` format is used. See PEP 623 for detail.

- bpo-43277: Add a new `PySet_CheckExact()` function to the C-API to check if an object is an instance of `set` but not an instance of a subtype. Patch by Pablo Galindo.

- bpo-42990: The `types.FunctionType` constructor now inherits the current builtins if the globals dictionary has no `"__builtins__"` key, rather than using `{"None": None}` as builtins: same behavior as `eval()` and `exec()` functions. Defining a function with `def function(...): ...` in Python is not affected, globals cannot be overridden with this syntax: it also inherits the current builtins. Patch by Victor Stinner.

- bpo-42990: Functions have a new `__builtins__` attribute which is used to look for builtin symbols when a function is executed, instead of looking into `__globals__['__builtins__']`. Patch by Mark Shannon and Victor Stinner.

- bpo-43149: Improve the error message in the parser for exception groups without parentheses. Patch by Pablo Galindo.

- bpo-43121: Fixed an incorrect `SyntaxError` message for missing comma in literals. Patch by Pablo Galindo.

- bpo-42819: `readline`: Explicitly disable bracketed paste in the interactive interpreter, even if it’s set in the inputrc, is enabled by default (eg GNU Readline 8.1), or a user calls `readline.read_init_file()`. The Python REPL has not implemented bracketed paste support. Also, bracketed mode writes the `"\x1b[?2004h"` escape sequence into stdout which causes test failures in applications that don’t support it. It can still be explicitly enabled by calling `readline.parse_and_bind("set enable-bracketed-paste on")`. Patch by Dustin Rodrigues.

- bpo-42808: Simple calls to `type(object)` are now faster due to the `vectorcall` calling convention. Patch by Dennis Sweeney.

- bpo-42217: Make the compiler merges same co_code and co_linetable objects in a module like already did for co_consts.

- bpo-41972: Substring search functions such as `str1 in str2` and `str2.find(str1)` now sometimes use the “Two-Way” string comparison algorithm to avoid quadratic behavior on long strings.

- bpo-42128: Implement PEP 634 (structural pattern matching). Patch by Brandt Bucher.

- bpo-40692: In the `concurrent.futures.ProcessPoolExecutor`, validate that `multiprocess.synchronize()` is available on a given platform and rely on that check in the `concurrent.futures` test suite so we can run tests that are unrelated to `ProcessPoolExecutor` on those platforms.

- bpo-38302: If `object.__ipow__()` returns `NotImplemented`, the operator will correctly fall back to `object.__pow__()` and `object.__rpow__()` as expected.

### Library

- bpo-43316: The `python -m gzip` command line application now properly fails when detecting an unsupported extension. It exits with a non-zero exit code and prints an error message to stderr.

- bpo-43317: Set the chunk size for the `gzip` module main function to io.DEFAULT_BUFFER_SIZE. This is slightly faster than the 1024 bytes constant that was used previously.

- bpo-43146: Handle None in single-arg versions of `print_exception()` and `format_exception()`.

- bpo-43260: Fix TextIOWrapper can not flush internal buffer forever after very large text is written.

- bpo-43258: Prevent needless allocation of `sqlite3` aggregate function context when no rows match an aggregate query. Patch by Erlend E. Aasland.

- bpo-43251: Improve `sqlite3` error handling: `sqlite3_column_name()` failures now result in `MemoryError`. Patch by Erlend E. Aasland.

- bpo-40956: Fix segfault in `sqlite3.Connection.backup()` if no argument was provided. The regression was introduced by PR 23838. Patch by Erlend E. Aasland.

- bpo-43172: The readline module now passes its tests when built directly against libedit. Existing irreconcilable API differences remain in `readline.get_begidx()` and `readline.get_endidx()` behavior based on libreadline vs libedit use.

- bpo-43163: Fix a bug in `codeop` that was causing it to not ask for more input when multi-line snippets have unclosed parentheses. Patch by Pablo Galindo

- bpo-43162: deprecate unsupported ability to access enum members as attributes of other enum members

- bpo-43146: Fix recent regression in None argument handling in `traceback` module functions.

- bpo-43102: The namedtuple __new__ method had its __builtins__ set to None instead of an actual dictionary. This created problems for introspection tools.

- bpo-43106: Added `O_EVTONLY`, `O_FSYNC`, `O_SYMLINK` and `O_NOFOLLOW_ANY` for macOS. Patch by Donghee Na.

- bpo-42960: Adds `resource.RLIMIT_KQUEUES` constant from FreeBSD to the `resource` module.

- bpo-42151: Make the pure Python implementation of `xml.etree.ElementTree` behave the same as the C implementation (`_elementree`) regarding default attribute values (by not setting `specified_attributes=1`).

- bpo-29753: In ctypes, now packed bitfields are calculated properly and the first item of packed bitfields is now shrank correctly.

### Documentation

- bpo-27646: Clarify that ‘yield from <expr>’ works with any iterable, not just iterators.

- bpo-36346: Update some deprecated unicode APIs which are documented as “will be removed in 4.0” to “3.12”. See PEP 623 for detail.

### Tests

- bpo-43288: Fix test_importlib to correctly skip Unicode file tests if the filesystem does not support them.

### Build

- bpo-43174: Windows build now uses `/utf-8` compiler option.

- bpo-43103: Add a new configure `--without-static-libpython` option to not build the `libpythonMAJOR.MINOR.a` static library and not install the `python.o` object file.

- bpo-13501: The configure script can now use libedit instead of readline with the command line option `--with-readline=editline`.

- bpo-42603: Make configure script use pkg-config to detect the location of Tcl/Tk headers and libraries, used to build tkinter.

  On macOS, a Tcl/Tk configuration provided by pkg-config will be preferred over Tcl/Tk frameworks installed in `/{System/,}Library/Frameworks`. If both exist and the latter is preferred, the appropriate `--with-tcltk-*` configuration options need to be explicitly set.

- bpo-39448: Add the “regen-frozen” makefile target that regenerates the code for the frozen `__hello__` module.

### Windows

- bpo-43155: `PyCMethod_New()` is now present in `python3.lib`.

### macOS

- bpo-41837: Update macOS installer build to use OpenSSL 1.1.1j.

### IDLE

- bpo-43283: Document why printing to IDLE’s Shell is often slower than printing to a system terminal and that it can be made faster by pre-formatting a single string before printing.

### C API

- bpo-43278: Always put compiler and system information on the first line of the REPL welcome message.

- bpo-43270: Remove the private `_PyErr_OCCURRED()` macro: use the public `PyErr_Occurred()` function instead.

- bpo-35134: Move odictobject.h, parser_interface.h, picklebufobject.h, pydebug.h, and pyfpe.h into the cpython/ directory. They must not be included directly, as they are already included by Python.h: Include Files.

- bpo-35134: Move pyarena.h, pyctype.h, and pytime.h into the cpython/ directory. They must not be included directly, as they are already included by Python.h: Include Files.

- bpo-40170: `PyExceptionClass_Name()` is now always declared as a function, in order to hide implementation details. The macro accessed `PyTypeObject.tp_name` directly. Patch by Erlend E. Aasland.

- bpo-43239: The `PyCFunction_New()` function is now exported in the ABI when compiled with `-fvisibility=hidden`.

- bpo-40170: `PyIter_Check()` is now always declared as a function, in order to hide implementation details. The macro accessed `PyTypeObject.tp_iternext` directly. Patch by Erlend E. Aasland.

- bpo-40170: Convert `PyDescr_IsData()` macro to a function to hide implementation details: The macro accessed `PyTypeObject.tp_descr_set` directly. Patch by Erlend E. Aasland.

- bpo-43181: Convert `PyObject_TypeCheck()` macro to a static inline function. Patch by Erlend E. Aasland.

## Python 3.10.0 alpha 5

Release date: 2021-02-02

### Security

- bpo-42938: Avoid static buffers when computing the repr of `ctypes.c_double` and `ctypes.c_longdouble` values.

### Core and Builtins

- bpo-42990: Refactor the `PyEval_` family of functions.

  - An new function `_PyEval_Vector` is added to simplify calls to Python from C.

  - `_PyEval_EvalCodeWithName` is removed

  - `PyEval_EvalCodeEx` is retained as part of the API, but is not used internally

- bpo-38631: Replace `Py_FatalError()` calls in the compiler with regular `SystemError` exceptions. Patch by Victor Stinner.

- bpo-42997: Improve error message for missing “:” before blocks. Patch by Pablo Galindo.

- bpo-43017: Improve error message in the parser when using un-parenthesised tuples in comprehensions. Patch by Pablo Galindo.

- bpo-42986: Fix parser crash when reporting syntax errors in f-string with newlines. Patch by Pablo Galindo.

- bpo-40176: Syntax errors for unterminated string literals now point to the start of the string instead of reporting EOF/EOL.

- bpo-42927: The inline cache for `LOAD_ATTR` now also optimizes access to attributes defined by `__slots__`. This makes reading such attribute up to 30% faster.

- bpo-42864: Improve error messages in the parser when parentheses are not closed. Patch by Pablo Galindo.

- bpo-42924: Fix `bytearray` repetition incorrectly copying data from the start of the buffer, even if the data is offset within the buffer (e.g. after reassigning a slice at the start of the `bytearray` to a shorter byte string).

- bpo-42882: Fix the `_PyUnicode_FromId()` function (_Py_IDENTIFIER(var) API) when `Py_Initialize()` / `Py_Finalize()` is called multiple times: preserve `_PyRuntime.unicode_ids.next_index` value.

- bpo-42827: Fix a crash when working out the error line of a `SyntaxError` in some multi-line expressions.

- bpo-42823: frame.f_lineno is correct even if frame.f_trace is set to True

- bpo-37324: Remove deprecated aliases to Collections Abstract Base Classes from the `collections` module.

- bpo-41994: Fixed possible leak in `import` when `sys.modules` is not a `dict`.

- bpo-27772: In string formatting, preceding the width field by `'0'` no longer affects the default alignment for strings.

### Library

- bpo-43108: Fixed a reference leak in the `curses` module. Patch by Pablo Galindo

- bpo-43077: Update the bundled pip to 21.0.1 and setuptools to 52.0.0.

- bpo-41282: Deprecate `distutils` in documentation and add warning on import.

- bpo-43014: Improve performance of `tokenize` by 20-30%. Patch by Anthony Sottile.

- bpo-42323: Fix `math.nextafter()` for NaN on AIX.

- bpo-42955: Add `sys.stdlib_module_names`, containing the list of the standard library module names. Patch by Victor Stinner.

- bpo-42944: Fix `random.Random.sample` when `counts` argument is not `None`.

- bpo-42934: Use `TracebackException`’s new `compact` param in `TestResult` to reduce time and memory consumed by traceback formatting.

- bpo-42931: Add `randbytes()` to `random.__all__`.

- bpo-38250: [Enum] Flags consisting of a single bit are now considered canonical, and will be the only flags returned from listing and iterating over a Flag class or a Flag member. Multi-bit flags are considered aliases; they will be returned from lookups and operations that result in their value. Iteration for both Flag and Flag members is in definition order.

- bpo-42877: Added the `compact` parameter to the constructor of `traceback.TracebackException` to reduce time and memory for use cases that only need to call `TracebackException.format()` and `TracebackException.format_exception_only()`.

- bpo-42923: The `Py_FatalError()` function and the `faulthandler` module now dump the list of extension modules on a fatal error.

- bpo-42848: Removed recursion from `TracebackException` to allow it to handle long exception chains.

- bpo-42901: [Enum] move member creation from `EnumMeta.__new__` to `_proto_member.__set_name__`, allowing members to be created and visible in `__init_subclass__`.

- bpo-42780: Fix os.set_inheritable() for O_PATH file descriptors on Linux.

- bpo-42866: Fix a reference leak in the `getcodec()` function of CJK codecs. Patch by Victor Stinner.

- bpo-42846: Convert the 6 CJK codec extension modules (_codecs_cn, _codecs_hk, _codecs_iso2022, _codecs_jp, _codecs_kr and _codecs_tw) to the multiphase initialization API (PEP 489). Patch by Victor Stinner.

- bpo-42851: remove __init_subclass__ support for Enum members

- bpo-42834: Make internal caches of the `_json` module compatible with subinterpreters.

- bpo-41748: Fix HTMLParser parsing rules for element attributes containing commas with spaces. Patch by Karl Dubost.

- bpo-40810: Require SQLite 3.7.15 or newer. Patch by Erlend E. Aasland.

- bpo-1635741: Convert the _multibytecodec extension module (CJK codecs) to multi-phase initialization (PEP 489). Patch by Erlend E. Aasland.

- bpo-42802: The distutils `bdist_wininst` command deprecated in Python 3.8 has been removed. The distutils `bdist_wheel` command is now recommended to distribute binary packages on Windows.

- bpo-24464: The undocumented built-in function `sqlite3.enable_shared_cache` is now deprecated, scheduled for removal in Python 3.12. Its use is strongly discouraged by the SQLite3 documentation. Patch by Erlend E. Aasland.

- bpo-42384: Make pdb populate sys.path[0] exactly the same as regular python execution.

- bpo-42383: Fix pdb: previously pdb would fail to restart the debugging target if it was specified using a relative path and the current directory changed.

- bpo-42005: Fix CLI of `cProfile` and `profile` to catch `BrokenPipeError`.

- bpo-41604: Don’t decrement the reference count of the previous user_ptr when set_panel_userptr fails.

- bpo-41149: Allow executing callables that have a boolean value of `False` when passed to `Threading.thread` as the target. Patch contributed by Barney Stratford.

- bpo-38307: Add an ‘end_lineno’ attribute to the Class and Function objects that appear in the tree returned by pyclbr functions. This and the existing ‘lineno’ attribute define the extent of class and def statements. Patch by Aviral Srivastava.

- bpo-39273: The `BUTTON5_*` constants are now exposed in the `curses` module if available.

- bpo-33289: Correct call to `tkinter.colorchooser` to return RGB triplet of ints instead of floats. Patch by Cheryl Sabella.

### Documentation

- bpo-40304: Fix doc for type(name, bases, dict). Patch by Boris Verkhovskiy and Éric Araujo.

- bpo-42811: Updated importlib.util.resolve_name() doc to use __spec__.parent instead of __package__. (Thanks Yair Frid.)

### Tests

- bpo-40823: Use `unittest.TestLoader().loadTestsFromTestCase()` instead of `unittest.makeSuite()` in `sqlite3` tests. Patch by Erlend E. Aasland.

- bpo-40810: In `sqlite3`, fix `CheckTraceCallbackContent` for SQLite pre 3.7.15.

### Build

- bpo-43031: Pass `--timeout=$(TESTTIMEOUT)` option to the default profile task `./python -m test --pgo` command.

- bpo-36143: `make regen-all` now also runs `regen-keyword`. Patch by Victor Stinner.

- bpo-42874: Removed the grep -q and -E flags in the tzpath validation section of the configure script to better accommodate users of some platforms (specifically Solaris 10).

- bpo-31904: Add library search path by wr-cc in add_cross_compiling_paths() for VxWorks.

- bpo-42856: Add `--with-wheel-pkg-dir=PATH` option to the `./configure` script. If specified, the `ensurepip` module looks for `setuptools` and `pip` wheel packages in this directory: if both are present, these wheel packages are used instead of ensurepip bundled wheel packages.

  Some Linux distribution packaging policies recommend against bundling dependencies. For example, Fedora installs wheel packages in the `/usr/share/python-wheels/` directory and don’t install the `ensurepip._bundled` package.

### Windows

- bpo-41837: Updated Windows installer to include OpenSSL 1.1.1i

- bpo-42584: Upgrade Windows installer to use SQLite 3.34.0.

### macOS

- bpo-42504: Ensure that the value of sysconfig.get_config_var(‘MACOSX_DEPLOYMENT_TARGET’) is always a string, even in when the value is parsable as an integer.

### IDLE

- bpo-43008: Make IDLE invoke `sys.excepthook()` in normal, 2-process mode. Patch by Ken Hilton.

- bpo-33065: Fix problem debugging user classes with __repr__ method.

- bpo-23544: Disable Debug=>Stack Viewer when user code is running or Debugger is active, to prevent hang or crash. Patch by Zackery Spytz.

- bpo-32631: Finish zzdummy example extension module: make menu entries work; add docstrings and tests with 100% coverage.

### C API

- bpo-42979: When Python is built in debug mode (with C assertions), calling a type slot like `sq_length` (`__len__()` in Python) now fails with a fatal error if the slot succeeded with an exception set, or failed with no exception set. The error message contains the slot, the type name, and the current exception (if an exception is set). Patch by Victor Stinner.

- bpo-43030: Fixed a compiler warning in `Py_UNICODE_ISSPACE()` on platforms with signed `wchar_t`.

## Python 3.10.0 alpha 4

Release date: 2021-01-04

### Core and Builtins

- bpo-42814: Fix undefined behavior in `Objects/genericaliasobject.c`.

- bpo-42806: Fix the column offsets for f-strings `ast` nodes surrounded by parentheses and for nodes that spawn multiple lines. Patch by Pablo Galindo.

- bpo-40631: Fix regression where a single parenthesized starred expression was a valid assignment target.

- bpo-27794: Improve the error message for failed writes/deletes to property objects. When possible, the attribute name is now shown. Patch provided by Yurii Karabas.

- bpo-42745: Make the type attribute lookup cache per-interpreter. Patch by Victor Stinner.

- bpo-42246: Jumps to jumps are not eliminated when it would break PEP 626.

- bpo-42246: Make sure that the `f_lasti` and `f_lineno` attributes of a frame are set correctly when an exception is raised or re-raised. Required for PEP 626.

- bpo-32381: The coding cookie (ex: `# coding: latin1`) is now ignored in the command passed to the `-c` command line option. Patch by Victor Stinner.

- bpo-30858: Improve error location in expressions that contain assignments. Patch by Pablo Galindo and Lysandros Nikolaou.

- bpo-42615: Remove jump commands made redundant by the deletion of unreachable bytecode blocks

- bpo-42639: Make the `atexit` module state per-interpreter. It is now safe have more than one `atexit` module instance. Patch by Donghee Na and Victor Stinner.

- bpo-32381: Fix encoding name when running a `.pyc` file on Windows: `PyRun_SimpleFileExFlags()` now uses the correct encoding to decode the filename.

- bpo-42195: The `__args__` of the parameterized generics for `typing.Callable` and `collections.abc.Callable` are now consistent. The `__args__` for `collections.abc.Callable` are now flattened while `typing.Callable`’s have not changed. To allow this change, `types.GenericAlias` can now be subclassed and `collections.abc.Callable`’s `__class_getitem__` will now return a subclass of `types.GenericAlias`. Tests for typing were also updated to not subclass things like `Callable[..., T]` as that is not a valid base class. Finally, both `Callable`s no longer validate their `argtypes`, in `Callable[[argtypes], resulttype]` to prepare for PEP 612. Patch by Ken Jin.

- bpo-40137: Convert functools module to use `PyType_FromModuleAndSpec()`.

- bpo-40077: Convert `array` to use heap types, and establish module state for these.

- bpo-42008: Fix _random.Random() seeding.

- bpo-1635741: Port the `pyexpat` extension module to multi-phase initialization (PEP 489).

- bpo-40521: Make the Unicode dictionary of interned strings compatible with subinterpreters. Patch by Victor Stinner.

- bpo-39465: Make `_PyUnicode_FromId()` function compatible with subinterpreters. Each interpreter now has an array of identifier objects (interned strings decoded from UTF-8). Patch by Victor Stinner.

### Library

- bpo-42257: Handle empty string in variable executable in platform.libc_ver()

- bpo-42772: randrange() now raises a TypeError when step is specified without a stop argument. Formerly, it silently ignored the step argument.

- bpo-42759: Fixed equality comparison of `tkinter.Variable` and `tkinter.font.Font`. Objects which belong to different Tcl interpreters are now always different, even if they have the same name.

- bpo-42756: Configure LMTP Unix-domain socket to use socket global default timeout when a timeout is not explicitly provided.

- bpo-23328: Allow / character in username, password fields on _PROXY envars.

- bpo-42740: `typing.get_args()` and `typing.get_origin()` now support PEP 604 union types and PEP 612 additions to `Callable`.

- bpo-42655: `subprocess` extra_groups is now correctly passed into setgroups() system call.

- bpo-42727: `EnumMeta.__prepare__` now accepts `**kwds` to properly support `__init_subclass__`

- bpo-38308: Add optional weights to statistics.harmonic_mean().

- bpo-42721: When simple query dialogs (`tkinter.simpledialog`), message boxes (`tkinter.messagebox`) or color choose dialog (`tkinter.colorchooser`) are created without arguments master and parent, and the default root window is not yet created, and `NoDefaultRoot()` was not called, a new temporal hidden root window will be created automatically. It will not be set as the default root window and will be destroyed right after closing the dialog window. It will help to use these simple dialog windows in programs which do not need other GUI.

- bpo-25246: Optimized `collections.deque.remove()`.

- bpo-35728: Added a root parameter to `tkinter.font.nametofont()`.

- bpo-15303: `tkinter` supports now widgets with boolean value False.

- bpo-42681: Fixed range checks for color and pair numbers in `curses`.

- bpo-42685: Improved placing of simple query windows in Tkinter (such as `tkinter.simpledialog.askinteger()`). They are now centered at the center of the parent window if it is specified and shown, otherwise at the center of the screen.

- bpo-9694: Argparse help no longer uses the confusing phrase, “optional arguments”. It uses “options” instead.

- bpo-1635741: Port the `_thread` extension module to the multiphase initialization API (PEP 489) and convert its static types to heap types.

- bpo-37961: Fix crash in `tracemalloc.Traceback.__repr__()` (regressed in Python 3.9).

- bpo-42630: `tkinter` functions and constructors which need a default root window raise now `RuntimeError` with descriptive message instead of obscure `AttributeError` or `NameError` if it is not created yet or cannot be created automatically.

- bpo-42639: `atexit._run_exitfuncs()` now logs callback exceptions using `sys.unraisablehook`, rather than logging them directly into `sys.stderr` and raise the last exception.

- bpo-42644: `logging.disable` will now validate the types and value of its parameter. It also now accepts strings representing the levels (as does `logging.setLevel`) instead of only the numerical values.

- bpo-42639: At Python exit, if a callback registered with `atexit.register()` fails, its exception is now logged. Previously, only some exceptions were logged, and the last exception was always silently ignored.

- bpo-36541: Fixed lib2to3.pgen2 to be able to parse PEP-570 positional only argument syntax.

- bpo-42382: In `importlib.metadata`: - `EntryPoint` objects now expose a `.dist` object referencing the `Distribution` when constructed from a `Distribution`. - Add support for package discovery under package normalization rules. - The object returned by `metadata()` now has a formally defined protocol called `PackageMetadata` with declared support for the `.get_all()` method. - Synced with importlib_metadata 3.3.

- bpo-41877: A check is added against misspellings of autospect, auto_spec and set_spec being passed as arguments to patch, patch.object and create_autospec.

- bpo-39717: [tarfile] update nested exception raising to use `from None` or `from e`

- bpo-41877: AttributeError for suspected misspellings of assertions on mocks are now pointing out that the cause are misspelled assertions and also what to do if the misspelling is actually an intended attribute name. The unittest.mock document is also updated to reflect the current set of recognised misspellings.

- bpo-41559: Implemented PEP 612: added `ParamSpec` and `Concatenate` to `typing`. Patch by Ken Jin.

- bpo-42385: StrEnum: fix _generate_next_value_ to return a str

- bpo-31904: Define THREAD_STACK_SIZE for VxWorks.

- bpo-34750: [Enum] `_EnumDict.update()` is now supported.

- bpo-42517: Enum: private names do not become members / do not generate errors – they remain normal attributes

- bpo-42678: `Enum`: call `__init_subclass__` after members have been added

- bpo-28964: `ast.literal_eval()` adds line number information (if available) in error message for malformed nodes.

- bpo-42470: `random.sample()` no longer warns on a sequence which is also a set.

- bpo-31904: `posixpath.expanduser()` returns the input path unchanged if user home directory is None on VxWorks.

- bpo-42388: Fix subprocess.check_output(…, input=None) behavior when text=True to be consistent with that of the documentation and universal_newlines=True.

- bpo-34463: Fixed discrepancy between `traceback` and the interpreter in formatting of SyntaxError with lineno not set (`traceback` was changed to match interpreter).

- bpo-42393: Raise `OverflowError` instead of silent truncation in `socket.ntohs()` and `socket.htons()`. Silent truncation was deprecated in Python 3.7. Patch by Erlend E. Aasland

- bpo-42222: Harmonized `random.randrange()` argument handling to match `range()`.

  - The integer test and conversion in `randrange()` now uses `operator.index()`.

  - Non-integer arguments to `randrange()` are deprecated.

  - The `ValueError` is deprecated in favor of a `TypeError`.

  - It now runs a little faster than before.

  (Contributed by Raymond Hettinger and Serhiy Storchaka.)

- bpo-42163: Restore compatibility for `uname_result` around deepcopy and _replace.

- bpo-42090: `zipfile.Path.joinpath` now accepts arbitrary arguments, same as `pathlib.Path.joinpath`.

- bpo-1635741: Port the _csv module to the multi-phase initialization API (PEP 489).

- bpo-42059: `typing.TypedDict` types created using the alternative call-style syntax now correctly respect the `total` keyword argument when setting their `__required_keys__` and `__optional_keys__` class attributes.

- bpo-41960: Add `globalns` and `localns` parameters to the `inspect.signature()` and `inspect.Signature.from_callable()`.

- bpo-41907: fix `format()` behavior for `IntFlag`

- bpo-41891: Ensure asyncio.wait_for waits for task completion

- bpo-24792: Fixed bug where `zipimporter` sometimes reports an incorrect cause of import errors.

- bpo-31904: Fix site and sysconfig modules for VxWorks RTOS which has no home directories.

- bpo-41462: Add `os.set_blocking()` support for VxWorks RTOS.

- bpo-40219: Lowered `tkinter.ttk.LabeledScale` dummy widget to prevent hiding part of the content label.

- bpo-37193: Fixed memory leak in `socketserver.ThreadingMixIn` introduced in Python 3.7.

- bpo-39068: Fix initialization race condition in `a85encode()` and `b85encode()` in `base64`. Patch by Brandon Stansbury.

### Documentation

- bpo-17140: Add documentation for the `multiprocessing.pool.ThreadPool` class.

- bpo-34398: Prominently feature listings from the glossary in documentation search results. Patch by Ammar Askar.

### Tests

- bpo-42794: Update test_nntplib to use official group name of news.aioe.org for testing. Patch by Donghee Na.

- bpo-31904: Skip some asyncio tests on VxWorks.

- bpo-42641: Enhance `test_select.test_select()`: it now takes 500 milliseconds rather than 10 seconds. Use Python rather than a shell to make the test more portable.

- bpo-31904: Skip some tests in _test_all_chown_common() on VxWorks.

- bpo-42199: Fix bytecode helper assertNotInBytecode.

- bpo-41443: Add more attribute checking in test_posix.py

- bpo-31904: Disable os.popen and impacted tests on VxWorks

- bpo-41439: Port test_ssl and test_uuid to VxWorks RTOS.

### Build

- bpo-42692: Fix __builtin_available check on older compilers. Patch by Joshua Root.

- bpo-27640: Added `--disable-test-modules` option to the `configure` script: don’t build nor install test modules. Patch by Xavier de Gaye, Thomas Petazzoni and Peixing Xin.

- bpo-42604: Now all platforms use a value for the “EXT_SUFFIX” build variable derived from SOABI (for instance in freeBSD, “EXT_SUFFIX” is now “.cpython-310d.so” instead of “.so”). Previously only Linux, Mac and VxWorks were using a value for “EXT_SUFFIX” that included “SOABI”.

- bpo-42598: Fix implicit function declarations in configure which could have resulted in incorrect configuration checks. Patch contributed by Joshua Root.

- bpo-31904: Enable libpython3.so for VxWorks.

- bpo-29076: Add fish shell support to macOS installer.

### macOS

- bpo-42361: Update macOS installer build to use Tcl/Tk 8.6.11 (rc2, expected to be final release).

- bpo-41837: Update macOS installer build to use OpenSSL 1.1.1i.

- bpo-42584: Update macOS installer to use SQLite 3.34.0.

### Tools/Demos

- bpo-42726: Fixed Python 3 compatibility issue with gdb/libpython.py handling of attribute dictionaries.

- bpo-42613: Fix `freeze.py` tool to use the prope config and library directories. Patch by Victor Stinner.

### C API

- bpo-42591: Export the `Py_FrozenMain()` function: fix a Python 3.9.0 regression. Python 3.9 uses `-fvisibility=hidden` and the function was not exported explicitly and so not exported.

- bpo-32381: Remove the private `_Py_fopen()` function which is no longer needed. Use `_Py_wfopen()` or `_Py_fopen_obj()` instead. Patch by Victor Stinner.

- bpo-1635741: Port `resource` extension module to module state

- bpo-42111: Update the `xxlimited` module to be a better example of how to use the limited C API.

- bpo-40052: Fix an alignment build warning/error in function `PyVectorcall_Function()`. Patch by Andreas Schneider, Antoine Pitrou and Petr Viktorin.

## Python 3.10.0 alpha 3

Release date: 2020-12-07

### Security

- bpo-40791: Add `volatile` to the accumulator variable in `hmac.compare_digest`, making constant-time-defeating optimizations less likely.

### Core and Builtins

- bpo-42576: `types.GenericAlias` will now raise a `TypeError` when attempting to initialize with a keyword argument. Previously, this would cause the interpreter to crash if the interpreter was compiled with debug symbols. This does not affect interpreters compiled for release. Patch by Ken Jin.

- bpo-42536: Several built-in and standard library types now ensure that their internal result tuples are always tracked by the garbage collector:

  - `collections.OrderedDict.items()`

  - `dict.items()`

  - `enumerate()`

  - `functools.reduce()`

  - `itertools.combinations()`

  - `itertools.combinations_with_replacement()`

  - `itertools.permutations()`

  - `itertools.product()`

  - `itertools.zip_longest()`

  - `zip()`

  Previously, they could have become untracked by a prior garbage collection. Patch by Brandt Bucher.

- bpo-42500: Improve handling of exceptions near recursion limit. Converts a number of Fatal Errors in RecursionErrors.

- bpo-42246: PEP 626: After a return, the f_lineno attribute of a frame is always the last line executed.

- bpo-42435: Speed up comparison of bytes objects with non-bytes objects when option `-b` is specified. Speed up comparison of bytarray objects with non-buffer object.

- bpo-1635741: Port the `_warnings` extension module to the multi-phase initialization API (PEP 489). Patch by Victor Stinner.

- bpo-41686: On Windows, the `SIGINT` event, `_PyOS_SigintEvent()`, is now created even if Python is configured to not install signal handlers (if `PyConfig.install_signal_handlers` equals to 0, or `Py_InitializeEx(0)`).

- bpo-42381: Allow assignment expressions in set literals and set comprehensions as per PEP 572. Patch by Pablo Galindo.

- bpo-42202: Change function parameters annotations internal representation to tuple of strings. Patch provided by Yurii Karabas.

- bpo-42374: Fix a regression introduced by the new parser, where an unparenthesized walrus operator was not allowed within generator expressions.

- bpo-42316: Allow an unparenthesized walrus in subscript indexes.

- bpo-42349: Make sure that the compiler front-end produces a well-formed control flow graph. Be be more aggressive in the compiler back-end, as it is now safe to do so.

- bpo-42296: On Windows, fix a regression in signal handling which prevented to interrupt a program using CTRL+C. The signal handler can be run in a thread different than the Python thread, in which case the test deciding if the thread can handle signals is wrong.

- bpo-42332: `types.GenericAlias` objects can now be the targets of weakrefs.

- bpo-42282: Optimise constant subexpressions that appear as part of named expressions (previously the AST optimiser did not descend into named expressions). Patch by Nick Coghlan.

- bpo-42266: Fixed a bug with the LOAD_ATTR opcode cache that was not respecting monkey-patching a class-level attribute to make it a descriptor. Patch by Pablo Galindo.

- bpo-40077: Convert `queue` to use heap types.

- bpo-42246: Improved accuracy of line tracing events and f_lineno attribute of Frame objects. See PEP 626 for details.

- bpo-40077: Convert `mmap` to use heap types.

- bpo-42233: Allow `GenericAlias` objects to use union type expressions. This allows expressions like `list[int] | dict[float, str]` where previously a `TypeError` would have been thrown. This also fixes union type expressions not de-duplicating `GenericAlias` objects. (Contributed by Ken Jin in bpo-42233.)

- bpo-26131: The import system triggers a `ImportWarning` when it falls back to using `load_module()`.

### Library

- bpo-5054: CGIHTTPRequestHandler.run_cgi() HTTP_ACCEPT improperly parsed. Replace the special purpose getallmatchingheaders with generic get_all method and add relevant tests.

  Original Patch by Martin Panter. Modified by Senthil Kumaran.

- bpo-42562: Fix issue when dis failed to parse function that has no line numbers. Patch provided by Yurii Karabas.

- bpo-17735: `inspect.findsource()` now raises `OSError` instead of `IndexError` when `co_lineno` of a code object is greater than the file length. This can happen, for example, when a file is edited after it was imported. PR by Irit Katriel.

- bpo-42116: Fix handling of trailing comments by `inspect.getsource()`.

- bpo-42532: Remove unexpected call of `__bool__` when passing a `spec_arg` argument to a Mock.

- bpo-38200: Added itertools.pairwise()

- bpo-41818: Fix test_master_read() so that it succeeds on all platforms that either raise OSError or return b”” upon reading from master.

- bpo-42487: ChainMap.__iter__ no longer calls __getitem__ on underlying maps

- bpo-42482: `TracebackException` no longer holds a reference to the exception’s traceback object. Consequently, instances of TracebackException for equivalent but non-equal exceptions now compare as equal.

- bpo-41818: Make test_openpty() avoid unexpected success due to number of rows and/or number of columns being == 0.

- bpo-42392: Remove loop parameter from `asyncio.subprocess` and `asyncio.tasks` functions. Patch provided by Yurii Karabas.

- bpo-42392: Remove loop parameter from `asyncio.open_connection` and `asyncio.start_server` functions. Patch provided by Yurii Karabas.

- bpo-28468: Add `platform.freedesktop_os_release()` function to parse freedesktop.org `os-release` files.

- bpo-42299: Removed the `formatter` module, which was deprecated in Python 3.4. It is somewhat obsolete, little used, and not tested. It was originally scheduled to be removed in Python 3.6, but such removals were delayed until after Python 2.7 EOL. Existing users should copy whatever classes they use into their code. Patch by Donghee Na and and Terry J. Reedy.

- bpo-26131: Deprecate zipimport.zipimporter.load_module() in favour of exec_module().

- bpo-41818: Updated tests for the pty library. test_basic() has been changed to test_openpty(); this additionally checks if slave termios and slave winsize are being set properly by pty.openpty(). In order to add support for FreeBSD, NetBSD, OpenBSD, and Darwin, this also adds test_master_read(), which demonstrates that pty.spawn() should not depend on an OSError to exit from its copy loop.

- bpo-42392: Remove loop parameter from `__init__` in all `asyncio.locks` and `asyncio.Queue` classes. Patch provided by Yurii Karabas.

- bpo-15450: Make `filecmp.dircmp` respect subclassing. Now the `filecmp.dircmp.subdirs` behaves as expected when subclassing dircmp.

- bpo-42413: The exception `socket.timeout` is now an alias of `TimeoutError`.

- bpo-31904: Support signal module on VxWorks.

- bpo-42406: We fixed an issue in `pickle.whichmodule` in which importing `multiprocessing` could change the how pickle identifies which module an object belongs to, potentially breaking the unpickling of those objects.

- bpo-42403: Simplify the `importlib` external bootstrap code: `importlib._bootstrap_external` now uses regular imports to import builtin modules. When it is imported, the builtin `__import__()` function is already fully working and so can be used to import builtin modules like `sys`. Patch by Victor Stinner.

- bpo-1635741: Convert _sre module types to heap types (PEP 384). Patch by Erlend E. Aasland.

- bpo-42375: subprocess module update for DragonFlyBSD support.

- bpo-41713: Port the `_signal` extension module to the multi-phase initialization API (PEP 489). Patch by Victor Stinner and Mohamed Koubaa.

- bpo-37205: `time.time()`, `time.perf_counter()` and `time.monotonic()` functions can no longer fail with a Python fatal error, instead raise a regular Python exception on failure.

- bpo-42328: Fixed `tkinter.ttk.Style.map()`. The function accepts now the representation of the default state as empty sequence (as returned by `Style.map()`). The structure of the result is now the same on all platform and does not depend on the value of `wantobjects`.

- bpo-42345: Fix various issues with `typing.Literal` parameter handling (flatten, deduplicate, use type to cache key). Patch provided by Yurii Karabas.

- bpo-37205: `time.perf_counter()` on Windows and `time.monotonic()` on macOS are now system-wide. Previously, they used an offset computed at startup to reduce the precision loss caused by the float type. Use `time.perf_counter_ns()` and `time.monotonic_ns()` added in Python 3.7 to avoid this precision loss.

- bpo-42318: Fixed support of non-BMP characters in `tkinter` on macOS.

- bpo-42350: Fix the `threading.Thread` class at fork: do nothing if the thread is already stopped (ex: fork called at Python exit). Previously, an error was logged in the child process.

- bpo-42333: Port _ssl extension module to heap types.

- bpo-42014: The `onerror` callback from `shutil.rmtree` now receives correct function when `os.open` fails.

- bpo-42237: Fix `os.sendfile()` on illumos.

- bpo-42308: Add `threading.__excepthook__` to allow retrieving the original value of `threading.excepthook()` in case it is set to a broken or a different value. Patch by Mario Corchero.

- bpo-42131: Implement PEP 451/spec methods on zipimport.zipimporter: find_spec(), create_module(), and exec_module().

  This also allows for the documented deprecation of find_loader(), find_module(), and load_module().

- bpo-41877: Mock objects which are not unsafe will now raise an AttributeError if an attribute with the prefix asert, aseert, or assrt is accessed, in addition to this already happening for the prefixes assert or assret.

- bpo-42264: `sqlite3.OptimizedUnicode` has been undocumented and obsolete since Python 3.3, when it was made an alias to `str`. It is now deprecated, scheduled for removal in Python 3.12.

- bpo-42251: Added `threading.gettrace()` and `threading.getprofile()` to retrieve the functions set by `threading.settrace()` and `threading.setprofile()` respectively. Patch by Mario Corchero.

- bpo-42249: Fixed writing binary Plist files larger than 4 GiB.

- bpo-42236: On Unix, the `os.device_encoding()` function now returns `'UTF-8'` rather than the device encoding if the Python UTF-8 Mode is enabled.

- bpo-41754: webbrowser: Ignore NotADirectoryError when calling `xdg-settings`.

- bpo-42183: Fix a stack overflow error for asyncio Task or Future repr().

  The overflow occurs under some circumstances when a Task or Future recursively returns itself.

- bpo-42140: Improve asyncio.wait function to create the futures set just one time.

- bpo-42133: Update various modules in the stdlib to fall back on `__spec__.loader` when `__loader__` isn’t defined on a module.

- bpo-26131: The `load_module()` methods found in `importlib` now trigger a `DeprecationWarning`.

- bpo-39825: Windows: Change `sysconfig.get_config_var('EXT_SUFFIX')` to the expected full `platform_tag.extension` format. Previously it was hard-coded to `.pyd`, now it is compatible with `distutils.sysconfig` and will result in something like `.cp38-win_amd64.pyd`. This brings windows into conformance with the other platforms.

- bpo-26389: The `traceback.format_exception()`, `traceback.format_exception_only()`, and `traceback.print_exception()` functions can now take an exception object as a positional-only argument.

- bpo-41889: Enum: fix regression involving inheriting a multiply inherited enum

- bpo-41861: Convert `sqlite3` to use heap types (PEP 384). Patch by Erlend E. Aasland.

- bpo-40624: Added support for the XPath `!=` operator in xml.etree

- bpo-28850: Fix `pprint.PrettyPrinter.format()` overrides being ignored for contents of small containers. The `pprint._safe_repr()` function was removed.

- bpo-41625: Expose the `splice()` as `os.splice()` in the `os` module. Patch by Pablo Galindo

- bpo-34215: Clarify the error message for `asyncio.IncompleteReadError` when `expected` is `None`.

- bpo-41543: Add async context manager support for contextlib.nullcontext.

- bpo-21041: `pathlib.PurePath.parents` now supports negative indexing. Patch contributed by Yaroslav Pankovych.

- bpo-41332: Added missing connect_accepted_socket() method to `asyncio.AbstractEventLoop`.

- bpo-12800: Extracting a symlink from a tarball should succeed and overwrite the symlink if it already exists. The fix is to remove the existing file or symlink before extraction. Based on patch by Chris AtLee, Jeffrey Kintscher, and Senthil Kumaran.

- bpo-40968: `urllib.request` and `http.client` now send `http/1.1` ALPN extension during TLS handshake when no custom context is supplied.

- bpo-41001: Add `os.eventfd()` to provide a low level interface for Linux’s event notification file descriptor.

- bpo-40816: Add AsyncContextDecorator to contextlib to support async context manager as a decorator.

- bpo-40550: Fix time-of-check/time-of-action issue in subprocess.Popen.send_signal.

- bpo-39411: Add an `is_async` identifier to `pyclbr`’s `Function` objects. Patch by Batuhan Taskaya

- bpo-35498: Add slice support to `pathlib.PurePath.parents`.

### Documentation

- bpo-42238: Tentative to deprecate `make suspicious` by first removing it from the CI and documentation builds, but keeping it around for manual uses.

- bpo-42153: Fix the URL for the IMAP protocol documents.

- bpo-41028: Language and version switchers, previously maintained in every cpython branches, are now handled by docsbuild-script.

### Tests

- bpo-41473: Re-enable test_gdb on gdb 9.2 and newer: https://bugzilla.redhat.com/show_bug.cgi?id=1866884 bug is fixed in gdb 10.1.

- bpo-42553: Fix `test_asyncio.test_call_later()` race condition: don’t measure asyncio performance in the `call_later()` unit test. The test failed randomly on the CI.

- bpo-31904: Fix test_netrc on VxWorks: create temporary directories using temp_cwd().

- bpo-31904: skip test_getaddrinfo_ipv6_scopeid_symbolic and test_getnameinfo_ipv6_scopeid_symbolic on VxWorks

- bpo-31904: skip test_test of test_mailcap on VxWorks

- bpo-31904: add shell requirement for test_pipes

- bpo-31904: skip some tests related to fifo on VxWorks

- bpo-31904: Fix test_doctest.py failures for VxWorks.

- bpo-40754: Include `_testinternalcapi` module in Windows installer for test suite

- bpo-41561: test_ssl: skip test_min_max_version_mismatch when TLS 1.0 is not available

- bpo-31904: Fix os module failures for VxWorks RTOS.

- bpo-31904: Fix fifo test cases for VxWorks RTOS.

### Build

- bpo-31904: remove libnet dependency from detect_socket() for VxWorks

- bpo-42398: Fix a race condition in “make regen-all” when make -jN option is used to run jobs in parallel. The clinic.py script now only use atomic write to write files. Moveover, generated files are now left unchanged if the content does not change, to not change the file modification time.

- bpo-41617: Fix building `pycore_bitutils.h` internal header on old clang version without `__builtin_bswap16()` (ex: Xcode 4.6.3 on Mac OS X 10.7). Patch by Joshua Root and Victor Stinner.

- bpo-38823: It is no longer possible to build the `_ctypes` extension module without `wchar_t` type: remove `CTYPES_UNICODE` macro. Anyway, the `wchar_t` type is required to build Python. Patch by Victor Stinner.

- bpo-42087: Support was removed for AIX 5.3 and below. See bpo-40680.

- bpo-40998: Addressed three compiler warnings found by undefined behavior sanitizer (ubsan).

### Windows

- bpo-42120: Remove macro definition of `copysign` (to `_copysign`) in headers.

- bpo-38506: The Windows launcher now properly handles Python 3.10 when listing installed Python versions.

### macOS

- bpo-42504: Fix build on macOS Big Sur when MACOSX_DEPLOYMENT_TARGET=11

- bpo-41116: Ensure distutils.unixxcompiler.find_library_file can find system provided libraries on macOS 11.

- bpo-41100: Add support for macOS 11 and Apple Silicon systems.

  It is now possible to build “Universal 2” binaries using “–enable-universalsdk –with-universal-archs=universal2”.

  Binaries build on later macOS versions can be deployed back to older versions (tested up to macOS 10.9), when using the correct deployment target. This is tested using Xcode 11 and later.

- bpo-42232: Added Darwin specific madvise options to mmap module.

- bpo-38443: The `--enable-universalsdk` and `--with-universal-archs` options for the configure script now check that the specified architectures can be used.

### IDLE

- bpo-42508: Keep IDLE running on macOS. Remove obsolete workaround that prevented running files with shortcuts when using new universal2 installers built on macOS 11.

- bpo-42426: Fix reporting offset of the RE error in searchengine.

- bpo-42415: Get docstrings for IDLE calltips more often by using inspect.getdoc.

### Tools/Demos

- bpo-42212: The smelly.py script now also checks the Python dynamic library and extension modules, not only the Python static library. Make also the script more verbose: explain what it does.

- bpo-36310: Allow `Tools/i18n/pygettext.py` to detect calls to `gettext` in f-strings.

### C API

- bpo-42423: The `PyType_FromSpecWithBases()` and `PyType_FromModuleAndSpec()` functions now accept a single class as the bases argument.

- bpo-1635741: Port `select` extension module to multiphase initialization (PEP 489).

- bpo-1635741: Port _posixsubprocess extension module to multiphase initialization (PEP 489).

- bpo-1635741: Port _posixshmem extension module to multiphase initialization (PEP 489)

- bpo-1635741: Port _struct extension module to multiphase initialization (PEP 489)

- bpo-1635741: Port `spwd` extension module to multiphase initialization (PEP 489)

- bpo-1635741: Port `gc` extension module to multiphase initialization (PEP 489)

- bpo-1635741: Port _queue extension module to multiphase initialization (PEP 489)

- bpo-39573: Convert `Py_TYPE()` and `Py_SIZE()` back to macros to allow using them as an l-value. Many third party C extension modules rely on the ability of using Py_TYPE() and Py_SIZE() to set an object type and size: `Py_TYPE(obj) = type;` and `Py_SIZE(obj) = size;`.

- bpo-1635741: Port `symtable` extension module to multiphase initialization (PEP 489)

- bpo-1635741: Port `grp` and `pwd` extension modules to multiphase initialization (PEP 489)

- bpo-1635741: Port _random extension module to multiphase initialization (PEP 489)

- bpo-1635741: Port _hashlib extension module to multiphase initialization (PEP 489)

- bpo-41713: Removed the undocumented `PyOS_InitInterrupts()` function. Initializing Python already implicitly installs signal handlers: see `PyConfig.install_signal_handlers`. Patch by Victor Stinner.

- bpo-40170: The `Py_TRASHCAN_BEGIN` macro no longer accesses PyTypeObject attributes, but now can get the condition by calling the new private `_PyTrash_cond()` function which hides implementation details.

- bpo-42260: `Py_GetPath()`, `Py_GetPrefix()`, `Py_GetExecPrefix()`, `Py_GetProgramFullPath()`, `Py_GetPythonHome()` and `Py_GetProgramName()` functions now return `NULL` if called before `Py_Initialize()` (before Python is initialized). Use the new Python Initialization Configuration API to get the Python Path Configuration.. Patch by Victor Stinner.

- bpo-42260: The `PyConfig_Read()` function now only parses `PyConfig.argv` arguments once: `PyConfig.parse_argv` is set to `2` after arguments are parsed. Since Python arguments are strippped from `PyConfig.argv`, parsing arguments twice would parse the application options as Python options.

- bpo-42262: Added `Py_NewRef()` and `Py_XNewRef()` functions to increment the reference count of an object and return the object. Patch by Victor Stinner.

- bpo-42260: When `Py_Initialize()` is called twice, the second call now updates more `sys` attributes for the configuration, rather than only `sys.argv`. Patch by Victor Stinner.

- bpo-41832: The `PyType_FromModuleAndSpec()` function now accepts NULL `tp_doc` slot.

- bpo-1635741: Added `PyModule_AddObjectRef()` function: similar to `PyModule_AddObject()` but don’t steal a reference to the value on success. Patch by Victor Stinner.

- bpo-42171: The `METH_FASTCALL` calling convention is added to the limited API. The functions `PyModule_AddType()`, `PyType_FromModuleAndSpec()`, `PyType_GetModule()` and `PyType_GetModuleState()` are added to the limited API on Windows.

- bpo-42085: Add dedicated entry to PyAsyncMethods for sending values

- bpo-41073: `PyType_GetSlot()` can now accept static types.

- bpo-30459: `PyList_SET_ITEM()`, `PyTuple_SET_ITEM()` and `PyCell_SET()` macros can no longer be used as l-value or r-value. For example, `x = PyList_SET_ITEM(a, b, c)` and `PyList_SET_ITEM(a, b, c) = x` now fail with a compiler error. It prevents bugs like `if (PyList_SET_ITEM (a, b, c) < 0) ...` test. Patch by Zackery Spytz and Victor Stinner.

## Python 3.10.0 alpha 2

Release date: 2020-11-03

### Security

- bpo-42103: Prevented potential DoS attack via CPU and RAM exhaustion when processing malformed Apple Property List files in binary format.

- bpo-42051: The `plistlib` module no longer accepts entity declarations in XML plist files to avoid XML vulnerabilities. This should not affect users as entity declarations are not used in regular plist files.

### Core and Builtins

- bpo-42236: If the `nl_langinfo(CODESET)` function returns an empty string, Python now uses UTF-8 as the filesystem encoding. Patch by Victor Stinner.

- bpo-42218: Fixed a bug in the PEG parser that was causing crashes in debug mode. Now errors are checked in left-recursive rules to avoid cases where such errors do not get handled in time and appear as long-distance crashes in other places.

- bpo-42214: Fixed a possible crash in the PEG parser when checking for the ‘!=’ token in the `barry_as_flufl` rule. Patch by Pablo Galindo.

- bpo-42206: Propagate and raise the errors caused by `PyAST_Validate()` in the parser.

- bpo-41796: The `ast` module internal state is now per interpreter. Patch by Victor Stinner.

- bpo-42143: Fix handling of errors during creation of `PyFunctionObject`, which resulted in operations on uninitialized memory. Patch by Yonatan Goldschmidt.

- bpo-41659: Fix a bug in the parser, where a curly brace following a `primary` didn’t fail immediately. This led to invalid expressions like `a {b}` to throw a `SyntaxError` with a wrong offset, or invalid expressions ending with a curly brace like `a {` to not fail immediately in the REPL.

- bpo-42150: Fix possible buffer overflow in the new parser when checking for continuation lines. Patch by Pablo Galindo.

- bpo-42123: Run the parser two times. On the first run, disable all the rules that only generate better error messages to gain performance. If there’s a parse failure, run the parser a second time with those enabled.

- bpo-42093: The `LOAD_ATTR` instruction now uses new “per opcode cache” mechanism and it is about 36% faster now. Patch by Pablo Galindo and Yury Selivanov.

- bpo-42030: Support for the legacy AIX-specific shared library loading support has been removed. All versions of AIX since 4.3 have supported and defaulted to using the common Unix mechanism instead.

- bpo-41984: The garbage collector now tracks all user-defined classes. Patch by Brandt Bucher.

- bpo-41993: Fixed potential issues with removing not completely initialized module from `sys.modules` when import fails.

- bpo-41979: Star-unpacking is now allowed for with item’s targets in the PEG parser.

- bpo-41974: Removed special methods `__int__`, `__float__`, `__floordiv__`, `__mod__`, `__divmod__`, `__rfloordiv__`, `__rmod__` and `__rdivmod__` of the `complex` class. They always raised a `TypeError`.

- bpo-41902: Micro optimization when compute `sq_item` and `mp_subscript` of `range`. Patch by Donghee Na.

- bpo-41894: When loading a native module and a load failure occurs, prevent a possible UnicodeDecodeError when not running in a UTF-8 locale by decoding the load error message using the current locale’s encoding.

- bpo-41902: Micro optimization for range.index if step is 1. Patch by Donghee Na.

- bpo-41435: Add `sys._current_exceptions()` function to retrieve a dictionary mapping each thread’s identifier to the topmost exception currently active in that thread at the time the function is called.

- bpo-38605: Enable `from __future__ import annotations` (PEP 563) by default. The values found in `__annotations__` dicts are now strings, for example `{"x": "int"}` instead of `{"x": int}`.

### Library

- bpo-35455: On Solaris, `thread_time()` is now implemented with `gethrvtime()` because `clock_gettime(CLOCK_THREAD_CPUTIME_ID)` is not always available. Patch by Jakub Kulik.

- bpo-42233: The `repr()` of `typing` types containing Generic Alias Types previously did not show the parameterized types in the `GenericAlias`. They have now been changed to do so.

- bpo-29566: `binhex.binhex()` consistently writes macOS 9 line endings.

- bpo-26789: The `logging.FileHandler` class now keeps a reference to the builtin `open()` function to be able to open or reopen the file during Python finalization. Fix errors like: `NameError: name 'open' is not defined`. Patch by Victor Stinner.

- bpo-42157: Removed the `unicodedata.ucnhash_CAPI` attribute which was an internal PyCapsule object. The related private `_PyUnicode_Name_CAPI` structure was moved to the internal C API. Patch by Victor Stinner.

- bpo-42157: Convert the `unicodedata` extension module to the multiphase initialization API (PEP 489) and convert the `unicodedata.UCD` static type to a heap type. Patch by Mohamed Koubaa and Victor Stinner.

- bpo-42146: Fix memory leak in `subprocess.Popen()` in case an uid (gid) specified in `user` (`group`, `extra_groups`) overflows `uid_t` (`gid_t`).

- bpo-42103: `InvalidFileException` and `RecursionError` are now the only errors caused by loading malformed binary Plist file (previously ValueError and TypeError could be raised in some specific cases).

- bpo-41490: In `importlib.resources`, `.path` method is more aggressive about releasing handles to zipfile objects early, enabling use-cases like certifi to leave the context open but delete the underlying zip file.

- bpo-41052: Pickling heap types implemented in C with protocols 0 and 1 raises now an error instead of producing incorrect data.

- bpo-42089: In `importlib.metadata.PackageNotFoundError`, make reference to the package metadata being missing to improve the user experience.

- bpo-41491: plistlib: fix parsing XML plists with hexadecimal integer values

- bpo-42065: Fix an incorrectly formatted error from `_codecs.charmap_decode()` when called with a mapped value outside the range of valid Unicode code points. PR by Max Bernstein.

- bpo-41966: Fix pickling pure Python `datetime.time` subclasses. Patch by Dean Inwood.

- bpo-19270: `sched.scheduler.cancel()` will now cancel the correct event, if two events with same priority are scheduled for the same time. Patch by Bar Harel.

- bpo-28660: `textwrap.wrap()` now attempts to break long words after hyphens when `break_long_words=True` and `break_on_hyphens=True`.

- bpo-35823: Use `vfork()` instead of `fork()` for `subprocess.Popen()` on Linux to improve performance in cases where it is deemed safe.

- bpo-42043: Add support for `zipfile.Path` inheritance. `zipfile.Path.is_file()` now returns False for non-existent names. `zipfile.Path` objects now expose a `.filename` attribute and rely on that to resolve `.name` and `.parent` when the `Path` object is at the root of the zipfile.

- bpo-42021: Fix possible ref leaks in `sqlite3` module init.

- bpo-39101: Fixed tests using IsolatedAsyncioTestCase from hanging on BaseExceptions.

- bpo-41976: Fixed a bug that was causing `ctypes.util.find_library()` to return `None` when triying to locate a library in an environment when gcc>=9 is available and `ldconfig` is not. Patch by Pablo Galindo

- bpo-41943: Fix bug where TestCase.assertLogs doesn’t correctly filter messages by level.

- bpo-41923: Implement PEP 613, introducing `typing.TypeAlias` annotation.

- bpo-41905: A new function in abc: update_abstractmethods to re-calculate an abstract class’s abstract status. In addition, dataclass has been changed to call this function.

- bpo-23706: Added newline parameter to `pathlib.Path.write_text()`.

- bpo-41876: Tkinter font class repr uses font name

- bpo-41831: `str()` for the `type` attribute of the `tkinter.Event` object always returns now the numeric code returned by Tk instead of the name of the event type.

- bpo-39337: `encodings.normalize_encoding()` now ignores non-ASCII characters.

- bpo-41747: Ensure all methods that generated from `dataclasses.dataclass()` objects now have the proper `__qualname__` attribute referring to the class they belong to. Patch by Batuhan Taskaya.

- bpo-30681: Handle exceptions caused by unparsable date headers when using email “default” policy. Patch by Tim Bell, Georges Toth

- bpo-41586: Add F_SETPIPE_SZ and F_GETPIPE_SZ to fcntl module. Allow setting pipesize on subprocess.Popen.

- bpo-41229: Add `contextlib.aclosing` for deterministic cleanup of async generators which is analogous to `contextlib.closing` for non-async generators. Patch by Joongi Kim and John Belmonte.

- bpo-16396: Allow `ctypes.wintypes` to be imported on non-Windows systems.

- bpo-4356: Add a key function to the bisect module.

- bpo-40592: `shutil.which()` now ignores empty entries in `PATHEXT` instead of treating them as a match.

- bpo-40492: Fix `--outfile` for `cProfile` / `profile` not writing the output file in the original directory when the program being profiled changes the working directory. PR by Anthony Sottile.

- bpo-34204: The `shelve` module now uses `pickle.DEFAULT_PROTOCOL` by default instead of `pickle` protocol `3`.

- bpo-27321: Fixed KeyError exception when flattening an email to a string attempts to replace a non-existent Content-Transfer-Encoding header.

- bpo-38976: The `http.cookiejar` module now supports the parsing of cookies in CURL-style cookiejar files through MozillaCookieJar on all platforms. Previously, such cookie entries would be silently ignored when loading a cookiejar with such entries.

  Additionally, the HTTP Only attribute is persisted in the object, and will be correctly written to file if the MozillaCookieJar object is subsequently dumped.

### Documentation

- bpo-42061: Document __format__ functionality for IP addresses.

- bpo-41910: Document the default implementation of `object.__eq__`.

- bpo-42010: Clarify that subscription expressions are also valid for certain classes and types in the standard library, and for user-defined classes and types if the classmethod `__class_getitem__()` is provided.

- bpo-41805: Documented generic alias type and `types.GenericAlias`. Also added an entry in glossary for generic types.

- bpo-39693: Fix tarfile’s extractfile documentation

- bpo-39416: Document some restrictions on the default string representations of numeric classes.

### Tests

- bpo-41739: Fix test_logging.test_race_between_set_target_and_flush(): the test now waits until all threads complete to avoid leaking running threads.

- bpo-41970: Avoid a test failure in `test_lib2to3` if the module has already imported at the time the test executes. Patch by Pablo Galindo.

- bpo-41944: Tests for CJK codecs no longer call `eval()` on content received via HTTP.

- bpo-41306: Fixed a failure in `test_tk.test_widgets.ScaleTest` happening when executing the test with Tk 8.6.10.

### Build

- bpo-38980: Add `-fno-semantic-interposition` to both the compile and link line when building with `--enable-optimizations`. Patch by Victor Stinner and Pablo Galindo.

### Windows

- bpo-38439: Updates the icons for IDLE in the Windows Store package.

- bpo-38252: Use 8-byte step to detect ASCII sequence in 64-bit Windows build.

- bpo-39107: Update Tcl and Tk to 8.6.10 in Windows installer.

- bpo-41557: Update Windows installer to use SQLite 3.33.0.

- bpo-38324: Avoid Unicode errors when accessing certain locale data on Windows.

### macOS

- bpo-41471: Ignore invalid prefix lengths in system proxy excludes.

### IDLE

- bpo-33987: Mostly finish using ttk widgets, mainly for editor, settings, and searches. Some patches by Mark Roseman.

- bpo-40511: Typing opening and closing parentheses inside the parentheses of a function call will no longer cause unnecessary “flashing” off and on of an existing open call-tip, e.g. when typed in a string literal.

- bpo-38439: Add a 256×256 pixel IDLE icon to the Windows .ico file. Created by Andrew Clover. Remove the low-color gif variations from the .ico file.

### C API

- bpo-42157: The private `_PyUnicode_Name_CAPI` structure of the PyCapsule API `unicodedata.ucnhash_CAPI` has been moved to the internal C API. Patch by Victor Stinner.

- bpo-42015: Fix potential crash in deallocating method objects when dynamically allocated `PyMethodDef`’s lifetime is managed through the `self` argument of a `PyCFunction`.

- bpo-40423: The `subprocess` module and `os.closerange` will now use the `close_range(low, high, flags)` syscall when it is available for more efficient closing of ranges of descriptors.

- bpo-41845: `PyObject_GenericGetDict()` is available again in the limited API when targeting 3.10 or later.

- bpo-40422: Add `_Py_closerange` function to provide performant closing of a range of file descriptors.

- bpo-41986: `Py_FileSystemDefaultEncodeErrors` and `Py_UTF8Mode` are available again in limited API.

- bpo-41756: Add `PyIter_Send` function to allow sending value into generator/coroutine/iterator without raising StopIteration exception to signal return.

- bpo-41784: Added `PyUnicode_AsUTF8AndSize` to the limited C API.

## Python 3.10.0 alpha 1

Release date: 2020-10-05

### Security

- bpo-41304: Fixes `python3x._pth` being ignored on Windows, caused by the fix for bpo-29778 (CVE 2020-15801).

- bpo-41162: Audit hooks are now cleared later during finalization to avoid missing events.

- bpo-29778: Ensure `python3.dll` is loaded from correct locations when Python is embedded (CVE 2020-15523).

- bpo-41004: The __hash__() methods of ipaddress.IPv4Interface and ipaddress.IPv6Interface incorrectly generated constant hash values of 32 and 128 respectively. This resulted in always causing hash collisions. The fix uses hash() to generate hash values for the tuple of (address, mask length, network address).

- bpo-39603: Prevent http header injection by rejecting control characters in http.client.putrequest(…).

### Core and Builtins

- bpo-41909: Fixed stack overflow in `issubclass()` and `isinstance()` when getting the `__bases__` attribute leads to infinite recursion.

- bpo-41922: Speed up calls to `reversed()` by using the PEP 590 `vectorcall` calling convention. Patch by Donghee Na.

- bpo-41873: Calls to `float()` are now faster due to the `vectorcall` calling convention. Patch by Dennis Sweeney.

- bpo-41870: Speed up calls to `bool()` by using the PEP 590 `vectorcall` calling convention. Patch by Donghee Na.

- bpo-1635741: Port the `_bisect` module to the multi-phase initialization API (PEP 489).

- bpo-39934: Correctly count control blocks in ‘except’ in compiler. Ensures that a syntax error, rather a fatal error, occurs for deeply nested, named exception handlers.

- bpo-41780: Fix `__dir__()` of `types.GenericAlias`. Patch by Batuhan Taskaya.

- bpo-1635741: Port the `_lsprof` extension module to multi-phase initialization (PEP 489).

- bpo-1635741: Port the `cmath` extension module to multi-phase initialization (PEP 489).

- bpo-1635741: Port the `_scproxy` extension module to multi-phase initialization (PEP 489).

- bpo-1635741: Port the `termios` extension module to multi-phase initialization (PEP 489).

- bpo-1635741: Convert the `_sha256` extension module types to heap types.

- bpo-41690: Fix a possible stack overflow in the parser when parsing functions and classes with a huge amount of arguments. Patch by Pablo Galindo.

- bpo-1635741: Port the `_overlapped` extension module to multi-phase initialization (PEP 489).

- bpo-1635741: Port the `_curses_panel` extension module to multi-phase initialization (PEP 489).

- bpo-1635741: Port the `_opcode` extension module to multi-phase initialization (PEP 489).

- bpo-41681: Fixes the wrong error description in the error raised by using 2 `,` in format string in f-string and `str.format()`.

- bpo-41675: The implementation of `signal.siginterrupt()` now uses `sigaction()` (if it is available in the system) instead of the deprecated `siginterrupt()`. Patch by Pablo Galindo.

- bpo-41670: Prevent line trace being skipped on platforms not compiled with `USE_COMPUTED_GOTOS`. Fixes issue where some lines nested within a try-except block were not being traced on Windows.

- bpo-41654: Fix a crash that occurred when destroying subclasses of `MemoryError`. Patch by Pablo Galindo.

- bpo-1635741: Port the `zlib` extension module to multi-phase initialization (PEP 489).

- bpo-41631: The `_ast` module uses again a global state. Using a module state per module instance is causing subtle practical problems. For example, the Mercurial project replaces the `__import__()` function to implement lazy import, whereas Python expected that `import _ast` always return a fully initialized `_ast` module.

- bpo-40077: Convert `_operator` to use `PyType_FromSpec()`.

- bpo-1653741: Port `_sha3` to multi-phase init. Convert static types to heap types.

- bpo-1635741: Port the `_blake2` extension module to the multi-phase initialization API (PEP 489).

- bpo-41533: Free the stack allocated in `va_build_stack` if `do_mkstack` fails and the stack is not a `small_stack`.

- bpo-41531: Fix a bug that was dropping keys when compiling dict literals with more than 0xFFFF elements. Patch by Pablo Galindo.

- bpo-41525: The output of `python --help` contains now only ASCII characters.

- bpo-1635741: Port the `_sha1`, `_sha512`, and `_md5` extension modules to multi-phase initialization API (PEP 489).

- bpo-41431: Optimize `dict_merge()` for copying dict (e.g. `dict(d)` and `{}.update(d)`).

- bpo-41428: Implement PEP 604. This supports (int | str) etc. in place of Union[str, int].

- bpo-41340: Removed fallback implementation for `strdup`.

- bpo-38156: Handle interrupts that come after EOF correctly in `PyOS_StdioReadline`.

- bpo-41342: `round()` with integer argument is now faster (9–60%).

- bpo-41334: Constructors `str()`, `bytes()` and `bytearray()` are now faster (around 30–40% for small objects).

- bpo-41295: Resolve a regression in CPython 3.8.4 where defining “__setattr__” in a multi-inheritance setup and calling up the hierarchy chain could fail if builtins/extension types were involved in the base types.

- bpo-41323: Bytecode optimizations are performed directly on the control flow graph. This will result in slightly more compact code objects in some circumstances.

- bpo-41247: Always cache the running loop holder when running `asyncio.set_running_loop`.

- bpo-41252: Fix incorrect refcounting in _ssl.c’s `_servername_callback()`.

- bpo-1635741: Port `multiprocessing` to multi-phase initialization

- bpo-1635741: Port `winapi` to multiphase initialization

- bpo-41215: Use non-NULL default values in the PEG parser keyword list to overcome a bug that was preventing Python from being properly compiled when using the XLC compiler. Patch by Pablo Galindo.

- bpo-41218: Python 3.8.3 had a regression where compiling with ast.PyCF_ALLOW_TOP_LEVEL_AWAIT would aggressively mark list comprehension with CO_COROUTINE. Now only list comprehension making use of async/await will tagged as so.

- bpo-1635741: Port `faulthandler` to multiphase initialization.

- bpo-1635741: Port `sha256` to multiphase initialization

- bpo-41175: Guard against a NULL pointer dereference within bytearrayobject triggered by the `bytearray() + bytearray()` operation.

- bpo-41100: add arm64 to the allowable Mac OS arches in mpdecimal.h

- bpo-41094: Fix decoding errors with audit when open files with non-ASCII names on non-UTF-8 locale.

- bpo-39960: The “hackcheck” that prevents sneaking around a type’s __setattr__() by calling the superclass method was rewritten to allow C implemented heap types.

- bpo-41084: Prefix the error message with ‘f-string: ‘, when parsing an f-string expression which throws a `SyntaxError`.

- bpo-40521: Empty frozensets are no longer singletons.

- bpo-41076: Pre-feed the parser with the location of the f-string expression, not the f-string itself, which allows us to skip the shifting of the AST node locations after the parsing is completed.

- bpo-41056: Fixes a reference to deallocated stack space during startup when constructing sys.path involving a relative symlink when code was supplied via -c. (discovered via Coverity)

- bpo-41061: Fix incorrect expressions and asserts in hashtable code and tests.

- bpo-41052: Opt out serialization/deserialization for _random.Random

- bpo-40939: Rename `PyPegen*` functions to `PyParser*`, so that we can remove the old set of `PyParser*` functions that were using the old parser, but keep everything backwards-compatible.

- bpo-35975: Stefan Behnel reported that cf_feature_version is used even when PyCF_ONLY_AST is not set. This is against the intention and against the documented behavior, so it’s been fixed.

- bpo-40939: Remove the remaining files from the old parser and the `symbol` module.

- bpo-40077: Convert `_bz2` to use `PyType_FromSpec()`.

- bpo-41006: The `encodings.latin_1` module is no longer imported at startup. Now it is only imported when it is the filesystem encoding or the stdio encoding.

- bpo-40636: `zip()` now supports PEP 618’s `strict` parameter, which raises a `ValueError` if the arguments are exhausted at different lengths. Patch by Brandt Bucher.

- bpo-1635741: Port `_gdbm` to multiphase initialization.

- bpo-40985: Fix a bug that caused the `SyntaxError` text to be empty when a file ends with a line ending in a line continuation character (i.e. backslash). The error text should contain the text of the last line.

- bpo-40958: Fix a possible buffer overflow in the PEG parser when gathering information for emitting syntax errors. Patch by Pablo Galindo.

- bpo-1635741: Port `_dbm` to multiphase initialization.

- bpo-40957: Fix refleak in _Py_fopen_obj() when PySys_Audit() fails

- bpo-40950: Add a state to the `nis` module (PEP 3121) and apply the multiphase initialization. Patch by Donghee Na.

- bpo-40947: The Python Path Configuration now takes `PyConfig.platlibdir` in account.

- bpo-40939: Remove the old parser, the `parser` module and all associated support code, command-line options and environment variables. Patch by Pablo Galindo.

- bpo-40847: Fix a bug where a line with only a line continuation character is not considered a blank line at tokenizer level. In such cases, more than a single `NEWLINE` token was emitted. The old parser was working around the issue, but the new parser threw a `SyntaxError` for valid input due to this. For example, an empty line following a line continuation character was interpreted as a `SyntaxError`.

- bpo-40890: Each dictionary view now has a `mapping` attribute that provides a `types.MappingProxyType` wrapping the original dictionary. Patch contributed by Dennis Sweeney.

- bpo-40889: Improved the performance of symmetric difference operations on dictionary item views. Patch by Dennis Sweeney.

- bpo-40904: Fix possible segfault in the new PEG parser when parsing f-string containing yield statements with no value (`f"{yield}"`). Patch by Pablo Galindo

- bpo-40903: Fixed a possible segfault in the new PEG parser when producing error messages for invalid assignments of the form `p=p=`. Patch by Pablo Galindo

- bpo-40880: Fix invalid memory read in the new parser when checking newlines in string literals. Patch by Pablo Galindo.

- bpo-40883: Fix memory leak in when parsing f-strings in the new parser. Patch by Pablo Galindo

- bpo-40870: Raise `ValueError` when validating custom AST’s where the constants `True`, `False` and `None` are used within a `ast.Name` node.

- bpo-40854: Allow overriding `sys.platlibdir` via a new `PYTHONPLATLIBDIR` environment variable.

- bpo-40826: Fix GIL usage in `PyOS_Readline()`: lock the GIL to set an exception and pass the Python thread state when checking if there is a pending signal.

- bpo-1635741: Port `fcntl` to multiphase initialization.

- bpo-19468: Delete unnecessary instance check in importlib.reload(). Patch by Furkan Önder.

- bpo-40824: Unexpected errors in calling the `__iter__` method are no longer masked by `TypeError` in the `in` operator and functions `contains()`, `indexOf()` and `countOf()` of the `operator` module.

- bpo-40792: Attributes `start`, `stop` and `step` of the `range` object now always has exact type `int`. Previously, they could have been an instance of a subclass of `int`.

- bpo-40780: Fix a corner case where g-style string formatting of a float failed to remove trailing zeros.

- bpo-38964: When there’s a `SyntaxError` in the expression part of an fstring, the filename attribute of the `SyntaxError` gets correctly set to the name of the file the fstring resides in.

- bpo-40750: Support the “-d” debug flag in the new PEG parser. Patch by Pablo Galindo

- bpo-40217: Instances of types created with `PyType_FromSpecWithBases()` will no longer automatically visit their class object when traversing references in the garbage collector. The user is expected to manually visit the object’s class. Patch by Pablo Galindo.

- bpo-39573: `Py_TYPE()` is changed to the inline static function. Patch by Donghee Na.

- bpo-40696: Fix a hang that can arise after `generator.throw()` due to a cycle in the exception context chain.

- bpo-40521: Each interpreter now its has own free lists, singletons and caches:

  - Free lists: float, tuple, list, dict, frame, context, asynchronous generator, MemoryError.

  - Singletons: empty tuple, empty bytes string, empty Unicode string, single byte character, single Unicode (latin1) character.

  - Slice cache.

  They are no longer shared by all interpreters.

- bpo-40679: Certain `TypeError` messages about missing or extra arguments now include the function’s qualified name. Patch by Dennis Sweeney.

- bpo-29590: Make the stack trace correct after calling `generator.throw()` on a generator that has yielded from a `yield from`.

- bpo-4022: Improve performance of generators by not raising internal StopIteration.

- bpo-1635741: Port `mmap` to multiphase initialization.

- bpo-1635741: Port `_lzma` to multiphase initialization.

- bpo-37999: Builtin and extension functions that take integer arguments no longer accept `Decimal`s, `Fraction`s and other objects that can be converted to integers only with a loss (e.g. that have the `__int__()` method but do not have the `__index__()` method).

- bpo-29882: Add `int.bit_count()`, counting the number of ones in the binary representation of an integer. Patch by Niklas Fiekas.

- bpo-36982: Use ncurses extended color functions when available to support terminals with 256 colors, and add the new function `curses.has_extended_color_support()` to indicate whether extended color support is provided by the underlying ncurses library.

- bpo-19569: Add the private macros `_Py_COMP_DIAG_PUSH`, `_Py_COMP_DIAG_IGNORE_DEPR_DECLS`, and `_Py_COMP_DIAG_POP`.

- bpo-26680: The int type now supports the x.is_integer() method for compatibility with float.

### Library

- bpo-41900: C14N 2.0 serialisation in xml.etree.ElementTree failed for unprefixed attributes when a default namespace was defined.

- bpo-41887: Strip leading spaces and tabs on `ast.literal_eval()`. Also document stripping of spaces and tabs for `eval()`.

- bpo-41773: Note in documentation that `random.choices()` doesn’t support non-finite weights, raise `ValueError` when given non-finite weights.

- bpo-41840: Fix a bug in the `symtable` module that was causing module-scope global variables to not be reported as both local and global. Patch by Pablo Galindo.

- bpo-41842: Add `codecs.unregister()` function to unregister a codec search function.

- bpo-40564: In `zipfile.Path`, mutate the passed ZipFile object type instead of making a copy. Prevents issues when both the local copy and the caller’s copy attempt to close the same file handle.

- bpo-40670: More reliable validation of statements in `timeit.Timer`. It now accepts “empty” statements (only whitespaces and comments) and rejects misindentent statements.

- bpo-41833: The `threading.Thread` constructor now uses the target name if the target argument is specified but the name argument is omitted.

- bpo-41817: fix `tkinter.EventType` Enum so all members are strings, and none are tuples

- bpo-41810: `types.EllipsisType`, `types.NotImplementedType` and `types.NoneType` have been reintroduced, providing a new set of types readily interpretable by static type checkers.

- bpo-41815: Fix SQLite3 segfault when backing up closed database. Patch contributed by Peter David McCormick.

- bpo-41816: StrEnum added: it ensures that all members are already strings or string candidates

- bpo-41517: fix bug allowing Enums to be extended via multiple inheritance

- bpo-39587: use the correct mix-in data type when constructing Enums

- bpo-41792: Add is_typeddict function to typing.py to check if a type is a TypedDict class

  Previously there was no way to check that without using private API. See the relevant issue in python/typing.

- bpo-41789: Honor `object` overrides in `Enum` class creation (specifically, `__str__`, `__repr__`, `__format__`, and `__reduce_ex__`).

- bpo-32218: `enum.Flag` and `enum.IntFlag` members are now iterable.

- bpo-39651: Fix a race condition in the `call_soon_threadsafe()` method of `asyncio.ProactorEventLoop`: do nothing if the self-pipe socket has been closed.

- bpo-1635741: Port the `mashal` extension module to the multi-phase initialization API (PEP 489).

- bpo-1635741: Port the `_string` extension module to the multi-phase initialization API (PEP 489).

- bpo-41732: Added an iterator to `memoryview`.

- bpo-41720: Fixed `turtle.Vec2D.__rmul__()` for arguments which are not int or float.

- bpo-41696: Fix handling of debug mode in `asyncio.run()`. This allows setting `PYTHONASYNCIODEBUG` or `-X dev` to enable asyncio debug mode when using `asyncio.run()`.

- bpo-41687: Fix implementation of sendfile to be compatible with Solaris.

- bpo-41662: No longer override exceptions raised in `__len__()` of a sequence of parameters in `sqlite3` with `ProgrammingError`.

- bpo-39010: Restarting a `ProactorEventLoop` on Windows no longer logs spurious `ConnectionResetErrors`.

- bpo-41638: `ProgrammingError` message for absent parameter in `sqlite3` contains now the name of the parameter instead of its index when parameters are supplied as a dict.

- bpo-41662: Fixed crash when mutate list of parameters during iteration in `sqlite3`.

- bpo-41513: Improved the accuracy of math.hypot(). Internally, each step is computed with extra precision so that the result is now almost always correctly rounded.

- bpo-41609: The pdb whatis command correctly reports instance methods as ‘Method’ rather than ‘Function’.

- bpo-39994: Fixed pprint’s handling of dict subclasses that override __repr__.

- bpo-32751: When cancelling the task due to a timeout, `asyncio.wait_for()` will now wait until the cancellation is complete also in the case when timeout is <= 0, like it does with positive timeouts.

- bpo-37658: `asyncio.wait_for()` now properly handles races between cancellation of itself and the completion of the wrapped awaitable.

- bpo-40782: Change the method asyncio.AbstractEventLoop.run_in_executor to not be a coroutine.

- bpo-41520: Fix `codeop` regression that prevented turning compile warnings into errors.

- bpo-41528: turtle uses math module functions to convert degrees to radians and vice versa and to calculate vector norm

- bpo-41513: Minor algorithmic improvement to math.hypot() and math.dist() giving small gains in speed and accuracy.

- bpo-41503: Fixed a race between setTarget and flush in logging.handlers.MemoryHandler.

- bpo-41497: Fix potential UnicodeDecodeError in dis module.

- bpo-41467: On Windows, fix asyncio `recv_into()` return value when the socket/pipe is closed (`BrokenPipeError`): return `0` rather than an empty byte string (`b''`).

- bpo-41425: Make tkinter doc example runnable.

- bpo-41421: Make an algebraic simplification to random.paretovariate(). It now is slightly less subject to round-off error and is slightly faster. Inputs that used to cause ZeroDivisionError now cause an OverflowError instead.

- bpo-41440: Add `os.cpu_count()` support for VxWorks RTOS.

- bpo-41316: Fix the `tarfile` module to write only basename of TAR file to GZIP compression header.

- bpo-41384: Raise TclError instead of TypeError when an unknown option is passed to tkinter.OptionMenu.

- bpo-41317: Use add_done_callback() in asyncio.loop.sock_accept() to unsubscribe reader early on cancellation.

- bpo-41364: Reduce import overhead of `uuid`.

- bpo-35328: Set the environment variable `VIRTUAL_ENV_PROMPT` at `venv` activation.

- bpo-41341: Recursive evaluation of `typing.ForwardRef` in `get_type_hints`.

- bpo-41344: Prevent creating `shared_memory.SharedMemory` objects with `size=0`.

- bpo-41333: `collections.OrderedDict.pop()` is now 2 times faster.

- bpo-41288: Unpickling invalid NEWOBJ_EX opcode with the C implementation raises now UnpicklingError instead of crashing.

- bpo-39017: Avoid infinite loop when reading specially crafted TAR files using the tarfile module (CVE 2019-20907).

- bpo-41273: Speed up any transport using `_ProactorReadPipeTransport` by calling `recv_into` instead of `recv`, thus not creating a new buffer for each `recv` call in the transport’s read loop.

- bpo-41235: Fix the error handling in `ssl.SSLContext.load_dh_params()`.

- bpo-41207: In distutils.spawn, restore expectation that DistutilsExecError is raised when the command is not found.

- bpo-29727: Register `array.array` as a `MutableSequence`. Patch by Pablo Galindo.

- bpo-39168: Remove the `__new__` method of `typing.Generic`.

- bpo-41194: Fix a crash in the `_ast` module: it can no longer be loaded more than once. It now uses a global state rather than a module state.

- bpo-41195: Add read-only ssl.SSLContext.security_level attribute to retrieve the context’s security level.

- bpo-41193: The `write_history()` atexit function of the readline completer now ignores any `OSError` to ignore error if the filesystem is read-only, instead of only ignoring `FileNotFoundError` and `PermissionError`.

- bpo-41182: selector: use DefaultSelector based upon implementation

- bpo-41161: The decimal module now requires libmpdec-2.5.0. Users of –with-system-libmpdec should update their system library.

- bpo-40874: The decimal module now requires libmpdec-2.5.0.

- bpo-41138: Fixed the `trace` module CLI for Python source files with non-UTF-8 encoding.

- bpo-31082: Use the term “iterable” in the docstring for `functools.reduce()`.

- bpo-40521: Remove freelist from collections.deque().

- bpo-31938: Fix default-value signatures of several functions in the `select` module - by Anthony Sottile.

- bpo-41068: Fixed reading files with non-ASCII names from ZIP archive directly after writing them.

- bpo-41058: `pdb.find_function()` now correctly determines the source file encoding.

- bpo-41056: Invalid file descriptor values are now prevented from being passed to os.fpathconf. (discovered by Coverity)

- bpo-41056: Fix a NULL pointer dereference within the ssl module during a MemoryError in the keylog callback. (discovered by Coverity)

- bpo-41056: Fixed an instance where a MemoryError within the zoneinfo module might not be reported or not reported at its source. (found by Coverity)

- bpo-41048: `mimetypes.read_mime_types()` function reads the rule file using UTF-8 encoding, not the locale encoding. Patch by Srinivas Reddy Thatiparthy.

- bpo-41043: Fixed the use of `glob()` in the stdlib: literal part of the path is now always correctly escaped.

- bpo-41025: Fixed an issue preventing the C implementation of `zoneinfo.ZoneInfo` from being subclassed.

- bpo-35018: Add the `xml.sax.handler.LexicalHandler` class that is present in other SAX XML implementations.

- bpo-41002: Improve performance of HTTPResponse.read with a given amount. Patch by Bruce Merry.

- bpo-40448: `ensurepip` now disables the use of `pip` cache when installing the bundled versions of `pip` and `setuptools`. Patch by Krzysztof Konopko.

- bpo-40967: Removed `asyncio.Task.current_task()` and `asyncio.Task.all_tasks()`. Patch contributed by Rémi Lapeyre.

- bpo-40924: Ensure `importlib.resources.path` returns an extant path for the SourceFileLoader’s resource reader. Avoids the regression identified in master while a long-term solution is devised.

- bpo-40955: Fix a minor memory leak in `subprocess` module when extra_groups was specified.

- bpo-40855: The standard deviation and variance functions in the statistics module were ignoring their mu and xbar arguments.

- bpo-40939: Use the new PEG parser when generating the stdlib `keyword` module.

- bpo-23427: Add `sys.orig_argv` attribute: the list of the original command line arguments passed to the Python executable.

- bpo-33689: Ignore empty or whitespace-only lines in .pth files. This matches the documentated behavior. Before, empty lines caused the site-packages dir to appear multiple times in sys.path. By Ido Michael, contributors Malcolm Smith and Tal Einat.

- bpo-40884: Added a `defaults` parameter to `logging.Formatter`, to allow specifying default values for custom fields. Patch by Asaf Alon and Bar Harel.

- bpo-40876: Clarify error message in the `csv` module.

- bpo-39791: Refresh importlib.metadata from importlib_metadata 1.6.1.

- bpo-40807: Stop codeop._maybe_compile, used by code.InteractiveInterpreter (and IDLE). from emitting each warning three times.

- bpo-32604: Fix reference leak in the `select` module when the module is imported in a subinterpreter.

- bpo-39791: Built-in loaders (SourceFileLoader and ZipImporter) now supply `TraversableResources` implementations for `ResourceReader`, and the fallback function has been removed.

- bpo-39314: `rlcompleter.Completer` and the standard Python shell now close the parenthesis for functions that take no arguments. Patch contributed by Rémi Lapeyre.

- bpo-17005: The topological sort functionality that was introduced initially in the `functools` module has been moved to a new `graphlib` module to better accommodate the new tools and keep the original scope of the `functools` module. Patch by Pablo Galindo

- bpo-40834: Fix truncate when sending str object with_xxsubinterpreters.channel_send.

- bpo-40755: Add rich comparisons to collections.Counter().

- bpo-26407: Unexpected errors in calling the `__iter__` method are no longer masked by `TypeError` in `csv.reader()`, `csv.writer.writerow()` and `csv.writer.writerows()`.

- bpo-39384: Fixed email.contentmanager to allow set_content() to set a null string.

- bpo-40744: The `sqlite3` module uses SQLite API functions that require SQLite v3.7.3 or higher. This patch removes support for older SQLite versions, and explicitly requires SQLite 3.7.3 both at build, compile and runtime. Patch by Sergey Fedoseev and Erlend E. Aasland.

- bpo-40777: Initialize PyDateTime_IsoCalendarDateType.tp_base at run-time to avoid errors on some compilers.

- bpo-38488: Update ensurepip to install pip 20.1.1 and setuptools 47.1.0.

- bpo-40792: The result of `operator.index()` now always has exact type `int`. Previously, the result could have been an instance of a subclass of `int`.

- bpo-40767: `webbrowser` now properly finds the default browser in pure Wayland systems by checking the WAYLAND_DISPLAY environment variable. Patch contributed by Jérémy Attali.

- bpo-40791: `hashlib.compare_digest()` uses OpenSSL’s `CRYPTO_memcmp()` function when OpenSSL is available.

- bpo-40795: `ctypes` module: If ctypes fails to convert the result of a callback or if a ctypes callback function raises an exception, sys.unraisablehook is now called with an exception set. Previously, the error was logged into stderr by `PyErr_Print()`.

- bpo-16995: Add `base64.b32hexencode()` and `base64.b32hexdecode()` to support the Base32 Encoding with Extended Hex Alphabet.

- bpo-30008: Fix `ssl` code to be compatible with OpenSSL 1.1.x builds that use `no-deprecated` and `--api=1.1.0`.

- bpo-30064: Fix asyncio `loop.sock_*` race condition issue

- bpo-40759: Deprecate the `symbol` module.

- bpo-40756: The second argument (extra) of `LoggerAdapter.__init__` now defaults to None.

- bpo-37129: Add a new `os.RWF_APPEND` flag for `os.pwritev()`.

- bpo-40737: Fix possible reference leak for `sqlite3` initialization.

- bpo-40726: Handle cases where the `end_lineno` is `None` on `ast.increment_lineno()`.

- bpo-40698: `distutils` upload creates SHA2-256 and Blake2b-256 digests. MD5 digests is skipped if platform blocks MD5.

- bpo-40695: `hashlib` no longer falls back to builtin hash implementations when OpenSSL provides a hash digest and the algorithm is blocked by security policy.

- bpo-9216: `hashlib.new()` passed `usedforsecurity` to OpenSSL EVP constructor `_hashlib.new()`. test_hashlib and test_smtplib handle strict security policy better.

- bpo-40614: `ast.parse()` will not parse self documenting expressions in f-strings when passed `feature_version` is less than `(3, 8)`.

- bpo-40626: Add h5 file extension as MIME Type application/x-hdf5, as per HDF Group recommendation for HDF5 formatted data files. Patch contributed by Mark Schwab.

- bpo-25920: On macOS, when building Python for macOS 10.4 and older, which wasn’t the case for python.org macOS installer, `socket.getaddrinfo()` no longer uses an internal lock to prevent race conditions when calling `getaddrinfo()` which is thread-safe since macOS 10.5. Python 3.9 requires macOS 10.6 or newer. The internal lock caused random hang on fork when another thread was calling `socket.getaddrinfo()`. The lock was also used on FreeBSD older than 5.3, OpenBSD older than 201311 and NetBSD older than 4.

- bpo-40671: Prepare `_hashlib` for PEP 489 and use `PyModule_AddType()`.

- bpo-32309: Added a new coroutine `asyncio.to_thread()`. It is mainly used for running IO-bound functions in a separate thread to avoid blocking the event loop, and essentially works as a high-level version of `run_in_executor()` that can directly take keyword arguments.

- bpo-36543: Restored the deprecated `xml.etree.cElementTree` module.

- bpo-40611: `MAP_POPULATE` constant has now been added to the list of exported `mmap` module flags.

- bpo-39881: PEP 554 for use in the test suite. (Patch By Joannah Nanjekye)

- bpo-13097: `ctypes` now raises an `ArgumentError` when a callback is invoked with more than 1024 arguments.

- bpo-39385: A new test assertion context-manager, `unittest.assertNoLogs()` will ensure a given block of code emits no log messages using the logging module. Contributed by Kit Yan Choi.

- bpo-23082: Updated the error message and docs of PurePath.relative_to() to better reflect the function behaviour.

- bpo-40318: Use SQLite3 trace v2 API, if it is available.

- bpo-40105: ZipFile truncates files to avoid corruption when a shorter comment is provided in append (“a”) mode. Patch by Jan Mazur.

- bpo-40084: Fix `Enum.__dir__`: dir(Enum.member) now includes attributes as well as methods.

- bpo-31122: ssl.wrap_socket() now raises ssl.SSLEOFError rather than OSError when peer closes connection during TLS negotiation

- bpo-39728: fix default `_missing_` so a duplicate `ValueError` is not set as the `__context__` of the original `ValueError`.

- bpo-39244: Fixed `multiprocessing.context.get_all_start_methods` to properly return the default method first on macOS.

- bpo-39040: Fix parsing of invalid mime headers parameters by collapsing whitespace between encoded words in a bare-quote-string.

- bpo-38731: Add `--quiet` option to command-line interface of `py_compile`. Patch by Gregory Schevchenko.

- bpo-35714: `struct.error` is now raised if there is a null character in a `struct` format string.

- bpo-38144: Added the root_dir and dir_fd parameters in `glob.glob()`.

- bpo-26543: Fix `IMAP4.noop()` when debug mode is enabled (ex: `imaplib.Debug = 3`).

- bpo-12178: `csv.writer()` now correctly escapes escapechar when input contains escapechar. Patch by Catalin Iacob, Berker Peksag, and Itay Elbirt.

- bpo-36290: AST nodes are now raising `TypeError` on conflicting keyword arguments. Patch contributed by Rémi Lapeyre.

- bpo-33944: Added site.py site-packages tracing in verbose mode.

- bpo-35078: Refactor formatweekday, formatmonthname methods in LocaleHTMLCalendar and LocaleTextCalendar classes in calendar module to call the base class methods.This enables customizable CSS classes for LocaleHTMLCalendar. Patch by Srinivas Reddy Thatiparthy

- bpo-29620: `assertWarns()` no longer raises a `RuntimeException` when accessing a module’s `__warningregistry__` causes importation of a new module, or when a new module is imported in another thread. Patch by Kernc.

- bpo-31844: Remove `ParserBase.error()` method from the private and undocumented `_markupbase` module. `html.parser.HTMLParser` is the only subclass of `ParserBase` and its `error()` implementation was deprecated in Python 3.4 and removed in Python 3.5.

- bpo-34226: Fix `cgi.parse_multipart` without content_length. Patch by Roger Duran

- bpo-33660: Fix pathlib.PosixPath to resolve a relative path located on the root directory properly.

- bpo-28557: Improve the error message for a misbehaving `rawio.readinto`

- bpo-26680: The d.is_integer() method is added to the Decimal type, for compatibility with other number types.

- bpo-26680: The x.is_integer() method is incorporated into the abstract types of the numeric tower, Real, Rational and Integral, with appropriate default implementations.

### Documentation

- bpo-41428: Add documentation for PEP 604 (Allow writing union types as `X | Y`).

- bpo-41774: In Programming FAQ “Sequences (Tuples/Lists)” section, add “How do you remove multiple items from a list”.

- bpo-35293: Fix RemovedInSphinx40Warning when building the documentation. Patch by Donghee Na.

- bpo-37149: Change Shipman tkinter doc link from archive.org to TkDocs. (The doc has been removed from the NMT server.) The new link responds much faster and includes a short explanatory note.

- bpo-41726: Update the refcounts info of `PyType_FromModuleAndSpec`.

- bpo-41624: Fix the signature of `typing.Coroutine`.

- bpo-40204: Enable Sphinx 3.2 `c_allow_pre_v3` option and disable `c_warn_on_allowed_pre_v3` option to make the documentation compatible with Sphinx 2 and Sphinx 3.

- bpo-41045: Add documentation for debug feature of f-strings.

- bpo-41314: Changed the release when `from __future__ import annotations` becomes the default from `4.0` to `3.10` (following a change in PEP 563).

- bpo-40979: Refactored typing.rst, arranging more than 70 classes, functions, and decorators into new sub-sections.

- bpo-40552: Fix in tutorial section 4.2. Code snippet is now correct.

- bpo-39883: Make code, examples, and recipes in the Python documentation be licensed under the more permissive BSD0 license in addition to the existing Python 2.0 license.

- bpo-37703: Updated Documentation to comprehensively elaborate on the behaviour of gather.cancel()

### Tests

- bpo-41939: Fix test_site.test_license_exists_at_url(): call `urllib.request.urlcleanup()` to reset the global `urllib.request._opener`. Patch by Victor Stinner.

- bpo-41731: Make test_cmd_line_script pass with option ‘-vv’.

- bpo-41602: Add tests for SIGINT handling in the runpy module.

- bpo-41521: `test.support`: Rename `blacklist` parameter of `check__all__()` to `not_exported`.

- bpo-41477: Make ctypes optional in test_genericalias.

- bpo-41085: Fix integer overflow in the `array.array.index()` method on 64-bit Windows for index larger than `2**31`.

- bpo-41069: `test.support.TESTFN` and the current directory for tests when run via `test.regrtest` contain now non-ascii characters if possible.

- bpo-38377: On Linux, skip tests using multiprocessing if the current user cannot create a file in `/dev/shm/` directory. Add the `skip_if_broken_multiprocessing_synchronize()` function to the `test.support` module.

- bpo-41009: Fix use of `support.require_{linux|mac|freebsd}_version()` decorators as class decorator.

- bpo-41003: Fix `test_copyreg` when `numpy` is installed: `test.pickletester` now saves/restores warnings filters when importing `numpy`, to ignore filters installed by `numpy`.

- bpo-40964: Disable remote `imaplib` tests, host cyrus.andrew.cmu.edu is blocking incoming connections.

- bpo-40927: Fix test_binhex when run twice: it now uses import_fresh_module() to ensure that it raises DeprecationWarning each time.

- bpo-17258: Skip some `multiprocessing` tests when MD5 hash digest is blocked.

- bpo-31904: Increase LOOPBACK_TIMEOUT to 10 for VxWorks RTOS.

- bpo-38169: Increase code coverage for SharedMemory and ShareableList

- bpo-34401: Make test_gdb properly run on HP-UX. Patch by Michael Osipov.

### Build

- bpo-38249: Update `Py_UNREACHABLE` to use __builtin_unreachable() if only the compiler is able to use it. Patch by Donghee Na.

- bpo-41617: Fix `pycore_bitutils.h` header file to support old clang versions: `__builtin_bswap16()` is not available in LLVM clang 3.0.

- bpo-40204: Pin Sphinx version to 2.3.1 in `Doc/Makefile`.

- bpo-36020: The C99 functions `snprintf()` and `vsnprintf()` are now required to build Python.

- bpo-40684: `make install` now uses the `PLATLIBDIR` variable for the destination `lib-dynload/` directory when `./configure --with-platlibdir` is used.

- bpo-40683: Fixed an issue where the `zoneinfo` module and its tests were not included when Python is installed with `make`.

### Windows

- bpo-41744: Fixes automatic import of props file when using the Nuget package.

- bpo-41627: The user site directory for 32-bit now includes a `-32` suffix to distinguish it from the 64-bit interpreter’s directory.

- bpo-41526: Fixed layout of final page of the installer by removing the special thanks to Mark Hammond (with his permission).

- bpo-41492: Fixes the description that appears in UAC prompts.

- bpo-40948: Improve post-install message to direct people to the “py” command.

- bpo-41412: The installer will now fail to install on Windows 7 and Windows 8. Further, the UCRT dependency is now always downloaded on demand.

- bpo-40741: Update Windows release to include SQLite 3.32.3.

- bpo-41142: `msilib` now supports creating CAB files with non-ASCII file path and adding files with non-ASCII file path to them.

- bpo-41074: Fixed support of non-ASCII names in functions `msilib.OpenDatabase()` and `msilib.init_database()` and non-ASCII SQL in method `msilib.Database.OpenView()`.

- bpo-41039: Stable ABI redirection DLL (python3.dll) now uses `#pragma comment(linker)` for re-exporting.

- bpo-40164: Updates Windows OpenSSL to 1.1.1g

- bpo-39631: Changes the registered MIME type for `.py` files on Windows to `text/x-python` instead of `text/plain`.

- bpo-40677: Manually define IO_REPARSE_TAG_APPEXECLINK in case some old Windows SDK doesn’t have it.

- bpo-37556: Extend py.exe help to mention overrides via venv, shebang, environmental variables & ini files.

### macOS

- bpo-41557: Update macOS installer to use SQLite 3.33.0.

- bpo-39580: Avoid opening Finder window if running installer from the command line. Patch contributed by Rick Heil.

- bpo-41100: Fix configure error when building on macOS 11. Note that the current Python release was released shortly after the first developer preview of macOS 11 (Big Sur); there are other known issues with building and running on the developer preview. Big Sur is expected to be fully supported in a future bugfix release of Python 3.8.x and with 3.9.0.

- bpo-40741: Update macOS installer to use SQLite 3.32.3.

- bpo-41005: fixed an XDG settings issue not allowing macos to open browser in webbrowser.py

- bpo-40741: Update macOS installer to use SQLite 3.32.2.

### IDLE

- bpo-41775: Use ‘IDLE Shell’ as shell title

- bpo-35764: Rewrite the Calltips doc section.

- bpo-40181: In calltips, stop reminding that ‘/’ marks the end of positional-only arguments.

- bpo-41468: Improve IDLE run crash error message (which users should never see).

- bpo-41373: Save files loaded with no line ending, as when blank, or different line endings, by setting its line ending to the system default. Fix regression in 3.8.4 and 3.9.0b4.

- bpo-41300: Save files with non-ascii chars. Fix regression released in 3.9.0b4 and 3.8.4.

- bpo-37765: Add keywords to module name completion list. Rewrite Completions section of IDLE doc.

- bpo-41152: The encoding of `stdin`, `stdout` and `stderr` in IDLE is now always UTF-8.

- bpo-41144: Make Open Module open a special module such as os.path.

- bpo-39885: Make context menu Cut and Copy work again when right-clicking within a selection.

- bpo-40723: Make test_idle pass when run after import.

### C API

- bpo-41936: Removed undocumented macros `Py_ALLOW_RECURSION` and `Py_END_ALLOW_RECURSION` and the `recursion_critical` field of the `PyInterpreterState` structure.

- bpo-41692: The `PyUnicode_InternImmortal()` function is now deprecated and will be removed in Python 3.12: use `PyUnicode_InternInPlace()` instead. Patch by Victor Stinner.

- bpo-41842: Add `PyCodec_Unregister()` function to unregister a codec search function.

- bpo-41834: Remove the `_Py_CheckRecursionLimit` variable: it has been replaced by `ceval.recursion_limit` of the `PyInterpreterState` structure. Patch by Victor Stinner.

- bpo-41689: Types created with `PyType_FromSpec()` now make any signature in their `tp_doc` slot accessible from `__text_signature__`.

- bpo-41524: Fix bug in PyOS_mystrnicmp and PyOS_mystricmp that incremented pointers beyond the end of a string.

- bpo-41324: Add a minimal decimal capsule API. The API supports fast conversions between Decimals up to 38 digits and their triple representation as a C struct.

- bpo-30155: Add `PyDateTime_DATE_GET_TZINFO()` and `PyDateTime_TIME_GET_TZINFO()` macros for accessing the `tzinfo` attributes of `datetime.datetime` and `datetime.time` objects.

- bpo-40170: Revert `PyType_HasFeature()` change: it reads again directly the `PyTypeObject.tp_flags` member when the limited C API is not used, rather than always calling `PyType_GetFlags()` which hides implementation details.

- bpo-41123: Remove `PyUnicode_AsUnicodeCopy`.

- bpo-41123: Removed `PyLong_FromUnicode()`.

- bpo-41123: Removed `PyUnicode_GetMax()`.

- bpo-41123: Removed `Py_UNICODE_str*` functions manipulating `Py_UNICODE*` strings.

- bpo-41103: `PyObject_AsCharBuffer()`, `PyObject_AsReadBuffer()`, `PyObject_CheckReadBuffer()`, and `PyObject_AsWriteBuffer()` are removed. Please migrate to new buffer protocol; `PyObject_GetBuffer()` and `PyBuffer_Release()`.

- bpo-36346: Raises DeprecationWarning for `PyUnicode_FromUnicode(NULL, size)` and `PyUnicode_FromStringAndSize(NULL, size)` with `size > 0`.

- bpo-36346: Mark `Py_UNICODE_COPY`, `Py_UNICODE_FILL`, `PyUnicode_WSTR_LENGTH`, `PyUnicode_FromUnicode`, `PyUnicode_AsUnicode`, and `PyUnicode_AsUnicodeAndSize` as deprecated in C. Remove `Py_UNICODE_MATCH` which was deprecated and broken since Python 3.3.

- bpo-40989: The `PyObject_INIT()` and `PyObject_INIT_VAR()` macros become aliases to, respectively, `PyObject_Init()` and `PyObject_InitVar()` functions.

- bpo-36020: On Windows, `#include "pyerrors.h"` no longer defines `snprintf` and `vsnprintf` macros.

- bpo-40943: The `PY_SSIZE_T_CLEAN` macro must now be defined to use `PyArg_ParseTuple()` and `Py_BuildValue()` formats which use `#`: `es#`, `et#`, `s#`, `u#`, `y#`, `z#`, `U#` and `Z#`. See Parsing arguments and building values and the PEP 353.

- bpo-40910: Export explicitly the `Py_GetArgcArgv()` function to the C API and document the function. Previously, it was exported implicitly which no longer works since Python is built with `-fvisibility=hidden`.

- bpo-40724: Allow defining buffer slots in type specs.

- bpo-40679: Fix a `_PyEval_EvalCode()` crash if qualname argument is NULL.

- bpo-40839: Calling `PyDict_GetItem()` without GIL held had been allowed for historical reason. It is no longer allowed.

- bpo-40826: `PyOS_InterruptOccurred()` now fails with a fatal error if it is called with the GIL released.

- bpo-40792: The result of `PyNumber_Index()` now always has exact type `int`. Previously, the result could have been an instance of a subclass of `int`.

- bpo-39573: Convert `Py_REFCNT()` and `Py_SIZE()` macros to static inline functions. They cannot be used as l-value anymore: use `Py_SET_REFCNT()` and `Py_SET_SIZE()` to set an object reference count and size. This change is backward incompatible on purpose, to prepare the C API for an opaque `PyObject` structure.

- bpo-40703: The PyType_FromSpec*() functions no longer overwrite the type’s “__module__” attribute if it is set via “Py_tp_members” or “Py_tp_getset”.

- bpo-39583: Remove superfluous “extern C” declarations from `Include/cpython/*.h`.

## Python 3.9.0 beta 1

Release date: 2020-05-19

### Security

- bpo-40501: `uuid` no longer uses `ctypes` to load `libuuid` or `rpcrt4.dll` at runtime.

### Core and Builtins

- bpo-40663: Correctly generate annotations where parentheses are omitted but required (e.g: `Type[(str, int, *other))]`.

- bpo-40596: Fixed `str.isidentifier()` for non-canonicalized strings containing non-BMP characters on Windows.

- bpo-40593: Improved syntax errors for invalid characters in source code.

- bpo-40585: Fixed a bug when using `codeop.compile_command()` that was causing exceptions to be swallowed with the new parser. Patch by Pablo Galindo

- bpo-40566: Apply PEP 573 to `abc`.

- bpo-40502: Initialize `n->n_col_offset`. (Patch by Joannah Nanjekye)

- bpo-40527: Fix command line argument parsing: no longer write errors multiple times into stderr.

- bpo-1635741: Port `errno` to multiphase initialization (PEP 489).

- bpo-40523: Add pass-throughs for `hash()` and `reversed()` to `weakref.proxy` objects. Patch by Pablo Galindo.

- bpo-1635741: Port `syslog` to multiphase initialization (PEP 489).

- bpo-40246: Reporting a specialised error message for invalid string prefixes, which was introduced in bpo-40246, is being reverted due to backwards compatibility concerns for strings that immediately follow a reserved keyword without whitespace between them. Constructs like `bg="#d00" if clear else"#fca"` were failing to parse, which is not an acceptable breakage on such short notice.

- bpo-40417: Fix imp module deprecation warning when PyImport_ReloadModule is called. Patch by Robert Rouhani.

- bpo-40408: Fixed support of nested type variables in GenericAlias (e.g. `list[list[T]]`).

- bpo-1635741: Port _stat module to multiphase initialization (PEP 489).

- bpo-29587: Enable implicit exception chaining when calling `generator.throw()`.

- bpo-40328: Add tools for generating mappings headers for CJKCodecs.

- bpo-40228: Setting frame.f_lineno is now robust w.r.t. changes in the source-to-bytecode compiler

- bpo-38880: Added the ability to list interpreters associated with channel ends in the internal subinterpreters module.

- bpo-37986: Improve performance of `PyLong_FromDouble()` for values that fit into long.

### Library

- bpo-40662: Fixed `ast.get_source_segment()` for ast nodes that have incomplete location information. Patch by Irit Katriel.

- bpo-40665: Convert `bisect` to use Argument Clinic.

- bpo-40536: Added the `available_timezones()` function to the `zoneinfo` module. Patch by Paul Ganssle.

- bpo-40645: The `hmac.HMAC` exposes internal implementation details. The attributes `digest_cons`, `inner`, and `outer` are deprecated and will be removed in the future.

- bpo-40645: The internal module `_hashlib` wraps and exposes OpenSSL’s HMAC API. The new code will be used in Python 3.10 after the internal implementation details of the pure Python HMAC module are no longer part of the public API.

- bpo-40637: Builtin hash modules can now be disabled or selectively enabled with `configure --with-builtin-hashlib-hashes=sha3,blake1` or `--without-builtin-hashlib-hashes`.

- bpo-37630: The `hashlib` module can now use SHA3 hashes and SHAKE XOF from OpenSSL when available.

- bpo-40479: The `hashlib` now compiles with OpenSSL 3.0.0-alpha2.

- bpo-40257: Revert changes to `inspect.getdoc()`.

- bpo-40607: When cancelling a task due to timeout, `asyncio.wait_for()` will now propagate the exception if an error happens during cancellation. Patch by Roman Skurikhin.

- bpo-40612: Fix edge cases in SyntaxError formatting. If the offset is <= 0, no caret is printed. If the offset is > line length, the caret is printed pointing just after the last character.

- bpo-40597: If text content lines are longer than policy.max_line_length, always use a content-encoding to make sure they are wrapped.

- bpo-40571: Added functools.cache() as a simpler, more discoverable way to access the unbounded cache variant of lru_cache(maxsize=None).

- bpo-40503: PEP 615, the `zoneinfo` module. Adds support for the IANA time zone database.

- bpo-40397: Removed attributes `__args__` and `__parameters__` from special generic aliases like `typing.List` (not subscripted).

- bpo-40549: Convert posixmodule.c (“posix” or “nt” module) to the multiphase initialization (PEP 489).

- bpo-31033: Add a `msg` argument to `Future.cancel()` and `Task.cancel()`.

- bpo-40541: Added an optional counts parameter to random.sample().

- bpo-40515: The `ssl` and `hashlib` modules now actively check that OpenSSL is build with thread support. Python 3.7.0 made thread support mandatory and no longer works safely with a no-thread builds.

- bpo-31033: When a `asyncio.Task` is cancelled, the exception traceback now chains all the way back to where the task was first interrupted.

- bpo-40504: `functools.lru_cache()` objects can now be the targets of weakrefs.

- bpo-40559: Fix possible memory leak in the C implementation of `asyncio.Task`.

- bpo-40480: `fnmatch.fnmatch()` could take exponential time in the presence of multiple `*` pattern characters. This was repaired by generating more elaborate regular expressions to avoid futile backtracking.

- bpo-40495: `compileall` is now able to use hardlinks to prevent duplicates in a case when `.pyc` files for different optimization levels have the same content.

- bpo-40457: The ssl module now support OpenSSL builds without TLS 1.0 and 1.1 methods.

- bpo-40355: Improve error reporting in `ast.literal_eval()` in the presence of malformed `ast.Dict` nodes instead of silently ignoring any non-conforming elements. Patch by Curtis Bucher.

- bpo-40465: Deprecated the optional random argument to random.shuffle().

- bpo-40459: `platform.win32_ver()` now produces correct ptype strings instead of empty strings.

- bpo-39435: The first argument of `pickle.loads()` is now positional-only.

- bpo-39305: Update `nntplib` to merge `nntplib.NNTP` and `nntplib._NNTPBase`. Patch by Donghee Na.

- bpo-32494: Update `dbm.gnu` to use gdbm_count if possible when calling `len()`. Patch by Donghee Na.

- bpo-40453: Add `isolated=True` keyword-only parameter to `_xxsubinterpreters.create()`. An isolated subinterpreter cannot spawn threads, spawn a child process or call `os.fork()`.

- bpo-40286: Remove `_random.Random.randbytes()`: the C implementation of `randbytes()`. Implement the method in Python to ease subclassing: `randbytes()` now directly reuses `getrandbits()`.

- bpo-40394: Added default arguments to `difflib.SequenceMatcher.find_longest_match()`.

- bpo-39995: Fix a race condition in concurrent.futures._ThreadWakeup: access to _ThreadWakeup is now protected with the shutdown lock.

- bpo-30966: `Process.shutdown(wait=True)` of `concurrent.futures` now closes explicitly the result queue.

- bpo-30966: Add a new `close()` method to the `SimpleQueue` class to explicitly close the queue.

- bpo-39966: Revert bpo-25597. `unittest.mock.MagicMock` with wraps’ set uses default return values for magic methods.

- bpo-39791: Added `files()` function to importlib.resources with support for subdirectories in package data, matching backport in importlib_resources 1.5.

- bpo-40375: `imaplib.IMAP4.unselect()` is added. Patch by Donghee Na.

- bpo-40389: `repr()` now returns `typing.Optional[T]` when called for `typing.Union` of two types, one of which is `NoneType`.

- bpo-40291: Add support for CAN_J1939 sockets (available on Linux 5.4+)

- bpo-40273: `types.MappingProxyType` is now reversible.

- bpo-39075: The repr for `types.SimpleNamespace` is now insertion ordered rather than alphabetical.

- bpo-40192: On AIX, `thread_time()` is now implemented with `thread_cputime()` which has nanosecond resolution, rather than `clock_gettime(CLOCK_THREAD_CPUTIME_ID)` which has a resolution of 10 milliseconds. Patch by Batuhan Taskaya.

- bpo-40025: Raise TypeError when _generate_next_value_ is defined after members. Patch by Ethan Onstott.

- bpo-39058: In the argparse module, the repr for Namespace() and other argument holders now displayed in the order attributes were added. Formerly, it displayed in alphabetical order even though argument order is preserved the user visible parts of the module.

- bpo-24416: The `isocalendar()` methods of `datetime.date` and `datetime.datetime` now return a named tuple instead of a `tuple`.

### Documentation

- bpo-34790: Add version of removal for explicit passing of coros to `asyncio.wait()`’s documentation

- bpo-40561: Provide docstrings for webbrowser open functions.

- bpo-40499: Mention that `asyncio.wait()` requires a non-empty set of awaitables.

- bpo-39705: Tutorial example for sorted() in the Loop Techniques section is given a better explanation. Also a new example is included to explain sorted()’s basic behavior.

- bpo-39435: Fix an incorrect signature for `pickle.loads()` in the docs

### Tests

- bpo-40055: distutils.tests now saves/restores warnings filters to leave them unchanged. Importing tests imports docutils which imports pkg_resources which adds a warnings filter.

- bpo-40436: test_gdb and test.pythoninfo now check gdb command exit code.

### Build

- bpo-40653: Move _dirnameW out of HAVE_SYMLINK to fix a potential compiling issue.

- bpo-40514: Add `--with-experimental-isolated-subinterpreters` build option to `configure`: better isolate subinterpreters, experimental build mode.

### Windows

- bpo-40650: Include winsock2.h in pytime.c for timeval.

- bpo-40458: Increase reserved stack space to prevent overflow crash on Windows.

- bpo-39148: Add IPv6 support to `asyncio` datagram endpoints in ProactorEventLoop. Change the raised exception for unknown address families to ValueError as it’s not coming from Windows API.

### macOS

- bpo-34956: When building Python on macOS from source, `_tkinter` now links with non-system Tcl and Tk frameworks if they are installed in `/Library/Frameworks`, as had been the case on older releases of macOS. If a macOS SDK is explicitly configured, by using `--enable-universalsdk=` or `-isysroot`, only the SDK itself is searched. The default behavior can still be overridden with `--with-tcltk-includes` and `--with-tcltk-libs`.

- bpo-35569: Expose RFC 3542 IPv6 socket options.

### Tools/Demos

- bpo-40479: Update multissltest helper to test with latest OpenSSL 1.0.2, 1.1.0, 1.1.1, and 3.0.0-alpha.

- bpo-40431: Fix a syntax typo in `turtledemo` that now raises a `SyntaxError`.

- bpo-40163: Fix multissltest tool. OpenSSL has changed download URL for old releases. The multissltest tool now tries to download from current and old download URLs.

### C API

- bpo-39465: Remove the `_PyUnicode_ClearStaticStrings()` function from the C API.

- bpo-38787: Add PyCFunction_CheckExact() macro for exact type checks now that we allow subtypes of PyCFunction, as well as PyCMethod_CheckExact() and PyCMethod_Check() for the new PyCMethod subtype.

- bpo-40545: Declare `_PyErr_GetTopmostException()` with `PyAPI_FUNC()` to properly export the function in the C API. The function remains private (`_Py`) prefix.

- bpo-40412: Nullify inittab_copy during finalization, preventing future interpreter initializations in an embedded situation from crashing. Patch by Gregory Szorc.

- bpo-40429: The `PyThreadState_GetFrame()` function now returns a strong reference to the frame.

- bpo-40428: Remove the following functions from the C API. Call `PyGC_Collect()` explicitly to free all free lists.

  - `PyAsyncGen_ClearFreeLists()`

  - `PyContext_ClearFreeList()`

  - `PyDict_ClearFreeList()`

  - `PyFloat_ClearFreeList()`

  - `PyFrame_ClearFreeList()`

  - `PyList_ClearFreeList()`

  - `PySet_ClearFreeList()`

  - `PyTuple_ClearFreeList()`

- bpo-40421: New `PyFrame_GetBack()` function: get the frame next outer frame.

- bpo-40421: New `PyFrame_GetCode()` function: return a borrowed reference to the frame code.

- bpo-40217: Ensure that instances of types created with `PyType_FromSpecWithBases()` will visit its class object when traversing references in the garbage collector (implemented as an extension of the provided `tp_traverse`). Patch by Pablo Galindo.

- bpo-38787: Module C state is now accessible from C-defined heap type methods (PEP 573). Patch by Marcel Plch and Petr Viktorin.

## Python 3.9.0 alpha 6

Release date: 2020-04-27

### Security

- bpo-40121: Fixes audit events raised on creating a new socket.

- bpo-39073: Disallow CR or LF in email.headerregistry.Address arguments to guard against header injection attacks.

- bpo-39503: CVE 2020-8492: The `AbstractBasicAuthHandler` class of the `urllib.request` module uses an inefficient regular expression which can be exploited by an attacker to cause a denial of service. Fix the regex to prevent the catastrophic backtracking. Vulnerability reported by Ben Caller and Matt Schwager.

### Core and Builtins

- bpo-40313: Improve the performance of bytes.hex().

- bpo-40334: Switch to a new parser, based on PEG. For more details see PEP 617. To temporarily switch back to the old parser, use `-X oldparser` or `PYTHONOLDPARSER=1`. In Python 3.10 we will remove the old parser completely, including the `parser` module (already deprecated) and anything that depends on it.

- bpo-40267: Fix the tokenizer to display the correct error message, when there is a `SyntaxError` on the last input character and no newline follows. It used to be `unexpected EOF while parsing`, while it should be `invalid syntax`.

- bpo-39522: Correctly unparse explicit `u` prefix for strings when postponed evaluation for annotations activated. Patch by Batuhan Taskaya.

- bpo-40246: Report a specialized error message, `invalid string prefix`, when the tokenizer encounters a string with an invalid prefix.

- bpo-40082: Fix the signal handler: it now always uses the main interpreter, rather than trying to get the current Python thread state.

- bpo-37388: str.encode() and str.decode() no longer check the encoding and errors in development mode or in debug mode during Python finalization. The codecs machinery can no longer work on very late calls to str.encode() and str.decode().

- bpo-40077: Fix possible refleaks in `_json`, memo of PyScannerObject should be traversed.

- bpo-37207: Speed up calls to `dict()` by using the PEP 590 `vectorcall` calling convention.

- bpo-40141: Add column and line information to `ast.keyword` nodes. Patch by Pablo Galindo.

- bpo-1635741: Port `resource` to multiphase initialization (PEP 489).

- bpo-1635741: Port `math` to multiphase initialization (PEP 489).

- bpo-1635741: Port _uuid module to multiphase initialization (PEP 489).

- bpo-40077: Convert json module to use `PyType_FromSpec()`.

- bpo-40067: Improve the error message for multiple star expressions in an assignment. Patch by Furkan Onder

- bpo-1635741: Port _functools module to multiphase initialization (PEP 489). Patch by Paulo Henrique Silva.

- bpo-1635741: Port operator module to multiphase initialization (PEP 489). Patch by Paulo Henrique Silva.

- bpo-20526: Fix `PyThreadState_Clear()`. `PyThreadState.frame` is a borrowed reference, not a strong reference: `PyThreadState_Clear()` must not call `Py_CLEAR(tstate->frame)`.

- bpo-1635741: Port time module to multiphase initialization (PEP 489). Patch by Paulo Henrique Silva.

- bpo-1635741: Port _weakref extension module to multiphase initialization (PEP 489).

- bpo-40020: Fix a leak and subsequent crash in parsetok.c caused by realloc misuse on a rare codepath.

- bpo-39939: Added str.removeprefix and str.removesuffix methods and corresponding bytes, bytearray, and collections.UserString methods to remove affixes from a string if present. See PEP 616 for a full description. Patch by Dennis Sweeney.

- bpo-39481: Implement PEP 585. This supports list[int], tuple[str, …] etc.

- bpo-32894: Support unparsing of infinity numbers in postponed annotations. Patch by Batuhan Taşkaya.

- bpo-37207: Speed up calls to `list()` by using the PEP 590 `vectorcall` calling convention. Patch by Mark Shannon.

### Library

- bpo-40398: `typing.get_args()` now always returns an empty tuple for special generic aliases.

- bpo-40396: Functions `typing.get_origin()`, `typing.get_args()` and `typing.get_type_hints()` support now generic aliases like `list[int]`.

- bpo-38061: Optimize the `subprocess` module on FreeBSD using `closefrom()`. A single `close(fd)` syscall is cheap, but when `sysconf(_SC_OPEN_MAX)` is high, the loop calling `close(fd)` on each file descriptor can take several milliseconds.

  The workaround on FreeBSD to improve performance was to load and mount the fdescfs kernel module, but this is not enabled by default.

  Initial patch by Ed Maste (emaste), Conrad Meyer (cem), Kyle Evans (kevans) and Kubilay Kocak (koobs): https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=242274

- bpo-38061: On FreeBSD, `os.closerange(fd_low, fd_high)` now calls `closefrom(fd_low)` if fd_high is greater than or equal to `sysconf(_SC_OPEN_MAX)`.

  Initial patch by Ed Maste (emaste), Conrad Meyer (cem), Kyle Evans (kevans) and Kubilay Kocak (koobs): https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=242274

- bpo-40360: The `lib2to3` module is pending deprecation due to PEP 617.

- bpo-40138: Fix the Windows implementation of `os.waitpid()` for exit code larger than `INT_MAX >> 8`. The exit status is now interpreted as an unsigned number.

- bpo-39942: Set “__main__” as the default module name when “__name__” is missing in `typing.TypeVar`. Patch by Weipeng Hong.

- bpo-40275: The `logging` package is now imported lazily in `unittest` only when the `assertLogs()` assertion is used.

- bpo-40275: The `asyncio` package is now imported lazily in `unittest` only when the `IsolatedAsyncioTestCase` class is used.

- bpo-40330: In `ShareableList.__setitem__()`, check the size of a new string item after encoding it to utf-8, not before.

- bpo-40148: Added `pathlib.Path.with_stem()` to create a new Path with the stem replaced.

- bpo-40325: Deprecated support for set objects in random.sample().

- bpo-40257: Improved help for the `typing` module. Docstrings are now shown for all special forms and special generic aliases (like `Union` and `List`). Using `help()` with generic alias like `List[int]` will show the help for the correspondent concrete type (`list` in this case).

- bpo-40257: `inspect.getdoc()` no longer returns docstring inherited from the type of the object or from parent class if it is a class if it is not defined in the object itself. In `pydoc` the documentation string is now shown not only for class, function, method etc, but for any object that has its own `__doc__` attribute.

- bpo-40287: Fixed `SpooledTemporaryFile.seek()` to return the position.

- bpo-40290: Added zscore() to statistics.NormalDist().

- bpo-40282: Allow `random.getrandbits(0)` to succeed and to return 0.

- bpo-40286: Add `random.randbytes()` function and `random.Random.randbytes()` method to generate random bytes.

- bpo-40277: `collections.namedtuple()` now provides a human-readable repr for its field accessors.

- bpo-40270: The included copy of sqlite3 on Windows is now compiled with the json extension. This allows the use of functions such as `json_object`.

- bpo-29255: Wait in `KqueueSelector.select` when no fds are registered

- bpo-40260: Ensure `modulefinder` uses `io.open_code()` and respects coding comments.

- bpo-40234: Allow again to spawn daemon threads in subinterpreters (revert change which denied them).

- bpo-39207: Workers in `ProcessPoolExecutor` are now spawned on demand, only when there are no available idle workers to reuse. This optimizes startup overhead and reduces the amount of lost CPU time to idle workers. Patch by Kyle Stanley.

- bpo-40091: Fix a hang at fork in the logging module: the new private _at_fork_reinit() method is now used to reinitialize locks at fork in the child process.

- bpo-40149: Implement traverse and clear slots in _abc._abc_data type.

- bpo-40208: Remove deprecated `symtable.SymbolTable.has_exec()`.

- bpo-40196: Fix a bug in the `symtable` module that was causing incorrectly report global variables as local. Patch by Pablo Galindo.

- bpo-40190: Add support for `_SC_AIX_REALMEM` to `posix.sysconf()`.

- bpo-40182: Removed the `_field_types` attribute of the `typing.NamedTuple` class.

- bpo-36517: Multiple inheritance with `typing.NamedTuple` now raises an error instead of silently ignoring other types.

- bpo-40126: Fixed reverting multiple patches in unittest.mock. Patcher’s `__exit__()` is now never called if its `__enter__()` is failed. Returning true from `__exit__()` silences now the exception.

- bpo-40094: CGIHTTPRequestHandler of http.server now logs the CGI script exit code, rather than the CGI script exit status of os.waitpid(). For example, if the script is killed by signal 11, it now logs: “CGI script exit code -11.”

- bpo-40108: Improve the error message when triying to import a module using `runpy` and incorrectly using the “.py” extension at the end of the module name. Patch by Pablo Galindo.

- bpo-40094: Add `os.waitstatus_to_exitcode()` function: convert a wait status to an exit code.

- bpo-40089: Fix threading._after_fork(): if fork was not called by a thread spawned by threading.Thread, threading._after_fork() now creates a _MainThread instance for _main_thread, instead of a _DummyThread instance.

- bpo-40089: Add a private `_at_fork_reinit()` method to `_thread.Lock`, `_thread.RLock`, `threading.RLock` and `threading.Condition` classes: reinitialize the lock at fork in the child process, reset the lock to the unlocked state. Rename also the private `_reset_internal_locks()` method of `threading.Event` to `_at_fork_reinit()`.

- bpo-25780: Expose `CAN_RAW_JOIN_FILTERS` in the `socket` module.

- bpo-39503: `AbstractBasicAuthHandler` of `urllib.request` now parses all WWW-Authenticate HTTP headers and accepts multiple challenges per header: use the realm of the first Basic challenge.

- bpo-39812: Removed daemon threads from `concurrent.futures` by adding an internal `threading._register_atexit()`, which calls registered functions prior to joining all non-daemon threads. This allows for compatibility with subinterpreters, which don’t support daemon threads.

- bpo-40050: Fix `importlib._bootstrap_external`: avoid creating a new `winreg` builtin module if it’s already available in `sys.modules`, and remove redundant imports.

- bpo-40014: Fix `os.getgrouplist()`: if `getgrouplist()` function fails because the group list is too small, retry with a larger group list. On failure, the glibc implementation of `getgrouplist()` sets `ngroups` to the total number of groups. For other implementations, double the group list size.

- bpo-40017: Add `time.CLOCK_TAI` constant if the operating system support it.

- bpo-40016: In re docstring, clarify the relationship between inline and argument compile flags.

- bpo-39953: Update internal table of OpenSSL error codes in the `ssl` module.

- bpo-36144: Added PEP 584 operators to `weakref.WeakValueDictionary`.

- bpo-36144: Added PEP 584 operators to `weakref.WeakKeyDictionary`.

- bpo-38891: Fix linear runtime behaviour of the `__getitem__` and `__setitem__` methods in `multiprocessing.shared_memory.ShareableList`. This avoids quadratic performance when iterating a `ShareableList`. Patch by Thomas Krennwallner.

- bpo-39682: Remove undocumented support for closing a `pathlib.Path` object via its context manager. The context manager magic methods remain, but they are now a no-op, making `Path` objects immutable.

- bpo-36144: Added PEP 584 operators (`|` and `|=`) to `collections.ChainMap`.

- bpo-39011: Normalization of line endings in ElementTree attributes was removed, as line endings which were replaced by entity numbers should be preserved in original form.

- bpo-38410: Properly handle `sys.audit()` failures in `sys.set_asyncgen_hooks()`.

- bpo-36541: lib2to3 now recognizes named assignment expressions (the walrus operator, `:=`)

- bpo-35967: In platform, delay the invocation of ‘uname -p’ until the processor attribute is requested.

- bpo-35113: `inspect.getsource()` now returns correct source code for inner class with same name as module level class. Decorators are also returned as part of source of the class. Patch by Karthikeyan Singaravelan.

- bpo-33262: Deprecate passing None as an argument for `shlex.split()`’s `s` parameter. Patch by Zackery Spytz.

- bpo-31758: Prevent crashes when using an uninitialized `_elementtree.XMLParser` object. Patch by Oren Milman.

### Documentation

- bpo-27635: The pickle documentation incorrectly claimed that `__new__` isn’t called by default when unpickling.

- bpo-39879: Updated Data model docs to include `dict()` insertion order preservation. Patch by Furkan Onder and Samy Lahfa.

- bpo-38387: Document `PyDoc_STRVAR` macro in the C-API reference.

- bpo-13743: Some methods within xml.dom.minidom.Element class are now better documented.

### Tests

- bpo-31904: Set expected default encoding in test_c_locale_coercion.py for VxWorks RTOS.

- bpo-40162: Update Travis CI configuration to OpenSSL 1.1.1f.

- bpo-40146: Update OpenSSL to 1.1.1f in Azure Pipelines.

- bpo-40094: Add `test.support.wait_process()` function.

- bpo-40003: `test.bisect_cmd` now copies Python command line options like `-O` or `-W`. Moreover, emit a warning if `test.bisect_cmd` is used with `-w`/`--verbose2` option.

- bpo-39380: Add the encoding in `ftplib.FTP` and `ftplib.FTP_TLS` to the constructor as keyword-only and change the default from `latin-1` to `utf-8` to follow RFC 2640.

- bpo-39793: Use the same domain when testing `make_msgid`. Patch by Batuhan Taskaya.

- bpo-1812: Fix newline handling in doctest.testfile when loading from a package whose loader has a get_data method. Patch by Peter Donis.

### Build

- bpo-38360: Support single-argument form of macOS -isysroot flag.

- bpo-40158: Fix CPython MSBuild Properties in NuGet Package (build/native/python.props)

- bpo-38527: Fix configure check on Solaris for “float word ordering”: sometimes, the correct “grep” command was not being used. Patch by Arnon Yaari.

### Windows

- bpo-40164: Updates Windows to OpenSSL 1.1.1f

- bpo-8901: Ignore the Windows registry when the `-E` option is used.

### macOS

- bpo-38329: python.org macOS installers now update the Current version symlink of /Library/Frameworks/Python.framework/Versions for 3.9 installs. Previously, Current was only updated for Python 2.x installs. This should make it easier to embed Python 3 into other macOS applications.

- bpo-40164: Update macOS installer builds to use OpenSSL 1.1.1g.

### IDLE

- bpo-38439: Add a 256×256 pixel IDLE icon to support more modern environments. Created by Andrew Clover. Delete the unused macOS idle.icns icon file.

- bpo-38689: IDLE will no longer freeze when inspect.signature fails when fetching a calltip.

### Tools/Demos

- bpo-40385: Removed the checkpyc.py tool. Please see compileall without force mode as a potential alternative.

- bpo-40179: Fixed translation of `#elif` in Argument Clinic.

- bpo-40094: Fix `which.py` script exit code: it now uses `os.waitstatus_to_exitcode()` to convert `os.system()` exit status into an exit code.

### C API

- bpo-40241: Move the `PyGC_Head` structure to the internal C API.

- bpo-40170: Convert `PyObject_IS_GC()` macro to a function to hide implementation details.

- bpo-40241: Add the functions `PyObject_GC_IsTracked()` and `PyObject_GC_IsFinalized()` to the public API to allow to query if Python objects are being currently tracked or have been already finalized by the garbage collector respectively. Patch by Pablo Galindo.

- bpo-40170: The `PyObject_NEW()` macro becomes an alias to the `PyObject_New()` macro, and the `PyObject_NEW_VAR()` macro becomes an alias to the `PyObject_NewVar()` macro, to hide implementation details. They no longer access directly the `PyTypeObject.tp_basicsize` member.

- bpo-40170: `PyType_HasFeature()` now always calls `PyType_GetFlags()` to hide implementation details. Previously, it accessed directly the `PyTypeObject.tp_flags` member when the limited C API was not used.

- bpo-40170: Convert the `PyObject_GET_WEAKREFS_LISTPTR()` macro to a function to hide implementation details: the macro accessed directly to the `PyTypeObject.tp_weaklistoffset` member.

- bpo-40170: Convert `PyObject_CheckBuffer()` macro to a function to hide implementation details: the macro accessed directly the `PyTypeObject.tp_as_buffer` member.

- bpo-40170: Always declare `PyIndex_Check()` as an opaque function to hide implementation details: remove `PyIndex_Check()` macro. The macro accessed directly the `PyTypeObject.tp_as_number` member.

- bpo-39947: Add `PyThreadState_GetID()` function: get the unique identifier of a Python thread state.

## Python 3.9.0 alpha 5

Release date: 2020-03-23

### Security

- bpo-38576: Disallow control characters in hostnames in http.client, addressing CVE 2019-18348. Such potentially malicious header injection URLs now cause a InvalidURL to be raised.

### Core and Builtins

- bpo-40010: Optimize pending calls in multithreaded applications. If a thread different than the main thread schedules a pending call (`Py_AddPendingCall()`), the bytecode evaluation loop is no longer interrupted at each bytecode instruction to check for pending calls which cannot be executed. Only the main thread can execute pending calls.

  Previously, the bytecode evaluation loop was interrupted at each instruction until the main thread executes pending calls.

- bpo-1635741: Port _weakref extension module to multiphase initialization (PEP 489).

- bpo-1635741: Port _collections module to multiphase initialization (PEP 489).

- bpo-40010: Optimize signal handling in multithreaded applications. If a thread different than the main thread gets a signal, the bytecode evaluation loop is no longer interrupted at each bytecode instruction to check for pending signals which cannot be handled. Only the main thread of the main interpreter can handle signals.

  Previously, the bytecode evaluation loop was interrupted at each instruction until the main thread handles signals.

- bpo-39984: If `Py_AddPendingCall()` is called in a subinterpreter, the function is now scheduled to be called from the subinterpreter, rather than being called from the main interpreter. Each subinterpreter now has its own list of scheduled calls.

- bpo-1635741: Port _heapq module to multiphase initialization.

- bpo-1635741: Port itertools module to multiphase initialization (PEP 489).

- bpo-37207: Speed up calls to `frozenset()` by using the PEP 590 `vectorcall` calling convention. Patch by Donghee Na.

- bpo-39984: subinterpreters: Move `_PyRuntimeState.ceval.tracing_possible` to `PyInterpreterState.ceval.tracing_possible`: each interpreter now has its own variable.

- bpo-37207: Speed up calls to `set()` by using the PEP 590 `vectorcall` calling convention. Patch by Donghee Na.

- bpo-1635741: Port _statistics module to multiphase initialization (PEP 489).

- bpo-39968: Use inline function to replace extension modules’ get_module_state macros.

- bpo-39965: Correctly raise `SyntaxError` if await is used inside non-async functions and `PyCF_ALLOW_TOP_LEVEL_AWAIT` is set (like in the asyncio REPL). Patch by Pablo Galindo.

- bpo-39562: Allow executing asynchronous comprehensions on the top level when the `PyCF_ALLOW_TOP_LEVEL_AWAIT` flag is given. Patch by Batuhan Taskaya.

- bpo-37207: Speed up calls to `tuple()` by using the PEP 590 `vectorcall` calling convention. Patch by Donghee Na.

- bpo-38373: Changed list overallocation strategy. It no longer overallocates if the new size is closer to overallocated size than to the old size and adds padding.

- bpo-39926: Update Unicode database to Unicode version 13.0.0.

- bpo-19466: Clear the frames of daemon threads earlier during the Python shutdown to call objects destructors. So “unclosed file” resource warnings are now emitted for daemon threads in a more reliable way.

- bpo-38894: Fix a bug that was causing incomplete results when calling `pathlib.Path.glob` in the presence of symlinks that point to files where the user does not have read access. Patch by Pablo Galindo and Matt Wozniski.

- bpo-39877: Fix `PyEval_RestoreThread()` random crash at exit with daemon threads. It now accesses the `_PyRuntime` variable directly instead of using `tstate->interp->runtime`, since `tstate` can be a dangling pointer after `Py_Finalize()` has been called. Moreover, the daemon thread now exits before trying to take the GIL.

- bpo-39871: Fix a possible `SystemError` in `math.{atan2,copysign,remainder}()` when the first argument cannot be converted to a `float`. Patch by Zackery Spytz.

- bpo-39776: Fix race condition where threads created by PyGILState_Ensure() could get a duplicate id.

  This affects consumers of tstate->id like the contextvar caching machinery, which could return invalid cached objects under heavy thread load (observed in embedded scenarios).

- bpo-39778: Fixed a crash due to incorrect handling of weak references in `collections.OrderedDict` classes. Patch by Pablo Galindo.

- bpo-1635741: Port audioop extension module to multiphase initialization (PEP 489).

- bpo-39702: Relax decorator grammar restrictions to allow any valid expression (PEP 614).

- bpo-38091: Tweak import deadlock detection code to not deadlock itself.

- bpo-1635741: Port _locale extension module to multiphase initialization (PEP 489).

- bpo-39087: Optimize `PyUnicode_AsUTF8()` and `PyUnicode_AsUTF8AndSize()` slightly when they need to create internal UTF-8 cache.

- bpo-39520: Fix unparsing of ext slices with no items (`foo[:,]`). Patch by Batuhan Taskaya.

- bpo-39220: Do not optimize annotations if ‘from __future__ import annotations’ is used. Patch by Pablo Galindo.

- bpo-35712: Using `NotImplemented` in a boolean context has been deprecated. Patch contributed by Josh Rosenberg.

- bpo-22490: Don’t leak environment variable `__PYVENV_LAUNCHER__` into the interpreter session on macOS.

### Library

- bpo-39830: Add `zipfile.Path` to `__all__` in the `zipfile` module.

- bpo-40000: Improved error messages for validation of `ast.Constant` nodes. Patch by Batuhan Taskaya.

- bpo-39999: `__module__` of the AST node classes is now set to “ast” instead of “_ast”. Added docstrings for dummy AST node classes and deprecated attributes.

- bpo-39991: `uuid.getnode()` now skips IPv6 addresses with the same string length than a MAC address (17 characters): only use MAC addresses.

- bpo-39988: Deprecated `ast.AugLoad` and `ast.AugStore` node classes because they are no longer used.

- bpo-39656: Ensure `bin/python3.#` is always present in virtual environments on POSIX platforms - by Anthony Sottile.

- bpo-39969: Deprecated `ast.Param` node class because it’s no longer used. Patch by Batuhan Taskaya.

- bpo-39360: Ensure all workers exit when finalizing a `multiprocessing.Pool` implicitly via the module finalization handlers of multiprocessing. This fixes a deadlock situation that can be experienced when the Pool is not properly finalized via the context manager or a call to `multiprocessing.Pool.terminate`. Patch by Batuhan Taskaya and Pablo Galindo.

- bpo-35370: sys.settrace(), sys.setprofile() and _lsprof.Profiler.enable() now properly report `PySys_Audit()` error if “sys.setprofile” or “sys.settrace” audit event is denied.

- bpo-39936: AIX: Fix _aix_support module when the subprocess is not available, when building Python from scratch. It now uses new private _bootsubprocess module, rather than having two implementations depending if subprocess is available or not. So _aix_support.aix_platform() result is now the same if subprocess is available or not.

- bpo-36144: `collections.OrderedDict` now implements `|` and `|=` (PEP 584).

- bpo-39652: The column name found in `sqlite3.Cursor.description` is now truncated on the first ‘[’ only if the PARSE_COLNAMES option is set.

- bpo-39915: Ensure `unittest.mock.AsyncMock.await_args_list` has call objects in the order of awaited arguments instead of using `unittest.mock.Mock.call_args` which has the last value of the call. Patch by Karthikeyan Singaravelan.

- bpo-36144: Updated `os.environ` and `os.environb` to support PEP 584’s merge (`|`) and update (`|=`) operators.

- bpo-38662: The `ensurepip` module now invokes `pip` via the `runpy` module. Hence it is no longer tightly coupled with the internal API of the bundled `pip` version, allowing easier updates to a newer `pip` version both internally and for distributors.

- bpo-38075: Fix the `random.Random.seed()` method when a `bool` is passed as the seed.

- bpo-39916: More reliable use of `os.scandir()` in `Path.glob()`. It no longer emits a ResourceWarning when interrupted.

- bpo-39850: `multiprocessing` now supports abstract socket addresses (if abstract sockets are supported in the running platform). When creating arbitrary addresses (like when default-constructing `multiprocessing.connection.Listener` objects) abstract sockets are preferred to avoid the case when the temporary-file-generated address is too large for an AF_UNIX socket address. Patch by Pablo Galindo.

- bpo-36287: `ast.dump()` no longer outputs optional fields and attributes with default values. The default values for optional fields and attributes of AST nodes are now set as class attributes (e.g. `Constant.kind` is set to `None`).

- bpo-39889: Fixed `ast.unparse()` for extended slices containing a single element (e.g. `a[i:j,]`). Remove redundant tuples when index with a tuple (e.g. `a[i, j]`).

- bpo-39828: Fix `json.tool` to catch `BrokenPipeError`. Patch by Donghee Na.

- bpo-13487: Avoid a possible “RuntimeError: dictionary changed size during iteration” from `inspect.getmodule()` when it tried to loop through `sys.modules`.

- bpo-39674: Revert “bpo-37330: open() no longer accept ‘U’ in file mode”. The “U” mode of open() is kept in Python 3.9 to ease transition from Python 2.7, but will be removed in Python 3.10.

- bpo-28577: The hosts method on 32-bit prefix length IPv4Networks and 128-bit prefix IPv6Networks now returns a list containing the single Address instead of an empty list.

- bpo-39826: Add getConnection method to logging HTTPHandler to enable custom connections.

- bpo-39763: Reimplement `distutils.spawn.spawn` function with the `subprocess` module.

- bpo-39794: Add –without-decimal-contextvar build option. This enables a thread-local rather than a coroutine local context.

- bpo-36144: `collections.defaultdict` now implements `|` (PEP 584).

- bpo-39517: Fix runpy.run_path() when using pathlike objects

- bpo-39775: Change `inspect.Signature.parameters` back to `collections.OrderedDict`. This was changed to `dict` in Python 3.9.0a4.

- bpo-39678: Refactor queue_manager in `concurrent.futures.ProcessPoolExecutor` to make it easier to maintain.

- bpo-39764: Fix AttributeError when calling get_stack on a PyAsyncGenObject Task

- bpo-39769: The `compileall.compile_dir()` function’s ddir parameter and the compileall command line flag `-d` no longer write the wrong pathname to the generated pyc file for submodules beneath the root of the directory tree being compiled. This fixes a regression introduced with Python 3.5.

- bpo-36144: `types.MappingProxyType` objects now support the merge (`|`) operator from PEP 584.

- bpo-38691: The `importlib` module now ignores the `PYTHONCASEOK` environment variable when the `-E` or `-I` command line options are being used.

- bpo-39719: Remove `tempfile.SpooledTemporaryFile.softspace()` as files no longer have the `softspace` attribute in Python 3. Patch by Shantanu.

- bpo-39667: Improve pathlib.Path compatibility on zipfile.Path and correct performance degradation as found in zipp 3.0.

- bpo-39638: Keep ASDL signatures in the docstrings for `AST` nodes. Patch by Batuhan Taskaya

- bpo-39639: Deprecated `ast.Suite` node class because it’s no longer used. Patch by Batuhan Taskaya.

- bpo-39609: Add thread_name_prefix to default asyncio executor

- bpo-39548: Fix handling of header in `urllib.request.AbstractDigestAuthHandler` when the optional `qop` parameter is not present.

- bpo-39509: HTTP status codes `103 EARLY_HINTS` and `425 TOO_EARLY` are added to `http.HTTPStatus`. Patch by Donghee Na.

- bpo-39507: Adding HTTP status 418 “I’m a Teapot” to HTTPStatus in http library. Patch by Ross Rhodes.

- bpo-39495: Remove default value from attrs parameter of `xml.etree.ElementTree.TreeBuilder.start()` for consistency between Python and C implementations.

- bpo-38971: Open issue in the BPO indicated a desire to make the implementation of codecs.open() at parity with io.open(), which implements a try/except to assure file stream gets closed before an exception is raised.

- bpo-38641: Added starred expressions support to `return` and `yield` statements for `lib2to3`. Patch by Vlad Emelianov.

- bpo-37534: When using minidom module to generate XML documents the ability to add Standalone Document Declaration is added. All the changes are made to generate a document in compliance with Extensible Markup Language (XML) 1.0 (Fifth Edition) W3C Recommendation (available here: https://www.w3.org/TR/xml/#sec-prolog-dtd).

- bpo-34788: Add support for scoped IPv6 addresses to `ipaddress`. Patch by Oleksandr Pavliuk.

- bpo-34822: Simplified AST for subscription. Simple indices are now represented by their value, extended slices are represented as tuples. `ast` classes `Index` and `ExtSlice` are considered deprecated and will be removed in future Python versions. In the meantime, `Index(value)` now returns a `value` itself, `ExtSlice(slices)` returns `Tuple(slices, Load())`.

### Documentation

- bpo-39868: Updated the Language Reference for PEP 572.

- bpo-13790: Change ‘string’ to ‘specification’ in format doc.

- bpo-17422: The language reference no longer restricts default class namespaces to dicts only.

- bpo-39530: Fix misleading documentation about mixed-type numeric comparisons.

- bpo-39718: Update `token` documentation to reflect additions in Python 3.8

- bpo-39677: Changed operand name of MAKE_FUNCTION from argc to flags for module `dis`

### Tests

- bpo-40019: test_gdb now skips tests if it detects that gdb failed to read debug information because the Python binary is optimized.

- bpo-27807: `test_site.test_startup_imports()` is now skipped if a path of `sys.path` contains a `.pth` file.

- bpo-26067: Do not fail test_shutil test_chown test when uid or gid of user cannot be resolved to a name.

- bpo-39855: test_subprocess.test_user() now skips the test on an user name if the user name doesn’t exist. For example, skip the test if the user “nobody” doesn’t exist on Linux.

### Build

- bpo-39761: Fix build with DTrace but without additional DFLAGS.

- bpo-39763: setup.py now uses a basic implementation of the `subprocess` module if the `subprocess` module is not available: before required C extension modules are built.

- bpo-1294959: Add `--with-platlibdir` option to the configure script: name of the platform-specific library directory, stored in the new `sys.platlibdir` attribute. It is used to build the path of platform-specific extension modules and the path of the standard library. It is equal to `"lib"` on most platforms. On Fedora and SuSE, it is equal to `"lib64"` on 64-bit platforms. Patch by Jan Matějek, Matěj Cepl, Charalampos Stratakis and Victor Stinner.

### Windows

- bpo-39930: Ensures the required `vcruntime140.dll` is included in install packages.

- bpo-39847: Avoid hang when computer is hibernated whilst waiting for a mutex (for lock-related objects from `threading`) around 49-day uptime.

- bpo-38597: `distutils` will no longer statically link `vcruntime140.dll` when a redistributable version is unavailable. All future releases of CPython will include a copy of this DLL to ensure distributed extensions can continue to load.

- bpo-38380: Update Windows builds to use SQLite 3.31.1

- bpo-39789: Update Windows release build machines to Visual Studio 2019 (MSVC 14.2).

- bpo-34803: Package for nuget.org now includes repository reference and bundled icon image.

### macOS

- bpo-38380: Update macOS builds to use SQLite 3.31.1

### IDLE

- bpo-27115: For ‘Go to Line’, use a Query box subclass with IDLE standard behavior and improved error checking.

- bpo-39885: Since clicking to get an IDLE context menu moves the cursor, any text selection should be and now is cleared.

- bpo-39852: Edit “Go to line” now clears any selection, preventing accidental deletion. It also updates Ln and Col on the status bar.

- bpo-39781: Selecting code context lines no longer causes a jump.

### Tools/Demos

- bpo-36184: Port python-gdb.py to FreeBSD. python-gdb.py now checks for “take_gil” function name to check if a frame tries to acquire the GIL, instead of checking for “pthread_cond_timedwait” which is specific to Linux and can be a different condition than the GIL.

- bpo-38080: Added support to fix `getproxies` in the `lib2to3.fixes.fix_urllib` module. Patch by José Roberto Meza Cabrera.

### C API

- bpo-40024: Add `PyModule_AddType()` helper function: add a type to a module. Patch by Donghee Na.

- bpo-39946: Remove `_PyRuntime.getframe` hook and remove `_PyThreadState_GetFrame` macro which was an alias to `_PyRuntime.getframe`. They were only exposed by the internal C API. Remove also `PyThreadFrameGetter` type.

- bpo-39947: Add `PyThreadState_GetFrame()` function: get the current frame of a Python thread state.

- bpo-37207: Add _PyArg_NoKwnames helper function. Patch by Donghee Na.

- bpo-39947: Add `PyThreadState_GetInterpreter()`: get the interpreter of a Python thread state.

- bpo-39947: Add `PyInterpreterState_Get()` function to the limited C API.

- bpo-35370: If `PySys_Audit()` fails in `PyEval_SetProfile()` or `PyEval_SetTrace()`, log the error as an unraisable exception.

- bpo-39947: Move the static inline function flavor of Py_EnterRecursiveCall() and Py_LeaveRecursiveCall() to the internal C API: they access PyThreadState attributes. The limited C API provides regular functions which hide implementation details.

- bpo-39947: Py_TRASHCAN_BEGIN_CONDITION and Py_TRASHCAN_END macro no longer access PyThreadState attributes, but call new private _PyTrash_begin() and _PyTrash_end() functions which hide implementation details.

- bpo-39884: `PyDescr_NewMethod()` and `PyCFunction_NewEx()` now include the method name in the SystemError “bad call flags” error message to ease debug.

- bpo-39877: Deprecated `PyEval_InitThreads()` and `PyEval_ThreadsInitialized()`. Calling `PyEval_InitThreads()` now does nothing.

- bpo-38249: `Py_UNREACHABLE` is now implemented with `__builtin_unreachable()` and analogs in release mode.

- bpo-38643: `PyNumber_ToBase()` now raises a `SystemError` instead of crashing when called with invalid base.

- bpo-39882: The `Py_FatalError()` function is replaced with a macro which logs automatically the name of the current function, unless the `Py_LIMITED_API` macro is defined.

- bpo-39824: Extension modules: `m_traverse`, `m_clear` and `m_free` functions of `PyModuleDef` are no longer called if the module state was requested but is not allocated yet. This is the case immediately after the module is created and before the module is executed (`Py_mod_exec` function). More precisely, these functions are not called if `m_size` is greater than 0 and the module state (as returned by `PyModule_GetState()`) is `NULL`.

  Extension modules without module state (`m_size <= 0`) are not affected.

- bpo-38913: Fixed segfault in `Py_BuildValue()` called with a format containing “#” and undefined PY_SSIZE_T_CLEAN whwn an exception is set.

- bpo-38500: Add a private API to get and set the frame evaluation function: add `_PyInterpreterState_GetEvalFrameFunc()` and `_PyInterpreterState_SetEvalFrameFunc()` C functions. The `_PyFrameEvalFunction` function type now takes a tstate parameter.

## Python 3.9.0 alpha 4

Release date: 2020-02-25

### Security

- bpo-39184: Add audit events to functions in `fcntl`, `msvcrt`, `os`, `resource`, `shutil`, `signal` and `syslog`.

- bpo-39401: Avoid unsafe DLL load at startup on Windows 7 and earlier.

- bpo-39184: Add audit events to command execution functions in os and pty modules.

### Core and Builtins

- bpo-39382: Fix a use-after-free in the single inheritance path of `issubclass()`, when the `__bases__` of an object has a single reference, and so does its first item. Patch by Yonatan Goldschmidt.

- bpo-39573: Update clinic tool to use `Py_IS_TYPE()`. Patch by Donghee Na.

- bpo-39619: Enable use of `os.chroot()` on HP-UX systems.

- bpo-39573: Add `Py_IS_TYPE()` static inline function to check whether the object o type is type.

- bpo-39606: Fix regression caused by fix for bpo-39386, that prevented calling `aclose` on an async generator that had already been closed or exhausted.

- bpo-39579: Change the ending column offset of `Attribute` nodes constructed in `ast_for_dotted_name` to point at the end of the current node and not at the end of the last `NAME` node.

- bpo-1635741: Port _crypt extension module to multiphase initialization (PEP 489).

- bpo-1635741: Port _contextvars extension module to multiphase initialization (PEP 489).

- bpo-39510: Fix segfault in `readinto()` method on closed BufferedReader.

- bpo-39502: Fix `time.localtime()` on 64-bit AIX to support years before 1902 and after 2038. Patch by M Felt.

- bpo-39492: Fix a reference cycle in the C Pickler that was preventing the garbage collection of deleted, pickled objects.

- bpo-39453: Fixed a possible crash in `list.__contains__()` when a list is changed during comparing items. Patch by Donghee Na.

- bpo-39434: floor division of float operation now has a better performance. Also the message of `ZeroDivisionError` for this operation is updated. Patch by Donghee Na.

- bpo-1635741: Port _codecs extension module to multiphase initialization (PEP 489).

- bpo-1635741: Port _bz2 extension module to multiphase initialization (PEP 489).

- bpo-1635741: Port _abc extension module to multiphase initialization (PEP 489).

- bpo-39320: Replace two complex bytecodes for building dicts with two simpler ones. The new bytecodes `DICT_MERGE` and `DICT_UPDATE` have been added The old bytecodes `BUILD_MAP_UNPACK` and `BUILD_MAP_UNPACK_WITH_CALL` have been removed.

- bpo-39219: Syntax errors raised in the tokenizer now always set correct “text” and “offset” attributes.

- bpo-36051: Drop the GIL during large `bytes.join` operations. Patch by Bruce Merry.

- bpo-38960: Fix DTrace build issues on FreeBSD. Patch by David Carlier.

- bpo-37207: Speed up calls to `range()` by about 30%, by using the PEP 590 `vectorcall` calling convention. Patch by Mark Shannon.

- bpo-36144: `dict` (and `collections.UserDict`) objects now support PEP 584’s merge (`|`) and update (`|=`) operators. Patch by Brandt Bucher.

- bpo-32856: Optimized the idiom for assignment a temporary variable in comprehensions. Now `for y in [expr]` in comprehensions is as fast as a simple assignment `y = expr`.

### Library

- bpo-30566: Fix `IndexError` when trying to decode an invalid string with punycode codec.

- bpo-39649: Remove obsolete check for `__args__` in `bdb.Bdb.format_stack_entry`.

- bpo-39648: Expanded `math.gcd()` and `math.lcm()` to handle multiple arguments.

- bpo-39681: Fix a regression where the C pickle module wouldn’t allow unpickling from a file-like object that doesn’t expose a readinto() method.

- bpo-35950: Raise `io.UnsupportedOperation` in `io.BufferedReader.truncate()` when it is called on a read-only `io.BufferedReader` instance.

- bpo-39479: Add `math.lcm()` function: least common multiple.

- bpo-39674: Revert “Do not expose abstract collection classes in the collections module” change (bpo-25988). Aliases to ABC like collections.Mapping are kept in Python 3.9 to ease transition from Python 2.7, but will be removed in Python 3.10.

- bpo-39104: Fix hanging ProcessPoolExcutor on `shutdown(wait=False)` when a task has failed pickling.

- bpo-39627: Fixed TypedDict totality check for inherited keys.

- bpo-39474: Fixed starting position of AST for expressions like `(a)(b)`, `(a)[b]` and `(a).b`.

- bpo-21016: The `pydoc` and `trace` modules now use the `sysconfig` module to get the path to the Python standard library, to support uncommon installation path like `/usr/lib64/python3.9/` on Fedora. Patch by Jan Matějek.

- bpo-39590: Collections.deque now holds strong references during deque.__contains__ and deque.count, fixing crashes.

- bpo-39586: The distutils `bdist_msi` command is deprecated in Python 3.9, use `bdist_wheel` (wheel packages) instead.

- bpo-39595: Improved performance of zipfile.Path for files with a large number of entries. Also improved performance and fixed minor issue as published with importlib_metadata 1.5.

- bpo-39350: Fix regression in `fractions.Fraction` if the numerator and/or the denominator is an `int` subclass. The `math.gcd()` function is now used to normalize the numerator and denominator. `math.gcd()` always return a `int` type. Previously, the GCD type depended on numerator and denominator.

- bpo-39567: Added audit for `os.walk()`, `os.fwalk()`, `pathlib.Path.glob()` and `pathlib.Path.rglob()`.

- bpo-39559: Remove unused, undocumented argument `getters` from `uuid.getnode()`

- bpo-38149: `sys.audit()` is now called only once per call of `glob.glob()` and `glob.iglob()`.

- bpo-39546: Fix a regression in `ArgumentParser` where `allow_abbrev=False` was ignored for long options that used a prefix character other than “-“.

- bpo-39450: Striped whitespace from docstring before returning it from `unittest.case.shortDescription()`.

- bpo-12915: A new function `resolve_name` has been added to the `pkgutil` module. This resolves a string of the form `'a.b.c.d'` or `'a.b:c.d'` to an object. In the example, `a.b` is a package/module and `c.d` is an object within that package/module reached via recursive attribute access.

- bpo-39353: The `binascii.crc_hqx()` function is no longer deprecated.

- bpo-39493: Mark `typing.IO.closed` as a property

- bpo-39491: Add `typing.Annotated` and `include_extras` parameter to `typing.get_type_hints()` as part of PEP 593. Patch by Till Varoquaux, documentation by Till Varoquaux and Konstantin Kashin.

- bpo-39485: Fix a bug in `unittest.mock.create_autospec()` that would complain about the wrong number of arguments for custom descriptors defined in an extension module returning functions.

- bpo-38932: Mock fully resets child objects on reset_mock(). Patch by Vegard Stikbakke

- bpo-39082: Allow AsyncMock to correctly patch static/class methods

- bpo-39432: Implement PEP-489 algorithm for non-ascii “PyInit_…” symbol names in distutils to make it export the correct init symbol also on Windows.

- bpo-18819: Omit `devmajor` and `devminor` fields for non-device files in `tarfile` archives, enabling bit-for-bit compatibility with GNU `tar(1)`.

- bpo-39349: Added a new cancel_futures parameter to `concurrent.futures.Executor.shutdown()` that cancels all pending futures which have not started running, instead of waiting for them to complete before shutting down the executor.

- bpo-39274: `bool(fraction.Fraction)` now returns a boolean even if (numerator != 0) does not return a boolean (ex: numpy number).

- bpo-34793: Remove support for `with (await asyncio.lock):` and `with (yield from asyncio.lock):`. The same is correct for `asyncio.Condition` and `asyncio.Semaphore`.

- bpo-25597: Ensure, if `wraps` is supplied to `unittest.mock.MagicMock`, it is used to calculate return values for the magic methods instead of using the default return values. Patch by Karthikeyan Singaravelan.

- bpo-36350: `inspect.Signature.parameters` and `inspect.BoundArguments.arguments` are now dicts instead of OrderedDicts. Patch contributed by Rémi Lapeyre.

- bpo-35727: Fix sys.exit() and sys.exit(None) exit code propagation when used in multiprocessing.Process.

- bpo-32173: * Add `lazycache` function to `__all__`. * Use `dict.clear` to clear the cache. * Refactoring `getline` function and `checkcache` function.

### Documentation

- bpo-17422: The language reference now specifies restrictions on class namespaces. Adapted from a patch by Ethan Furman.

- bpo-39572: Updated documentation of `total` flag of `TypedDict`.

- bpo-39654: In pyclbr doc, update ‘class’ to ‘module’ where appropriate and add readmodule comment. Patch by Hakan Çelik.

- bpo-39153: Clarify refcounting semantics for the following functions: - PyObject_SetItem - PyMapping_SetItemString - PyDict_SetItem - PyDict_SetItemString

- bpo-39392: Explain that when filling with turtle, overlap regions may be left unfilled.

- bpo-39369: Update mmap readline method description. The fact that the readline method does update the file position should not be ignored since this might give the impression for the programmer that it doesn’t update it.

- bpo-9056: Include subsection in TOC for PDF version of docs.

### Tests

- bpo-38325: Skip tests on non-BMP characters of test_winconsoleio.

- bpo-39502: Skip test_zipfile.test_add_file_after_2107() if `time.localtime()` fails with `OverflowError`. It is the case on AIX 6.1 for example.

### Build

- bpo-39489: Remove `COUNT_ALLOCS` special build.

### Windows

- bpo-39553: Delete unused code related to SxS manifests.

- bpo-39439: Honor the Python path when a virtualenv is active on Windows.

- bpo-39393: Improve the error message when attempting to load a DLL with unresolved dependencies.

- bpo-38883: `home()` and `expanduser()` on Windows now prefer `USERPROFILE` and no longer use `HOME`, which is not normally set for regular user accounts. This makes them again behave like `os.path.expanduser()`, which was changed to ignore `HOME` in 3.8, see bpo-36264.

- bpo-39185: The build.bat script has additional options for very-quiet output (-q) and very-verbose output (-vv)

### IDLE

- bpo-39663: Add tests for pyparse find_good_parse_start().

- bpo-39600: In the font configuration window, remove duplicated font names.

- bpo-30780: Add remaining configdialog tests for buttons and highlights and keys tabs.

- bpo-39388: IDLE Settings Cancel button now cancels pending changes

- bpo-38792: Close an IDLE shell calltip if a `KeyboardInterrupt` or shell restart occurs. Patch by Zackery Spytz.

### C API

- bpo-35081: Move the `bytes_methods.h` header file to the internal C API as `pycore_bytes_methods.h`: it only contains private symbols (prefixed by `_Py`), except of the `PyDoc_STRVAR_shared()` macro.

- bpo-35081: Move the `dtoa.h` header file to the internal C API as `pycore_dtoa.h`: it only contains private functions (prefixed by `_Py`). The `math` and `cmath` modules must now be compiled with the `Py_BUILD_CORE` macro defined.

- bpo-39573: Add `Py_SET_SIZE()` function to set the size of an object.

- bpo-39500: `PyUnicode_IsIdentifier()` does not call `Py_FatalError()` anymore if the string is not ready.

- bpo-39573: Add `Py_SET_TYPE()` function to set the type of an object.

- bpo-39573: Add a `Py_SET_REFCNT()` function to set the reference counter of an object.

- bpo-39542: Convert `PyType_HasFeature()`, `PyType_Check()` and `PyType_CheckExact()` macros to static inline functions.

- bpo-39542: In the limited C API, `PyObject_INIT()` and `PyObject_INIT_VAR()` are now defined as aliases to `PyObject_Init()` and `PyObject_InitVar()` to make their implementation opaque. It avoids to leak implementation details in the limited C API. Exclude the following functions from the limited C API: `_Py_NewReference()`, `_Py_ForgetReference()`, `_PyTraceMalloc_NewReference()` and `_Py_GetRefTotal()`.

- bpo-39542: Exclude trashcan mechanism from the limited C API: it requires access to PyTypeObject and PyThreadState structure fields, whereas these structures are opaque in the limited C API.

- bpo-39511: The `PyThreadState_Clear()` function now calls the `PyThreadState.on_delete` callback. Previously, that happened in `PyThreadState_Delete()`.

- bpo-38076: Fix to clear the interpreter state only after clearing module globals to guarantee module state access from C Extensions during runtime destruction

- bpo-39245: The Vectorcall API (PEP 590) was made public, adding the functions `PyObject_Vectorcall`, `PyObject_VectorcallMethod`, `PyVectorcall_Function`, `PyObject_CallOneArg`, `PyObject_CallMethodNoArgs`, `PyObject_CallMethodOneArg`, `PyObject_FastCallDict`, and the flag `Py_TPFLAGS_HAVE_VECTORCALL`.

## Python 3.9.0 alpha 3

Release date: 2020-01-24

### Core and Builtins

- bpo-39427: Document all possibilities for the `-X` options in the command line help section. Patch by Pablo Galindo.

- bpo-39421: Fix possible crashes when operating with the functions in the `heapq` module and custom comparison operators.

- bpo-39386: Prevent double awaiting of async iterator.

- bpo-17005: Add `functools.TopologicalSorter` to the `functools` module to offers functionality to perform topological sorting of graphs. Patch by Pablo Galindo, Tim Peters and Larry Hastings.

- bpo-39320: Replace four complex bytecodes for building sequences with three simpler ones.

  The following four bytecodes have been removed:

  - BUILD_LIST_UNPACK

  - BUILD_TUPLE_UNPACK

  - BUILD_SET_UNPACK

  - BUILD_TUPLE_UNPACK_WITH_CALL

  The following three bytecodes have been added:

  - LIST_TO_TUPLE

  - LIST_EXTEND

  - SET_UPDATE

- bpo-39336: Import loaders which publish immutable module objects can now publish immutable packages in addition to individual modules.

- bpo-39322: Added a new function `gc.is_finalized()` to check if an object has been finalized by the garbage collector. Patch by Pablo Galindo.

- bpo-39048: Improve the displayed error message when incorrect types are passed to `async with` statements by looking up the `__aenter__()` special method before the `__aexit__()` special method when entering an asynchronous context manager. Patch by Géry Ogam.

- bpo-39235: Fix AST end location for lone generator expression in function call, e.g. f(i for i in a).

- bpo-39209: Correctly handle multi-line tokens in interactive mode. Patch by Pablo Galindo.

- bpo-1635741: Port _json extension module to multiphase initialization (PEP 489).

- bpo-39216: Fix constant folding optimization for positional only arguments - by Anthony Sottile.

- bpo-39215: Fix `SystemError` when nested function has annotation on positional-only argument - by Anthony Sottile.

- bpo-39200: Correct the error message when calling the `min()` or `max()` with no arguments. Patch by Donghee Na.

- bpo-39200: Correct the error message when trying to construct `range` objects with no arguments. Patch by Pablo Galindo.

- bpo-39166: Fix incorrect line execution reporting in trace functions when tracing the last iteration of asynchronous for loops. Patch by Pablo Galindo.

- bpo-39114: Fix incorrect line execution reporting in trace functions when tracing exception handlers with name binding. Patch by Pablo Galindo.

- bpo-39156: Split the COMPARE_OP bytecode instruction into four distinct instructions.

  - COMPARE_OP for rich comparisons

  - IS_OP for ‘is’ and ‘is not’ tests

  - CONTAINS_OP for ‘in’ and ‘is not’ tests

  - JUMP_IF_NOT_EXC_MATCH for checking exceptions in ‘try-except’ statements.

  This improves the clarity of the interpreter and should provide a modest speedup.

- bpo-38588: Fix possible crashes in dict and list when calling `PyObject_RichCompareBool()`.

- bpo-13601: By default, `sys.stderr` is line-buffered now, even if `stderr` is redirected to a file. You can still make `sys.stderr` unbuffered by passing the `-u` command-line option or setting the `PYTHONUNBUFFERED` environment variable.

  (Contributed by Jendrik Seipp in bpo-13601.)

- bpo-38610: Fix possible crashes in several list methods by holding strong references to list elements when calling `PyObject_RichCompareBool()`.

- bpo-32021: Include brotli .br encoding in mimetypes encodings_map

### Library

- bpo-39430: Fixed race condition in lazy imports in `tarfile`.

- bpo-39413: The `os.unsetenv()` function is now also available on Windows.

- bpo-39390: Fixed a regression with the `ignore` callback of `shutil.copytree()`. The argument types are now `str` and `List[str]` again.

- bpo-39395: The `os.putenv()` and `os.unsetenv()` functions are now always available.

- bpo-39406: If `setenv()` C function is available, `os.putenv()` is now implemented with `setenv()` instead of `putenv()`, so Python doesn’t have to handle the environment variable memory.

- bpo-39396: Fix `math.nextafter(-0.0, +0.0)` on AIX 7.1.

- bpo-29435: Allow `tarfile.is_tarfile()` to be used with file and file-like objects, like `zipfile.is_zipfile()`. Patch by William Woodruff.

- bpo-39377: Removed `encoding` option from `json.loads()`. It has been deprecated since Python 3.1.

- bpo-39389: Write accurate compression level metadata in `gzip` archives, rather than always signaling maximum compression.

- bpo-39366: The previously deprecated `xpath()` and `xgtitle()` methods of `nntplib.NNTP` have been removed.

- bpo-39357: Remove the buffering parameter of `bz2.BZ2File`. Since Python 3.0, it was ignored and using it was emitting `DeprecationWarning`. Pass an open file object, to control how the file is opened. The compresslevel parameter becomes keyword-only.

- bpo-39353: Deprecate binhex4 and hexbin4 standards. Deprecate the `binhex` module and the following `binascii` functions: `b2a_hqx()`, `a2b_hqx()`, `rlecode_hqx()`, `rledecode_hqx()`, `crc_hqx()`.

- bpo-39351: Remove `base64.encodestring()` and `base64.decodestring()`, aliases deprecated since Python 3.1: use `base64.encodebytes()` and `base64.decodebytes()` instead.

- bpo-39350: Remove `fractions.gcd()` function, deprecated since Python 3.5 (bpo-22486): use `math.gcd()` instead.

- bpo-39329: `LMTP` constructor now has an optional timeout parameter. Patch by Donghee Na.

- bpo-39313: Add a new `exec_function` option (–exec-function in the CLI) to `RefactoringTool` for making `exec` a function. Patch by Batuhan Taskaya.

- bpo-39259: `FTP_TLS` and `FTP_TLS` now raise a `ValueError` if the given timeout for their constructor is zero to prevent the creation of a non-blocking socket. Patch by Donghee Na.

- bpo-39259: `SMTP` and `SMTP_SSL` now raise a `ValueError` if the given timeout for their constructor is zero to prevent the creation of a non-blocking socket. Patch by Donghee Na.

- bpo-39310: Add `math.ulp()`: return the value of the least significant bit of a float.

- bpo-39297: Improved performance of importlib.metadata distribution discovery and resilients to inaccessible sys.path entries (importlib_metadata v1.4.0).

- bpo-39259: `NNTP` and `NNTP_SSL` now raise a `ValueError` if the given timeout for their constructor is zero to prevent the creation of a non-blocking socket. Patch by Donghee Na.

- bpo-38901: When you specify prompt=’.’ or equivalently python -m venv –prompt . … the basename of the current directory is used to set the created venv’s prompt when it’s activated.

- bpo-39288: Add `math.nextafter()`: return the next floating-point value after x towards y.

- bpo-39259: `POP3` and `POP3_SSL` now raise a `ValueError` if the given timeout for their constructor is zero to prevent the creation of a non-blocking socket. Patch by Donghee Na.

- bpo-39242: Updated the Gmane domain from news.gmane.org to news.gmane.io which is used for examples of `NNTP` news reader server and nntplib tests.

- bpo-35292: Proxy the `SimpleHTTPRequestHandler.guess_type` to `mimetypes.guess_type` so the `mimetypes.init` is called lazily to avoid unnecessary costs when `http.server` module is imported.

- bpo-39239: The `select.epoll.unregister()` method no longer ignores the `EBADF` error.

- bpo-38907: In http.server script, restore binding to IPv4 on Windows.

- bpo-39152: Fix ttk.Scale.configure([name]) to return configuration tuple for name or all options. Giovanni Lombardo contributed part of the patch.

- bpo-39198: If an exception were to be thrown in `Logger.isEnabledFor` (say, by asyncio timeouts or stopit) , the `logging` global lock may not be released appropriately, resulting in deadlock. This change wraps that block of code with `try...finally` to ensure the lock is released.

- bpo-39191: Perform a check for running loop before starting a new task in `loop.run_until_complete()` to fail fast; it prevents the side effect of new task spawning before exception raising.

- bpo-38871: Correctly parenthesize filter-based statements that contain lambda expressions in `lib2to3`. Patch by Donghee Na.

- bpo-39142: A change was made to logging.config.dictConfig to avoid converting instances of named tuples to ConvertingTuple. It’s assumed that named tuples are too specialised to be treated like ordinary tuples; if a user of named tuples requires ConvertingTuple functionality, they will have to implement that themselves in their named tuple class.

- bpo-39158: ast.literal_eval() now supports empty sets.

- bpo-39129: Fix import path for `asyncio.TimeoutError`

- bpo-39057: `urllib.request.proxy_bypass_environment()` now ignores leading dots and no longer ignores a trailing newline.

- bpo-39056: Fixed handling invalid warning category in the -W option. No longer import the re module if it is not needed.

- bpo-39055: `base64.b64decode()` with `validate=True` raises now a binascii.Error if the input ends with a single `\n`.

- bpo-21600: Fix `mock.patch.stopall()` to stop active patches that were created with `mock.patch.dict()`.

- bpo-39019: Implement dummy `__class_getitem__` for `tempfile.SpooledTemporaryFile`.

- bpo-39019: Implement dummy `__class_getitem__` for `subprocess.Popen`, `subprocess.CompletedProcess`

- bpo-38914: Adjusted the wording of the warning issued by distutils’ `check` command when the `author` and `maintainer` fields are supplied but no corresponding e-mail field (`author_email` or `maintainer_email`) is found. The wording now reflects the fact that these fields are suggested, but not required. Patch by Juergen Gmach.

- bpo-38878: Fixed __subclasshook__ of `os.PathLike` to return a correct result upon inheritance. Patch by Bar Harel.

- bpo-38615: `IMAP4` and `IMAP4_SSL` now have an optional timeout parameter for their constructors. Also, the `open()` method now has an optional timeout parameter with this change. The overridden methods of `IMAP4_SSL` and `IMAP4_stream` were applied to this change. Patch by Donghee Na.

- bpo-35182: Fixed `Popen.communicate()` subsequent call crash when the child process has already closed any piped standard stream, but still continues to be running. Patch by Andriy Maletsky.

- bpo-38630: On Unix, `subprocess.Popen.send_signal()` now polls the process status. Polling reduces the risk of sending a signal to the wrong process if the process completed, the `subprocess.Popen.returncode` attribute is still `None`, and the pid has been reassigned (recycled) to a new different process.

- bpo-38536: Removes trailing space in formatted currency with `international=True` and a locale with symbol following value. E.g. `locale.currency(12.34, international=True)` returned `'12,34 EUR '` instead of `'12,34 EUR'`.

- bpo-38473: Use signature from inner mock for autospecced methods attached with `unittest.mock.attach_mock()`. Patch by Karthikeyan Singaravelan.

- bpo-38361: Fixed an issue where `ident` could include a leading path separator when `syslog.openlog()` was called without arguments.

- bpo-38293: Add `copy.copy()` and `copy.deepcopy()` support to `property()` objects.

- bpo-37958: Added the pstats.Stats.get_profile_dict() method to return the profile data as a StatsProfile instance.

- bpo-28367: Termios magic constants for the following baud rates: - B500000 - B576000 - B921600 - B1000000 - B1152000 - B1500000 - B2000000 - B2500000 - B3000000 - B3500000 - B4000000 Patch by Andrey Smirnov

### Documentation

- bpo-39381: Mention in docs that `asyncio.get_event_loop()` implicitly creates new event loop only if called from the main thread.

- bpo-38918: Add an entry for `__module__` in the “function” & “method” sections of the `inspect` docs’ Types and members table.

- bpo-3530: In the `ast` module documentation, fix a misleading `NodeTransformer` example and add advice on when to use the `fix_missing_locations` function.

### Build

- bpo-39395: On non-Windows platforms, the `setenv()` and `unsetenv()` functions are now required to build Python.

- bpo-39160: Updated the documentation in `./configure --help` to show default values, reference documentation where required and add additional explanation where needed.

- bpo-39144: The ctags and etags build targets both include Modules/_ctypes and Python standard library source files.

### IDLE

- bpo-39050: Make IDLE Settings dialog Help button work again.

- bpo-34118: Tag memoryview, range, and tuple as classes, the same as list, etcetera, in the library manual built-in functions list.

- bpo-32989: Add tests for editor newline_and_indent_event method. Remove dead code from pyparse find_good_parse_start method.

### C API

- bpo-39372: Clean header files of interfaces defined but with no implementation. The public API symbols being removed are: `_PyBytes_InsertThousandsGroupingLocale`, `_PyBytes_InsertThousandsGrouping`, `_Py_InitializeFromArgs`, `_Py_InitializeFromWideArgs`, `_PyFloat_Repr`, `_PyFloat_Digits`, `_PyFloat_DigitsInit`, `PyFrame_ExtendStack`, `_PyAIterWrapper_Type`, `PyNullImporter_Type`, `PyCmpWrapper_Type`, `PySortWrapper_Type`, `PyNoArgsFunction`.

- bpo-39164: Add a private `_PyErr_GetExcInfo()` function to retrieve exception information of the specified Python thread state.

## Python 3.9.0 alpha 2

Release date: 2019-12-18

### Security

- bpo-38945: Newline characters have been escaped when performing uu encoding to prevent them from overflowing into to content section of the encoded file. This prevents malicious or accidental modification of data during the decoding process.

- bpo-37228: Due to significant security concerns, the reuse_address parameter of `asyncio.loop.create_datagram_endpoint()` is no longer supported. This is because of the behavior of `SO_REUSEADDR` in UDP. For more details, see the documentation for `loop.create_datagram_endpoint()`. (Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in bpo-37228.)

- bpo-38804: Fixes a ReDoS vulnerability in `http.cookiejar`. Patch by Ben Caller.

### Core and Builtins

- bpo-39028: Slightly improve the speed of keyword argument parsing with many kwargs by strengthening the assumption that kwargs are interned strings.

- bpo-39080: Fix the value of end_col_offset for Starred Expression AST nodes when they are among the elements in the args attribute of Call AST nodes.

- bpo-39031: When parsing an “elif” node, lineno and col_offset of the node now point to the “elif” keyword and not to its condition, making it consistent with the “if” node. Patch by Lysandros Nikolaou.

- bpo-20443: In Python 3.9.0a1, sys.argv[0] was made an absolute path if a filename was specified on the command line. Revert this change, since most users expect sys.argv to be unmodified.

- bpo-39008: `PySys_Audit()` now requires `Py_ssize_t` to be used for size arguments in the format string, regardless of whether `PY_SSIZE_T_CLEAN` was defined at include time.

- bpo-38673: In REPL mode, don’t switch to PS2 if the line starts with comment or whitespace. Based on work by Batuhan Taşkaya.

- bpo-38922: Calling `replace` on a code object now raises the `code.__new__` audit event.

- bpo-38920: Add audit hooks for when `sys.excepthook()` and `sys.unraisablehook()` are invoked.

- bpo-38892: Improve documentation for audit events table and functions.

- bpo-38852: Set the thread stack size to 8 Mb for debug builds on android platforms.

- bpo-38858: Each Python subinterpreter now has its own “small integer singletons”: numbers in [-5; 257] range. It is no longer possible to change the number of small integers at build time by overriding `NSMALLNEGINTS` and `NSMALLPOSINTS` macros: macros should now be modified manually in `pycore_pystate.h` header file.

- bpo-36854: The garbage collector state becomes per interpreter (`PyInterpreterState.gc`), rather than being global (`_PyRuntimeState.gc`).

- bpo-38835: The `PyFPE_START_PROTECT()` and `PyFPE_END_PROTECT()` macros are empty: they have been doing nothing for the last year, so stop using them.

- bpo-38328: Sped up the creation time of constant `list` and `set` displays. Patch by Brandt Bucher.

- bpo-38707: `MainThread.native_id` is now correctly reset in child processes spawned using `multiprocessing.Process`, instead of retaining the parent’s value.

- bpo-38629: Added `__floor__` and `__ceil__` methods to float object. Patch by Batuhan Taşkaya.

- bpo-27145: int + int and int - int operators can now return small integer singletons. Patch by hongweipeng.

- bpo-38021: Provide a platform tag for AIX that is sufficient for PEP425 binary distribution identification. Patch by Michael Felt.

- bpo-35409: Ignore GeneratorExit exceptions when throwing an exception into the aclose coroutine of an asynchronous generator.

- bpo-33387: Removed WITH_CLEANUP_START, WITH_CLEANUP_FINISH, BEGIN_FINALLY, END_FINALLY, CALL_FINALLY and POP_FINALLY bytecodes. Replaced with RERAISE and WITH_EXCEPT_START bytecodes. The compiler now generates different code for exceptional and non-exceptional branches for ‘with’ and ‘try-except’ statements. For ‘try-finally’ statements the ‘finally’ block is replicated for each exit from the ‘try’ body.

### Library

- bpo-39033: Fix `NameError` in `zipimport`. Patch by Karthikeyan Singaravelan.

- bpo-39022: Update importlib.metadata to include improvements from importlib_metadata 1.3 including better serialization of EntryPoints and improved documentation for custom finders.

- bpo-39006: Fix asyncio when the ssl module is missing: only check for ssl.SSLSocket instance if the ssl module is available.

- bpo-38708: Fix a potential IndexError in email parser when parsing an empty msg-id.

- bpo-38698: Add a new `InvalidMessageID` token to email parser to represent invalid Message-ID headers. Also, add defects when there is remaining value after parsing the header.

- bpo-38994: Implement `__class_getitem__` for `os.PathLike`, `pathlib.Path`.

- bpo-38979: Return class from `ContextVar.__class_getitem__` to simplify subclassing.

- bpo-38978: Implement `__class_getitem__` on asyncio objects (Future, Task, Queue). Patch by Batuhan Taskaya.

- bpo-38916: `array.array`: Remove `tostring()` and `fromstring()` methods. They were aliases to `tobytes()` and `frombytes()`, deprecated since Python 3.2.

- bpo-38986: Make repr of C accelerated TaskWakeupMethWrapper the same as of pure Python version.

- bpo-38982: Fix asyncio `PidfdChildWatcher`: handle `waitpid()` error. If `waitpid()` is called elsewhere, `waitpid()` call fails with `ChildProcessError`: use return code 255 in this case, and log a warning. It ensures that the pidfd file descriptor is closed if this error occurs.

- bpo-38529: Drop too noisy asyncio warning about deletion of a stream without explicit `.close()` call.

- bpo-27413: Added ability to pass through `ensure_ascii` options to json.dumps in the `json.tool` command-line interface.

- bpo-38634: The `readline` module now detects if Python is linked to libedit at runtime on all platforms. Previously, the check was only done on macOS.

- bpo-33684: Fix `json.tool` failed to read a JSON file with non-ASCII characters when locale encoding is not UTF-8.

- bpo-38698: Prevent UnboundLocalError to pop up in parse_message_id.

  parse_message_id() was improperly using a token defined inside an exception handler, which was raising `UnboundLocalError` on parsing an invalid value. Patch by Claudiu Popa.

- bpo-38927: Use `python -m pip` instead of `pip` to upgrade dependencies in venv.

- bpo-26730: Fix `SpooledTemporaryFile.rollover()` might corrupt the file when it is in text mode. Patch by Serhiy Storchaka.

- bpo-38881: random.choices() now raises a ValueError when all the weights are zero.

- bpo-38876: Raise pickle.UnpicklingError when loading an item from memo for invalid input.

  The previous code was raising a `KeyError` for both the Python and C implementation. This was caused by the specified index of an invalid input which did not exist in the memo structure, where the pickle stores what objects it has seen. The malformed input would have caused either a `BINGET` or `LONG_BINGET` load from the memo, leading to a `KeyError` as the determined index was bogus. Patch by Claudiu Popa.

- bpo-38688: Calling func:`shutil.copytree` to copy a directory tree from one directory to another subdirectory resulted in an endless loop and a RecursionError. A fix was added to consume an iterator and create the list of the entries to be copied, avoiding the recursion for newly created directories. Patch by Bruno P. Kinoshita.

- bpo-38863: Improve `is_cgi()` function in `http.server`, which enables processing the case that cgi directory is a child of another directory other than root.

- bpo-37838: `typing.get_type_hints()` properly handles functions decorated with `functools.wraps()`.

- bpo-38870: Expose `ast.unparse()` as a function of the `ast` module that can be used to unparse an `ast.AST` object and produce a string with code that would produce an equivalent `ast.AST` object when parsed. Patch by Pablo Galindo and Batuhan Taskaya.

- bpo-38859: AsyncMock now returns StopAsyncIteration on the exhaustion of a side_effects iterable. Since PEP-479 its Impossible to raise a StopIteration exception from a coroutine.

- bpo-38857: AsyncMock fix for return values that are awaitable types. This also covers side_effect iterable values that happened to be awaitable, and wraps callables that return an awaitable type. Before these awaitables were being awaited instead of being returned as is.

- bpo-38834: `typing.TypedDict` subclasses now track which keys are optional using the `__required_keys__` and `__optional_keys__` attributes, to enable runtime validation by downstream projects. Patch by Zac Hatfield-Dodds.

- bpo-38821: Fix unhandled exceptions in `argparse` when internationalizing error messages for arguments with `nargs` set to special (non-integer) values. Patch by Federico Bond.

- bpo-38820: Make Python compatible with OpenSSL 3.0.0. `ssl.SSLSocket.getpeercert()` no longer returns IPv6 addresses with a trailing new line.

- bpo-38811: Fix an unhandled exception in `pathlib` when `os.link()` is missing. Patch by Toke Høiland-Jørgensen.

- bpo-38686: Added support for multiple `qop` values in `urllib.request.AbstractDigestAuthHandler`.

- bpo-38712: Add the Linux-specific `signal.pidfd_send_signal()` function, which allows sending a signal to a process identified by a file descriptor rather than a pid.

- bpo-38348: Add `-i` and `--indent` (indentation level), and `--no-type-comments` (type comments) command line options to ast parsing tool.

- bpo-37523: Change `zipfile.ZipExtFile` to raise `ValueError` when trying to access the underlying file object after it has been closed. This new behavior is consistent with how accessing closed files is handled in other parts of Python.

- bpo-38045: Improve the performance of `enum._decompose()` in `enum`. Patch by hongweipeng.

- bpo-36820: Break cycle generated when saving an exception in socket.py, codeop.py and dyld.py as they keep alive not only the exception but user objects through the `__traceback__` attribute. Patch by Mario Corchero.

- bpo-36406: Handle namespace packages in `doctest`. Patch by Karthikeyan Singaravelan.

- bpo-34776: Fix dataclasses to support forward references in type annotations

- bpo-20928: ElementTree supports recursive XInclude processing. Patch by Stefan Behnel.

- bpo-29636: Add whitespace options for formatting JSON with the `json.tool` CLI. The following mutually exclusive options are now supported: `--indent` for setting the indent level in spaces; `--tab` for indenting with tabs; `--no-indent` for suppressing newlines; and `--compact` for suppressing all whitespace. The default behavior remains the same as `--indent=4`.

### Documentation

- bpo-38928: Correct when venv’s `upgrade_dependencies()` and `--upgrade-deps` are added.

- bpo-38899: Update documentation to state that to activate virtual environments under fish one should use `source`, not `.` as documented at https://fishshell.com/docs/current/cmds/source.html.

- bpo-22377: Improves documentation of the values that `datetime.datetime.strptime()` accepts for `%Z`. Patch by Karl Dubost.

### Tests

- bpo-38546: Fix test_ressources_gced_in_workers() of test_concurrent_futures: explicitly stop the manager to prevent leaking a child process running in the background after the test completes.

- bpo-38546: Multiprocessing and concurrent.futures tests now stop the resource tracker process when tests complete.

- bpo-38614: Replace hardcoded timeout constants in tests with new `test.support` constants: `LOOPBACK_TIMEOUT`, `INTERNET_TIMEOUT`, `SHORT_TIMEOUT` and `LONG_TIMEOUT`. It becomes easier to adjust these four timeout constants for all tests at once, rather than having to adjust every single test file.

- bpo-38547: Fix test_pty: if the process is the session leader, closing the master file descriptor raises a SIGHUP signal: simply ignore SIGHUP when running the tests.

- bpo-38992: Fix a test for `math.fsum()` that was failing due to constant folding.

- bpo-38991: `test.support`: `run_python_until_end()`, `assert_python_ok()` and `assert_python_failure()` functions no longer strip whitespaces from stderr. Remove `test.support.strip_python_stderr()` function.

- bpo-38965: Fix test_faulthandler on GCC 10. Use the “volatile” keyword in `faulthandler._stack_overflow()` to prevent tail call optimization on any compiler, rather than relying on compiler specific pragma.

- bpo-38875: test_capi: trashcan tests now require the test “cpu” resource.

- bpo-38841: Skip asyncio test_create_datagram_endpoint_existing_sock_unix on platforms lacking a functional bind() for named unix domain sockets.

- bpo-38692: Skip the test_posix.test_pidfd_open() test if `os.pidfd_open()` fails with a `PermissionError`. This situation can happen in a Linux sandbox using a syscall whitelist which doesn’t allow the `pidfd_open()` syscall yet.

- bpo-38839: Fix some unused functions in tests. Patch by Adam Johnson.

- bpo-38669: Raise `TypeError` when passing target as a string with `unittest.mock.patch.object()`.

- bpo-37957: test.regrtest now can receive a list of test patterns to ignore (using the -i/–ignore argument) or a file with a list of patterns to ignore (using the –ignore-file argument). Patch by Pablo Galindo.

### Build

- bpo-37404: `asyncio` now raises `TypeError` when calling incompatible methods with an `ssl.SSLSocket` socket. Patch by Ido Michael.

- bpo-36500: Added an optional “regen” project to the Visual Studio solution that will regenerate all grammar, tokens, and opcodes.

### Windows

- bpo-39007: Add auditing events to functions in `winreg`.

- bpo-33125: Add support for building and releasing Windows ARM64 packages.

### macOS

- bpo-37931: Fixed a crash on OSX dynamic builds that occurred when re-initializing the posix module after a Py_Finalize if the environment had changed since the previous `import posix`. Patch by Benoît Hudson.

### IDLE

- bpo-38944: Escape key now closes IDLE completion windows. Patch by Johnny Najera.

- bpo-38943: Fix IDLE autocomplete windows not always appearing on some systems. Patch by Johnny Najera.

- bpo-38862: ‘Strip Trailing Whitespace’ on the Format menu removes extra newlines at the end of non-shell files.

- bpo-38636: Fix IDLE Format menu tab toggle and file indent width. These functions (default shortcuts Alt-T and Alt-U) were mistakenly disabled in 3.7.5 and 3.8.0.

### C API

- bpo-38896: Remove `PyUnicode_ClearFreeList()` function: the Unicode free list has been removed in Python 3.3.

- bpo-37340: Remove `PyMethod_ClearFreeList()` and `PyCFunction_ClearFreeList()` functions: the free lists of bound method objects have been removed.

- bpo-38835: Exclude `PyFPE_START_PROTECT()` and `PyFPE_END_PROTECT()` macros of `pyfpe.h` from `Py_LIMITED_API` (stable API).

## Python 3.9.0 alpha 1

Release date: 2019-11-19

### Security

- bpo-38722: `runpy` now uses `io.open_code()` to open code files. Patch by Jason Killen.

- bpo-38622: Add additional audit events for the `ctypes` module.

- bpo-38418: Fixes audit event for `os.system()` to be named `os.system`.

- bpo-38243: Escape the server title of `xmlrpc.server.DocXMLRPCServer` when rendering the document page as HTML. (Contributed by Donghee Na in bpo-38243.)

- bpo-38174: Update vendorized expat library version to 2.2.8, which resolves CVE 2019-15903.

- bpo-37764: Fixes email._header_value_parser.get_unstructured going into an infinite loop for a specific case in which the email header does not have trailing whitespace, and the case in which it contains an invalid encoded word. Patch by Ashwin Ramaswami.

- bpo-37461: Fix an infinite loop when parsing specially crafted email headers. Patch by Abhilash Raj.

- bpo-37363: Adds audit events for the range of supported run commands (see Command line and environment).

- bpo-37463: ssl.match_hostname() no longer accepts IPv4 addresses with additional text after the address and only quad-dotted notation without trailing whitespaces. Some inet_aton() implementations ignore whitespace and all data after whitespace, e.g. ‘127.0.0.1 whatever’.

- bpo-37363: Adds audit events for `ensurepip`, `ftplib`, `glob`, `imaplib`, `nntplib`, `pdb`, `poplib`, `shutil`, `smtplib`, `sqlite3`, `subprocess`, `telnetlib`, `tempfile` and `webbrowser`, as well as `os.listdir()`, `os.scandir()` and `breakpoint()`.

- bpo-37364: `io.open_code()` is now used when reading `.pth` files.

- bpo-34631: Updated OpenSSL to 1.1.1c in Windows installer

- bpo-34155: Fix parsing of invalid email addresses with more than one `@` (e.g. a@b@c.com.) to not return the part before 2nd `@` as valid email address. Patch by maxking & jpic.

### Core and Builtins

- bpo-38631: Replace `Py_FatalError()` call with a regular `RuntimeError` exception in `float.__getformat__()`.

- bpo-38639: Optimized `math.floor()`, `math.ceil()` and `math.trunc()` for floats.

- bpo-38640: Fixed a bug in the compiler that was causing to raise in the presence of break statements and continue statements inside always false while loops. Patch by Pablo Galindo.

- bpo-38613: Optimized some set operations (e.g. `|`, `^`, and `-`) of `dict_keys`. `d.keys() | other` was slower than `set(d) | other` but they are almost same performance for now.

- bpo-28029: `"".replace("", s, n)` now returns `s` instead of an empty string for all non-zero `n`. There are similar changes for `bytes` and `bytearray` objects.

- bpo-38535: Fixed line numbers and column offsets for AST nodes for calls without arguments in decorators.

- bpo-38525: Fix a segmentation fault when using reverse iterators of empty `dict` objects. Patch by Donghee Na and Inada Naoki.

- bpo-38465: `bytearray`, `array` and `mmap` objects allow now to export more than `2**31` buffers at a time.

- bpo-38469: Fixed a bug where the scope of named expressions was not being resolved correctly in the presence of the global keyword. Patch by Pablo Galindo.

- bpo-38437: Activate the `GC_DEBUG` macro for debug builds of the interpreter (when `Py_DEBUG` is set). Patch by Pablo Galindo.

- bpo-38379: When the garbage collector makes a collection in which some objects resurrect (they are reachable from outside the isolated cycles after the finalizers have been executed), do not block the collection of all objects that are still unreachable. Patch by Pablo Galindo and Tim Peters.

- bpo-38379: When cyclic garbage collection (gc) runs finalizers that resurrect unreachable objects, the current gc run ends, without collecting any cyclic trash. However, the statistics reported by `collect()` and `get_stats()` claimed that all cyclic trash found was collected, and that the resurrected objects were collected. Changed the stats to report that none were collected.

- bpo-38392: In debug mode, `PyObject_GC_Track()` now calls `tp_traverse()` of the object type to ensure that the object is valid: test that objects visited by `tp_traverse()` are valid.

- bpo-38210: Remove unnecessary intersection and update set operation in dictview with empty set. (Contributed by Donghee Na in bpo-38210.)

- bpo-38402: Check the error from the system’s underlying `crypt` or `crypt_r`.

- bpo-37474: On FreeBSD, Python no longer calls `fedisableexcept()` at startup to control the floating-point control mode. The call became useless since FreeBSD 6: it became the default mode.

- bpo-38006: Fix a bug due to the interaction of weakrefs and the cyclic garbage collector. We must clear any weakrefs in garbage in order to prevent their callbacks from executing and causing a crash.

- bpo-38317: Fix warnings options priority: `PyConfig.warnoptions` has the highest priority, as stated in the PEP 587.

- bpo-38310: Predict `BUILD_MAP_UNPACK_WITH_CALL` -> `CALL_FUNCTION_EX` opcode pairs in the main interpreter loop. Patch by Brandt Bucher.

- bpo-36871: Improve error handling for the assert_has_calls and assert_has_awaits methods of mocks. Fixed a bug where any errors encountered while binding the expected calls to the mock’s spec were silently swallowed, leading to misleading error output.

- bpo-11410: Better control over symbol visibility is provided through use of the visibility attributes available in gcc >= 4.0, provided in a uniform way across POSIX and Windows. The POSIX build files have been updated to compile with -fvisibility=hidden, minimising exported symbols.

- bpo-38219: Optimized the `dict` constructor and the `update()` method for the case when the argument is a dict.

- bpo-38236: Python now dumps path configuration if it fails to import the Python codecs of the filesystem and stdio encodings.

- bpo-38013: Allow to call `async_generator_athrow().throw(...)` even for non-started async generator helper. It fixes annoying warning at the end of `asyncio.run()` call.

- bpo-38124: Fix an off-by-one error in PyState_AddModule that could cause out-of-bounds memory access.

- bpo-38116: The select module is now PEP-384 compliant and no longer has static state

- bpo-38113: ast module updated to PEP-384 and all statics removed

- bpo-38076: The struct module is now PEP-384 compatible

- bpo-38075: The random module is now PEP-384 compatible

- bpo-38074: zlib module made PEP-384 compatible

- bpo-38073: Make pwd extension module PEP-384 compatible

- bpo-38072: grp module made PEP-384 compatible

- bpo-38069: Make _posixsubprocess PEP-384 compatible

- bpo-38071: Make termios extension module PEP-384 compatible

- bpo-38005: Fixed comparing and creating of InterpreterID and ChannelID.

- bpo-36946: Fix possible signed integer overflow when handling slices. Patch by hongweipeng.

- bpo-37994: Fixed silencing arbitrary errors if an attribute lookup fails in several sites. Only AttributeError should be silenced.

- bpo-8425: Optimize set difference_update for the case when the other set is much larger than the base set. (Suggested by Evgeny Kapun with code contributed by Michele Orrù).

- bpo-37966: The implementation of `is_normalized()` has been greatly sped up on strings that aren’t normalized, by implementing the full normalization-quick-check algorithm from the Unicode standard.

- bpo-37947: Adjust correctly the recursion level in the symtable generation for named expressions. Patch by Pablo Galindo.

- bpo-37812: The `CHECK_SMALL_INT` macro used inside `Object/longobject.c` has been replaced with an explicit `return` at each call site.

- bpo-37751: Fix `codecs.lookup()` to normalize the encoding name the same way than `encodings.normalize_encoding()`, except that `codecs.lookup()` also converts the name to lower case.

- bpo-37830: Fixed compilation of `break` and `continue` in the `finally` block when the corresponding `try` block contains `return` with a non-constant value.

- bpo-20490: Improve import error message for partially initialized module on circular `from` imports - by Anthony Sottile.

- bpo-37840: Fix handling of negative indices in `sq_item` of `bytearray`. Patch by Sergey Fedoseev.

- bpo-37802: Slightly improve performance of `PyLong_FromUnsignedLong()`, `PyLong_FromUnsignedLongLong()` and `PyLong_FromSize_t()`. Patch by Sergey Fedoseev.

- bpo-37409: Ensure explicit relative imports from interactive sessions and scripts (having no parent package) always raise ImportError, rather than treating the current module as the package. Patch by Ben Lewis.

- bpo-32912: Reverted bpo-32912: emitting `SyntaxWarning` instead of `DeprecationWarning` for invalid escape sequences in string and bytes literals.

- bpo-37757: PEP 572: As described in the PEP, assignment expressions now raise `SyntaxError` when their interaction with comprehension scoping results in an ambiguous target scope.

  The `TargetScopeError` subclass originally proposed by the PEP has been removed in favour of just raising regular syntax errors for the disallowed cases.

- bpo-36279: Fix potential use of uninitialized memory in `os.wait3()`.

- bpo-36311: Decoding bytes objects larger than 2GiB is faster and no longer fails when a multibyte characters spans a chunk boundary.

- bpo-34880: The `assert` statement now works properly if the `AssertionError` exception is being shadowed. Patch by Zackery Spytz.

- bpo-37340: Removed object cache (`free_list`) for bound method objects. Temporary bound method objects are less used than before thanks to the `LOAD_METHOD` opcode and the `_PyObject_VectorcallMethod` C API.

- bpo-37648: Fixed minor inconsistency in `list.__contains__()`, `tuple.__contains__()` and a few other places. The collection’s item is now always at the left and the needle is on the right of `==`.

- bpo-37444: Update differing exception between `builtins.__import__()` and `importlib.__import__()`.

- bpo-37619: When adding a wrapper descriptor from one class to a different class (for example, setting `__add__ = str.__add__` on an `int` subclass), an exception is correctly raised when the operator is called.

- bpo-37593: Swap the positions of the posonlyargs and args parameters in the constructor of `ast.parameters` nodes.

- bpo-37543: Optimized pymalloc for non PGO build.

- bpo-37537: Compute allocated pymalloc blocks inside _Py_GetAllocatedBlocks(). This slows down _Py_GetAllocatedBlocks() but gives a small speedup to _PyObject_Malloc() and _PyObject_Free().

- bpo-37467: Fix `sys.excepthook()` and `PyErr_Display()` if a filename is a bytes string. For example, for a SyntaxError exception where the filename attribute is a bytes string.

- bpo-37433: Fix `SyntaxError` indicator printing too many spaces for multi-line strings - by Anthony Sottile.

- bpo-37417: `bytearray.extend()` now correctly handles errors that arise during iteration. Patch by Brandt Bucher.

- bpo-37414: The undocumented `sys.callstats()` function has been removed. Since Python 3.7, it was deprecated and always returned `None`. It required a special build option `CALL_PROFILE` which was already removed in Python 3.7.

- bpo-37392: Remove `sys.getcheckinterval()` and `sys.setcheckinterval()` functions. They were deprecated since Python 3.2. Use `sys.getswitchinterval()` and `sys.setswitchinterval()` instead. Remove also `check_interval` field of the `PyInterpreterState` structure.

- bpo-37388: In development mode and in debug build, encoding and errors arguments are now checked on string encoding and decoding operations. Examples: `open()`, `str.encode()` and `bytes.decode()`.

  By default, for best performances, the errors argument is only checked at the first encoding/decoding error, and the encoding argument is sometimes ignored for empty strings.

- bpo-37348: Optimized decoding short ASCII string with UTF-8 and ascii codecs. `b"foo".decode()` is about 15% faster. Patch by Inada Naoki.

- bpo-24214: Improved support of the surrogatepass error handler in the UTF-8 and UTF-16 incremental decoders.

- bpo-37330: `open()`, `io.open()`, `codecs.open()` and `fileinput.FileInput` no longer accept `'U'` (“universal newline”) in the file mode. This flag was deprecated since Python 3.3.

- bpo-35224: Reverse evaluation order of key: value in dict comprehensions as proposed in PEP 572. I.e. in `{k: v for ...}`, `k` will be evaluated before `v`.

- bpo-37316: Fix the `PySys_Audit()` call in `mmap.mmap`.

- bpo-37300: Remove an unnecessary Py_XINCREF in classobject.c.

- bpo-37269: Fix a bug in the peephole optimizer that was not treating correctly constant conditions with binary operators. Patch by Pablo Galindo.

- bpo-20443: Python now gets the absolute path of the script filename specified on the command line (ex: “python3 script.py”): the __file__ attribute of the __main__ module and sys.path[0] become an absolute path, rather than a relative path.

- bpo-37257: Python’s small object allocator (`obmalloc.c`) now allows (no more than) one empty arena to remain available for immediate reuse, without returning it to the OS. This prevents thrashing in simple loops where an arena could be created and destroyed anew on each iteration.

- bpo-37231: The dispatching of type slots to special methods (for example calling `__mul__` when doing `x * y`) has been made faster.

- bpo-36974: Implemented separate vectorcall functions for every calling convention of builtin functions and methods. This improves performance for calls.

- bpo-37213: Handle correctly negative line offsets in the peephole optimizer. Patch by Pablo Galindo.

- bpo-37219: Remove erroneous optimization for empty set differences.

- bpo-15913: Implement `PyBuffer_SizeFromFormat()` function (previously documented but not implemented): call `struct.calcsize()`. Patch by Joannah Nanjekye.

- bpo-36922: Slot functions optimize any callable with `Py_TPFLAGS_METHOD_DESCRIPTOR` instead of only instances of `function`.

- bpo-36974: The slot `tp_vectorcall_offset` is inherited unconditionally to support `super().__call__()` when the base class uses vectorcall.

- bpo-37160: `threading.get_native_id()` now also supports NetBSD.

- bpo-37077: Add `threading.get_native_id()` support for AIX. Patch by M. Felt

- bpo-36781: `sum()` has been optimized for boolean values.

- bpo-34556: Add `--upgrade-deps` to venv module. Patch by Cooper Ry Lees

- bpo-20523: `pdb.Pdb` supports ~/.pdbrc in Windows 7. Patch by Tim Hopper and Dan Lidral-Porter.

- bpo-35551: Updated encodings: - Removed the “tis260” encoding, which was an alias for the nonexistent “tactis” codec. - Added “mac_centeuro” as an alias for the mac_latin2 encoding.

- bpo-19072: The `classmethod` decorator can now wrap other descriptors such as property objects. Adapted from a patch written by Graham Dumpleton.

- bpo-27575: Improve speed of dictview intersection by directly using set intersection logic. Patch by David Su.

- bpo-30773: Prohibit parallel running of aclose() / asend() / athrow(). Fix ag_running to reflect the actual running status of the AG.

### Library

- bpo-36589: The `curses.update_lines_cols()` function now returns `None` instead of `1` on success.

- bpo-38807: Update `TypeError` messages for `os.path.join()` to include `os.PathLike` objects as acceptable input types.

- bpo-38724: Add a repr for `subprocess.Popen` objects. Patch by Andrey Doroschenko.

- bpo-38786: pydoc now recognizes and parses HTTPS URLs. Patch by python273.

- bpo-38785: Prevent asyncio from crashing if parent `__init__` is not called from a constructor of object derived from `asyncio.Future`.

- bpo-38723: `pdb` now uses `io.open_code()` to trigger auditing events.

- bpo-27805: Allow opening pipes and other non-seekable files in append mode with `open()`.

- bpo-38438: Simplify the `argparse` usage message for `nargs="*"`.

- bpo-38761: WeakSet is now registered as a collections.abc.MutableSet.

- bpo-38716: logging: change RotatingHandler namer and rotator to class-level attributes. This stops __init__ from setting them to None in the case where a subclass defines them with eponymous methods.

- bpo-38713: Add `os.P_PIDFD` constant, which may be passed to `os.waitid()` to wait on a Linux process file descriptor.

- bpo-38692: Add `asyncio.PidfdChildWatcher`, a Linux-specific child watcher implementation that polls process file descriptors.

- bpo-38692: Expose the Linux `pidfd_open` syscall as `os.pidfd_open()`.

- bpo-38602: Added constants `F_OFD_GETLK`, `F_OFD_SETLK` and `F_OFD_SETLKW` to the `fcntl` module. Patch by Donghee Na.

- bpo-38334: Fixed seeking backward on an encrypted `zipfile.ZipExtFile`.

- bpo-38312: Add `curses.get_escdelay()`, `curses.set_escdelay()`, `curses.get_tabsize()`, and `curses.set_tabsize()` functions - by Anthony Sottile.

- bpo-38586: Now `fileConfig()` correctly sets the .name of handlers loaded.

- bpo-38565: Add new cache_parameters() method for functools.lru_cache() to better support pickling.

- bpo-34679: asynci.ProactorEventLoop.close() now only calls signal.set_wakeup_fd() in the main thread.

- bpo-31202: The case the result of `pathlib.WindowsPath.glob()` matches now the case of the pattern for literal parts.

- bpo-36321: Remove misspelled attribute. The 3.8 changelog noted that this would be removed in 3.9.

- bpo-38521: Fixed erroneous equality comparison in statistics.NormalDist().

- bpo-38493: Added `CLD_KILLED` and `CLD_STOPPED` for `si_code`. Patch by Donghee Na.

- bpo-38478: Fixed a bug in `inspect.signature.bind()` that was causing it to fail when handling a keyword argument with same name as positional-only parameter. Patch by Pablo Galindo.

- bpo-33604: Fixed `hmac.new` and `hmac.HMAC` to raise TypeError instead of ValueError when the digestmod parameter, now required in 3.8, is omitted. Also clarified the hmac module documentation and docstrings.

- bpo-38378: Parameters out and in of `os.sendfile()` was renamed to out_fd and in_fd.

- bpo-38417: Added support for setting the umask in the child process to the subprocess module on POSIX systems.

- bpo-38449: Revert PR 15522, which introduces a regression in `mimetypes.guess_type()` due to improper handling of filenames as urls.

- bpo-38431: Fix `__repr__` method for `dataclasses.InitVar` to support typing objects, patch by Samuel Colvin.

- bpo-38109: Add missing `stat.S_IFDOOR`, `stat.S_IFPORT`, `stat.S_IFWHT`, `stat.S_ISDOOR()`, `stat.S_ISPORT()`, and `stat.S_ISWHT()` values to the Python implementation of `stat`.

- bpo-38422: Clarify docstrings of pathlib suffix(es)

- bpo-38405: Nested subclasses of `typing.NamedTuple` are now pickleable.

- bpo-38332: Prevent `KeyError` thrown by `_encoded_words.decode()` when given an encoded-word with invalid content-type encoding from propagating all the way to `email.message.get()`.

- bpo-38371: Deprecated the `split()` method in `_tkinter.TkappType` in favour of the `splitlist()` method which has more consistent and predictable behavior.

- bpo-38341: Add `smtplib.SMTPNotSupportedError` to the `smtplib` exported names.

- bpo-38319: sendfile() used in socket and shutil modules was raising OverflowError for files >= 2GiB on 32-bit architectures. (patch by Giampaolo Rodola)

- bpo-38242: Revert the new asyncio Streams API

- bpo-13153: OS native encoding is now used for converting between Python strings and Tcl objects. This allows to display, copy and paste to clipboard emoji and other non-BMP characters. Converting strings from Tcl to Python and back now never fails (except MemoryError).

- bpo-38019: Correctly handle pause/resume reading of closed asyncio unix pipe.

- bpo-38163: Child mocks will now detect their type as either synchronous or asynchronous, asynchronous child mocks will be AsyncMocks and synchronous child mocks will be either MagicMock or Mock (depending on their parent type).

- bpo-38161: Removes _AwaitEvent from AsyncMock.

- bpo-38216: Allow the rare code that wants to send invalid http requests from the `http.client` library a way to do so. The fixes for bpo-30458 led to breakage for some projects that were relying on this ability to test their own behavior in the face of bad requests.

- bpo-28286: Deprecate opening `GzipFile` for writing implicitly. Always specify the mode argument for writing.

- bpo-38108: Any synchronous magic methods on an AsyncMock now return a MagicMock. Any asynchronous magic methods on a MagicMock now return an AsyncMock.

- bpo-38265: Update the length parameter of `os.pread()` to accept `Py_ssize_t` instead of int.

- bpo-38112: `compileall` has a higher default recursion limit and new command-line arguments for path manipulation, symlinks handling, and multiple optimization levels.

- bpo-38248: asyncio: Fix inconsistent immediate Task cancellation

- bpo-38237: The arguments for the builtin pow function are more descriptive. They can now also be passed in as keywords.

- bpo-34002: Improve efficiency in parts of email package by changing while-pop to a for loop, using isdisjoint instead of set intersections.

- bpo-38191: Constructors of `NamedTuple` and `TypedDict` types now accept arbitrary keyword argument names, including “cls”, “self”, “typename”, “_typename”, “fields” and “_fields”.

- bpo-38155: Add `__all__` to `datetime`. Patch by Tahia Khan.

- bpo-38185: Fixed case-insensitive string comparison in `sqlite3.Row` indexing.

- bpo-38136: Changes AsyncMock call count and await count to be two different counters. Now await count only counts when a coroutine has been awaited, not when it has been called, and vice-versa. Update the documentation around this.

- bpo-37828: Fix default mock name in `unittest.mock.Mock.assert_called()` exceptions. Patch by Abraham Toriz Cruz.

- bpo-38175: Fix a memory leak in comparison of `sqlite3.Row` objects.

- bpo-33936: _hashlib no longer calls obsolete OpenSSL initialization function with OpenSSL 1.1.0+.

- bpo-34706: Preserve subclassing in inspect.Signature.from_callable.

- bpo-38153: Names of hashing algorithms from OpenSSL are now normalized to follow Python’s naming conventions. For example OpenSSL uses sha3-512 instead of sha3_512 or blake2b512 instead of blake2b.

- bpo-38115: Fix a bug in dis.findlinestarts() where it would return invalid bytecode offsets. Document that a code object’s co_lnotab can contain invalid bytecode offsets.

- bpo-38148: Add slots to `asyncio` transport classes, which can reduce memory usage.

- bpo-38142: The _hashlib OpenSSL wrapper extension module is now PEP-384 compliant.

- bpo-9216: hashlib constructors now support usedforsecurity flag to signal that a hashing algorithm is not used in a security context.

- bpo-36991: Fixes a potential incorrect AttributeError exception escaping ZipFile.extract() in some unsupported input error situations.

- bpo-38134: Remove obsolete copy of PBKDF2_HMAC_fast. All supported OpenSSL versions contain a fast implementation.

- bpo-38132: The OpenSSL hashlib wrapper uses a simpler implementation. Several Macros and pointless caches are gone. The hash name now comes from OpenSSL’s EVP. The algorithm name stays the same, except it is now always lower case.

- bpo-38008: Fix parent class check in protocols to correctly identify the module that provides a builtin protocol, instead of assuming they all come from the `collections.abc` module

- bpo-34037: For `asyncio`, add a new coroutine `loop.shutdown_default_executor()`. The new coroutine provides an API to schedule an executor shutdown that waits on the threadpool to finish closing. Also, `asyncio.run()` has been updated to utilize the new coroutine. Patch by Kyle Stanley.

- bpo-37405: Fixed regression bug for socket.getsockname() for non-CAN_ISOTP AF_CAN address family sockets by returning a 1-tuple instead of string.

- bpo-38121: Update parameter names on functions in importlib.metadata matching the changes in the 0.22 release of importlib_metadata.

- bpo-38110: The os.closewalk() implementation now uses the libc fdwalk() API on platforms where it is available.

- bpo-38093: Fixes AsyncMock so it doesn’t crash when used with AsyncContextManagers or AsyncIterators.

- bpo-37488: Add warning to `datetime.utctimetuple()`, `datetime.utcnow()` and `datetime.utcfromtimestamp()` .

- bpo-35640: Allow passing a path-like object as `directory` argument to the `http.server.SimpleHTTPRequestHandler` class. Patch by Géry Ogam.

- bpo-38086: Update importlib.metadata with changes from importlib_metadata 0.21.

- bpo-37251: Remove `__code__` check in AsyncMock that incorrectly evaluated function specs as async objects but failed to evaluate classes with `__await__` but no `__code__` attribute defined as async objects.

- bpo-38037: Fix reference counters in the `signal` module.

- bpo-38066: Hide internal asyncio.Stream methods: feed_eof(), feed_data(), set_exception() and set_transport().

- bpo-38059: inspect.py now uses sys.exit() instead of exit()

- bpo-38049: Added command-line interface for the `ast` module.

- bpo-37953: In `typing`, improved the `__hash__` and `__eq__` methods for `ForwardReferences`.

- bpo-38026: Fixed `inspect.getattr_static()` used `isinstance` while it should avoid dynamic lookup.

- bpo-35923: Update `importlib.machinery.BuiltinImporter` to use `loader._ORIGIN` instead of a hardcoded value. Patch by Donghee Na.

- bpo-38010: In `importlib.metadata` sync with `importlib_metadata` 0.20, clarifying behavior of `files()` and fixing issue where only one requirement was returned for `requires()` on `dist-info` packages.

- bpo-38006: weakref.WeakValueDictionary defines a local remove() function used as callback for weak references. This function was created with a closure. Modify the implementation to avoid the closure.

- bpo-37995: Added the indent option to `ast.dump()` which allows it to produce a multiline indented output.

- bpo-34410: Fixed a crash in the `tee()` iterator when re-enter it. RuntimeError is now raised in this case.

- bpo-37140: Fix a ctypes regression of Python 3.8. When a ctypes.Structure is passed by copy to a function, ctypes internals created a temporary object which had the side effect of calling the structure finalizer (__del__) twice. The Python semantics requires a finalizer to be called exactly once. Fix ctypes internals to no longer call the finalizer twice.

- bpo-37587: `_json.scanstring` is now up to 3x faster when there are many backslash escaped characters in the JSON string.

- bpo-37834: Prevent shutil.rmtree exception when built on non-Windows system without fd system call support, like older versions of macOS.

- bpo-10978: Semaphores and BoundedSemaphores can now release more than one waiting thread at a time.

- bpo-37972: Subscripts to the `unittest.mock.call` objects now receive the same chaining mechanism as any other custom attributes, so that the following usage no longer raises a `TypeError`:

  `call().foo().__getitem__('bar')`

  Patch by blhsing

- bpo-37965: Fix C compiler warning caused by distutils.ccompiler.CCompiler.has_function.

- bpo-37964: Add `F_GETPATH` command to `fcntl`.

- bpo-37960: `repr()` of buffered and text streams now silences only expected exceptions when get the value of “name” and “mode” attributes.

- bpo-37961: Add a `total_nframe` field to the traces collected by the tracemalloc module. This field indicates the original number of frames before it was truncated.

- bpo-37951: Most features of the subprocess module now work again in subinterpreters. Only preexec_fn is restricted in subinterpreters.

- bpo-36205: Fix the rusage implementation of time.process_time() to correctly report the sum of the system and user CPU time.

- bpo-37950: Fix `ast.dump()` when call with incompletely initialized node.

- bpo-34679: Restores instantiation of Windows IOCP event loops from the non-main thread.

- bpo-36917: Add default implementation of the `ast.NodeVisitor.visit_Constant()` method which emits a deprecation warning and calls corresponding methods `visit_Num()`, `visit_Str()`, etc.

- bpo-37798: Update test_statistics.py to verify that the statistics module works well for both C and Python implementations. Patch by Donghee Na

- bpo-26589: Added a new status code to the http module: 451 UNAVAILABLE_FOR_LEGAL_REASONS

- bpo-37915: Fix a segmentation fault that appeared when comparing instances of `datetime.timezone` and `datetime.tzinfo` objects. Patch by Pablo Galindo.

- bpo-32554: Deprecate having random.seed() call hash on arbitrary types.

- bpo-9938: Add optional keyword argument `exit_on_error` for `ArgumentParser`.

- bpo-37851: The `faulthandler` module no longer allocates its alternative stack at Python startup. Now the stack is only allocated at the first faulthandler usage.

- bpo-32793: Fix a duplicated debug message when `smtplib.SMTP.connect()` is called.

- bpo-37885: venv: Don’t generate unset variable warning on deactivate.

- bpo-37868: Fix dataclasses.is_dataclass when given an instance that never raises AttributeError in __getattr__. That is, an object that returns something for __dataclass_fields__ even if it’s not a dataclass.

- bpo-37811: Fix `socket` module’s `socket.connect(address)` function being unable to establish connection in case of interrupted system call. The problem was observed on all OSes which `poll(2)` system call can take only non-negative integers and -1 as a timeout value.

- bpo-37863: Optimizations for Fraction.__hash__ suggested by Tim Peters.

- bpo-21131: Fix `faulthandler.register(chain=True)` stack. faulthandler now allocates a dedicated stack of `SIGSTKSZ*2` bytes, instead of just `SIGSTKSZ` bytes. Calling the previous signal handler in faulthandler signal handler uses more than `SIGSTKSZ` bytes of stack memory on some platforms.

- bpo-37798: Add C fastpath for statistics.NormalDist.inv_cdf() Patch by Donghee Na

- bpo-37804: Remove the deprecated method `threading.Thread.isAlive()`. Patch by Donghee Na.

- bpo-37819: Add Fraction.as_integer_ratio() to match the corresponding methods in bool, int, float, and decimal.

- bpo-14465: Add an xml.etree.ElementTree.indent() function for pretty-printing XML trees. Contributed by Stefan Behnel.

- bpo-37810: Fix `difflib` `?` hint in diff output when dealing with tabs. Patch by Anthony Sottile.

- bpo-37772: In `zipfile.Path`, when adding implicit dirs, ensure that ancestral directories are added and that duplicates are excluded.

- bpo-18578: Renamed and documented `test.bytecode_helper` as `test.support.bytecode_helper`. Patch by Joannah Nanjekye.

- bpo-37785: Fix xgettext warnings in `argparse`.

- bpo-34488: `writelines()` method of `io.BytesIO` is now slightly faster when many small lines are passed. Patch by Sergey Fedoseev.

- bpo-37449: `ensurepip` now uses `importlib.resources.read_binary()` to read data instead of `pkgutil.get_data()`. Patch by Joannah Nanjekye.

- bpo-28292: Mark calendar.py helper functions as being private. The follows PEP 8 guidance to maintain the style conventions in the module and it addresses a known case of user confusion.

- bpo-18049: Add definition of THREAD_STACK_SIZE for AIX in Python/thread_pthread.h The default thread stacksize caused crashes with the default recursion limit Patch by M Felt

- bpo-37742: The logging.getLogger() API now returns the root logger when passed the name ‘root’, whereas previously it returned a non-root logger named ‘root’. This could affect cases where user code explicitly wants a non-root logger named ‘root’, or instantiates a logger using logging.getLogger(__name__) in some top-level module called ‘root.py’.

- bpo-37738: Fix the implementation of curses `addch(str, color_pair)`: pass the color pair to `setcchar()`, instead of always passing 0 as the color pair.

- bpo-37723: Fix performance regression on regular expression parsing with huge character sets. Patch by Yann Vaginay.

- bpo-35943: The function `PyImport_GetModule()` now ensures any module it returns is fully initialized. Patch by Joannah Nanjekye.

- bpo-32178: Fix IndexError in `email` package when trying to parse invalid address fields starting with `:`.

- bpo-37268: The `parser` module is deprecated and will be removed in future versions of Python.

- bpo-11953: Completing WSA* error codes in `socket`.

- bpo-37685: Fixed comparisons of `datetime.timedelta` and `datetime.timezone`.

- bpo-37697: Synchronize `importlib.metadata` with importlib_metadata 0.19, improving handling of EGG-INFO files and fixing a crash when entry point names contained colons.

- bpo-37695: Correct `curses.unget_wch()` error message. Patch by Anthony Sottile.

- bpo-37689: Add `is_relative_to()` in `PurePath` to determine whether or not one path is relative to another.

- bpo-29553: Fixed `argparse.ArgumentParser.format_usage()` for mutually exclusive groups. Patch by Andrew Nester.

- bpo-37691: Let math.dist() accept coordinates as sequences (or iterables) rather than just tuples.

- bpo-37685: Fixed `__eq__`, `__lt__` etc implementations in some classes. They now return `NotImplemented` for unsupported type of the other operand. This allows the other operand to play role (for example the equality comparison with `ANY` will return `True`).

- bpo-37354: Make Activate.ps1 Powershell script static to allow for signing it.

- bpo-37664: Update wheels bundled with ensurepip (pip 19.2.3 and setuptools 41.2.0)

- bpo-37663: Bring consistency to venv shell activation scripts by always using __VENV_PROMPT__.

- bpo-37642: Allowed the pure Python implementation of `datetime.timezone` to represent sub-minute offsets close to minimum and maximum boundaries, specifically in the ranges (23:59, 24:00) and (-23:59, 24:00). Patch by Ngalim Siregar

- bpo-36161: In `posix`, use `ttyname_r` instead of `ttyname` for thread safety.

- bpo-36324: Make internal attributes for statistics.NormalDist() private.

- bpo-37555: Fix `NonCallableMock._call_matcher` returning tuple instead of `_Call` object when `self._spec_signature` exists. Patch by Elizabeth Uselton

- bpo-29446: Make `from tkinter import *` import only the expected objects.

- bpo-16970: Adding a value error when an invalid value in passed to nargs Patch by Robert Leenders

- bpo-34443: Exceptions from `enum` now use the `__qualname` of the enum class in the exception message instead of the `__name__`.

- bpo-37491: Fix `IndexError` when parsing email headers with unexpectedly ending bare-quoted string value. Patch by Abhilash Raj.

- bpo-37587: Make json.loads faster for long strings. (Patch by Marco Paolini)

- bpo-18378: Recognize “UTF-8” as a valid value for LC_CTYPE in locale._parse_localename.

- bpo-37579: Return `NotImplemented` in Python implementation of `__eq__` for `timedelta` and `time` when the other object being compared is not of the same type to match C implementation. Patch by Karthikeyan Singaravelan.

- bpo-21478: Record calls to parent when autospecced object is attached to a mock using `unittest.mock.attach_mock()`. Patch by Karthikeyan Singaravelan.

- bpo-37531: “python3 -m test -jN –timeout=TIMEOUT” now kills a worker process if it runs longer than TIMEOUT seconds.

- bpo-37482: Fix serialization of display name in originator or destination address fields with both encoded words and special chars.

- bpo-36993: Improve error reporting for corrupt zip files with bad zip64 extra data. Patch by Daniel Hillier.

- bpo-37502: pickle.loads() no longer raises TypeError when the buffers argument is set to None

- bpo-37520: Correct behavior for zipfile.Path.parent when the path object identifies a subdirectory.

- bpo-18374: Fix the `.col_offset` attribute of nested `ast.BinOp` instances which had a too large value in some situations.

- bpo-37424: Fixes a possible hang when using a timeout on `subprocess.run()` while capturing output. If the child process spawned its own children or otherwise connected its stdout or stderr handles with another process, we could hang after the timeout was reached and our child was killed when attempting to read final output from the pipes.

- bpo-37421: Fix `multiprocessing.util.get_temp_dir()` finalizer: clear also the ‘tempdir’ configuration of the current process, so next call to `get_temp_dir()` will create a new temporary directory, rather than reusing the removed temporary directory.

- bpo-37481: The distutils `bdist_wininst` command is deprecated in Python 3.8, use `bdist_wheel` (wheel packages) instead.

- bpo-37479: When `Enum.__str__` is overridden in a derived class, the override will be used by `Enum.__format__` regardless of whether mixin classes are present.

- bpo-37440: http.client now enables TLS 1.3 post-handshake authentication for default context or if a cert_file is passed to HTTPSConnection.

- bpo-37437: Update vendorized expat version to 2.2.7.

- bpo-37428: SSLContext.post_handshake_auth = True no longer sets SSL_VERIFY_POST_HANDSHAKE verify flag for client connections. Although the option is documented as ignored for clients, OpenSSL implicitly enables cert chain validation when the flag is set.

- bpo-37420: `os.sched_setaffinity()` now correctly handles errors that arise during iteration over its `mask` argument. Patch by Brandt Bucher.

- bpo-37412: The `os.getcwdb()` function now uses the UTF-8 encoding on Windows, rather than the ANSI code page: see PEP 529 for the rationale. The function is no longer deprecated on Windows.

- bpo-37406: The sqlite3 module now raises TypeError, rather than ValueError, if operation argument type is not str: execute(), executemany() and calling a connection.

- bpo-29412: Fix IndexError in parsing a header value ending unexpectedly. Patch by Abhilash Raj.

- bpo-36546: The dist argument for statistics.quantiles() is now positional only. The current name doesn’t reflect that the argument can be either a dataset or a distribution. Marking the parameter as positional avoids confusion and makes it possible to change the name later.

- bpo-37394: Fix a bug that was causing the `queue` module to fail if the accelerator module was not available. Patch by Pablo Galindo.

- bpo-37376: `pprint` now has support for `types.SimpleNamespace`. Patch by Carl Bordum Hansen.

- bpo-26967: An `ArgumentParser` with `allow_abbrev=False` no longer disables grouping of short flags, such as `-vv`, but only disables abbreviation of long flags as documented. Patch by Zac Hatfield-Dodds.

- bpo-37212: `unittest.mock.call()` now preserves the order of keyword arguments in repr output. Patch by Karthikeyan Singaravelan.

- bpo-37372: Fix error unpickling datetime.time objects from Python 2 with seconds>=24. Patch by Justin Blanchard.

- bpo-37345: Add formal support for UDPLITE sockets. Support was present before, but it is now easier to detect support with `hasattr(socket, 'IPPROTO_UDPLITE')` and there are constants defined for each of the values needed: `socket.IPPROTO_UDPLITE`, `UDPLITE_SEND_CSCOV`, and `UDPLITE_RECV_CSCOV`. Patch by Gabe Appleton.

- bpo-37358: Optimized `functools.partial` by using vectorcall.

- bpo-37347: `sqlite3.Connection.create_aggregate()`, `sqlite3.Connection.create_function()`, `sqlite3.Connection.set_authorizer()`, `sqlite3.Connection.set_progress_handler()` `sqlite3.Connection.set_trace_callback()` methods lead to segfaults if some of these methods are called twice with an equal object but not the same. Now callbacks are stored more carefully. Patch by Aleksandr Balezin.

- bpo-37163: The obj argument of `dataclasses.replace()` is positional-only now.

- bpo-37085: Add the optional Linux SocketCAN Broadcast Manager constants, used as flags to configure the BCM behaviour, in the socket module. Patch by Karl Ding.

- bpo-37328: `HTMLParser.unescape` is removed. It was undocumented and deprecated since Python 3.4.

- bpo-37305: Add .webmanifest -> application/manifest+json to list of recognized file types and content type headers

- bpo-37320: `aifc.openfp()` alias to `aifc.open()`, `sunau.openfp()` alias to `sunau.open()`, and `wave.openfp()` alias to `wave.open()` have been removed. They were deprecated since Python 3.7.

- bpo-37315: Deprecated accepting floats with integral value (like `5.0`) in `math.factorial()`.

- bpo-37312: `_dummy_thread` and `dummy_threading` modules have been removed. These modules were deprecated since Python 3.7 which requires threading support.

- bpo-33972: Email with single part but content-type set to `multipart/*` doesn’t raise AttributeError anymore.

- bpo-37280: Use threadpool for reading from file for sendfile fallback mode.

- bpo-37279: Fix asyncio sendfile support when sendfile sends extra data in fallback mode.

- bpo-19865: `ctypes.create_unicode_buffer()` now also supports non-BMP characters on platforms with 16-bit `wchar_t` (for example, Windows and AIX).

- bpo-37266: In a subinterpreter, spawning a daemon thread now raises an exception. Daemon threads were never supported in subinterpreters. Previously, the subinterpreter finalization crashed with a Python fatal error if a daemon thread was still running.

- bpo-37210: Allow pure Python implementation of `pickle` to work even when the C `_pickle` module is unavailable.

- bpo-21872: Fix `lzma`: module decompresses data incompletely. When decompressing a FORMAT_ALONE format file, and it doesn’t have the end marker, sometimes the last one to dozens bytes can’t be output. Patch by Ma Lin.

- bpo-35922: Fix `RobotFileParser.crawl_delay()` and `RobotFileParser.request_rate()` to return `None` rather than raise `AttributeError` when no relevant rule is defined in the robots.txt file. Patch by Rémi Lapeyre.

- bpo-35766: Change the format of feature_version to be a (major, minor) tuple.

- bpo-36607: Eliminate `RuntimeError` raised by `asyncio.all_tasks()` if internal tasks weak set is changed by another thread during iteration.

- bpo-18748: `_pyio.IOBase` destructor now does nothing if getting the `closed` attribute fails to better mimic `_io.IOBase` finalizer.

- bpo-36402: Fix a race condition at Python shutdown when waiting for threads. Wait until the Python thread state of all non-daemon threads get deleted (join all non-daemon threads), rather than just wait until non-daemon Python threads complete.

- bpo-37206: Default values which cannot be represented as Python objects no longer improperly represented as `None` in function signatures.

- bpo-37111: Added `encoding` and `errors` keyword parameters to `logging.basicConfig`.

- bpo-12144: Ensure cookies with `expires` attribute are handled in `CookieJar.make_cookies()`.

- bpo-34886: Fix an unintended ValueError from `subprocess.run()` when checking for conflicting input and stdin or capture_output and stdout or stderr args when they were explicitly provided but with `None` values within a passed in `**kwargs` dict rather than as passed directly by name. Patch contributed by Rémi Lapeyre.

- bpo-37173: The exception message for `inspect.getfile()` now correctly reports the passed class rather than the builtins module.

- bpo-37178: Give math.perm() a one argument form that means the same as math.factorial().

- bpo-37178: For math.perm(n, k), let k default to n, giving the same result as factorial.

- bpo-37165: Converted _collections._count_elements to use the Argument Clinic.

- bpo-34767: Do not always create a `collections.deque` in `asyncio.Lock`.

- bpo-37158: Speed-up statistics.fmean() by switching from a function to a generator.

- bpo-34282: Remove `Enum._convert` method, deprecated in 3.8.

- bpo-37150: `argparse._ActionsContainer.add_argument` now throws error, if someone accidentally pass FileType class object instead of instance of FileType as `type` argument.

- bpo-28724: The socket module now has the `socket.send_fds()` and `socket.recv.fds()` methods. Contributed by Joannah Nanjekye, Shinya Okano and Victor Stinner.

- bpo-35621: Support running asyncio subprocesses when execution event loop in a thread on UNIX.

- bpo-36520: Lengthy email headers with UTF-8 characters are now properly encoded when they are folded. Patch by Jeffrey Kintscher.

- bpo-30835: Fixed a bug in email parsing where a message with invalid bytes in content-transfer-encoding of a multipart message can cause an AttributeError. Patch by Andrew Donnellan.

- bpo-31163: pathlib.Path instance’s rename and replace methods now return the new Path instance.

- bpo-25068: `urllib.request.ProxyHandler` now lowercases the keys of the passed dictionary.

- bpo-26185: Fix `repr()` on empty `ZipInfo` object. Patch by Mickaël Schoentgen.

- bpo-21315: Email headers containing RFC2047 encoded words are parsed despite the missing whitespace, and a defect registered. Also missing trailing whitespace after encoded words is now registered as a defect.

- bpo-31904: Port test_datetime to VxWorks: skip zoneinfo tests on VxWorks

- bpo-35805: Add parser for Message-ID header and add it to default HeaderRegistry. This should prevent folding of Message-ID using RFC 2048 encoded words.

- bpo-36871: Ensure method signature is used instead of constructor signature of a class while asserting mock object against method calls. Patch by Karthikeyan Singaravelan.

- bpo-35070: posix.getgrouplist() now works correctly when the user belongs to NGROUPS_MAX supplemental groups. Patch by Jeffrey Kintscher.

- bpo-31783: Fix race condition in ThreadPoolExecutor when worker threads are created during interpreter shutdown.

- bpo-36582: Fix `UserString.encode()` to correctly return `bytes` rather than a `UserString` instance.

- bpo-32424: Deprecate xml.etree.ElementTree.Element.copy() in favor of copy.copy().

  Patch by Gordon P. Hemsley

- bpo-36564: Fix infinite loop in email header folding logic that would be triggered when an email policy’s max_line_length is not long enough to include the required markup and any values in the message. Patch by Paul Ganssle

- bpo-36543: Removed methods Element.getchildren(), Element.getiterator() and ElementTree.getiterator() and the xml.etree.cElementTree module.

- bpo-36409: Remove the old plistlib API deprecated in Python 3.4

- bpo-36302: distutils sorts source file lists so that Extension .so files build more reproducibly by default

- bpo-36250: Ignore `ValueError` from `signal` with `interaction` in non-main thread.

- bpo-36046: Added `user`, `group` and `extra_groups` parameters to the subprocess.Popen constructor. Patch by Patrick McLean.

- bpo-32627: Fix compile error when `_uuid` headers conflicting included.

- bpo-35800: Deprecate `smtpd.MailmanProxy` ready for future removal.

- bpo-35168: `shlex.shlex.punctuation_chars` is now a read-only property.

- bpo-8538: Add support for boolean actions like `--foo` and `--no-foo` to argparse. Patch contributed by Rémi Lapeyre.

- bpo-20504: Fixes a bug in `cgi` module when a multipart/form-data request has no `Content-Length` header.

- bpo-25988: The abstract base classes in `collections.abc` no longer are exposed in the regular `collections` module.

- bpo-11122: Distutils won’t check for rpmbuild in specified paths only.

- bpo-34775: Division handling of PurePath now returns NotImplemented instead of raising a TypeError when passed something other than an instance of str or PurePath. Patch by Roger Aiudi.

- bpo-34749: `binascii.a2b_base64()` is now up to 2 times faster. Patch by Sergey Fedoseev.

- bpo-34519: Add additional aliases for HP Roman 8. Patch by Michael Osipov.

- bpo-28009: Fix uuid.getnode() on platforms with ‘.’ as MAC Addr delimiter as well fix for MAC Addr format that omits a leading 0 in MAC Addr values. Currently, AIX is the only know platform with these settings. Patch by Michael Felt.

- bpo-30618: Add `readlink()`. Patch by Girts Folkmanis.

- bpo-32498: Made `urllib.parse.unquote()` accept bytes in addition to strings. Patch by Stein Karlsen.

- bpo-33348: lib2to3 now recognizes expressions after `*` and `**` like in `f(*[] or [])`.

- bpo-32689: Update `shutil.move()` function to allow for Path objects to be used as source argument. Patch by Emily Morehouse and Maxwell “5.13b” McKinnon.

- bpo-32820: Added `__format__` to IPv4 and IPv6 classes. Always outputs a fully zero-padded string. Supports b/x/n modifiers (bin/hex/native format). Native format for IPv4 is bin, native format for IPv6 is hex. Also supports ‘#’ and ‘_’ modifiers.

- bpo-27657: Fix urllib.parse.urlparse() with numeric paths. A string like “path:80” is no longer parsed as a path but as a scheme (“path”) and a path (“80”).

- bpo-4963: Fixed non-deterministic behavior related to mimetypes extension mapping and module reinitialization.

### Documentation

- bpo-21767: Explicitly mention abc support in functools.singledispatch

- bpo-38816: Provides more details about the interaction between `fork()` and CPython’s runtime, focusing just on the C-API. This includes cautions about where `fork()` should and shouldn’t be called.

- bpo-38351: Modernize `email` examples from %-formatting to f-strings.

- bpo-38778: Document the fact that `RuntimeError` is raised if `os.fork()` is called in a subinterpreter.

- bpo-38592: Add Brazilian Portuguese to the language switcher at Python Documentation website.

- bpo-38294: Add list of no-longer-escaped chars to re.escape documentation

- bpo-38053: Modernized the plistlib documentation

- bpo-26868: Fix example usage of `PyModule_AddObject()` to properly handle errors.

- bpo-36797: Fix a dead link in the distutils API Reference.

- bpo-37977: Warn more strongly and clearly about pickle insecurity

- bpo-37979: Added a link to dateutil.parser.isoparse in the datetime.fromisoformat documentation. Patch by Paul Ganssle

- bpo-12707: Deprecate info(), geturl(), getcode() methods in favor of the headers, url, and status properties, respectively, for HTTPResponse and addinfourl. Also deprecate the code attribute of addinfourl in favor of the status attribute. Patch by Ashwin Ramaswami

- bpo-37937: Mention `frame.f_trace` in `sys.settrace()` docs.

- bpo-37878: Make `PyThreadState_DeleteCurrent()` Internal.

- bpo-37759: Beginning edits to Whatsnew 3.8

- bpo-37726: Stop recommending getopt in the tutorial for command line argument parsing and promote argparse.

- bpo-32910: Remove implementation-specific behaviour of how venv’s Deactivate works.

- bpo-37256: Fix wording of arguments for `Request` in `urllib.request`

- bpo-37284: Add a brief note to indicate that any new `sys.implementation` required attributes must go through the PEP process.

- bpo-30088: Documented that `mailbox.Maildir` constructor doesn’t attempt to verify the maildir folder layout correctness. Patch by Sviatoslav Sydorenko.

- bpo-37521: Fix `importlib` examples to insert any newly created modules via importlib.util.module_from_spec() immediately into sys.modules instead of after calling loader.exec_module().

  Thanks to Benjamin Mintz for finding the bug.

- bpo-37456: Slash (‘/’) is now part of syntax.

- bpo-37487: Fix PyList_GetItem index description to include 0.

- bpo-37149: Replace the dead link to the Tkinter 8.5 reference by John Shipman, New Mexico Tech, with a link to the archive.org copy.

- bpo-37478: Added possible exceptions to the description of os.chdir().

- bpo-34903: Documented that in `datetime.datetime.strptime()`, the leading zero in some two-digit formats is optional. Patch by Mike Gleen.

- bpo-36260: Add decompression pitfalls to zipfile module documentation.

- bpo-37004: In the documentation for difflib, a note was added explicitly warning that the results of SequenceMatcher’s ratio method may depend on the order of the input strings.

- bpo-36960: Restructured the `datetime` docs in the interest of making them more user-friendly and improving readability. Patch by Brad Solomon.

- bpo-36487: Make C-API docs clear about what the “main” interpreter is.

- bpo-23460: The documentation for decimal string formatting using the `:g` specifier has been updated to reflect the correct exponential notation cutoff point. Original patch contributed by Tuomas Suutari.

- bpo-35803: Document and test that `tempfile` functions may accept a path-like object for the `dir` argument. Patch by Anthony Sottile.

- bpo-33944: Added a note about the intended use of code in .pth files.

- bpo-34293: Fix the Doc/Makefile regarding PAPER environment variable and PDF builds

- bpo-25237: Add documentation for tkinter modules

### Tests

- bpo-38614: Fix test_communicate() of test_asyncio.test_subprocess: use `support.LONG_TIMEOUT` (5 minutes), instead of just 1 minute.

- bpo-38614: Add timeout constants to `test.support`: `LOOPBACK_TIMEOUT`, `INTERNET_TIMEOUT`, `SHORT_TIMEOUT` and `LONG_TIMEOUT`.

- bpo-38502: test.regrtest now uses process groups in the multiprocessing mode (-jN command line option) if process groups are available: if `os.setsid()` and `os.killpg()` functions are available.

- bpo-35998: Fix a race condition in test_asyncio.test_start_tls_server_1(). Previously, there was a race condition between the test main() function which replaces the protocol and the test ServerProto protocol which sends ANSWER once it gets HELLO. Now, only the test main() function is responsible to send data, ServerProto no longer sends data.

- bpo-38470: Fix `test_compileall.test_compile_dir_maxlevels()` on Windows without long path support: only create 3 subdirectories instead of between 20 and 100 subdirectories.

- bpo-37531: On timeout, regrtest no longer attempts to call `popen.communicate()` again: it can hang until all child processes using stdout and stderr pipes completes. Kill the worker process and ignores its output. Change also the faulthandler timeout of the main process from 1 minute to 5 minutes, for Python slowest buildbots.

- bpo-38239: Fix test_gdb for Link Time Optimization (LTO) builds.

- bpo-38275: test_ssl now handles disabled TLS/SSL versions better. OpenSSL’s crypto policy and run-time settings are recognized and tests for disabled versions are skipped. Tests also accept more TLS minimum_versions for platforms that override OpenSSL’s default with strict settings.

- bpo-38271: The private keys for test_ssl were encrypted with 3DES in traditional PKCS#5 format. 3DES and the digest algorithm of PKCS#5 are blocked by some strict crypto policies. Use PKCS#8 format with AES256 encryption instead.

- bpo-38270: test.support now has a helper function to check for availability of a hash digest function. Several tests are refactored avoid MD5 and use SHA256 instead. Other tests are marked to use MD5 and skipped when MD5 is disabled.

- bpo-37123: Multiprocessing test test_mymanager() now also expects -SIGTERM, not only exitcode 0. BaseManager._finalize_manager() sends SIGTERM to the manager process if it takes longer than 1 second to stop, which happens on slow buildbots.

- bpo-38212: Multiprocessing tests: increase test_queue_feeder_donot_stop_onexc() timeout from 1 to 60 seconds.

- bpo-38117: Test with OpenSSL 1.1.1d

- bpo-38018: Increase code coverage for multiprocessing.shared_memory.

- bpo-37805: Add tests for json.dump(…, skipkeys=True). Patch by Donghee Na.

- bpo-37531: Enhance regrtest multiprocess timeout: write a message when killing a worker process, catch popen.kill() and popen.wait() exceptions, put a timeout on the second call to popen.communicate().

- bpo-37876: Add tests for ROT-13 codec.

- bpo-36833: Added tests for `PyDateTime_xxx_GET_xxx()` macros of the C API of the `datetime` module. Patch by Joannah Nanjekye.

- bpo-37558: Fix test_shared_memory_cleaned_after_process_termination name handling

- bpo-37526: Add `test.support.catch_threading_exception()`: context manager catching `threading.Thread` exception using `threading.excepthook()`.

- bpo-37421: test_concurrent_futures now explicitly stops the ForkServer instance if it’s running.

- bpo-37421: multiprocessing tests now stop the ForkServer instance if it’s running: close the “alive” file descriptor to ask the server to stop and then remove its UNIX address.

- bpo-37421: test_distutils.test_build_ext() is now able to remove the temporary directory on Windows: don’t import the newly built C extension (“xx”) in the current process, but test it in a separated process.

- bpo-37421: test_concurrent_futures now cleans up multiprocessing to remove immediately temporary directories created by multiprocessing.util.get_temp_dir().

- bpo-37421: test_winconsoleio doesn’t leak a temporary file anymore: use tempfile.TemporaryFile() to remove it when the test completes.

- bpo-37421: multiprocessing tests now explicitly call `_run_finalizers()` to immediately remove temporary directories created by tests.

- bpo-37421: urllib.request tests now call `urlcleanup()` to remove temporary files created by `urlretrieve()` tests and to clear the `_opener` global variable set by `urlopen()` and functions calling indirectly `urlopen()`.

- bpo-37472: Remove `Lib/test/outstanding_bugs.py`.

- bpo-37199: Fix test failures when IPv6 is unavailable or disabled.

- bpo-19696: Replace deprecated method “random.choose” with “random.choice” in “test_pkg_import.py”.

- bpo-37335: Remove no longer necessary code from c locale coercion tests

- bpo-37421: Fix test_shutil to no longer leak temporary files.

- bpo-37411: Fix test_wsgiref.testEnviron() to no longer depend on the environment variables (don’t fail if “X” variable is set).

- bpo-37400: Fix test_os.test_chown(): use os.getgroups() rather than grp.getgrall() to get groups. Rename also the test to test_chown_gid().

- bpo-37359: Add –cleanup option to python3 -m test to remove `test_python_*` directories of previous failed jobs. Add “make cleantest” to run `python3 -m test --cleanup`.

- bpo-37362: test_gdb no longer fails if it gets an “unexpected” message on stderr: it now ignores stderr. The purpose of test_gdb is to test that python-gdb.py commands work as expected, not to test gdb.

- bpo-35998: Avoid TimeoutError in test_asyncio: test_start_tls_server_1()

- bpo-37278: Fix test_asyncio ProactorLoopCtrlC: join the thread to prevent leaking a running thread and leaking a reference.

- bpo-37261: Fix `test.support.catch_unraisable_exception()`: its __exit__() method now ignores unraisable exception raised when clearing its `unraisable` attribute.

- bpo-37069: regrtest now uses `sys.unraisablehook()` to mark a test as “environment altered” (ENV_CHANGED) if it emits an “unraisable exception”. Moreover, regrtest logs a warning in this case.

  Use `python3 -m test --fail-env-changed` to catch unraisable exceptions in tests.

- bpo-37252: Fix assertions in `test_close` and `test_events_mask_overflow` devpoll tests.

- bpo-37169: Rewrite `_PyObject_IsFreed()` unit tests.

- bpo-37153: `test_venv.test_multiprocessing()` now explicitly calls `pool.terminate()` to wait until the pool completes.

- bpo-34001: Make test_ssl pass with LibreSSL. LibreSSL handles minimum and maximum TLS version differently than OpenSSL.

- bpo-36919: Make `test_source_encoding.test_issue2301` implementation independent. The test will work now for both CPython and IronPython.

- bpo-30202: Update `test.test_importlib.test_abc` to test `find_spec()`.

- bpo-28009: Modify the test_uuid logic to test when a program is available AND can be used to obtain a MACADDR as basis for an UUID. Patch by M. Felt

- bpo-34596: Fallback to a default reason when `unittest.skip()` is uncalled. Patch by Naitree Zhu.

### Build

- bpo-38809: On Windows, build scripts will now recognize and use python.exe from an active virtual env.

- bpo-38684: Fix _hashlib build when Blake2 is disabled, but OpenSSL supports it.

- bpo-38468: Misc/python-config.in now uses `getvar()` for all still existing `sysconfig.get_config_var()` calls. Patch by Joannah Nanjekye.

- bpo-37415: Fix stdatomic.h header check for ICC compiler: the ICC implementation lacks atomic_uintptr_t type which is needed by Python.

- bpo-38301: In Solaris family, we must be sure to use `-D_REENTRANT`. Patch by Jesús Cea Avión.

- bpo-36002: Locate `llvm-profdata` and `llvm-ar` binaries using `AC_PATH_TOOL` rather than `AC_PATH_TARGET_TOOL`.

- bpo-37936: The `.gitignore` file systematically keeps “rooted”, with a non-trailing slash, all the rules that are meant to apply to files in a specific place in the repo. Previously, when the intended file to ignore happened to be at the root of the repo, we’d most often accidentally also ignore files and directories with the same name anywhere in the tree.

- bpo-37760: The `Tools/unicode/makeunicodedata.py` script, which is used for converting information from the Unicode Character Database into generated code and data used by the methods of `str` and by the `unicodedata` module, now handles each character’s data as a `dataclass` with named attributes, rather than a length-18 list of different fields.

- bpo-37936: The `.gitignore` file no longer applies to any files that are in fact tracked in the Git repository. Patch by Greg Price.

- bpo-37725: Change “clean” makefile target to also clean the program guided optimization (PGO) data. Previously you would have to use “make clean” and “make profile-removal”, or “make clobber”.

- bpo-37707: Mark some individual tests to skip when –pgo is used. The tests marked increase the PGO task time significantly and likely don’t help improve optimization of the final executable.

- bpo-36044: Reduce the number of unit tests run for the PGO generation task. This speeds up the task by a factor of about 15x. Running the full unit test suite is slow. This change may result in a slightly less optimized build since not as many code branches will be executed. If you are willing to wait for the much slower build, the old behavior can be restored using ‘./configure [..] PROFILE_TASK=”-m test –pgo-extended”’. We make no guarantees as to which PGO task set produces a faster build. Users who care should run their own relevant benchmarks as results can depend on the environment, workload, and compiler tool chain.

- bpo-37468: `make install` no longer installs `wininst-*.exe` files used by distutils bdist_wininst: bdist_wininst only works on Windows.

- bpo-37189: Many `PyRun_XXX()` functions like `PyRun_String()` were no longer exported in `libpython38.dll` by mistake. Export them again to fix the ABI compatibility.

- bpo-25361: Enables use of SSE2 instructions in Windows 32-bit build.

- bpo-36210: Update optional extension module detection for AIX. ossaudiodev and spwd are not applicable for AIX, and are no longer reported as missing. 3rd-party packaging of ncurses (with ASIS support) conflicts with officially supported AIX curses library, so configure AIX to use libcurses.a. However, skip trying to build _curses_panel.

  patch by M Felt

### Windows

- bpo-38589: Fixes HTML Help shortcut when Windows is not installed to C drive

- bpo-38453: Ensure ntpath.realpath() correctly resolves relative paths.

- bpo-38519: Restores the internal C headers that were missing from the nuget.org and Microsoft Store packages.

- bpo-38492: Remove `pythonw.exe` dependency on the Microsoft C++ runtime.

- bpo-38344: Fix error message in activate.bat

- bpo-38359: Ensures `pyw.exe` launcher reads correct registry key.

- bpo-38355: Fixes `ntpath.realpath` failing on `sys.executable`.

- bpo-38117: Update bundled OpenSSL to 1.1.1d

- bpo-38092: Reduce overhead when using multiprocessing in a Windows virtual environment.

- bpo-38133: Allow py.exe launcher to locate installations from the Microsoft Store and improve display of active virtual environments.

- bpo-38114: The `pip.ini` is no longer included in the Nuget package.

- bpo-32592: Set Windows 8 as the minimum required version for API support

- bpo-36634: `os.cpu_count()` now returns active processors rather than maximum processors.

- bpo-36634: venv activate.bat now works when the existing variables contain double quote characters.

- bpo-38081: Prevent error calling `os.path.realpath()` on `'NUL'`.

- bpo-38087: Fix case sensitivity in test_pathlib and test_ntpath.

- bpo-38088: Fixes distutils not finding vcruntime140.dll with only the v142 toolset installed.

- bpo-37283: Ensure command-line and unattend.xml setting override previously detected states in Windows installer.

- bpo-38030: Fixes `os.stat()` failing for block devices on Windows

- bpo-38020: Fixes potential crash when calling `os.readlink()` (or indirectly through `realpath()`) on a file that is not a supported link.

- bpo-37705: Improve the implementation of `winerror_to_errno()`.

- bpo-37549: `os.dup()` no longer fails for standard streams on Windows 7.

- bpo-1311: The `nul` file on Windows now returns True from `exists()` and a valid result from `os.stat()` with `S_IFCHR` set.

- bpo-9949: Enable support for following symlinks in `os.realpath()`.

- bpo-37834: Treat all name surrogate reparse points on Windows in `os.lstat()` and other reparse points as regular files in `os.stat()`.

- bpo-36266: Add the module name in the formatted error message when DLL load fail happens during module import in `_PyImport_FindSharedFuncptrWindows()`. Patch by Srinivas Nyayapati.

- bpo-25172: Trying to import the `crypt` module on Windows will result in an `ImportError` with a message explaining that the module isn’t supported on Windows. On other platforms, if the underlying `_crypt` module is not available, the ImportError will include a message explaining the problem.

- bpo-37778: Fixes the icons used for file associations to the Microsoft Store package.

- bpo-37734: Fix use of registry values to launch Python from Microsoft Store app.

- bpo-37702: Fix memory leak on Windows in creating an SSLContext object or running `urllib.request.urlopen('https://...')`.

- bpo-37672: Switch Windows Store package’s pip to use bundled `pip.ini` instead of `PIP_USER` variable.

- bpo-10945: Officially drop support for creating bdist_wininst installers on non-Windows systems.

- bpo-37445: Include the `FORMAT_MESSAGE_IGNORE_INSERTS` flag in `FormatMessageW()` calls.

- bpo-37369: Fixes path for `sys.executable` when running from the Microsoft Store.

- bpo-37380: Don’t collect unfinished processes with `subprocess._active` on Windows to cleanup later. Patch by Ruslan Kuprieiev.

- bpo-37351: Removes libpython38.a from standard Windows distribution.

- bpo-35360: Update Windows builds to use SQLite 3.28.0.

- bpo-37267: On Windows, `os.dup()` no longer creates an inheritable fd when handling a character file.

- bpo-36779: Ensure `time.tzname` is correct on Windows when the active code page is set to CP_UTF7 or CP_UTF8.

- bpo-32587: Make `winreg.REG_MULTI_SZ` support zero-length strings.

- bpo-28269: Replace use of `strcasecmp()` for the system function `_stricmp()`. Patch by Minmin Gong.

- bpo-36590: Add native Bluetooth RFCOMM support to socket module.

### macOS

- bpo-38117: Updated OpenSSL to 1.1.1d in macOS installer.

- bpo-38089: Move Azure Pipelines to latest VM versions and make macOS tests optional

- bpo-18049: Increase the default stack size of threads from 5MB to 16MB on macOS, to match the stack size of the main thread. This avoids crashes on deep recursion in threads.

- bpo-34602: Avoid test suite failures on macOS by no longer calling resource.setrlimit to increase the process stack size limit at runtime. The runtime change is no longer needed since the interpreter is being built with a larger default stack size.

- bpo-35360: Update macOS installer to use SQLite 3.28.0.

- bpo-34631: Updated OpenSSL to 1.1.1c in macOS installer.

### IDLE

- bpo-26353: Stop adding newline when saving an IDLE shell window.

- bpo-4630: Add an option to toggle IDLE’s cursor blink for shell, editor, and output windows. See Settings, General, Window Preferences, Cursor Blink. Patch by Zackery Spytz.

- bpo-38598: Do not try to compile IDLE shell or output windows

- bpo-36698: IDLE no longer fails when write non-encodable characters to stderr. It now escapes them with a backslash, as the regular Python interpreter. Added the `errors` field to the standard streams.

- bpo-35379: When exiting IDLE, catch any AttributeError. One happens when EditorWindow.close is called twice. Printing a traceback, when IDLE is run from a terminal, is useless and annoying.

- bpo-38183: To avoid problems, test_idle ignores the user config directory. It no longer tries to create or access .idlerc or any files within. Users must run IDLE to discover problems with saving settings.

- bpo-38077: IDLE no longer adds ‘argv’ to the user namespace when initializing it. This bug only affected 3.7.4 and 3.8.0b2 to 3.8.0b4.

- bpo-38041: Shell restart lines now fill the window width, always start with ‘=’, and avoid wrapping unnecessarily. The line will still wrap if the included file name is long relative to the width.

- bpo-35771: To avoid occasional spurious test_idle failures on slower machines, increase the `hover_delay` in test_tooltip.

- bpo-37824: Properly handle user input warnings in IDLE shell. Cease turning SyntaxWarnings into SyntaxErrors.

- bpo-37929: IDLE Settings dialog now closes properly when there is no shell window.

- bpo-37902: Add mousewheel scrolling for IDLE module, path, and stack browsers. Patch by George Zhang.

- bpo-37849: Fixed completions list appearing too high or low when shown above the current line.

- bpo-36419: Refactor IDLE autocomplete and improve testing.

- bpo-37748: Reorder the Run menu. Put the most common choice, Run Module, at the top.

- bpo-37692: Improve highlight config sample with example shell interaction and better labels for shell elements.

- bpo-37628: Settings dialog no longer expands with font size.

- bpo-37627: Initialize the Customize Run dialog with the command line arguments most recently entered before. The user can optionally edit before submitting them.

- bpo-33610: Fix code context not showing the correct context when first toggled on.

- bpo-37530: Optimize code context to reduce unneeded background activity. Font and highlight changes now occur along with text changes instead of after a random delay.

- bpo-27452: Cleanup `config.py` by inlining `RemoveFile` and simplifying the handling of `file` in `CreateConfigHandlers`.

- bpo-37325: Fix tab focus traversal order for help source and custom run dialogs.

- bpo-37321: Both subprocess connection error messages now refer to the ‘Startup failure’ section of the IDLE doc.

- bpo-17535: Add optional line numbers for IDLE editor windows. Windows open without line numbers unless set otherwise in the General tab of the configuration dialog.

- bpo-26806: To compensate for stack frames added by IDLE and avoid possible problems with low recursion limits, add 30 to limits in the user code execution process. Subtract 30 when reporting recursion limits to make this addition mostly transparent.

- bpo-37177: Properly ‘attach’ search dialogs to their main window so that they behave like other dialogs and do not get hidden behind their main window.

- bpo-37039: Adjust “Zoom Height” to individual screens by momentarily maximizing the window on first use with a particular screen. Changing screen settings may invalidate the saved height. While a window is maximized, “Zoom Height” has no effect.

- bpo-35763: Make calltip reminder about ‘/’ meaning positional-only less obtrusive by only adding it when there is room on the first line.

- bpo-5680: Add ‘Run… Customized’ to the Run menu to run a module with customized settings. Any ‘command line arguments’ entered are added to sys.argv. One can suppress the normal Shell main module restart.

- bpo-36390: Gather Format menu functions into format.py. Combine paragraph.py, rstrip.py, and format methods from editor.py.

### Tools/Demos

- bpo-38118: Update Valgrind suppression file to ignore a false alarm in `PyUnicode_Decode()` when using GCC builtin strcmp().

- bpo-38347: pathfix.py: Assume all files that end on ‘.py’ are Python scripts when working recursively.

- bpo-37803: pdb’s `--help` and `--version` long options now work.

- bpo-37942: Improve ArgumentClinic converter for floats.

- bpo-37704: Remove `Tools/scripts/h2py.py`: use cffi to access a C API in Python.

- bpo-37675: 2to3 now works when run from a zipped standard library.

- bpo-37034: Argument Clinic now uses the argument name on errors with keyword-only argument instead of their position. Patch contributed by Rémi Lapeyre.

- bpo-37064: Add option -k to pathscript.py script: preserve shebang flags. Add option -a to pathscript.py script: add flags.

### C API

- bpo-37633: Re-export some function compatibility wrappers for macros in `pythonrun.h`.

- bpo-38644: Provide `Py_EnterRecursiveCall()` and `Py_LeaveRecursiveCall()` as regular functions for the limited API. Previously, there were defined as macros, but these macros didn’t work with the limited API which cannot access `PyThreadState.recursion_depth` field. Remove `_Py_CheckRecursionLimit` from the stable ABI.

- bpo-38650: The global variable `PyStructSequence_UnnamedField` is now a constant and refers to a constant string.

- bpo-38540: Fixed possible leak in `PyArg_Parse()` and similar functions for format units `"es#"` and `"et#"` when the macro `PY_SSIZE_T_CLEAN` is not defined.

- bpo-38395: Fix a crash in `weakref.proxy` objects due to incorrect lifetime management when calling some associated methods that may delete the last reference to object being referenced by the proxy. Patch by Pablo Galindo.

- bpo-36389: The `_PyObject_CheckConsistency()` function is now also available in release mode. For example, it can be used to debug a crash in the `visit_decref()` function of the GC.

- bpo-38266: Revert the removal of PyThreadState_DeleteCurrent() with documentation.

- bpo-38303: Update audioop extension module to use the stable ABI (PEP-384). Patch by Tyler Kieft.

- bpo-38234: `Py_SetPath()` now sets `sys.executable` to the program full path (`Py_GetProgramFullPath()`) rather than to the program name (`Py_GetProgramName()`).

- bpo-38234: Python ignored arguments passed to `Py_SetPath()`, `Py_SetPythonHome()` and `Py_SetProgramName()`: fix Python initialization to use specified arguments.

- bpo-38205: The `Py_UNREACHABLE()` macro now calls `Py_FatalError()`.

- bpo-38140: Make dict and weakref offsets opaque for C heap types by passing the offsets through PyMemberDef

- bpo-15088: The C function `PyGen_NeedsFinalizing` has been removed. It was not documented, tested or used anywhere within CPython after the implementation of PEP 442. Patch by Joannah Nanjekye. (Patch by Joannah Nanjekye)

- bpo-36763: Options added by `PySys_AddXOption()` are now handled the same way than `PyConfig.xoptions` and command line `-X` options.

- bpo-37926: Fix a crash in `PySys_SetArgvEx(0, NULL, 0)`.

- bpo-37879: Fix subtype_dealloc to suppress the type decref when the base type is a C heap type

- bpo-37645: Add `_PyObject_FunctionStr()` to get a user-friendly string representation of a function-like object. Patch by Jeroen Demeyer.

- bpo-29548: The functions `PyEval_CallObject`, `PyEval_CallFunction`, `PyEval_CallMethod` and `PyEval_CallObjectWithKeywords` are deprecated. Use `PyObject_Call()` and its variants instead.

- bpo-37151: `PyCFunction_Call` is now a deprecated alias of `PyObject_Call()`.

- bpo-37540: The vectorcall protocol now requires that the caller passes only strings as keyword names.

- bpo-37207: The vectorcall protocol is now enabled for `type` objects: set `tp_vectorcall` to a vectorcall function to be used instead of `tp_new` and `tp_init` when calling the class itself.

- bpo-21120: Exclude Python-ast.h, ast.h and asdl.h from the limited API.

- bpo-37483: Add new function `_PyObject_CallOneArg` for calling an object with one positional argument.

- bpo-36763: Add `PyConfig_SetWideStringList()` function.

- bpo-37337: Add fast functions for calling methods: `_PyObject_VectorcallMethod()`, `_PyObject_CallMethodNoArgs()` and `_PyObject_CallMethodOneArg()`.

- bpo-28805: The `METH_FASTCALL` calling convention has been documented.

- bpo-37221: The new function `PyCode_NewWithPosOnlyArgs()` allows to create code objects like `PyCode_New()`, but with an extra posonlyargcount parameter for indicating the number of positonal-only arguments.

- bpo-37215: Fix dtrace issue introduce by bpo-36842

- bpo-37194: Add a new public `PyObject_CallNoArgs()` function to the C API: call a callable Python object without any arguments. It is the most efficient way to call a callback without any argument. On x86-64, for example, `PyObject_CallFunctionObjArgs(func, NULL)` allocates 960 bytes on the stack per call, whereas `PyObject_CallNoArgs(func)` only allocates 624 bytes per call.

- bpo-37170: Fix the cast on error in `PyLong_AsUnsignedLongLongMask()`.

- bpo-35381: Convert posixmodule.c statically allocated types `DirEntryType` and `ScandirIteratorType` to heap-allocated types.

- bpo-34331: Use singular/plural noun in error message when instantiating an abstract class with non-overridden abstract method(s).

## Python 3.8.0 beta 1

Release date: 2019-06-04

### Security

- bpo-35907: CVE 2019-9948: Avoid file reading by disallowing `local-file://` and `local_file://` URL schemes in `URLopener().open()` and `URLopener().retrieve()` of `urllib.request`.

- bpo-33529: Prevent fold function used in email header encoding from entering infinite loop when there are too many non-ASCII characters in a header.

- bpo-33164: Updated blake2 implementation which uses secure memset implementation provided by platform.

### Core and Builtins

- bpo-35814: Allow unpacking in the right hand side of annotated assignments. In particular, `t: Tuple[int, ...] = x, y, *z` is now allowed.

- bpo-37126: All structseq objects are now tracked by the garbage collector. Patch by Pablo Galindo.

- bpo-37122: Make the co_argcount attribute of code objects represent the total number of positional arguments (including positional-only arguments). The value of co_posonlyargcount can be used to distinguish which arguments are positional only, and the difference (co_argcount - co_posonlyargcount) is the number of positional-or-keyword arguments. Patch by Pablo Galindo.

- bpo-20092: Constructors of `int`, `float` and `complex` will now use the `__index__()` special method, if available and the corresponding method `__int__()`, `__float__()` or `__complex__()` is not available.

- bpo-37087: Add native thread ID (TID) support to OpenBSD.

- bpo-26219: Implemented per opcode cache mechanism and `LOAD_GLOBAL` instruction use it. `LOAD_GLOBAL` is now about 40% faster. Contributed by Yury Selivanov, and Inada Naoki.

- bpo-37072: Fix crash in PyAST_FromNodeObject() when flags is NULL.

- bpo-37029: Freeing a great many small objects could take time quadratic in the number of arenas, due to using linear search to keep `obmalloc.c`’s list of usable arenas sorted by order of number of free memory pools. This is accomplished without search now, leaving the worst-case time linear in the number of arenas. For programs where this quite visibly matters (typically with more than 100 thousand small objects alive simultaneously), this can greatly reduce the time needed to release their memory.

- bpo-26423: Fix possible overflow in `wrap_lenfunc()` when `sizeof(long) < sizeof(Py_ssize_t)` (e.g., 64-bit Windows).

- bpo-37050: Improve the AST for “debug” f-strings, which use ‘=’ to print out the source of the expression being evaluated. Delete expr_text from the FormattedValue node, and instead use a Constant string node (possibly merged with adjacent constant expressions inside the f-string).

- bpo-22385: The `bytes.hex`, `bytearray.hex`, and `memoryview.hex` methods as well as the `binascii.hexlify` and `b2a_hex` functions now have the ability to include an optional separator between hex bytes. This functionality was inspired by MicroPython’s hexlify implementation.

- bpo-26836: Add `os.memfd_create()`.

- bpo-37032: Added new `replace()` method to the code type (`types.CodeType`).

- bpo-37007: Implement `socket.if_nameindex()`, `socket.if_nametoindex()`, and `socket.if_indextoname()` on Windows.

- bpo-36829: `PyErr_WriteUnraisable()` now creates a traceback object if there is no current traceback. Moreover, call `PyErr_NormalizeException()` and `PyException_SetTraceback()` to normalize the exception value. Ignore any error.

- bpo-36878: Only accept text after `# type: ignore` if the first character is ASCII. This is to disallow things like `# type: ignoreé`.

- bpo-36878: Store text appearing after a `# type: ignore` comment in the AST. For example a type ignore like `# type: ignore[E1000]` will have the string `"[E1000]"` stored in its AST node.

- bpo-2180: Treat line continuation at EOF as a `SyntaxError` by Anthony Sottile.

- bpo-36907: Fix a crash when calling a C function with a keyword dict (`f(**kwargs)`) and changing the dict `kwargs` while that function is running.

- bpo-36946: Fix possible signed integer overflow when handling slices.

- bpo-36826: Add NamedExpression kind support to ast_unparse.c

- bpo-1875: A `SyntaxError` is now raised if a code blocks that will be optimized away (e.g. if conditions that are always false) contains syntax errors. Patch by Pablo Galindo.

- bpo-36027: Allow computation of modular inverses via three-argument `pow`: the second argument is now permitted to be negative in the case where the first and third arguments are relatively prime.

- bpo-36861: Update the Unicode database to version 12.1.0.

- bpo-28866: Avoid caching attributes of classes which type defines mro() to avoid a hard cache invalidation problem.

- bpo-36851: The `FrameType` stack is now correctly cleaned up if the execution ends with a return and the stack is not empty.

- bpo-34616: The `compile()` builtin functions now support the `ast.PyCF_ALLOW_TOP_LEVEL_AWAIT` flag, which allow to compile sources that contains top-level `await`, `async with` or `async for`. This is useful to evaluate async-code from with an already async functions; for example in a custom REPL.

- bpo-36842: Implement PEP 578, adding sys.audit, io.open_code and related APIs.

- bpo-27639: Correct return type for UserList slicing operations. Patch by Michael Blahay, Erick Cervantes, and vaultah

- bpo-36737: Move PyRuntimeState.warnings into per-interpreter state (via “module state”).

- bpo-36793: Removed `__str__` implementations from builtin types `bool`, `int`, `float`, `complex` and few classes from the standard library. They now inherit `__str__()` from `object`.

- bpo-36817: Add a `=` feature f-strings for debugging. This can precede `!s`, `!r`, or `!a`. It produces the text of the expression, followed by an equal sign, followed by the repr of the value of the expression. So `f'{3*9+15=}'` would be equal to the string `'3*9+15=42'`. If `=` is specified, the default conversion is set to `!r`, unless a format spec is given, in which case the formatting behavior is unchanged, and __format__ will be used.

- bpo-24048: Save the live exception during import.c’s `remove_module()`.

- bpo-27987: pymalloc returns memory blocks aligned by 16 bytes, instead of 8 bytes, on 64-bit platforms to conform x86-64 ABI. Recent compilers assume this alignment more often. Patch by Inada Naoki.

- bpo-36601: A long-since-meaningless check for `getpid() == main_pid` was removed from Python’s internal C signal handler.

- bpo-36594: Fix incorrect use of `%p` in format strings. Patch by Zackery Spytz.

- bpo-36045: `builtins.help()` now prefixes `async` for async functions.

- bpo-36084: Add native thread ID (TID) to threading.Thread objects (supported platforms: Windows, FreeBSD, Linux, macOS)

- bpo-36035: Added fix for broken symlinks in combination with pathlib

- bpo-35983: Added new trashcan macros to deal with a double deallocation that could occur when the `tp_dealloc` of a subclass calls the `tp_dealloc` of a base class and that base class uses the trashcan mechanism. Patch by Jeroen Demeyer.

- bpo-20602: Do not clear `sys.flags` and `sys.float_info` during shutdown. Patch by Zackery Spytz.

- bpo-26826: Expose `copy_file_range()` as a low level API in the `os` module.

- bpo-32388: Remove cross-version binary compatibility requirement in tp_flags.

- bpo-31862: Port binascii to PEP 489 multiphase initialization. Patch by Marcel Plch.

### Library

- bpo-37128: Added `math.perm()`.

- bpo-37120: Add SSLContext.num_tickets to control the number of TLSv1.3 session tickets.

- bpo-12202: Fix the error handling in `msilib.SummaryInformation.GetProperty()`. Patch by Zackery Spytz.

- bpo-26835: The fcntl module now contains file sealing constants for sealing of memfds.

- bpo-29262: Add `get_origin()` and `get_args()` introspection helpers to `typing` module.

- bpo-12639: `msilib.Directory.start_component()` no longer fails if keyfile is not `None`.

- bpo-36999: Add the `asyncio.Task.get_coro()` method to publicly expose the tasks’s coroutine object.

- bpo-35246: Make `asyncio.create_subprocess_exec()` accept path-like arguments.

- bpo-35279: Change default max_workers of `ThreadPoolExecutor` from `cpu_count() * 5` to `min(32, cpu_count() + 4)`. Previous value was unreasonably large on many cores machines.

- bpo-37076: `_thread.start_new_thread()` now logs uncaught exception raised by the function using `sys.unraisablehook()`, rather than `sys.excepthook()`, so the hook gets access to the function which raised the exception.

- bpo-33725: On macOS, the `multiprocessing` module now uses spawn start method by default.

- bpo-37054: Fix destructor `_pyio.BytesIO` and `_pyio.TextIOWrapper`: initialize their `_buffer` attribute as soon as possible (in the class body), because it’s used by `__del__()` which calls `close()`.

- bpo-37058: PEP 544: Add `Protocol` and `@runtime_checkable` to the `typing` module.

- bpo-36933: The functions `sys.set_coroutine_wrapper` and `sys.get_coroutine_wrapper` that were deprecated and marked for removal in 3.8 have been removed.

- bpo-37047: Handle late binding and attribute access in `unittest.mock.AsyncMock` setup for autospeccing. Document newly implemented async methods in `unittest.mock.MagicMock`.

- bpo-37049: PEP 589: Add `TypedDict` to the `typing` module.

- bpo-37046: PEP 586: Add `Literal` to the `typing` module.

- bpo-37045: PEP 591: Add `Final` qualifier and `@final` decorator to the `typing` module.

- bpo-37035: Don’t log OSError based exceptions if a fatal error has occurred in asyncio transport. Peer can generate almost any OSError, user cannot avoid these exceptions by fixing own code. Errors are still propagated to user code, it’s just logging them is pointless and pollute asyncio logs.

- bpo-37001: `symtable.symtable()` now accepts the same input types for source code as the built-in `compile()` function. Patch by Dino Viehland.

- bpo-37028: Implement asyncio REPL

- bpo-37027: Return safe to use proxy socket object from transport.get_extra_info(‘socket’)

- bpo-32528: Make asyncio.CancelledError a BaseException.

  This will address the common mistake many asyncio users make: an “except Exception” clause breaking Tasks cancellation.

  In addition to this change, we stop inheriting asyncio.TimeoutError and asyncio.InvalidStateError from their concurrent.futures.* counterparts. There’s no point for these exceptions to share the inheritance chain.

- bpo-1230540: Add a new `threading.excepthook()` function which handles uncaught `threading.Thread.run()` exception. It can be overridden to control how uncaught `threading.Thread.run()` exceptions are handled.

- bpo-36996: Handle `unittest.mock.patch()` used as a decorator on async functions.

- bpo-37008: Add support for calling `next()` with the mock resulting from `unittest.mock.mock_open()`

- bpo-27737: Allow whitespace only header encoding in `email.header` - by Batuhan Taskaya

- bpo-36969: PDB command `args` now display positional only arguments. Patch contributed by Rémi Lapeyre.

- bpo-36969: PDB command `args` now display keyword only arguments. Patch contributed by Rémi Lapeyre.

- bpo-36983: Add missing names to `typing.__all__`: `ChainMap`, `ForwardRef`, `OrderedDict` - by Anthony Sottile.

- bpo-36972: Add SupportsIndex protocol to the typing module to allow type checking to detect classes that can be passed to `hex()`, `oct()` and `bin()`.

- bpo-32972: Implement `unittest.IsolatedAsyncioTestCase` to help testing asyncio-based code.

- bpo-36952: `fileinput.input()` and `fileinput.FileInput` bufsize argument has been removed (was deprecated and ignored since Python 3.6), and as a result the mode and openhook arguments have been made keyword-only.

- bpo-36952: Starting with Python 3.3, importing ABCs from `collections` is deprecated, and import should be done from `collections.abc`. Still being able to import from `collections` was marked for removal in 3.8, but has been delayed to 3.9; documentation and `DeprecationWarning` clarified.

- bpo-36949: Implement __repr__ for WeakSet objects.

- bpo-36948: Fix `NameError` in `urllib.request.URLopener.retrieve()`. Patch by Karthikeyan Singaravelan.

- bpo-33524: Fix the folding of email header when the max_line_length is 0 or None and the header contains non-ascii characters. Contributed by Licht Takeuchi (@Licht-T).

- bpo-24564: `shutil.copystat()` now ignores `errno.EINVAL` on `os.setxattr()` which may occur when copying files on filesystems without extended attributes support.

  Original patch by Giampaolo Rodola, updated by Ying Wang.

- bpo-36888: Python child processes can now access the status of their parent process using multiprocessing.process.parent_process

- bpo-36921: Deprecate `@coroutine` for sake of `async def`.

- bpo-25652: Fix bug in `__rmod__` of `UserString` - by Batuhan Taskaya.

- bpo-36916: Remove a message about an unhandled exception in a task when writer.write() is used without await and writer.drain() fails with an exception.

- bpo-36889: Introduce `asyncio.Stream` class that merges `asyncio.StreamReader` and `asyncio.StreamWriter` functionality. `asyncio.Stream` can work in readonly, writeonly and readwrite modes. Provide `asyncio.connect()`, `asyncio.connect_unix()`, `asyncio.connect_read_pipe()` and `asyncio.connect_write_pipe()` factories to open `asyncio.Stream` connections. Provide `asyncio.StreamServer` and `UnixStreamServer` to serve servers with asyncio.Stream API. Modify `asyncio.create_subprocess_shell()` and `asyncio.create_subprocess_exec()` to use `asyncio.Stream` instead of deprecated `StreamReader` and `StreamWriter`. Deprecate `asyncio.StreamReader` and `asyncio.StreamWriter`. Deprecate usage of private classes, e.g. `asyncio.FlowControlMixing` and `asyncio.StreamReaderProtocol` outside of asyncio package.

- bpo-36845: Added validation of integer prefixes to the construction of IP networks and interfaces in the ipaddress module.

- bpo-23378: Add an extend action to argparser.

- bpo-36867: Fix a bug making a SharedMemoryManager instance and its parent process use two separate resource_tracker processes.

- bpo-23896: Adds a grammar to lib2to3.pygram that contains exec as a function not as statement.

- bpo-36895: The function `time.clock()` was deprecated in 3.3 in favor of `time.perf_counter()` and marked for removal in 3.8, it has removed.

- bpo-35545: Fix asyncio discarding IPv6 scopes when ensuring hostname resolutions internally

- bpo-36887: Add new function `math.isqrt()` to compute integer square roots.

- bpo-34632: Introduce the `importlib.metadata` module with (provisional) support for reading metadata from third-party packages.

- bpo-36878: When using `type_comments=True` in `ast.parse`, treat `# type: ignore` followed by a non-alphanumeric character and then arbitrary text as a type ignore, instead of requiring nothing but whitespace or another comment. This is to permit formations such as `# type: ignore[E1000]`.

- bpo-36778: `cp65001` encoding (Windows code page 65001) becomes an alias to `utf_8` encoding.

- bpo-36867: The multiprocessing.resource_tracker replaces the multiprocessing.semaphore_tracker module. Other than semaphores, resource_tracker also tracks shared_memory segments.

- bpo-30262: The `Cache` and `Statement` objects of the `sqlite3` module are not exposed to the user. Patch by Aviv Palivoda.

- bpo-24538: In `shutil.copystat()`, first copy extended file attributes and then file permissions, since extended attributes can only be set on the destination while it is still writeable.

- bpo-36829: Add new `sys.unraisablehook()` function which can be overridden to control how “unraisable exceptions” are handled. It is called when an exception has occurred but there is no way for Python to handle it. For example, when a destructor raises an exception or during garbage collection (`gc.collect()`).

- bpo-36832: Introducing `zipfile.Path`, a pathlib-compatible wrapper for traversing zip files.

- bpo-36814: Fix an issue where os.posix_spawnp() would incorrectly raise a TypeError when file_actions is None.

- bpo-33110: Handle exceptions raised by functions added by concurrent.futures add_done_callback correctly when the Future has already completed.

- bpo-26903: Limit `max_workers` in `ProcessPoolExecutor` to 61 to work around a WaitForMultipleObjects limitation.

- bpo-36813: Fix `QueueListener` to call `queue.task_done()` upon stopping. Patch by Bar Harel.

- bpo-36806: Forbid creation of asyncio stream objects like StreamReader, StreamWriter, Process, and their protocols outside of asyncio package.

- bpo-36802: Provide both sync and async calls for StreamWriter.write() and StreamWriter.close()

- bpo-36801: Properly handle SSL connection closing in asyncio StreamWriter.drain() call.

- bpo-36785: Implement PEP 574 (pickle protocol 5 with out-of-band buffers).

- bpo-36772: functools.lru_cache() can now be used as a straight decorator in addition to its existing usage as a function that returns a decorator.

- bpo-6584: Add a `BadGzipFile` exception to the `gzip` module.

- bpo-36748: Optimized write buffering in C implementation of `TextIOWrapper`. Writing ASCII string to `TextIOWrapper` with ascii, latin1, or utf-8 encoding is about 20% faster. Patch by Inada Naoki.

- bpo-8138: Don’t mark `wsgiref.simple_server.SimpleServer` as multi-threaded since `wsgiref.simple_server.WSGIServer` is single-threaded.

- bpo-22640: `py_compile.compile()` now supports silent mode. Patch by Joannah Nanjekye

- bpo-29183: Fix double exceptions in `wsgiref.handlers.BaseHandler` by calling its `close()` method only when no exception is raised.

- bpo-36548: Improved the repr of regular expression flags.

- bpo-36542: The signature of Python functions can now be overridden by specifying the `__text_signature__` attribute.

- bpo-36533: Reinitialize logging.Handler locks in forked child processes instead of attempting to acquire them all in the parent before forking only to be released in the child process. The acquire/release pattern was leading to deadlocks in code that has implemented any form of chained logging handlers that depend upon one another as the lock acquisition order cannot be guaranteed.

- bpo-35252: Throw a TypeError instead of an AssertionError when using an invalid type annotation with singledispatch.

- bpo-35900: Allow reduction methods to return a 6-item tuple where the 6th item specifies a custom state-setting method that’s called instead of the regular `__setstate__` method.

- bpo-35900: enable custom reduction callback registration for functions and classes in _pickle.c, using the new Pickler’s attribute `reducer_override`

- bpo-36368: Fix a bug crashing SharedMemoryManager instances in interactive sessions after a ctrl-c (KeyboardInterrupt) was sent

- bpo-31904: Fix mmap fail for VxWorks

- bpo-27497: `csv.DictWriter.writeheader()` now returns the return value of the underlying `csv.Writer.writerow()` method. Patch contributed by Ashish Nitin Patil.

- bpo-36239: Parsing .mo files now ignores comments starting and ending with #-#-#-#-#.

- bpo-26707: Enable plistlib to read and write binary plist files that were created as a KeyedArchive file. Specifically, this allows the plistlib to process 0x80 tokens as UID objects.

- bpo-31904: Add posix module support for VxWorks.

- bpo-35125: Asyncio: Remove inner callback on outer cancellation in shield

- bpo-35721: Fix `asyncio.SelectorEventLoop.subprocess_exec()` leaks file descriptors if `Popen` fails and called with `stdin=subprocess.PIPE`. Patch by Niklas Fiekas.

- bpo-31855: `unittest.mock.mock_open()` results now respects the argument of read([size]). Patch contributed by Rémi Lapeyre.

- bpo-35431: Implement `math.comb()` that returns binomial coefficient, that computes the number of ways to choose k items from n items without repetition and without order. Patch by Yash Aggarwal and Keller Fuchs.

- bpo-26660: Fixed permission errors in `TemporaryDirectory` clean up. Previously `TemporaryDirectory.cleanup()` failed when non-writeable or non-searchable files or directories were created inside a temporary directory.

- bpo-34271: Add debugging helpers to ssl module. It’s now possible to dump key material and to trace TLS protocol. The default and stdlib contexts also support SSLKEYLOGFILE env var.

- bpo-26467: Added AsyncMock to support using unittest to mock asyncio coroutines. Patch by Lisa Roach.

- bpo-33569: dataclasses.InitVar: Exposes the type used to create the init var.

- bpo-34424: Fix serialization of messages containing encoded strings when the policy.linesep is set to a multi-character string. Patch by Jens Troeger.

- bpo-34303: Performance of `functools.reduce()` is slightly improved. Patch by Sergey Fedoseev.

- bpo-33361: Fix a bug in `codecs.StreamRecoder` where seeking might leave old data in a buffer and break subsequent read calls. Patch by Ammar Askar.

- bpo-22454: The `shlex` module now exposes `shlex.join()`, the inverse of `shlex.split()`. Patch by Bo Bayles.

- bpo-31922: `asyncio.AbstractEventLoop.create_datagram_endpoint()`: Do not connect UDP socket when broadcast is allowed. This allows to receive replies after a UDP broadcast.

- bpo-24882: Change ThreadPoolExecutor to use existing idle threads before spinning up new ones.

- bpo-31961: Added support for bytes and path-like objects in `subprocess.Popen()` on Windows. The args parameter now accepts a path-like object if shell is `False` and a sequence containing bytes and path-like objects. The executable parameter now accepts a bytes and path-like object. The cwd parameter now accepts a bytes object. Based on patch by Anders Lorentsen.

- bpo-33123: `pathlib.Path.unlink` now accepts a missing_ok parameter to avoid a `FileNotFoundError` from being raised. Patch by Robert Buchholz.

- bpo-32941: Allow `mmap.mmap` objects to access the madvise() system call (through `mmap.mmap.madvise()`).

- bpo-22102: Added support for ZIP files with disks set to 0. Such files are commonly created by builtin tools on Windows when use ZIP64 extension. Patch by Francisco Facioni.

- bpo-32515: trace.py can now run modules via python3 -m trace -t –module module_name

- bpo-32299: Changed `unittest.mock.patch.dict()` to return the patched dictionary when used as context manager. Patch by Vadim Tsander.

- bpo-27141: Added a `__copy__()` to `collections.UserList` and `collections.UserDict` in order to correctly implement shallow copying of the objects. Patch by Bar Harel.

- bpo-31829: `\r`, `\0` and `\x1a` (end-of-file on Windows) are now escaped in protocol 0 pickles of Unicode strings. This allows to load them without loss from files open in text mode in Python 2.

- bpo-23395: `_thread.interrupt_main()` now avoids setting the Python error status if the `SIGINT` signal is ignored or not handled by Python.

### Documentation

- bpo-36896: Clarify that some types have unstable constructor signature between Python versions.

- bpo-36686: Improve documentation of the stdin, stdout, and stderr arguments of the `asyncio.subprocess_exec` function to specify which values are supported. Also mention that decoding as text is not supported.

  Add a few tests to verify that the various values passed to the std* arguments actually work.

- bpo-36984: Improve version added references in `typing` module - by Anthony Sottile.

- bpo-36868: What’s new now mentions SSLContext.hostname_checks_common_name instead of SSLContext.host_flags.

- bpo-35924: Add a note to the `curses.addstr()` documentation to warn that multiline strings can cause segfaults because of an ncurses bug.

- bpo-36783: Added C API Documentation for Time_FromTimeAndFold and PyDateTime_FromDateAndTimeAndFold as per PEP 495. Patch by Edison Abahurire.

- bpo-36797: More of the legacy distutils documentation has been either pruned, or else more clearly marked as being retained solely until the setuptools documentation covers it independently.

- bpo-22865: Add detail to the documentation on the `pty.spawn` function.

- bpo-35397: Remove deprecation and document urllib.parse.unwrap(). Patch contributed by Rémi Lapeyre.

- bpo-32995: Added the context variable in glossary.

- bpo-33519: Clarify that `copy()` is not part of the `MutableSequence` ABC.

- bpo-33482: Make `codecs.StreamRecoder.writelines` take a list of bytes.

- bpo-25735: Added documentation for func factorial to indicate that returns integer values

- bpo-20285: Expand object.__doc__ (docstring) to make it clearer. Modify pydoc.py so that help(object) lists object methods (for other classes, help omits methods of the object base class.)

### Tests

- bpo-37069: Modify test_coroutines, test_cprofile, test_generators, test_raise, test_ssl and test_yield_from to use `test.support.catch_unraisable_exception()` rather than `test.support.captured_stderr()`.

- bpo-37098: Fix test_memfd_create on older Linux Kernels.

- bpo-37081: Test with OpenSSL 1.1.1c

- bpo-36829: Add `test.support.catch_unraisable_exception()`: context manager catching unraisable exception using `sys.unraisablehook()`.

- bpo-36915: The main regrtest process now always removes all temporary directories of worker processes even if they crash or if they are killed on KeyboardInterrupt (CTRL+c).

- bpo-36719: “python3 -m test -jN …” now continues the execution of next tests when a worker process crash (CHILD_ERROR state). Previously, the test suite stopped immediately. Use –failfast to stop at the first error.

- bpo-36816: Update Lib/test/selfsigned_pythontestdotnet.pem to match self-signed.pythontest.net’s new TLS certificate.

- bpo-35925: Skip httplib and nntplib networking tests when they would otherwise fail due to a modern OS or distro with a default OpenSSL policy of rejecting connections to servers with weak certificates.

- bpo-36782: Add tests for several C API functions in the `datetime` module. Patch by Edison Abahurire.

- bpo-36342: Fix test_multiprocessing in test_venv if platform lacks functioning sem_open.

### Build

- bpo-36721: To embed Python into an application, a new `--embed` option must be passed to `python3-config --libs --embed` to get `-lpython3.8` (link the application to libpython). To support both 3.8 and older, try `python3-config --libs --embed` first and fallback to `python3-config --libs` (without `--embed`) if the previous command fails.

  Add a pkg-config `python-3.8-embed` module to embed Python into an application: `pkg-config python-3.8-embed --libs` includes `-lpython3.8`. To support both 3.8 and older, try `pkg-config python-X.Y-embed --libs` first and fallback to `pkg-config python-X.Y --libs` (without `--embed`) if the previous command fails (replace `X.Y` with the Python version).

  On the other hand, `pkg-config python3.8 --libs` no longer contains `-lpython3.8`. C extensions must not be linked to libpython (except on Android, case handled by the script); this change is backward incompatible on purpose.

- bpo-36786: “make install” now runs compileall in parallel.

### Windows

- bpo-36965: include of STATUS_CONTROL_C_EXIT without depending on MSC compiler

- bpo-35926: Update to OpenSSL 1.1.1b for Windows.

- bpo-29883: Add Windows support for UDP transports for the Proactor Event Loop. Patch by Adam Meily.

- bpo-33407: The `Py_DEPRECATED()` macro has been implemented for MSVC.

### macOS

- bpo-36231: Support building Python on macOS without /usr/include installed. As of macOS 10.14, system header files are only available within an SDK provided by either the Command Line Tools or the Xcode app.

### IDLE

- bpo-35610: Replace now redundant .context_use_ps1 with .prompt_last_line. This finishes change started in bpo-31858.

- bpo-37038: Make idlelib.run runnable; add test clause.

- bpo-36958: Print any argument other than None or int passed to SystemExit or sys.exit().

- bpo-36807: When saving a file, call os.fsync() so bits are flushed to e.g. USB drive.

- bpo-32411: In browser.py, remove extraneous sorting by line number since dictionary was created in line number order.

### Tools/Demos

- bpo-37053: Handle strings like u”bar” correctly in Tools/parser/unparse.py. Patch by Chih-Hsuan Yen.

### C API

- bpo-36763: Implement the PEP 587 “Python Initialization Configuration”.

- bpo-36379: Fix crashes when attempting to use the modulo parameter when `__ipow__` is implemented in C.

- bpo-37107: Update `PyObject_CallMethodObjArgs()` and `_PyObject_CallMethodIdObjArgs` to use `_PyObject_GetMethod` to avoid creating a bound method object in many cases. Patch by Michael J. Sullivan.

- bpo-36974: Implement PEP 590: Vectorcall: a fast calling protocol for CPython. This is a new protocol to optimize calls of custom callable objects.

- bpo-36763: `Py_Main()` now returns the exitcode rather than calling `Py_Exit(exitcode)` when calling `PyErr_Print()` if the current exception type is `SystemExit`.

- bpo-36922: Add new type flag `Py_TPFLAGS_METHOD_DESCRIPTOR` for objects behaving like unbound methods. These are objects supporting the optimization given by the `LOAD_METHOD`/`CALL_METHOD` opcodes. See PEP 590.

- bpo-36728: The `PyEval_ReInitThreads()` function has been removed from the C API. It should not be called explicitly: use `PyOS_AfterFork_Child()` instead.

## Python 3.8.0 alpha 4

Release date: 2019-05-06

### Security

- bpo-36742: Fixes mishandling of pre-normalization characters in urlsplit().

- bpo-30458: Address CVE 2019-9740 by disallowing URL paths with embedded whitespace or control characters through into the underlying http client request. Such potentially malicious header injection URLs now cause an http.client.InvalidURL exception to be raised.

- bpo-35755: `shutil.which()` now uses `os.confstr("CS_PATH")` if available and if the `PATH` environment variable is not set. Remove also the current directory from `posixpath.defpath`. On Unix, `shutil.which()` and the `subprocess` module no longer search the executable in the current directory if the `PATH` environment variable is not set.

### Core and Builtins

- bpo-36722: In debug build, import now also looks for C extensions compiled in release mode and for C extensions compiled in the stable ABI.

- bpo-32849: Fix Python Initialization code on FreeBSD to detect properly when stdin file descriptor (fd 0) is invalid.

- bpo-36623: Remove parser headers and related function declarations that lack implementations after the removal of pgen.

- bpo-20180: `dict.pop()` is now up to 33% faster thanks to Argument Clinic. Patch by Inada Naoki.

- bpo-36611: Debug memory allocators: disable serialno field by default from debug hooks on Python memory allocators to reduce the memory footprint by 5%. Enable `tracemalloc` to get the traceback where a memory block has been allocated when a fatal memory error is logged to decide where to put a breakpoint. Compile Python with `PYMEM_DEBUG_SERIALNO` defined to get back the field.

- bpo-36588: On AIX, `sys.platform` doesn’t contain the major version anymore. Always return `'aix'`, instead of `'aix3'` .. `'aix7'`. Since older Python versions include the version number, it is recommended to always use `sys.platform.startswith('aix')`. Contributed by M. Felt.

- bpo-36549: Change str.capitalize to use titlecase for the first character instead of uppercase.

- bpo-36540: Implement PEP 570 (Python positional-only parameters). Patch by Pablo Galindo.

- bpo-36475: `PyEval_AcquireLock()` and `PyEval_AcquireThread()` now terminate the current thread if called while the interpreter is finalizing, making them consistent with `PyEval_RestoreThread()`, `Py_END_ALLOW_THREADS()`, and `PyGILState_Ensure()`.

- bpo-36504: Fix signed integer overflow in _ctypes.c’s `PyCArrayType_new()`.

- bpo-20844: Fix running script with encoding cookie and LF line ending may fail on Windows.

- bpo-24214: Fixed support of the surrogatepass error handler in the UTF-8 incremental decoder.

- bpo-36452: Changing `dict` keys during iteration of the dict itself, `keys()`, `values()`, or `items()` will now be detected in certain corner cases where keys are deleted/added so that the number of keys isn’t changed. A `RuntimeError` will be raised after `len(dict)` iterations. Contributed by Thomas Perl.

- bpo-36459: Fix a possible double `PyMem_FREE()` due to tokenizer.c’s `tok_nextc()`.

- bpo-36433: Fixed TypeError message in classmethoddescr_call.

- bpo-36430: Fix a possible reference leak in `itertools.count()`.

- bpo-36440: Include node names in `ParserError` messages, instead of numeric IDs. Patch by A. Skrobov.

- bpo-36143: Regenerate `keyword` from the Grammar and Tokens file using pgen. Patch by Pablo Galindo.

- bpo-18372: Add missing `PyObject_GC_Track()` calls in the `pickle` module. Patch by Zackery Spytz.

### Library

- bpo-35952: Fix pythoninfo when the compiler is missing.

- bpo-28238: The `.find*()` methods of xml.etree.ElementTree can now search for wildcards like `{*}tag` and `{ns}*` that match a tag in any namespace or all tags in a namespace. Patch by Stefan Behnel.

- bpo-26978: `pathlib.path.link_to()` is now implemented. It creates a hard link pointing to a path.

- bpo-1613500: `fileinput.FileInput` now uses the input file mode to correctly set the output file mode (previously it was hardcoded to `'w'`) when `inplace=True` is passed to its constructor.

- bpo-36734: Fix compilation of `faulthandler.c` on HP-UX. Initialize `stack_t current_stack` to zero using `memset()`.

- bpo-13611: The xml.etree.ElementTree packages gained support for C14N 2.0 serialisation. Patch by Stefan Behnel.

- bpo-36669: Add missing matrix multiplication operator support to weakref.proxy.

- bpo-36676: The XMLParser() in xml.etree.ElementTree provides namespace prefix context to the parser target if it defines the callback methods “start_ns()” and/or “end_ns()”. Patch by Stefan Behnel.

- bpo-36673: The TreeBuilder and XMLPullParser in xml.etree.ElementTree gained support for parsing comments and processing instructions. Patch by Stefan Behnel.

- bpo-36650: The C version of functools.lru_cache() was treating calls with an empty `**kwargs` dictionary as being distinct from calls with no keywords at all. This did not result in an incorrect answer, but it did trigger an unexpected cache miss.

- bpo-28552: Fix `distutils.sysconfig` if `sys.executable` is `None` or an empty string: use `os.getcwd()` to initialize `project_base`. Fix also the distutils build command: don’t use `sys.executable` if it is `None` or an empty string.

- bpo-35755: `shutil.which()` and `distutils.spawn.find_executable` now use `os.confstr("CS_PATH")` if available instead of `os.defpath`, if the `PATH` environment variable is not set. Moreover, don’t use `os.confstr("CS_PATH")` nor `os.defpath` if the `PATH` environment variable is set to an empty string.

- bpo-25430: improve performance of `IPNetwork.__contains__()`

- bpo-30485: Path expressions in xml.etree.ElementTree can now avoid explicit namespace prefixes for tags (or the “{namespace}tag” notation) by passing a default namespace with an empty string prefix.

- bpo-36613: Fix `asyncio` wait() not removing callback if exception

- bpo-36598: Fix `isinstance` check for Mock objects with spec when the code is executed under tracing. Patch by Karthikeyan Singaravelan.

- bpo-18748: In development mode (`-X` `dev`) and in debug build, the `io.IOBase` destructor now logs `close()` exceptions. These exceptions are silent by default in release mode.

- bpo-36575: The `_lsprof` module now uses internal timer same to `time.perf_counter()` by default. `gettimeofday(2)` was used on Unix. New timer has better resolution on most Unix platforms and timings are no longer impacted by system clock updates since `perf_counter()` is monotonic. Patch by Inada Naoki.

- bpo-33461: `json.loads` now emits `DeprecationWarning` when `encoding` option is specified. Patch by Matthias Bussonnier.

- bpo-36559: The random module now prefers the lean internal _sha512 module over hashlib for seed(version=2) to optimize import time.

- bpo-17561: Set backlog=None as the default for socket.create_server.

- bpo-34373: Fix `time.mktime()` error handling on AIX for year before 1970.

- bpo-36232: Improve error message when trying to open existing DBM database that actually doesn’t exist. Patch by Marco Rougeth.

- bpo-36546: Add statistics.quantiles()

- bpo-36050: Optimized `http.client.HTTPResponse.read()` for large response. Patch by Inada Naoki.

- bpo-36522: If debuglevel is set to >0 in `http.client`, print all values for headers with multiple values for the same header name. Patch by Matt Houglum.

- bpo-36492: Deprecated passing required arguments like func as keyword arguments in functions which should accept arbitrary keyword arguments and pass them to other function. Arbitrary keyword arguments (even with names “self” and “func”) can now be passed to these functions if the required arguments are passed as positional arguments.

- bpo-27181: Add statistics.geometric_mean().

- bpo-30427: `os.path.normcase()` relies on `os.fspath()` to check the type of its argument. Redundant checks have been removed from its `posixpath.normcase()` and `ntpath.normcase()` implementations. Patch by Wolfgang Maier.

- bpo-36385: Stop rejecting IPv4 octets for being ambiguously octal. Leading zeros are ignored, and no longer are assumed to specify octal octets. Octets are always decimal numbers. Octets must still be no more than three digits, including leading zeroes.

- bpo-36434: Errors during writing to a ZIP file no longer prevent to properly close it.

- bpo-36407: Fixed wrong indentation writing for CDATA section in xml.dom.minidom. Patch by Vladimir Surjaninov.

- bpo-36326: inspect.getdoc() can now find docstrings for member objects when __slots__ is a dictionary.

- bpo-36366: Calling `stop()` on an unstarted or stopped `unittest.mock.patch()` object will now return `None` instead of raising `RuntimeError`, making the method idempotent. Patch by Karthikeyan Singaravelan.

- bpo-36348: The `imap.IMAP4.logout()` method no longer ignores silently arbitrary exceptions.

- bpo-31904: Add time module support and fix test_time failures for VxWorks.

- bpo-36227: Added support for keyword arguments `default_namespace` and `xml_declaration` in functions `ElementTree.tostring()` and `ElementTree.tostringlist()`.

- bpo-36004: Added new alternate constructors `datetime.date.fromisocalendar()` and `datetime.datetime.fromisocalendar()`, which construct date objects from ISO year, week number and weekday; these are the inverse of each class’s `isocalendar` method. Patch by Paul Ganssle.

- bpo-35936: `modulefinder` no longer depends on the deprecated `imp` module, and the initializer for `modulefinder.ModuleFinder` now has immutable default arguments. Patch by Brandt Bucher.

- bpo-35376: `modulefinder` correctly handles modules that have the same name as a bad package. Patch by Brandt Bucher.

- bpo-17396: `modulefinder` no longer crashes when encountering syntax errors in followed imports. Patch by Brandt Bucher.

- bpo-35934: Added `create_server()` and `has_dualstack_ipv6()` convenience functions to automate the necessary tasks usually involved when creating a server socket, including accepting both IPv4 and IPv6 connections on the same socket. (Contributed by Giampaolo Rodola in bpo-17561.)

- bpo-23078: Add support for `classmethod()` and `staticmethod()` to `unittest.mock.create_autospec()`. Initial patch by Felipe Ochoa.

- bpo-35416: Fix potential resource warnings in distutils. Patch by Mickaël Schoentgen.

- bpo-25451: Add transparency methods to `tkinter.PhotoImage`. Patch by Zackery Spytz.

- bpo-35082: Don’t return deleted attributes when calling dir on a `unittest.mock.Mock`.

- bpo-34547: `wsgiref.handlers.BaseHandler` now handles abrupt client connection terminations gracefully. Patch by Petter Strandmark.

- bpo-31658: `xml.sax.parse()` now supports path-like. Patch by Mickaël Schoentgen.

- bpo-34139: Remove stale unix datagram socket before binding

- bpo-33530: Implemented Happy Eyeballs in `asyncio.create_connection()`. Added two new arguments, happy_eyeballs_delay and interleave, to specify Happy Eyeballs behavior.

- bpo-33291: Do not raise AttributeError when calling the inspect functions isgeneratorfunction, iscoroutinefunction, isasyncgenfunction on a method created from an arbitrary callable. Instead, return False.

- bpo-31310: Fix the multiprocessing.semaphore_tracker so it is reused by child processes

- bpo-31292: Fix `setup.py check --restructuredtext` for files containing `include` directives.

### Documentation

- bpo-36625: Remove obsolete comments from docstrings in fractions.Fraction

- bpo-30840: Document relative imports

- bpo-36523: Add docstring for io.IOBase.writelines().

- bpo-36425: New documentation translation: Simplified Chinese.

- bpo-36345: Avoid the duplication of code from `Tools/scripts/serve.py` in using the `literalinclude` directive for the basic wsgiref-based web server in the documentation of `wsgiref`. Contributed by Stéphane Wirtel.

- bpo-36345: Using the code of the `Tools/scripts/serve.py` script as an example in the `wsgiref` documentation. Contributed by Stéphane Wirtel.

- bpo-36157: Added documentation for PyInterpreterState_Main().

- bpo-33043: Updates the docs.python.org page with the addition of a ‘Contributing to Docs’ link at the end of the page (between ‘Reporting Bugs’ and ‘About Documentation’). Updates the ‘Found a Bug’ page with additional links and information in the Documentation Bugs section.

- bpo-35581: @typing.type_check_only now allows type stubs to mark functions and classes not available during runtime.

- bpo-33832: Add glossary entry for ‘magic method’.

- bpo-32913: Added re.Match.groupdict example to regex HOWTO.

### Tests

- bpo-36719: regrtest now always detects uncollectable objects. Previously, the check was only enabled by `--findleaks`. The check now also works with `-jN/--multiprocess N`. `--findleaks` becomes a deprecated alias to `--fail-env-changed`.

- bpo-36725: When using multiprocessing mode (-jN), regrtest now better reports errors if a worker process fails, and it exits immediately on a worker thread failure or when interrupted.

- bpo-36454: Change test_time.test_monotonic() to test only the lower bound of elapsed time after a sleep command rather than the upper bound. This prevents unnecessary test failures on slow buildbots. Patch by Victor Stinner.

- bpo-32424: Improve test coverage for xml.etree.ElementTree. Patch by Gordon P. Hemsley.

- bpo-32424: Fix typo in test_cyclic_gc() test for xml.etree.ElementTree. Patch by Gordon P. Hemsley.

- bpo-36635: Add a new `_testinternalcapi` module to test the internal C API.

- bpo-36629: Fix `test_imap4_host_default_value()` of `test_imaplib`: catch also `errno.ENETUNREACH` error.

- bpo-36611: Fix `test_sys.test_getallocatedblocks()` when `tracemalloc` is enabled.

- bpo-36560: Fix reference leak hunting in regrtest: compute also deltas (of reference count, allocated memory blocks, file descriptor count) during warmup, to ensure that everything is initialized before starting to hunt reference leaks.

- bpo-36565: Fix reference hunting (`python3 -m test -R 3:3`) when Python has no built-in abc module.

- bpo-31904: Port test_resource to VxWorks: skip tests cases setting RLIMIT_FSIZE and RLIMIT_CPU.

- bpo-31904: Fix test_tabnanny on VxWorks: adjust ENOENT error message.

- bpo-36436: Fix `_testcapi.pymem_buffer_overflow()`: handle memory allocation failure.

- bpo-31904: Fix test_utf8_mode on VxWorks: Python always use UTF-8 on VxWorks.

- bpo-36341: Fix tests that may fail with PermissionError upon calling bind() on AF_UNIX sockets.

### Build

- bpo-36747: Remove the stale scriptsinstall Makefile target.

- bpo-21536: On Unix, C extensions are no longer linked to libpython except on Android and Cygwin.

  It is now possible for a statically linked Python to load a C extension built using a shared library Python.

  When Python is embedded, `libpython` must not be loaded with `RTLD_LOCAL`, but `RTLD_GLOBAL` instead. Previously, using `RTLD_LOCAL`, it was already not possible to load C extensions which were not linked to `libpython`, such as C extensions of the standard library built by the `*shared*` section of `Modules/Setup`.

  distutils, python-config and python-config.py have been modified.

- bpo-36707: `./configure --with-pymalloc` no longer adds the `m` flag to SOABI (sys.implementation.cache_tag). Enabling or disabling pymalloc has no impact on the ABI.

- bpo-36635: Change `PyAPI_FUNC(type)`, `PyAPI_DATA(type)` and `PyMODINIT_FUNC` macros of `pyport.h` when `Py_BUILD_CORE_MODULE` is defined. The `Py_BUILD_CORE_MODULE` define must be now be used to build a C extension as a dynamic library accessing Python internals: export the `PyInit_xxx()` function in DLL exports on Windows.

- bpo-31904: Don’t build the `_crypt` extension on VxWorks.

- bpo-36618: Add `-fmax-type-align=8` to CFLAGS when clang compiler is detected. The pymalloc memory allocator aligns memory on 8 bytes. On x86-64, clang expects alignment on 16 bytes by default and so uses MOVAPS instruction which can lead to segmentation fault. Instruct clang that Python is limited to alignment on 8 bytes to use MOVUPS instruction instead: slower but don’t trigger a SIGSEGV if the memory is not aligned on 16 bytes. Sadly, the flag must be added to `CFLAGS` and not just `CFLAGS_NODIST`, since third party C extensions can have the same issue.

- bpo-36605: `make tags` and `make TAGS` now also parse `Modules/_io/*.c` and `Modules/_io/*.h`.

- bpo-36465: Release builds and debug builds are now ABI compatible: defining the `Py_DEBUG` macro no longer implies the `Py_TRACE_REFS` macro, which introduces the only ABI incompatibility. The `Py_TRACE_REFS` macro, which adds the `sys.getobjects()` function and the `PYTHONDUMPREFS` environment variable, can be set using the new `./configure --with-trace-refs` build option.

- bpo-36577: setup.py now correctly reports missing OpenSSL headers and libraries again.

- bpo-36544: Fix regression introduced in bpo-36146 refactoring setup.py

- bpo-36508: `python-config --ldflags` no longer includes flags of the `LINKFORSHARED` variable. The `LINKFORSHARED` variable must only be used to build executables.

- bpo-36503: Remove references to “aix3” and “aix4”. Patch by M. Felt.

### Windows

- bpo-35920: Added platform.win32_edition() and platform.win32_is_iot(). Added support for cross-compiling packages for Windows ARM32. Skip tests that are not expected to work on Windows IoT Core ARM32.

- bpo-36649: Remove trailing spaces for registry keys when installed via the Store.

- bpo-34144: Fixed activate.bat to correctly update codepage when chcp.com returns dots in output. Patch by Lorenz Mende.

- bpo-36509: Added preset-iot layout for Windows IoT ARM containers. This layout doesn’t contain UI components like tkinter or IDLE. It also doesn’t contain files to support on-target builds since Windows ARM32 builds must be cross-compiled when using MSVC.

- bpo-35941: enum_certificates function of the ssl module now returns certificates from all available certificate stores inside windows in a query instead of returning only certificates from the system wide certificate store. This includes certificates from these certificate stores: local machine, local machine enterprise, local machine group policy, current user, current user group policy, services, users. ssl.enum_crls() function is changed in the same way to return all certificate revocation lists inside the windows certificate revocation list stores.

- bpo-36441: Fixes creating a venv when debug binaries are installed.

- bpo-36085: Enable better DLL resolution on Windows by using safe DLL search paths and adding `os.add_dll_directory()`.

- bpo-36010: Add the venv standard library module to the nuget distribution for Windows.

- bpo-29515: Add the following socket module constants on Windows: IPPROTO_AH IPPROTO_CBT IPPROTO_DSTOPTS IPPROTO_EGP IPPROTO_ESP IPPROTO_FRAGMENT IPPROTO_GGP IPPROTO_HOPOPTS IPPROTO_ICLFXBM IPPROTO_ICMPV6 IPPROTO_IDP IPPROTO_IGMP IPPROTO_IGP IPPROTO_IPV4 IPPROTO_IPV6 IPPROTO_L2TP IPPROTO_MAX IPPROTO_ND IPPROTO_NONE IPPROTO_PGM IPPROTO_PIM IPPROTO_PUP IPPROTO_RDP IPPROTO_ROUTING IPPROTO_SCTP IPPROTO_ST

- bpo-35947: Added current version of libffi to cpython-source-deps. Change _ctypes to use current version of libffi on Windows.

- bpo-34060: Report system load when running test suite on Windows. Patch by Ammar Askar. Based on prior work by Jeremy Kloth.

- bpo-31512: With the Windows 10 Creators Update, non-elevated users can now create symlinks as long as the computer has Developer Mode enabled.

### macOS

- bpo-34602: Avoid failures setting macOS stack resource limit with resource.setrlimit. This reverts an earlier fix for bpo-18075 which forced a non-default stack size when building the interpreter executable on macOS.

### IDLE

- bpo-36429: Fix starting IDLE with pyshell. Add idlelib.pyshell alias at top; remove pyshell alias at bottom. Remove obsolete __name__==’__main__’ command.

### Tools/Demos

- bpo-14546: Fix the argument handling in Tools/scripts/lll.py.

### C API

- bpo-36763: Fix memory leak in `Py_SetStandardStreamEncoding()`: release memory if the function is called twice.

- bpo-36641: PyDoc_VAR(name) and PyDoc_STRVAR(name, str) now create `static const char name[]` instead of `static char name[]`. Patch by Inada Naoki.

- bpo-36389: Change the value of `CLEANBYTE`, `DEADDYTE` and `FORBIDDENBYTE` internal constants used by debug hooks on Python memory allocators (`PyMem_SetupDebugHooks()` function). Byte patterns `0xCB`, `0xDB` and `0xFB` have been replaced with `0xCD`, `0xDD` and `0xFD` to use the same values than Windows CRT debug `malloc()` and `free()`.

- bpo-36443: Since Python 3.7.0, calling `Py_DecodeLocale()` before `Py_Initialize()` produces mojibake if the `LC_CTYPE` locale is coerced and/or if the UTF-8 Mode is enabled by the user configuration. The LC_CTYPE coercion and UTF-8 Mode are now disabled by default to fix the mojibake issue. They must now be enabled explicitly (opt-in) using the new `_Py_PreInitialize()` API with `_PyPreConfig`.

- bpo-36025: Fixed an accidental change to the datetime C API where the arguments to the `PyDate_FromTimestamp()` function were incorrectly interpreted as a single timestamp rather than an arguments tuple, which causes existing code to start raising `TypeError`. The backwards-incompatible change was only present in alpha releases of Python 3.8. Patch by Paul Ganssle.

- bpo-35810: Modify `PyObject_Init` to correctly increase the refcount of heap-allocated Type objects. Also fix the refcounts of the heap-allocated types that were either doing this manually or not decreasing the type’s refcount in tp_dealloc

## Python 3.8.0 alpha 3

Release date: 2019-03-25

### Security

- bpo-36216: Changes urlsplit() to raise ValueError when the URL contains characters that decompose under IDNA encoding (NFKC-normalization) into characters that affect how the URL is parsed.

- bpo-35121: Don’t send cookies of domain A without Domain attribute to domain B when domain A is a suffix match of domain B while using a cookiejar with `http.cookiejar.DefaultCookiePolicy` policy. Patch by Karthikeyan Singaravelan.

### Core and Builtins

- bpo-36421: Fix a possible double decref in _ctypes.c’s `PyCArrayType_new()`.

- bpo-36412: Fix a possible crash when creating a new dictionary.

- bpo-36398: Fix a possible crash in `structseq_repr()`.

- bpo-36256: Fix bug in parsermodule when parsing a state in a DFA that has two or more arcs with labels of the same type. Patch by Pablo Galindo.

- bpo-36365: repr(structseq) is no longer limited to 512 bytes.

- bpo-36374: Fix a possible null pointer dereference in `merge_consts_recursive()`. Patch by Zackery Spytz.

- bpo-36236: At Python initialization, the current directory is no longer prepended to `sys.path` if it has been removed.

- bpo-36352: Python initialization now fails with an error, rather than silently truncating paths, if a path is too long.

- bpo-36301: Python initialization now fails if decoding `pybuilddir.txt` configuration file fails at startup.

- bpo-36333: Fix leak in _PyRuntimeState_Fini. Contributed by Stéphane Wirtel.

- bpo-36332: The builtin `compile()` can now handle AST objects that contain assignment expressions. Patch by Pablo Galindo.

- bpo-36282: Improved error message for too much positional arguments in some builtin functions.

- bpo-30040: New empty dict uses fewer memory for now. It used more memory than empty dict created by `dict.clear()`. And empty dict creation and deletion is about 2x faster. Patch by Inada Naoki.

- bpo-36262: Fix an unlikely memory leak on conversion from string to float in the function `_Py_dg_strtod()` used by `float(str)`, `complex(str)`, `pickle.load()`, `marshal.load()`, etc.

- bpo-36252: Update Unicode databases to version 12.0.0.

- bpo-36218: Fix a segfault occurring when sorting a list of heterogeneous values. Patch contributed by Rémi Lapeyre and Elliot Gorokhovsky.

- bpo-36188: Cleaned up left-over vestiges of Python 2 unbound method handling in method objects and documentation. Patch by Martijn Pieters

- bpo-36124: Add a new interpreter-specific dict and expose it in the C-API via PyInterpreterState_GetDict(). This parallels PyThreadState_GetDict(). However, extension modules should continue using PyModule_GetState() for their own internal per-interpreter state.

- bpo-35975: Add a `feature_version` flag to `ast.parse()` (documented) and `compile()` (hidden) that allows tweaking the parser to support older versions of the grammar. In particular, if `feature_version` is 5 or 6, the hacks for the `async` and `await` keyword from PEP 492 are reinstated. (For 7 or higher, these are unconditionally treated as keywords, but they are still special tokens rather than `NAME` tokens that the parser driver recognizes.)

- bpo-31904: Use UTF-8 as the system encoding on VxWorks.

- bpo-36048: The `__index__()` special method will be used instead of `__int__()` for implicit conversion of Python numbers to C integers. Using the `__int__()` method in implicit conversions has been deprecated.

- bpo-35808: Retire pgen and use a modified version of pgen2 to generate the parser. Patch by Pablo Galindo.

### Library

- bpo-36401: The class documentation created by pydoc now has a separate section for readonly properties.

- bpo-36320: The typing.NamedTuple() class has deprecated the _field_types attribute in favor of the __annotations__ attribute which carried the same information. Also, both attributes were converted from OrderedDict to a regular dict.

- bpo-34745: Fix `asyncio` ssl memory issues caused by circular references

- bpo-36324: Add method to statistics.NormalDist for computing the inverse cumulative normal distribution.

- bpo-36321: collections.namedtuple() misspelled the name of an attribute. To be consistent with typing.NamedTuple, the attribute name should have been “_field_defaults” instead of “_fields_defaults”. For backwards compatibility, both spellings are now created. The misspelled version may be removed in the future.

- bpo-36297: “unicode_internal” codec is removed. It was deprecated since Python 3.3. Patch by Inada Naoki.

- bpo-36298: Raise ModuleNotFoundError in pyclbr when a module can’t be found. Thanks to ‘mental’ for the bug report.

- bpo-36268: Switch the default format used for writing tars with `tarfile` to the modern POSIX.1-2001 pax standard, from the vendor-specific GNU. Contributed by C.A.M. Gerlach.

- bpo-36285: Fix integer overflows in the array module. Patch by Stephan Hohe.

- bpo-31904: Add _signal module support for VxWorks.

- bpo-36272: `logging` does not silently ignore RecursionError anymore. Patch contributed by Rémi Lapeyre.

- bpo-36280: Add a kind field to ast.Constant. It is ‘u’ if the literal has a ‘u’ prefix (i.e. a Python 2 style unicode literal), else None.

- bpo-35931: The `pdb` `debug` command now gracefully handles all exceptions.

- bpo-36251: Fix format strings used for stderrprinter and re.Match reprs. Patch by Stephan Hohe.

- bpo-36235: Fix `CFLAGS` in `customize_compiler()` of `distutils.sysconfig`: when the `CFLAGS` environment variable is defined, don’t override `CFLAGS` variable with the `OPT` variable anymore. Initial patch written by David Malcolm.

- bpo-35807: Update ensurepip to install pip 19.0.3 and setuptools 40.8.0.

- bpo-36139: Release GIL when closing `mmap` objects.

- bpo-36179: Fix two unlikely reference leaks in _hashopenssl. The leaks only occur in out-of-memory cases.

- bpo-36169: Add overlap() method to statistics.NormalDist. Computes the overlapping coefficient for two normal distributions.

- bpo-36103: Default buffer size used by `shutil.copyfileobj()` is changed from 16 KiB to 64 KiB on non-Windows platform to reduce system call overhead. Contributed by Inada Naoki.

- bpo-36130: Fix `pdb` with `skip=...` when stepping into a frame without a `__name__` global. Patch by Anthony Sottile.

- bpo-35652: shutil.copytree(copy_function=…) erroneously pass DirEntry instead of a path string.

- bpo-35178: Ensure custom `warnings.formatwarning()` function can receive `line` as positional argument. Based on patch by Tashrif Billah.

- bpo-36106: Resolve potential name clash with libm’s sinpi(). Patch by Dmitrii Pasechnik.

- bpo-36091: Clean up reference to async generator in Lib/types. Patch by Henry Chen.

- bpo-36043: `FileCookieJar` supports path-like object. Contributed by Stéphane Wirtel

- bpo-35899: Enum has been fixed to correctly handle empty strings and strings with non-Latin characters (ie. ‘α’, ‘א’) without crashing. Original patch contributed by Maxwell. Assisted by Stéphane Wirtel.

- bpo-21269: Add `args` and `kwargs` properties to mock call objects. Contributed by Kumar Akshay.

- bpo-30670: `pprint.pp` has been added to pretty-print objects with dictionary keys being sorted with their insertion order by default. Parameter sort_dicts has been added to `pprint.pprint`, `pprint.pformat` and `pprint.PrettyPrinter`. Contributed by Rémi Lapeyre.

- bpo-35843: Implement `__getitem__` for `_NamespacePath`. Patch by Anthony Sottile.

- bpo-35802: Clean up code which checked presence of `os.stat` / `os.lstat` / `os.chmod` which are always present. Patch by Anthony Sottile.

- bpo-35715: Librates the return value of a ProcessPoolExecutor _process_worker after it’s no longer needed to free memory

- bpo-35493: Use `multiprocessing.connection.wait()` instead of polling each 0.2 seconds for worker updates in `multiprocessing.Pool`. Patch by Pablo Galindo.

- bpo-35661: Store the venv prompt in pyvenv.cfg.

- bpo-35121: Don’t set cookie for a request when the request path is a prefix match of the cookie’s path attribute but doesn’t end with “/”. Patch by Karthikeyan Singaravelan.

- bpo-21478: Calls to a child function created with `unittest.mock.create_autospec()` should propagate to the parent. Patch by Karthikeyan Singaravelan.

- bpo-35198: Fix C++ extension compilation on AIX

### Documentation

- bpo-36329: Declare the path of the Python binary for the usage of `Tools/scripts/serve.py` when executing `make -C Doc/ serve`. Contributed by Stéphane Wirtel

- bpo-36138: Improve documentation about converting datetime.timedelta to scalars.

- bpo-21314: A new entry was added to the Core Language Section of the Programming FAQ, which explaines the usage of slash(/) in the signature of a function. Patch by Lysandros Nikolaou

### Tests

- bpo-36234: test_posix.PosixUidGidTests: add tests for invalid uid/gid type (str). Initial patch written by David Malcolm.

- bpo-29571: Fix `test_re.test_locale_flag()`: use `locale.getpreferredencoding()` rather than `locale.getlocale()` to get the locale encoding. With some locales, `locale.getlocale()` returns the wrong encoding.

- bpo-36123: Fix race condition in test_socket.

### Build

- bpo-36356: Fix leaks that led to build failure when configured with address sanitizer.

- bpo-36146: Add `TEST_EXTENSIONS` constant to `setup.py` to allow to not build test extensions like `_testcapi`.

- bpo-36146: Fix setup.py on macOS: only add `/usr/include/ffi` to include directories of _ctypes, not for all extensions.

- bpo-31904: Enable build system to cross-build for VxWorks RTOS.

### Windows

- bpo-36312: Fixed decoders for the following code pages: 50220, 50221, 50222, 50225, 50227, 50229, 57002 through 57011, 65000 and 42.

- bpo-36264: Don’t honor POSIX `HOME` in `os.path.expanduser` on windows. Patch by Anthony Sottile.

- bpo-24643: Fix name collisions due to `#define timezone _timezone` in PC/pyconfig.h.

### IDLE

- bpo-36405: Use dict unpacking in idlelib.

- bpo-36396: Remove fgBg param of idlelib.config.GetHighlight(). This param was only used twice and changed the return type.

- bpo-36176: Fix IDLE autocomplete & calltip popup colors. Prevent conflicts with Linux dark themes (and slightly darken calltip background).

- bpo-23205: For the grep module, add tests for findfiles, refactor findfiles to be a module-level function, and refactor findfiles to use os.walk.

- bpo-23216: Add docstrings to IDLE search modules.

- bpo-36152: Remove colorizer.ColorDelegator.close_when_done and the corresponding argument of .close(). In IDLE, both have always been None or False since 2007.

- bpo-32129: Avoid blurry IDLE application icon on macOS with Tk 8.6. Patch by Kevin Walzer.

- bpo-36096: Refactor class variables to instance variables in colorizer.

- bpo-30348: Increase test coverage of idlelib.autocomplete by 30%. Patch by Louie Lu

### Tools/Demos

- bpo-35132: Fix py-list and py-bt commands of python-gdb.py on gdb7.

- bpo-32217: Fix freeze script on Windows.

### C API

- bpo-36381: Raise `DeprecationWarning` when ‘#’ formats are used for building or parsing values without `PY_SSIZE_T_CLEAN`.

- bpo-36142: The whole coreconfig.h header is now excluded from Py_LIMITED_API. Move functions definitions into a new internal pycore_coreconfig.h header.

## Python 3.8.0 alpha 2

Release date: 2019-02-25

### Core and Builtins

- bpo-36052: Raise a `SyntaxError` when assigning a value to `__debug__` with the Assignment Operator. Contributed by Stéphane Wirtel and Pablo Galindo.

- bpo-36012: Doubled the speed of class variable writes. When a non-dunder attribute was updated, there was an unnecessary call to update slots.

- bpo-35942: The error message emitted when returning invalid types from `__fspath__` in interfaces that allow passing `PathLike` objects has been improved and now it does explain the origin of the error.

- bpo-36016: `gc.get_objects` can now receive an optional parameter indicating a generation to get objects from. Patch by Pablo Galindo.

- bpo-1054041: When the main interpreter exits due to an uncaught KeyboardInterrupt, the process now exits in the appropriate manner for its parent process to detect that a SIGINT or ^C terminated the process. This allows shells and batch scripts to understand that the user has asked them to stop.

- bpo-35992: Fix `__class_getitem__()` not being called on a class with a custom non-subscriptable metaclass.

- bpo-35993: Fix a crash on fork when using subinterpreters. Contributed by Stéphane Wirtel

- bpo-35991: Fix a potential double free in Modules/_randommodule.c.

- bpo-35961: Fix a crash in slice_richcompare(): use strong references rather than stolen references for the two temporary internal tuples.

- bpo-35911: Enable the creation of cell objects by adding a `cell.__new__` method, and expose the type `cell` in `Lib/types.py` under the name CellType. Patch by Pierre Glaser.

- bpo-12822: Use monotonic clock for `pthread_cond_timedwait` when `pthread_condattr_setclock` and `CLOCK_MONOTONIC` are available.

- bpo-15248: The compiler emits now syntax warnings in the case when a comma is likely missed before tuple or list.

- bpo-35886: The implementation of PyInterpreterState has been moved into the internal header files (guarded by Py_BUILD_CORE).

- bpo-31506: Clarify the errors reported when `object.__new__` and `object.__init__` receive more than one argument. Contributed by Sanyam Khurana.

- bpo-35724: Signal-handling is now guaranteed to happen relative to the main interpreter.

- bpo-33608: We added a new internal _Py_AddPendingCall() that operates relative to the provided interpreter. This allows us to use the existing implementation to ask another interpreter to do work that cannot be done in the current interpreter, like decref an object the other interpreter owns. The existing Py_AddPendingCall() only operates relative to the main interpreter.

- bpo-33989: Fix a possible crash in `list.sort()` when sorting objects with `ob_type->tp_richcompare == NULL`. Patch by Zackery Spytz.

### Library

- bpo-35512: `unittest.mock.patch.dict()` used as a decorator with string target resolves the target during function call instead of during decorator construction. Patch by Karthikeyan Singaravelan.

- bpo-36018: Add statistics.NormalDist, a tool for creating and manipulating normal distributions of random variable. Features a composite class that treats the mean and standard deviation of measurement data as single entity.

- bpo-35904: Added statistics.fmean() as a faster, floating-point variant of the existing mean() function.

- bpo-35918: Removed broken `has_key` method from multiprocessing.managers.SyncManager.dict. Contributed by Rémi Lapeyre.

- bpo-18283: Add support for bytes to `shutil.which()`.

- bpo-35960: Fix `dataclasses.field()` throwing away empty mapping objects passed as metadata.

- bpo-35500: Write expected and actual call parameters on separate lines in `unittest.mock.Mock.assert_called_with()` assertion errors. Contributed by Susan Su.

- bpo-35931: The `pdb` `debug` command now gracefully handles syntax errors.

- bpo-24209: In http.server script, rely on getaddrinfo to bind to preferred address based on the bind parameter. Now default bind or binding to a name may bind to IPv6 or dual-stack, depending on the environment.

- bpo-35321: Set `__spec__.origin` of `_frozen_importlib` to frozen so that it matches the behavior of `_frozen_importlib_external`. Patch by Nina Zakharenko.

- bpo-35378: Fix a reference issue inside `multiprocessing.Pool` that caused the pool to remain alive if it was deleted without being closed or terminated explicitly. A new strong reference is added to the pool iterators to link the lifetime of the pool to the lifetime of its iterators so the pool does not get destroyed if a pool iterator is still alive.

- bpo-34294: re module, fix wrong capturing groups in rare cases. `re.search()`, `re.findall()`, `re.sub()` and other functions that scan through string looking for a match, should reset capturing groups between two match attempts. Patch by Ma Lin.

- bpo-35615: `weakref`: Fix a RuntimeError when copying a WeakKeyDictionary or a WeakValueDictionary, due to some keys or values disappearing while iterating.

- bpo-35606: Implement `math.prod()` as analogous function to `sum()` that returns the product of a ‘start’ value (default: 1) times an iterable of numbers. Patch by Pablo Galindo.

- bpo-32417: Performing arithmetic between `datetime.datetime` subclasses and `datetime.timedelta` now returns an object of the same type as the `datetime.datetime` subclass. As a result, `datetime.datetime.astimezone()` and alternate constructors like `datetime.datetime.now()` and `datetime.fromtimestamp()` called with a `tz` argument now also retain their subclass.

- bpo-35153: Add headers optional keyword-only parameter to `xmlrpc.client.ServerProxy`, `xmlrpc.client.Transport` and `xmlrpc.client.SafeTransport`. Patch by Cédric Krier.

- bpo-34572: Fix C implementation of pickle.loads to use importlib’s locking mechanisms, and thereby avoid using partially loaded modules. Patch by Tim Burgess.

### Documentation

- bpo-36083: Fix formatting of –check-hash-based-pycs options in the manpage Synopsis.

- bpo-36007: Bump minimum sphinx version to 1.8. Patch by Anthony Sottile.

- bpo-22062: Update documentation and docstrings for pathlib. Original patch by Mike Short.

### Tests

- bpo-27313: Avoid test_ttk_guionly ComboboxTest failure with macOS Cocoa Tk.

- bpo-36019: Add test.support.TEST_HTTP_URL and replace references of http://www.example.com by this new constant. Contributed by Stéphane Wirtel.

- bpo-36037: Fix test_ssl for strict OpenSSL configuration like RHEL8 strict crypto policy. Use older TLS version for minimum TLS version of the server SSL context if needed, to test TLS version older than default minimum TLS version.

- bpo-35798: Added `test.support.check_syntax_warning()`.

- bpo-35505: Make test_imap4_host_default_value independent on whether the local IMAP server is running.

- bpo-35917: multiprocessing: provide unit tests for SyncManager and SharedMemoryManager classes + all the shareable types which are supposed to be supported by them. (patch by Giampaolo Rodola)

- bpo-35704: Skip `test_shutil.test_unpack_archive_xztar` to prevent a MemoryError on 32-bit AIX when MAXDATA setting is less than 0x20000000.

  Patch by Michael Felt (aixtools)

- bpo-34720: Assert m_state != NULL to mimic GC traversal functions that do not correctly handle module creation when the module state has not been created.

### Windows

- bpo-35976: Added ARM build support to Windows build files in PCBuild.

- bpo-35692: `pathlib` no longer raises when checking file and directory existence on drives that are not ready

- bpo-35872: Uses the base Python executable when invoking venv in a virtual environment

- bpo-35873: Prevents venv paths being inherited by child processes

- bpo-35299: Fix sysconfig detection of the source directory and distutils handling of pyconfig.h during PGO profiling

### IDLE

- bpo-24310: IDLE – Document settings dialog font tab sample.

- bpo-35833: Revise IDLE doc for control codes sent to Shell. Add a code example block.

- bpo-35689: Add docstrings and unittests for colorizer.py.

## Python 3.8.0 alpha 1

Release date: 2019-02-03

### Security

- bpo-35746: CVE 2019-5010: Fix a NULL pointer deref in ssl module. The cert parser did not handle CRL distribution points with empty DP or URI correctly. A malicious or buggy certificate can result into segfault. Vulnerability (TALOS-2018-0758) reported by Colin Read and Nicolas Edet of Cisco.

- bpo-34812: The `-I` command line option (run Python in isolated mode) is now also copied by the `multiprocessing` and `distutils` modules when spawning child processes. Previously, only `-E` and `-s` options (enabled by `-I`) were copied.

- bpo-34791: The xml.sax and xml.dom.domreg no longer use environment variables to override parser implementations when sys.flags.ignore_environment is set by -E or -I arguments.

- bpo-17239: The xml.sax and xml.dom.minidom parsers no longer processes external entities by default. External DTD and ENTITY declarations no longer load files or create network connections.

- bpo-34623: CVE 2018-14647: The C accelerated _elementtree module now initializes hash randomization salt from _Py_HashSecret instead of libexpat’s default CSPRNG.

- bpo-34405: Updated to OpenSSL 1.1.0i for Windows builds.

- bpo-33871: Fixed sending the part of the file in `os.sendfile()` on macOS. Using the trailers argument could cause sending more bytes from the input file than was specified.

- bpo-32533: Fixed thread-safety of error handling in _ssl.

- bpo-33136: Harden ssl module against LibreSSL CVE 2018-8970. X509_VERIFY_PARAM_set1_host() is called with an explicit namelen. A new test ensures that NULL bytes are not allowed.

- bpo-33001: Minimal fix to prevent buffer overrun in os.symlink on Windows

- bpo-32981: Regexes in difflib and poplib were vulnerable to catastrophic backtracking. These regexes formed potential DOS vectors (REDOS). They have been refactored. This resolves CVE 2018-1060 and CVE 2018-1061. Patch by Jamie Davis.

- bpo-28414: The ssl module now allows users to perform their own IDN en/decoding when using SNI.

### Core and Builtins

- bpo-35877: Make parenthesis optional for named expressions in while statement. Patch by Karthikeyan Singaravelan.

- bpo-35814: Allow same right hand side expressions in annotated assignments as in normal ones. In particular, `x: Tuple[int, int] = 1, 2` (without parentheses on the right) is now allowed.

- bpo-35766: Add the option to parse PEP 484 type comments in the ast module. (Off by default.) This is merging the key functionality of the third party fork thereof, [typed_ast](https://github.com/python/typed_ast).

- bpo-35713: Reorganize Python initialization to get working exceptions and sys.stderr earlier.

- bpo-33416: Add end line and end column position information to the Python AST nodes. This is a C-level backwards incompatible change.

- bpo-35720: Fixed a minor memory leak in pymain_parse_cmdline_impl function in Modules/main.c

- bpo-35634: `func(**kwargs)` will now raise an error when `kwargs` is a mapping containing multiple entries with the same key. An error was already raised when other keyword arguments are passed before `**kwargs` since Python 3.6.

- bpo-35623: Fix a crash when sorting very long lists. Patch by Stephan Hohe.

- bpo-35214: clang Memory Sanitizer build instrumentation was added to work around false positives from posix, socket, time, test_io, and test_faulthandler.

- bpo-35560: Fix an assertion error in `format()` in debug build for floating-point formatting with “n” format, zero padding and small width. Release build is not impacted. Patch by Karthikeyan Singaravelan.

- bpo-35552: Format characters `%s` and `%V` in `PyUnicode_FromFormat()` and `%s` in `PyBytes_FromFormat()` no longer read memory past the limit if precision is specified.

- bpo-35504: Fix segfaults and `SystemError`s when deleting certain attributes. Patch by Zackery Spytz.

- bpo-35504: Fixed a SystemError when delete the characters_written attribute of an OSError.

- bpo-35494: Improved syntax error messages for unbalanced parentheses in f-string.

- bpo-35444: Fixed error handling in pickling methods when fail to look up builtin “getattr”. Sped up pickling iterators.

- bpo-35436: Fix various issues with memory allocation error handling. Patch by Zackery Spytz.

- bpo-35423: Separate the signal handling trigger in the eval loop from the “pending calls” machinery. There is no semantic change and the difference in performance is insignificant.

- bpo-35357: Internal attributes’ names of unittest.mock._Call and unittest.mock.MagicProxy (name, parent & from_kall) are now prefixed with _mock_ in order to prevent clashes with widely used object attributes. Fixed minor typo in test function name.

- bpo-35372: Fixed the code page decoder for input longer than 2 GiB containing undecodable bytes.

- bpo-35336: Fix PYTHONCOERCECLOCALE=1 environment variable: only coerce the C locale if the LC_CTYPE locale is “C”.

- bpo-31241: The lineno and col_offset attributes of AST nodes for list comprehensions, generator expressions and tuples are now point to the opening parenthesis or square brace. For tuples without parenthesis they point to the position of the first item.

- bpo-33954: For `str.format()`, `float.__format__()` and `complex.__format__()` methods for non-ASCII decimal point when using the “n” formatter.

- bpo-35269: Fix a possible segfault involving a newly created coroutine. Patch by Zackery Spytz.

- bpo-35224: Implement PEP 572 (assignment expressions). Patch by Emily Morehouse.

- bpo-32492: Speed up `namedtuple()` attribute access by 1.6x using a C fast-path for the name descriptors. Patch by Pablo Galindo.

- bpo-35214: Fixed an out of bounds memory access when parsing a truncated unicode escape sequence at the end of a string such as `'\N'`. It would read one byte beyond the end of the memory allocation.

- bpo-35214: The interpreter and extension modules have had annotations added so that they work properly under clang’s Memory Sanitizer. A new configure flag –with-memory-sanitizer has been added to make test builds of this nature easier to perform.

- bpo-35193: Fix an off by one error in the bytecode peephole optimizer where it could read bytes beyond the end of bounds of an array when removing unreachable code. This bug was present in every release of Python 3.6 and 3.7 until now.

- bpo-35169: Improved error messages for forbidden assignments.

- bpo-34022: Fix handling of hash-based bytecode files in `zipimport`. Patch by Elvis Pranskevichus.

- bpo-28401: Debug builds will no longer to attempt to import extension modules built for the ABI as they were never compatible to begin with. Patch by Stefano Rivera.

- bpo-29341: Clarify in the docstrings of `os` methods that path-like objects are also accepted as input parameters.

- bpo-35050: `socket`: Fix off-by-one bug in length check for `AF_ALG` name and type.

- bpo-29743: Raise `ValueError` instead of `OverflowError` in case of a negative `_length_` in a `ctypes.Array` subclass. Also raise `TypeError` instead of `AttributeError` for non-integer `_length_`. Original patch by Oren Milman.

- bpo-16806: Fix `lineno` and `col_offset` for multi-line string tokens.

- bpo-35029: `SyntaxWarning` raised as an exception at code generation time will be now replaced with a `SyntaxError` for better error reporting.

- bpo-34983: Expose `symtable.Symbol.is_nonlocal()` in the symtable module. Patch by Pablo Galindo.

- bpo-34974: `bytes` and `bytearray` constructors no longer convert unexpected exceptions (e.g. `MemoryError` and `KeyboardInterrupt`) to `TypeError`.

- bpo-34939: Allow annotated names in module namespace that are declared global before the annotation happens. Patch by Pablo Galindo.

- bpo-34973: Fixed crash in `bytes()` when the `list` argument is mutated while it is iterated.

- bpo-34876: The lineno and col_offset attributes of the AST for decorated function and class refer now to the position of the corresponding `def`, `async def` and `class` instead of the position of the first decorator. This leads to more correct line reporting in tracing. This is the only case when the position of child AST nodes can precede the position of the parent AST node.

- bpo-34879: Fix a possible null pointer dereference in bytesobject.c. Patch by Zackery Spytz.

- bpo-34784: Fix the implementation of PyStructSequence_NewType in order to create heap allocated StructSequences.

- bpo-32912: A `SyntaxWarning` is now emitted instead of a `DeprecationWarning` for invalid escape sequences in string and bytes literals.

- bpo-34854: Fixed a crash in compiling string annotations containing a lambda with a keyword-only argument that doesn’t have a default value.

- bpo-34850: The compiler now produces a `SyntaxWarning` when identity checks (`is` and `is not`) are used with certain types of literals (e.g. strings, ints). These can often work by accident in CPython, but are not guaranteed by the language spec. The warning advises users to use equality tests (`==` and `!=`) instead.

- bpo-34824: Fix a possible null pointer dereference in Modules/_ssl.c. Patch by Zackery Spytz.

- bpo-30156: The C function `property_descr_get()` uses a “cached” tuple to optimize function calls. But this tuple can be discovered in debug mode with `sys.getobjects()`. Remove the optimization, it’s not really worth it and it causes 3 different crashes last years.

- bpo-34762: Fix contextvars C API to use PyObject* pointer types.

- bpo-34751: The hash function for tuples is now based on xxHash which gives better collision results on (formerly) pathological cases. Additionally, on 64-bit systems it improves tuple hashes in general. Patch by Jeroen Demeyer with substantial contributions by Tim Peters.

- bpo-34735: Fix a memory leak in Modules/timemodule.c. Patch by Zackery Spytz.

- bpo-34683: Fixed a bug where some SyntaxError error pointed to locations that were off-by-one.

- bpo-34651: Only allow the main interpreter to fork. The avoids the possibility of affecting the main interpreter, which is critical to operation of the runtime.

- bpo-34653: Remove unused function PyParser_SimpleParseStringFilename.

- bpo-32236: Warn that line buffering is not supported if `open()` is called with binary mode and `buffering=1`.

- bpo-34641: Further restrict the syntax of the left-hand side of keyword arguments in function calls. In particular, `f((keyword)=arg)` is now disallowed.

- bpo-34637: Make the start argument to sum() visible as a keyword argument.

- bpo-1621: Do not assume signed integer overflow behavior (C undefined behavior) when performing set hash table resizing.

- bpo-34588: Fix an off-by-one in the recursive call pruning feature of traceback formatting.

- bpo-34485: On Windows, the LC_CTYPE is now set to the user preferred locale at startup. Previously, the LC_CTYPE locale was “C” at startup, but changed when calling setlocale(LC_CTYPE, “”) or setlocale(LC_ALL, “”).

- bpo-34485: Standard streams like sys.stdout now use the “surrogateescape” error handler, instead of “strict”, on the POSIX locale (when the C locale is not coerced and the UTF-8 Mode is disabled).

- bpo-34485: Fix the error handler of standard streams like sys.stdout: PYTHONIOENCODING=”:” is now ignored instead of setting the error handler to “strict”.

- bpo-34485: Python now gets the locale encoding with C code to initialize the encoding of standard streams like sys.stdout. Moreover, the encoding is now initialized to the Python codec name to get a normalized encoding name and to ensure that the codec is loaded. The change avoids importing _bootlocale and _locale modules at startup by default.

- bpo-34527: On FreeBSD, Py_DecodeLocale() and Py_EncodeLocale() now also forces the ASCII encoding if the LC_CTYPE locale is “POSIX”, not only if the LC_CTYPE locale is “C”.

- bpo-34527: The UTF-8 Mode is now also enabled by the “POSIX” locale, not only by the “C” locale.

- bpo-34403: On HP-UX with C or POSIX locale, sys.getfilesystemencoding() now returns “ascii” instead of “roman8” (when the UTF-8 Mode is disabled and the C locale is not coerced).

- bpo-34523: The Python filesystem encoding is now read earlier during the Python initialization.

- bpo-12458: Tracebacks show now correct line number for subexpressions in multiline expressions. Tracebacks show now the line number of the first line for multiline expressions instead of the line number of the last subexpression.

- bpo-34408: Prevent a null pointer dereference and resource leakage in `PyInterpreterState_New()`.

- bpo-34400: Fix undefined behavior in parsetok.c. Patch by Zackery Spytz.

- bpo-33073: Added as_integer_ratio to ints to make them more interoperable with floats.

- bpo-34377: Update valgrind suppression list to use `_PyObject_Free`/`_PyObject_Realloc` instead of `PyObject_Free`/`PyObject_Realloc`.

- bpo-34353: Added the “socket” option in the `stat.filemode()` Python implementation to match the C implementation.

- bpo-34320: Fix `dict(od)` didn’t copy iteration order of OrderedDict.

- bpo-34113: Fixed crash on debug builds when opcode stack was adjusted with negative numbers. Patch by Constantin Petrisor.

- bpo-34100: Compiler now merges constants in tuples and frozensets recursively. Code attributes like `co_names` are merged too.

- bpo-34151: Performance of list concatenation, repetition and slicing operations is slightly improved. Patch by Sergey Fedoseev.

- bpo-34170: -X dev: it is now possible to override the memory allocator using PYTHONMALLOC even if the developer mode is enabled.

- bpo-33237: Improved `AttributeError` message for partially initialized module.

- bpo-34149: Fix min and max functions to get default behavior when key is None.

- bpo-34125: Profiling of unbound built-in methods now works when `**kwargs` is given.

- bpo-34141: Optimized pickling atomic types (None, bool, int, float, bytes, str).

- bpo-34126: Fix crashes when profiling certain invalid calls of unbound methods. Patch by Jeroen Demeyer.

- bpo-24618: Fixed reading invalid memory when create the code object with too small varnames tuple or too large argument counts.

- bpo-34068: In `io.IOBase.close()`, ensure that the `closed` attribute is not set with a live exception. Patch by Zackery Spytz and Serhiy Storchaka.

- bpo-34087: Fix buffer overflow while converting unicode to numeric values.

- bpo-34080: Fixed a memory leak in the compiler when it raised some uncommon errors during tokenizing.

- bpo-34066: Disabled interruption by Ctrl-C between calling `open()` and entering a with block in `with open()`.

- bpo-34042: Fix dict.copy() to maintain correct total refcount (as reported by sys.gettotalrefcount()).

- bpo-33418: Fix potential memory leak in function object when it creates reference cycle.

- bpo-33985: Implement contextvars.ContextVar.name attribute.

- bpo-33956: Update vendored Expat library copy to version 2.2.5.

- bpo-24596: Decref the module object in `PyRun_SimpleFileExFlags()` before calling `PyErr_Print()`. Patch by Zackery Spytz.

- bpo-33451: Close directly executed pyc files before calling `PyEval_EvalCode()`.

- bpo-1617161: The hash of `BuiltinMethodType` instances (methods of built-in classes) now depends on the hash of the identity of __self__ instead of its value. The hash and equality of `ModuleType` and `MethodWrapperType` instances (methods of user-defined classes and some methods of built-in classes like `str.__add__`) now depend on the hash and equality of the identity of __self__ instead of its value. `MethodWrapperType` instances no longer support ordering.

- bpo-33824: Fix “LC_ALL=C python3.7 -V”: reset properly the command line parser when the encoding changes after reading the Python configuration.

- bpo-33803: Fix a crash in hamt.c caused by enabling GC tracking for an object that hadn’t all of its fields set to NULL.

- bpo-33738: Seven macro incompatibilities with the Limited API were fixed, and the macros `PyIter_Check()`, `PyIndex_Check()` and `PyExceptionClass_Name()` were added as functions. A script for automatic macro checks was added.

- bpo-33786: Fix asynchronous generators to handle GeneratorExit in athrow() correctly

- bpo-30167: `PyRun_SimpleFileExFlags` removes `__cached__` from module in addition to `__file__`.

- bpo-33706: Fix a crash in Python initialization when parsing the command line options. Thanks Christoph Gohlke for the bug report and the fix!

- bpo-33597: Reduce `PyGC_Head` size from 3 words to 2 words.

- bpo-30654: Fixed reset of the SIGINT handler to SIG_DFL on interpreter shutdown even when there was a custom handler set previously. Patch by Philipp Kerling.

- bpo-33622: Fixed a leak when the garbage collector fails to add an object with the `__del__` method or referenced by it into the `gc.garbage` list. `PyGC_Collect()` can now be called when an exception is set and preserves it.

- bpo-33462: Make dict and dict views reversible. Patch by Rémi Lapeyre.

- bpo-23722: A `RuntimeError` is now raised when the custom metaclass doesn’t provide the `__classcell__` entry in the namespace passed to `type.__new__`. A `DeprecationWarning` was emitted in Python 3.6–3.7.

- bpo-33499: Add `PYTHONPYCACHEPREFIX` environment variable and `-X` `pycache_prefix` command-line option to set an alternate root directory for writing module bytecode cache files.

- bpo-25711: The `zipimport` module has been rewritten in pure Python.

- bpo-33509: Fix module_globals parameter of warnings.warn_explicit(): don’t crash if module_globals is not a dict.

- bpo-31849: Fix signed/unsigned comparison warning in pyhash.c.

- bpo-33475: Fixed miscellaneous bugs in converting annotations to strings and optimized parentheses in the string representation.

- bpo-20104: Added support for the `setpgroup`, `resetids`, `setsigmask`, `setsigdef` and `scheduler` parameters of `posix_spawn`. Patch by Pablo Galindo.

- bpo-33391: Fix a leak in set_symmetric_difference().

- bpo-33363: Raise a SyntaxError for `async with` and `async for` statements outside of async functions.

- bpo-28055: Fix unaligned accesses in siphash24(). Patch by Rolf Eike Beer.

- bpo-33128: Fix a bug that causes PathFinder to appear twice on sys.meta_path. Patch by Pablo Galindo Salgado.

- bpo-33331: Modules imported last are now cleared first at interpreter shutdown.

- bpo-33312: Fixed clang ubsan (undefined behavior sanitizer) warnings in dictobject.c by adjusting how the internal struct _dictkeysobject shared keys structure is declared.

- bpo-33305: Improved syntax error messages for invalid numerical literals.

- bpo-33306: Improved syntax error messages for unbalanced parentheses.

- bpo-33234: The list constructor will pre-size and not over-allocate when the input length is known.

- bpo-33270: Intern the names for all anonymous code objects. Patch by Zackery Spytz.

- bpo-30455: The C and Python code and the documentation related to tokens are now generated from a single source file `Grammar/Tokens`.

- bpo-33176: Add a `toreadonly()` method to memoryviews.

- bpo-33231: Fix potential memory leak in `normalizestring()`.

- bpo-33205: Change dict growth function from `round_up_to_power_2(used*2+hashtable_size/2)` to `round_up_to_power_2(used*3)`. Previously, dict is shrinked only when `used == 0`. Now dict has more chance to be shrinked.

- bpo-29922: Improved error messages in ‘async with’ when `__aenter__()` or `__aexit__()` return non-awaitable object.

- bpo-33199: Fix `ma_version_tag` in dict implementation is uninitialized when copying from key-sharing dict.

- bpo-33053: When using the -m switch, sys.path[0] is now explicitly expanded as the starting working directory, rather than being left as the empty path (which allows imports from the current working directory at the time of the import)

- bpo-33138: Changed standard error message for non-pickleable and non-copyable types. It now says “cannot pickle” instead of “can’t pickle” or “cannot serialize”.

- bpo-33018: Improve consistency of errors raised by `issubclass()` when called with a non-class and an abstract base class as the first and second arguments, respectively. Patch by Josh Bronson.

- bpo-33083: `math.factorial` no longer accepts arguments that are not int-like. Patch by Pablo Galindo.

- bpo-33041: Added new opcode `END_ASYNC_FOR` and fixes the following issues:

  - Setting global `StopAsyncIteration` no longer breaks `async for` loops.

  - Jumping into an `async for` loop is now disabled.

  - Jumping out of an `async for` loop no longer corrupts the stack.

- bpo-25750: Fix rare Python crash due to bad refcounting in `type_getattro()` if a descriptor deletes itself from the class. Patch by Jeroen Demeyer.

- bpo-33041: Fixed bytecode generation for “async for” with a complex target. A StopAsyncIteration raised on assigning or unpacking will be now propagated instead of stopping the iteration.

- bpo-33026: Fixed jumping out of “with” block by setting f_lineno.

- bpo-33005: Fix a crash on fork when using a custom memory allocator (ex: using PYTHONMALLOC env var). _PyGILState_Reinit() and _PyInterpreterState_Enable() now use the default RAW memory allocator to allocate a new interpreters mutex on fork.

- bpo-32911: Due to unexpected compatibility issues discovered during downstream beta testing, reverted bpo-29463. `docstring` field is removed from Module, ClassDef, FunctionDef, and AsyncFunctionDef ast nodes which was added in 3.7a1. Docstring expression is restored as a first statement in their body. Based on patch by Inada Naoki.

- bpo-17288: Prevent jumps from ‘return’ and ‘exception’ trace events.

- bpo-32946: Importing names from already imported module with “from … import …” is now 30% faster if the module is not a package.

- bpo-32932: Make error message more revealing when there are non-str objects in `__all__`.

- bpo-32925: Optimized iterating and containing test for literal lists consisting of non-constants: `x in [a, b]` and `for x in [a, b]`. The case of all constant elements already was optimized.

- bpo-32889: Update Valgrind suppression list to account for the rename of `Py_ADDRESS_IN_RANG` to `address_in_range`.

- bpo-32836: Don’t use temporary variables in cases of list/dict/set comprehensions

- bpo-31356: Remove the new API added in bpo-31356 (gc.ensure_disabled() context manager).

- bpo-32305: For namespace packages, ensure that both `__file__` and `__spec__.origin` are set to None.

- bpo-32303: Make sure `__spec__.loader` matches `__loader__` for namespace packages.

- bpo-32711: Fix the warning messages for Python/ast_unparse.c. Patch by Stéphane Wirtel

- bpo-32583: Fix possible crashing in builtin Unicode decoders caused by write out-of-bound errors when using customized decode error handlers.

- bpo-32489: A `continue` statement is now allowed in the `finally` clause.

- bpo-17611: Simplified the interpreter loop by moving the logic of unrolling the stack of blocks into the compiler. The compiler emits now explicit instructions for adjusting the stack of values and calling the cleaning up code for `break`, `continue` and `return`.

  Removed opcodes `BREAK_LOOP`, `CONTINUE_LOOP`, `SETUP_LOOP` and `SETUP_EXCEPT`. Added new opcodes `ROT_FOUR`, `BEGIN_FINALLY` and `CALL_FINALLY` and `POP_FINALLY`. Changed the behavior of `END_FINALLY` and `WITH_CLEANUP_START`.

- bpo-32285: New function unicodedata.is_normalized, which can check whether a string is in a specific normal form.

- bpo-10544: Yield expressions are now disallowed in comprehensions and generator expressions except the expression for the outermost iterable.

- bpo-32117: Iterable unpacking is now allowed without parentheses in yield and return statements, e.g. `yield 1, 2, 3, *rest`. Thanks to David Cuthbert for the change and Jordan Chapman for added tests.

- bpo-31902: Fix the `col_offset` attribute for ast nodes `ast.AsyncFor`, `ast.AsyncFunctionDef`, and `ast.AsyncWith`. Previously, `col_offset` pointed to the keyword after `async`.

- bpo-25862: Fix assertion failures in the `tell()` method of `io.TextIOWrapper`. Patch by Zackery Spytz.

- bpo-21983: Fix a crash in `ctypes.cast()` in case the type argument is a ctypes structured data type. Patch by Eryk Sun and Oren Milman.

- bpo-31577: Fix a crash in `os.utime()` in case of a bad ns argument. Patch by Oren Milman.

- bpo-29832: Remove references to ‘getsockaddrarg’ from various socket error messages. Patch by Oren Milman.

### Library

- bpo-35845: Add ‘order’ parameter to memoryview.tobytes().

- bpo-35864: The _asdict() method for collections.namedtuple now returns a regular dict instead of an OrderedDict.

- bpo-35537: An ExitStack is now used internally within subprocess.Popen to clean up pipe file handles. No behavior change in normal operation. But if closing one handle were ever to cause an exception, the others will now be closed instead of leaked. (patch by Giampaolo Rodola)

- bpo-35847: RISC-V needed the CTYPES_PASS_BY_REF_HACK. Fixes ctypes Structure test_pass_by_value.

- bpo-35813: Shared memory submodule added to multiprocessing to avoid need for serialization between processes

- bpo-35780: Fix lru_cache() errors arising in recursive, reentrant, or multi-threaded code. These errors could result in orphan links and in the cache being trapped in a state with fewer than the specified maximum number of links. Fix handling of negative maxsize which should have been treated as zero. Fix errors in toggling the “full” status flag. Fix misordering of links when errors are encountered. Sync-up the C code and pure Python code for the space saving path in functions with a single positional argument. In this common case, the space overhead of an lru cache entry is reduced by almost half. Fix counting of cache misses. In error cases, the miss count was out of sync with the actual number of times the underlying user function was called.

- bpo-35537: `os.posix_spawn()` and `os.posix_spawnp()` now have a setsid parameter.

- bpo-23846: `asyncio.ProactorEventLoop` now catches and logs send errors when the self-pipe is full.

- bpo-34323: `asyncio`: Enhance `IocpProactor.close()` log: wait 1 second before the first log, then log every second. Log also the number of seconds since `close()` was called.

- bpo-35674: Add a new `os.posix_spawnp()` function. Patch by Joannah Nanjekye.

- bpo-35733: `ast.Constant(boolean)` no longer an instance of `ast.Num`. Patch by Anthony Sottile.

- bpo-35726: QueueHandler.prepare() now makes a copy of the record before modifying and enqueueing it, to avoid affecting other handlers in the chain.

- bpo-35719: Sped up multi-argument `math` functions atan2(), copysign(), remainder() and hypot() by 1.3–2.5 times.

- bpo-35717: Fix KeyError exception raised when using enums and compile. Patch contributed by Rémi Lapeyre.

- bpo-35699: Fixed detection of Visual Studio Build Tools 2017 in distutils

- bpo-32710: Fix memory leaks in asyncio ProactorEventLoop on overlapped operation failure.

- bpo-35702: The `time.CLOCK_UPTIME_RAW` constant is now available for macOS 10.12.

- bpo-32710: Fix a memory leak in asyncio in the ProactorEventLoop when `ReadFile()` or `WSASend()` overlapped operation fail immediately: release the internal buffer.

- bpo-35682: Fix `asyncio.ProactorEventLoop.sendfile()`: don’t attempt to set the result of an internal future if it’s already done.

- bpo-35283: Add a deprecated warning for the `threading.Thread.isAlive()` method. Patch by Donghee Na.

- bpo-35664: Improve operator.itemgetter() performance by 33% with optimized argument handling and with adding a fast path for the common case of a single non-negative integer index into a tuple (which is the typical use case in the standard library).

- bpo-35643: Fixed a SyntaxWarning: invalid escape sequence in Modules/_sha3/cleanup.py. Patch by Mickaël Schoentgen.

- bpo-35619: Improved support of custom data descriptors in `help()` and `pydoc`.

- bpo-28503: The `crypt` module now internally uses the `crypt_r()` library function instead of `crypt()` when available.

- bpo-35614: Fixed help() on metaclasses. Patch by Sanyam Khurana.

- bpo-35568: Expose `raise(signum)` as `raise_signal`

- bpo-35588: The floor division and modulo operations and the `divmod()` function on `fractions.Fraction` types are 2–4x faster. Patch by Stefan Behnel.

- bpo-35585: Speed-up building enums by value, e.g. http.HTTPStatus(200).

- bpo-30561: random.gammavariate(1.0, beta) now computes the same result as random.expovariate(1.0 / beta). This synchronizes the two algorithms and eliminates some idiosyncrasies in the old implementation. It does however produce a difference stream of random variables than it used to.

- bpo-35537: The `subprocess` module can now use the `os.posix_spawn()` function in some cases for better performance.

- bpo-35526: Delaying the ‘joke’ of barry_as_FLUFL.mandatory to Python version 4.0

- bpo-35523: Remove `ctypes` callback workaround: no longer create a callback at startup. Avoid SELinux alert on `import ctypes` and `import uuid`.

- bpo-31784: `uuid.uuid1()` now calls `time.time_ns()` rather than `int(time.time() * 1e9)`.

- bpo-35513: `TextTestRunner` of `unittest.runner` now uses `time.perf_counter()` rather than `time.time()` to measure the execution time of a test: `time.time()` can go backwards, whereas `time.perf_counter()` is monotonic.

- bpo-35502: Fixed reference leaks in `xml.etree.ElementTree.TreeBuilder` in case of unfinished building of the tree (in particular when an error was raised during parsing XML).

- bpo-35348: Make `platform.architecture()` parsing of `file` command output more reliable: add the `-b` option to the `file` command to omit the filename, force the usage of the C locale, and search also the “shared object” pattern.

- bpo-35491: `multiprocessing`: Add `Pool.__repr__()` and enhance `BaseProcess.__repr__()` (add pid and parent pid) to ease debugging. Pool state constant values are now strings instead of integers, for example `RUN` value becomes `'RUN'` instead of `0`.

- bpo-35477: `multiprocessing.Pool.__enter__()` now fails if the pool is not running: `with pool:` fails if used more than once.

- bpo-31446: Copy command line that was passed to CreateProcessW since this function can change the content of the input buffer.

- bpo-35471: Python 2.4 dropped MacOS 9 support. The macpath module was deprecated in Python 3.7. The module is now removed.

- bpo-23057: Unblock Proactor event loop when keyboard interrupt is received on Windows

- bpo-35052: Fix xml.dom.minidom cloneNode() on a document with an entity: pass the correct arguments to the user data handler of an entity.

- bpo-20239: Allow repeated assignment deletion of `unittest.mock.Mock` attributes. Patch by Pablo Galindo.

- bpo-17185: Set `__signature__` on mock for `inspect` to get signature. Patch by Karthikeyan Singaravelan.

- bpo-35445: Memory errors during creating posix.environ no longer ignored.

- bpo-35415: Validate fileno= argument to socket.socket().

- bpo-35424: `multiprocessing.Pool` destructor now emits `ResourceWarning` if the pool is still running.

- bpo-35330: When a `Mock` instance was used to wrap an object, if `side_effect` is used in one of the mocks of it methods, don’t call the original implementation and return the result of using the side effect the same way that it is done with return_value.

- bpo-35346: Drop Mac OS 9 and Rhapsody support from the `platform` module. Rhapsody last release was in 2000. Mac OS 9 last release was in 2001.

- bpo-10496: `check_environ()` of `distutils.utils` now catches `KeyError` on calling `pwd.getpwuid()`: don’t create the `HOME` environment variable in this case.

- bpo-10496: `posixpath.expanduser()` now returns the input path unchanged if the `HOME` environment variable is not set and the current user has no home directory (if the current user identifier doesn’t exist in the password database). This change fix the `site` module if the current user doesn’t exist in the password database (if the user has no home directory).

- bpo-35389: `platform.libc_ver()` now uses `os.confstr('CS_GNU_LIBC_VERSION')` if available and the executable parameter is not set.

- bpo-35394: Add empty slots to asyncio abstract protocols.

- bpo-35310: Fix a bug in `select.select()` where, in some cases, the file descriptor sequences were returned unmodified after a signal interruption, even though the file descriptors might not be ready yet. `select.select()` will now always return empty lists if a timeout has occurred. Patch by Oran Avraham.

- bpo-35380: Enable TCP_NODELAY on Windows for proactor asyncio event loop.

- bpo-35341: Add generic version of `collections.OrderedDict` to the `typing` module. Patch by Ismo Toijala.

- bpo-35371: Fixed possible crash in `os.utime()` on Windows when pass incorrect arguments.

- bpo-35346: `platform.uname()` now redirects `stderr` to `os.devnull` when running external programs like `cmd /c ver`.

- bpo-35066: Previously, calling the strftime() method on a datetime object with a trailing ‘%’ in the format string would result in an exception. However, this only occurred when the datetime C module was being used; the python implementation did not match this behavior. Datetime is now PEP-399 compliant, and will not throw an exception on a trailing ‘%’.

- bpo-35345: The function `platform.popen` has been removed, it was deprecated since Python 3.3: use `os.popen()` instead.

- bpo-35344: On macOS, `platform.platform()` now uses `platform.mac_ver()`, if it returns a non-empty release string, to get the macOS version rather than the darwin version.

- bpo-35312: Make `lib2to3.pgen2.parse.ParseError` round-trip pickle-able. Patch by Anthony Sottile.

- bpo-35308: Fix regression in `webbrowser` where default browsers may be preferred over browsers in the `BROWSER` environment variable.

- bpo-24746: Avoid stripping trailing whitespace in doctest fancy diff. Original patch by R. David Murray & Jairo Trad. Enhanced by Sanyam Khurana.

- bpo-28604: `locale.localeconv()` now sets temporarily the `LC_CTYPE` locale to the `LC_MONETARY` locale if the two locales are different and monetary strings are non-ASCII. This temporary change affects other threads.

- bpo-35277: Update ensurepip to install pip 18.1 and setuptools 40.6.2.

- bpo-24209: Adds IPv6 support when invoking http.server directly.

- bpo-35226: Recursively check arguments when testing for equality of `unittest.mock.call` objects and add note that tracking of parameters used to create ancestors of mocks in `mock_calls` is not possible.

- bpo-29564: The warnings module now suggests to enable tracemalloc if the source is specified, the tracemalloc module is available, but tracemalloc is not tracing memory allocations.

- bpo-35189: Modify the following fnctl function to retry if interrupted by a signal (EINTR): flock, lockf, fnctl

- bpo-30064: Use add_done_callback() in sock_* asyncio API to unsubscribe reader/writer early on calcellation.

- bpo-35186: Removed the “built with” comment added when `setup.py upload` is used with either `bdist_rpm` or `bdist_dumb`.

- bpo-35152: Allow sending more than 2 GB at once on a multiprocessing connection on non-Windows systems.

- bpo-35062: Fix incorrect parsing of `io.IncrementalNewlineDecoder`’s translate argument.

- bpo-35065: Remove `StreamReaderProtocol._untrack_reader`. The call to `_untrack_reader` is currently performed too soon, causing the protocol to forget about the reader before `connection_lost` can run and feed the EOF to the reader.

- bpo-34160: ElementTree and minidom now preserve the attribute order specified by the user.

- bpo-35079: Improve difflib.SequenceManager.get_matching_blocks doc by adding ‘non-overlapping’ and changing ‘!=’ to ‘<’.

- bpo-33710: Deprecated `l*gettext()` functions and methods in the `gettext` module. They return encoded bytes instead of Unicode strings and are artifacts from Python 2 times. Also deprecated functions and methods related to setting the charset for `l*gettext()` functions and methods.

- bpo-35017: `socketserver.BaseServer.serve_forever()` now exits immediately if it’s `shutdown()` method is called while it is polling for new events.

- bpo-35024: `importlib` no longer logs `wrote <bytecode path>` redundantly after `(created|could not create) <bytecode path>` is already logged. Patch by Quentin Agren.

- bpo-35047: `unittest.mock` now includes mock calls in exception messages if `assert_not_called`, `assert_called_once`, or `assert_called_once_with` fails. Patch by Petter Strandmark.

- bpo-31047: Fix `ntpath.abspath` regression where it didn’t remove a trailing separator on Windows. Patch by Tim Graham.

- bpo-35053: tracemalloc now tries to update the traceback when an object is reused from a “free list” (optimization for faster object creation, used by the builtin list type for example).

- bpo-31553: Add the –json-lines option to json.tool. Patch by hongweipeng.

- bpo-34794: Fixed a leak in Tkinter when pass the Python wrapper around Tcl_Obj back to Tcl/Tk.

- bpo-34909: Enum: fix grandchildren subclassing when parent mixed with concrete data types.

- bpo-35022: `unittest.mock.MagicMock` now supports the `__fspath__` method (from `os.PathLike`).

- bpo-35008: Fixed references leaks when call the `__setstate__()` method of `xml.etree.ElementTree.Element` in the C implementation for already initialized element.

- bpo-23420: Verify the value for the parameter ‘-s’ of the cProfile CLI. Patch by Robert Kuska

- bpo-33947: dataclasses now handle recursive reprs without raising RecursionError.

- bpo-34890: Make `inspect.iscoroutinefunction()`, `inspect.isgeneratorfunction()` and `inspect.isasyncgenfunction()` work with `functools.partial()`. Patch by Pablo Galindo.

- bpo-34521: Use `socket.CMSG_SPACE()` to calculate ancillary data size instead of `socket.CMSG_LEN()` in `multiprocessing.reduction.recvfds()` as RFC 3542 requires the use of the former for portable applications.

- bpo-31522: The `mailbox.mbox.get_string` function from_ parameter can now successfully be set to a non-default value.

- bpo-34970: Protect tasks weak set manipulation in `asyncio.all_tasks()`

- bpo-34969: gzip: Add –fast, –best on the gzip CLI, these parameters will be used for the fast compression method (quick) or the best method compress (slower, but smaller file). Also, change the default compression level to 6 (tradeoff).

- bpo-16965: The 2to3 `execfile` fixer now opens the file with mode `'rb'`. Patch by Zackery Spytz.

- bpo-34966: `pydoc` now supports aliases not only to methods defined in the end class, but also to inherited methods. The docstring is not duplicated for aliases.

- bpo-34926: `mimetypes.MimeTypes.guess_type()` now accepts path-like object in addition to url strings. Patch by Mayank Asthana.

- bpo-23831: Add `moveto()` method to the `tkinter.Canvas` widget. Patch by Juliette Monsel.

- bpo-34941: Methods `find()`, `findtext()` and `findall()` of the `Element` class in the `xml.etree.ElementTree` module are now able to find children which are instances of `Element` subclasses.

- bpo-32680: `smtplib.SMTP` objects now always have a `sock` attribute present

- bpo-34769: Fix for async generators not finalizing when event loop is in debug mode and garbage collector runs in another thread.

- bpo-34936: Fix `TclError` in `tkinter.Spinbox.selection_element()`. Patch by Juliette Monsel.

- bpo-34829: Add methods `selection_from`, `selection_range`, `selection_present` and `selection_to` to the `tkinter.Spinbox` for consistency with the `tkinter.Entry` widget. Patch by Juliette Monsel.

- bpo-34911: Added secure_protocols argument to http.cookiejar.DefaultCookiePolicy to allow for tweaking of protocols and also to add support by default for wss, the secure websocket protocol.

- bpo-34922: Fixed integer overflow in the `digest()` and `hexdigest()` methods for the SHAKE algorithm in the `hashlib` module.

- bpo-34925: 25% speedup in argument parsing for the functions in the bisect module.

- bpo-34900: Fixed `unittest.TestCase.debug()` when used to call test methods with subtests. Patch by Bruno Oliveira.

- bpo-34844: logging.Formatter enhancement - Ensure styles and fmt matches in logging.Formatter - Added validate method in each format style class: StrFormatStyle, PercentStyle, StringTemplateStyle. - This method is called in the constructor of logging.Formatter class - Also re-raise the KeyError in the format method of each style class, so it would a bit clear that it’s an error with the invalid format fields.

- bpo-34897: Adjust test.support.missing_compiler_executable check so that a nominal command name of “” is ignored. Patch by Michael Felt.

- bpo-34871: Fix inspect module polluted `sys.modules` when parsing `__text_signature__` of callable.

- bpo-34898: Add `mtime` argument to `gzip.compress` for reproducible output. Patch by Guo Ci Teo.

- bpo-28441: On Cygwin and MinGW, ensure that `sys.executable` always includes the full filename in the path, including the `.exe` suffix (unless it is a symbolic link).

- bpo-34866: Adding `max_num_fields` to `cgi.FieldStorage` to make DOS attacks harder by limiting the number of `MiniFieldStorage` objects created by `FieldStorage`.

- bpo-34711: http.server ensures it reports HTTPStatus.NOT_FOUND when the local path ends with “/” and is not a directory, even if the underlying OS (e.g. AIX) accepts such paths as a valid file reference. Patch by Michael Felt.

- bpo-34872: Fix self-cancellation in C implementation of asyncio.Task

- bpo-34849: Don’t log waiting for `selector.select` in asyncio loop iteration. The waiting is pretty normal for any asyncio program, logging its time just adds a noise to logs without any useful information provided.

- bpo-34022: The `SOURCE_DATE_EPOCH` environment variable no longer overrides the value of the invalidation_mode argument to `py_compile.compile()`, and determines its default value instead.

- bpo-34819: Use a monotonic clock to compute timeouts in `Executor.map()` and `as_completed()`, in order to prevent timeouts from deviating when the system clock is adjusted.

- bpo-34758: Add .wasm -> application/wasm to list of recognized file types and content type headers

- bpo-34789: `xml.sax.make_parser()` now accepts any iterable as its parser_list argument. Patch by Andrés Delfino.

- bpo-34334: In `QueueHandler`, clear `exc_text` from `LogRecord` to prevent traceback from being written twice.

- bpo-34687: On Windows, asyncio now uses ProactorEventLoop, instead of SelectorEventLoop, by default.

- bpo-5950: Support reading zip files with archive comments in `zipimport`.

- bpo-32892: The parser now represents all constants as `ast.Constant` instead of using specific constant AST types (`Num`, `Str`, `Bytes`, `NameConstant` and `Ellipsis`). These classes are considered deprecated and will be removed in future Python versions.

- bpo-34728: Add deprecation warning when `loop` is used in methods: `asyncio.sleep`, `asyncio.wait` and `asyncio.wait_for`.

- bpo-34738: ZIP files created by `distutils` will now include entries for directories.

- bpo-34659: Add an optional initial argument to itertools.accumulate().

- bpo-29577: Support multiple mixin classes when creating Enums.

- bpo-34670: Add SSLContext.post_handshake_auth and SSLSocket.verify_client_post_handshake for TLS 1.3’s post handshake authentication feature.

- bpo-32718: The Activate.ps1 script from venv works with PowerShell Core 6.1 and is now available under all operating systems.

- bpo-31177: Fix bug that prevented using `reset_mock` on mock instances with deleted attributes

- bpo-34672: Add a workaround, so the `'Z'` `time.strftime()` specifier on the musl C library can work in some cases.

- bpo-34666: Implement `asyncio.StreamWriter.awrite` and `asyncio.StreamWriter.aclose()` coroutines. Methods are needed for providing a consistent stream API with control flow switched on by default.

- bpo-6721: Acquire the logging module’s commonly used internal locks while fork()ing to avoid deadlocks in the child process.

- bpo-34658: Fix a rare interpreter unhandled exception state SystemError only seen when using subprocess with a preexec_fn while an after_parent handler has been registered with os.register_at_fork and the fork system call fails.

- bpo-34652: Ensure `os.lchmod()` is never defined on Linux.

- bpo-34638: Store a weak reference to stream reader to break strong references loop between reader and protocol. It allows to detect and close the socket if the stream is deleted (garbage collected) without `close()` call.

- bpo-34536: `Enum._missing_`: raise `ValueError` if None returned and `TypeError` if non-member is returned.

- bpo-34636: Speed up re scanning of many non-matching characters for s w and d within bytes objects. (microoptimization)

- bpo-24412: Add `addModuleCleanup()` and `addClassCleanup()` to unittest to support cleanups for `setUpModule()` and `setUpClass()`. Patch by Lisa Roach.

- bpo-34630: Don’t log SSL certificate errors in asyncio code (connection error logging is skipped already).

- bpo-32490: Prevent filename duplication in `subprocess` exception messages. Patch by Zackery Spytz.

- bpo-34363: dataclasses.asdict() and .astuple() now handle namedtuples correctly.

- bpo-34625: Update vendorized expat library version to 2.2.6.

- bpo-32270: The subprocess module no longer mistakenly closes redirected fds even when they were in pass_fds when outside of the default {0, 1, 2} set.

- bpo-34622: Create a dedicated `asyncio.CancelledError`, `asyncio.InvalidStateError` and `asyncio.TimeoutError` exception classes. Inherit them from corresponding exceptions from `concurrent.futures` package. Extract `asyncio` exceptions into a separate file.

- bpo-34610: Fixed iterator of `multiprocessing.managers.DictProxy`.

- bpo-34421: Fix distutils logging for non-ASCII strings. This caused installation issues on Windows.

- bpo-34604: Fix possible mojibake in the error message of `pwd.getpwnam` and `grp.getgrnam` using string representation because of invisible characters or trailing whitespaces. Patch by William Grzybowski.

- bpo-30977: Make uuid.UUID use `__slots__` to reduce its memory footprint. Based on original patch by Wouter Bolsterlee.

- bpo-34574: OrderedDict iterators are not exhausted during pickling anymore. Patch by Sergey Fedoseev.

- bpo-8110: Refactored `subprocess` to check for Windows-specific modules rather than `sys.platform == 'win32'`.

- bpo-34530: `distutils.spawn.find_executable()` now falls back on `os.defpath` if the `PATH` environment variable is not set.

- bpo-34563: On Windows, fix multiprocessing.Connection for very large read: fix _winapi.PeekNamedPipe() and _winapi.ReadFile() for read larger than INT_MAX (usually `2**31-1`).

- bpo-34558: Correct typo in Lib/ctypes/_aix.py

- bpo-34282: Move `Enum._convert` to `EnumMeta._convert_` and fix enum members getting shadowed by parent attributes.

- bpo-22872: When the queue is closed, `ValueError` is now raised by `multiprocessing.Queue.put()` and `multiprocessing.Queue.get()` instead of `AssertionError` and `OSError`, respectively. Patch by Zackery Spytz.

- bpo-34515: Fix parsing non-ASCII identifiers in `lib2to3.pgen2.tokenize` (PEP 3131).

- bpo-13312: Avoids a possible integer underflow (undefined behavior) in the time module’s year handling code when passed a very low negative year value.

- bpo-34472: Improved compatibility for streamed files in `zipfile`. Previously an optional signature was not being written and certain ZIP applications were not supported. Patch by Silas Sewell.

- bpo-34454: Fix the .fromisoformat() methods of datetime types crashing when given unicode with non-UTF-8-encodable code points. Specifically, datetime.fromisoformat() now accepts surrogate unicode code points used as the separator. Report and tests by Alexey Izbyshev, patch by Paul Ganssle.

- bpo-6700: Fix inspect.getsourcelines for module level frames/tracebacks. Patch by Vladimir Matveev.

- bpo-34171: Running the `trace` module no longer creates the `trace.cover` file.

- bpo-34441: Fix crash when an `ABC`-derived class with invalid `__subclasses__` is passed as the second argument to `issubclass()`. Patch by Alexey Izbyshev.

- bpo-34427: Fix infinite loop in `a.extend(a)` for `MutableSequence` subclasses.

- bpo-34412: Make `signal.strsignal()` work on HP-UX. Patch by Michael Osipov.

- bpo-20849: shutil.copytree now accepts a new `dirs_exist_ok` keyword argument. Patch by Josh Bronson.

- bpo-31715: Associate `.mjs` file extension with `application/javascript` MIME Type.

- bpo-34384: `os.readlink()` now accepts path-like and `bytes` objects on Windows.

- bpo-22602: The UTF-7 decoder now raises `UnicodeDecodeError` for ill-formed sequences starting with “+” (as specified in RFC 2152). Patch by Zackery Spytz.

- bpo-2122: The `mmap.flush()` method now returns `None` on success, raises an exception on error under all platforms.

- bpo-34341: Appending to the ZIP archive with the ZIP64 extension no longer grows the size of extra fields of existing entries.

- bpo-34333: Fix %-formatting in `pathlib.PurePath.with_suffix()` when formatting an error message.

- bpo-18540: The `imaplib.IMAP4` and `imaplib.IMAP4_SSL` classes now resolve to the local host IP correctly when the default value of host parameter (`''`) is used.

- bpo-26502: Implement `traceback.FrameSummary.__len__()` method to preserve compatibility with the old tuple API.

- bpo-34318: `assertRaises()`, `assertRaisesRegex()`, `assertWarns()` and `assertWarnsRegex()` no longer success if the passed callable is None. They no longer ignore unknown keyword arguments in the context manager mode. A DeprecationWarning was raised in these cases since Python 3.5.

- bpo-9372: Deprecate `__getitem__()` methods of `xml.dom.pulldom.DOMEventStream`, `wsgiref.util.FileWrapper` and `fileinput.FileInput`.

- bpo-33613: Fix a race condition in `multiprocessing.semaphore_tracker` when the tracker receives SIGINT before it can register signal handlers for ignoring it.

- bpo-34248: Report filename in the exception raised when the database file cannot be opened by `dbm.gnu.open()` and `dbm.ndbm.open()` due to OS-related error. Patch by Zsolt Cserna.

- bpo-33089: Add math.dist() to compute the Euclidean distance between two points.

- bpo-34246: `smtplib.SMTP.send_message()` no longer modifies the content of the mail_options argument. Patch by Pablo S. Blum de Aguiar.

- bpo-31047: Fix `ntpath.abspath` for invalid paths on windows. Patch by Franz Woellert.

- bpo-32321: Add pure Python fallback for functools.reduce. Patch by Robert Wright.

- bpo-34270: The default asyncio task class now always has a name which can be get or set using two new methods (`get_name()` and `set_name()`) and is visible in the `repr()` output. An initial name can also be set using the new `name` keyword argument to `asyncio.create_task()` or the `create_task()` method of the event loop. If no initial name is set, the default Task implementation generates a name like `Task-1` using a monotonic counter.

- bpo-34263: asyncio’s event loop will not pass timeouts longer than one day to epoll/select etc.

- bpo-34035: Fix several AttributeError in zipfile seek() methods. Patch by Mickaël Schoentgen.

- bpo-32215: Fix performance regression in `sqlite3` when a DML statement appeared in a different line than the rest of the SQL query.

- bpo-34075: Deprecate passing non-ThreadPoolExecutor instances to `AbstractEventLoop.set_default_executor()`.

- bpo-34251: Restore `msilib.Win64` to preserve backwards compatibility since it’s already used by `distutils`’ `bdist_msi` command.

- bpo-19891: Ignore errors caused by missing / non-writable homedir while writing history during exit of an interactive session. Patch by Anthony Sottile.

- bpo-33089: Enhanced math.hypot() to support more than two dimensions.

- bpo-34228: tracemalloc: PYTHONTRACEMALLOC=0 environment variable and -X tracemalloc=0 command line option are now allowed to disable explicitly tracemalloc at startup.

- bpo-13041: Use `shutil.get_terminal_size()` to calculate the terminal width correctly in the `argparse.HelpFormatter` class. Initial patch by Zbyszek Jędrzejewski-Szmek.

- bpo-34213: Allow frozen dataclasses to have a field named “object”. Previously this conflicted with an internal use of “object”.

- bpo-34052: `sqlite3.Connection.create_aggregate()`, `sqlite3.Connection.create_function()`, `sqlite3.Connection.set_authorizer()`, `sqlite3.Connection.set_progress_handler()` methods raises TypeError when unhashable objects are passed as callable. These methods now don’t pass such objects to SQLite API. Previous behavior could lead to segfaults. Patch by Sergey Fedoseev.

- bpo-34197: Attributes skipinitialspace, doublequote and strict of the dialect attribute of the `csv` reader are now `bool` instances instead of integers 0 or 1.

- bpo-32788: Errors other than `TypeError` raised in methods `__adapt__()` and `__conform__()` in the `sqlite3` module are now propagated to the user.

- bpo-21446: The `reload` fixer now uses `importlib.reload()` instead of deprecated `imp.reload()`.

- bpo-940286: pydoc’s `Helper.showtopic()` method now prints the cross references of a topic correctly.

- bpo-34164: `base64.b32decode()` could raise UnboundLocalError or OverflowError for incorrect padding. Now it always raises `base64.Error` in these cases.

- bpo-33729: Fixed issues with arguments parsing in `hashlib`.

- bpo-34097: ZipFile can zip files older than 1980-01-01 and newer than 2107-12-31 using a new `strict_timestamps` parameter at the cost of setting the timestamp to the limit.

- bpo-34108: Remove extraneous CR in 2to3 refactor.

- bpo-34070: Make sure to only check if the handle is a tty, when opening a file with `buffering=-1`.

- bpo-27494: Reverted bpo-27494. 2to3 rejects now a trailing comma in generator expressions.

- bpo-33967: functools.singledispatch now raises TypeError instead of IndexError when no positional arguments are passed.

- bpo-34041: Add the parameter deterministic to the `sqlite3.Connection.create_function()` method. Patch by Sergey Fedoseev.

- bpo-34056: Ensure the loader shim created by `imp.load_module` always returns bytes from its `get_data()` function. This fixes using `imp.load_module` with PEP 552 hash-based pycs.

- bpo-34054: The multiprocessing module now uses the monotonic clock `time.monotonic()` instead of the system clock `time.time()` to implement timeout.

- bpo-34043: Optimize tarfile uncompress performance about 15% when gzip is used.

- bpo-34044: `subprocess.Popen` now copies the startupinfo argument to leave it unchanged: it will modify the copy, so that the same `STARTUPINFO` object can be used multiple times.

- bpo-34010: Fixed a performance regression for reading streams with tarfile. The buffered read should use a list, instead of appending to a bytes object.

- bpo-34019: webbrowser: Correct the arguments passed to Opera Browser when opening a new URL using the `webbrowser` module. Patch by Bumsik Kim.

- bpo-34003: csv.DictReader now creates dicts instead of OrderedDicts. Patch by Michael Selik.

- bpo-33978: Closed existing logging handlers before reconfiguration via fileConfig and dictConfig. Patch by Karthikeyan Singaravelan.

- bpo-14117: Make minor tweaks to turtledemo. The ‘wikipedia’ example is now ‘rosette’, describing what it draws. The ‘penrose’ print output is reduced. The’1024’ output of ‘tree’ is eliminated.

- bpo-33974: Fixed passing lists and tuples of strings containing special characters `"`, `\`, `{`, `}` and `\n` as options to `ttk` widgets.

- bpo-27500: Fix getaddrinfo to resolve IPv6 addresses correctly.

- bpo-24567: Improve random.choices() to handle subnormal input weights that could occasionally trigger an IndexError.

- bpo-33871: Fixed integer overflow in `os.readv()`, `os.writev()`, `os.preadv()` and `os.pwritev()` and in `os.sendfile()` with headers or trailers arguments (on BSD-based OSes and macOS).

- bpo-25007: Add `copy.copy()` and `copy.deepcopy()` support to zlib compressors and decompressors. Patch by Zackery Spytz.

- bpo-33929: multiprocessing: Fix a race condition in Popen of multiprocessing.popen_spawn_win32. The child process now duplicates the read end of pipe instead of “stealing” it. Previously, the read end of pipe was “stolen” by the child process, but it leaked a handle if the child process had been terminated before it could steal the handle from the parent process.

- bpo-33899: Tokenize module now implicitly emits a NEWLINE when provided with input that does not have a trailing new line. This behavior now matches what the C tokenizer does internally. Contributed by Ammar Askar.

- bpo-33897: Added a ‘force’ keyword argument to logging.basicConfig().

- bpo-33695: `shutil.copytree()` uses `os.scandir()` function and all copy functions depending from it use cached `os.stat()` values. The speedup for copying a directory with 8000 files is around +9% on Linux, +20% on Windows and + 30% on a Windows SMB share. Also the number of `os.stat()` syscalls is reduced by 38% making `shutil.copytree()` especially faster on network filesystems. (Contributed by Giampaolo Rodola’ in bpo-33695.)

- bpo-33916: bz2 and lzma: When Decompressor.__init__() is called twice, free the old lock to not leak memory.

- bpo-32568: Make select.epoll() and its documentation consistent regarding sizehint and flags.

- bpo-33833: Fixed bug in asyncio where ProactorSocketTransport logs AssertionError if force closed during write.

- bpo-33663: Convert content length to string before putting to header.

- bpo-33721: `os.path` functions that return a boolean result like `exists()`, `lexists()`, `isdir()`, `isfile()`, `islink()`, and `ismount()`, and `pathlib.Path` methods that return a boolean result like `exists()`, `is_dir()`, `is_file()`, `is_mount()`, `is_symlink()`, `is_block_device()`, `is_char_device()`, `is_fifo()`, `is_socket()` now return `False` instead of raising `ValueError` or its subclasses `UnicodeEncodeError` and `UnicodeDecodeError` for paths that contain characters or bytes unrepresentable at the OS level.

- bpo-26544: Fixed implementation of `platform.libc_ver()`. It almost always returned version ‘2.9’ for glibc.

- bpo-33843: Remove deprecated `cgi.escape`, `cgi.parse_qs` and `cgi.parse_qsl`.

- bpo-33842: Remove `tarfile.filemode` which is deprecated since Python 3.3.

- bpo-30167: Prevent site.main() exception if PYTHONSTARTUP is set. Patch by Steve Weber.

- bpo-33805: Improve error message of dataclasses.replace() when an InitVar is not specified

- bpo-33687: Fix the call to `os.chmod()` for `uu.decode()` if a mode is given or decoded. Patch by Timo Furrer.

- bpo-33812: Datetime instance d with non-None tzinfo, but with d.tzinfo.utcoffset(d) returning None is now treated as naive by the astimezone() method.

- bpo-32108: In configparser, don’t clear section when it is assigned to itself.

- bpo-27397: Make email module properly handle invalid-length base64 strings.

- bpo-33578: Implement multibyte encoder/decoder state methods

- bpo-30805: Avoid race condition with debug logging

- bpo-33476: Fix _header_value_parser.py when address group is missing final ‘;’. Contributed by Enrique Perez-Terron

- bpo-33694: asyncio: Fix a race condition causing data loss on pause_reading()/resume_reading() when using the ProactorEventLoop.

- bpo-32493: Correct test for `uuid_enc_be` availability in `configure.ac`. Patch by Michael Felt.

- bpo-33792: Add asyncio.WindowsSelectorEventLoopPolicy and asyncio.WindowsProactorEventLoopPolicy.

- bpo-33274: W3C DOM Level 1 specifies return value of Element.removeAttributeNode() as “The Attr node that was removed.” xml.dom.minidom now complies with this requirement.

- bpo-33778: Update `unicodedata`’s database to Unicode version 11.0.0.

- bpo-33165: Added a stacklevel parameter to logging calls to allow use of wrapper/helper functions for logging APIs.

- bpo-33770: improve base64 exception message for encoded inputs of invalid length

- bpo-33769: asyncio/start_tls: Fix error message; cancel callbacks in case of an unhandled error; mark SSLTransport as closed if it is aborted.

- bpo-33767: The concatenation (`+`) and repetition (`*`) sequence operations now raise `TypeError` instead of `SystemError` when performed on `mmap.mmap` objects. Patch by Zackery Spytz.

- bpo-33734: asyncio/ssl: Fix AttributeError, increase default handshake timeout

- bpo-31014: Fixed creating a controller for `webbrowser` when a user specifies a path to an entry in the BROWSER environment variable. Based on patch by John Still.

- bpo-2504: Add gettext.pgettext() and variants.

- bpo-33197: Add description property for _ParameterKind

- bpo-32751: When cancelling the task due to a timeout, `asyncio.wait_for()` will now wait until the cancellation is complete.

- bpo-32684: Fix gather to propagate cancellation of itself even with return_exceptions.

- bpo-33654: Support protocol type switching in SSLTransport.set_protocol().

- bpo-33674: Pause the transport as early as possible to further reduce the risk of data_received() being called before connection_made().

- bpo-33671: `shutil.copyfile()`, `shutil.copy()`, `shutil.copy2()`, `shutil.copytree()` and `shutil.move()` use platform-specific fast-copy syscalls on Linux and macOS in order to copy the file more efficiently. On Windows `shutil.copyfile()` uses a bigger default buffer size (1 MiB instead of 16 KiB) and a `memoryview()`-based variant of `shutil.copyfileobj()` is used. The speedup for copying a 512MiB file is about +26% on Linux, +50% on macOS and +40% on Windows. Also, much less CPU cycles are consumed. (Contributed by Giampaolo Rodola’ in bpo-25427.)

- bpo-33674: Fix a race condition in SSLProtocol.connection_made() of asyncio.sslproto: start immediately the handshake instead of using call_soon(). Previously, data_received() could be called before the handshake started, causing the handshake to hang or fail.

- bpo-31647: Fixed bug where calling write_eof() on a _SelectorSocketTransport after it’s already closed raises AttributeError.

- bpo-32610: Make asyncio.all_tasks() return only pending tasks.

- bpo-32410: Avoid blocking on file IO in sendfile fallback code

- bpo-33469: Fix RuntimeError after closing loop that used run_in_executor

- bpo-33672: Fix Task.__repr__ crash with Cython’s bogus coroutines

- bpo-33654: Fix transport.set_protocol() to support switching between asyncio.Protocol and asyncio.BufferedProtocol. Fix loop.start_tls() to work with asyncio.BufferedProtocols.

- bpo-33652: Pickles of type variables and subscripted generics are now future-proof and compatible with older Python versions.

- bpo-32493: Fixed `uuid.uuid1()` on FreeBSD.

- bpo-33238: Add `InvalidStateError` to `concurrent.futures`. `Future.set_result` and `Future.set_exception` now raise `InvalidStateError` if the futures are not pending or running. Patch by Jason Haydaman.

- bpo-33618: Finalize and document preliminary and experimental TLS 1.3 support with OpenSSL 1.1.1

- bpo-33625: Release GIL on `grp.getgrnam`, `grp.getgrgid`, `pwd.getpwnam` and `pwd.getpwuid` if reentrant variants of these functions are available. Patch by William Grzybowski.

- bpo-33623: Fix possible SIGSGV when asyncio.Future is created in __del__

- bpo-11874: Use a better regex when breaking usage into wrappable parts. Avoids bogus assertion errors from custom metavar strings.

- bpo-30877: Fixed a bug in the Python implementation of the JSON decoder that prevented the cache of parsed strings from clearing after finishing the decoding. Based on patch by c-fos.

- bpo-33604: Remove HMAC default to md5 marked for removal in 3.8 (removal originally planned in 3.6, bump to 3.8 in PR 7062).

- bpo-33582: Emit a deprecation warning for inspect.formatargspec

- bpo-21145: Add `functools.cached_property` decorator, for computed properties cached for the life of the instance.

- bpo-33570: Change TLS 1.3 cipher suite settings for compatibility with OpenSSL 1.1.1-pre6 and newer. OpenSSL 1.1.1 will have TLS 1.3 ciphers enabled by default.

- bpo-28556: Do not simplify arguments to `typing.Union`. Now `Union[Manager, Employee]` is not simplified to `Employee` at runtime. Such simplification previously caused several bugs and limited possibilities for introspection.

- bpo-12486: `tokenize.generate_tokens()` is now documented as a public API to tokenize unicode strings. It was previously present but undocumented.

- bpo-33540: Add a new `block_on_close` class attribute to `ForkingMixIn` and `ThreadingMixIn` classes of `socketserver`.

- bpo-33548: tempfile._candidate_tempdir_list should consider common TEMP locations

- bpo-33109: argparse subparsers are once again not required by default, reverting the change in behavior introduced by bpo-26510 in 3.7.0a2.

- bpo-33541: Remove unused private method `_strptime.LocaleTime.__pad` (a.k.a. `_LocaleTime__pad`).

- bpo-33536: dataclasses.make_dataclass now checks for invalid field names and duplicate fields. Also, added a check for invalid field specifications.

- bpo-33542: Prevent `uuid.get_node` from using a DUID instead of a MAC on Windows. Patch by Zvi Effron

- bpo-26819: Fix race condition with `ReadTransport.resume_reading` in Windows proactor event loop.

- Fix failure in `typing.get_type_hints()` when ClassVar was provided as a string forward reference.

- bpo-33516: `unittest.mock.MagicMock` now supports the `__round__` magic method.

- bpo-28612: Added support for Site Maps to urllib’s `RobotFileParser` as `RobotFileParser.site_maps()`. Patch by Lady Red, based on patch by Peter Wirtz.

- bpo-28167: Remove platform.linux_distribution, which was deprecated since 3.5.

- bpo-33504: Switch the default dictionary implementation for `configparser` from `collections.OrderedDict` to the standard `dict` type.

- bpo-33505: Optimize asyncio.ensure_future() by reordering if checks: 1.17x faster.

- bpo-33497: Add errors param to cgi.parse_multipart and make an encoding in FieldStorage use the given errors (needed for Twisted). Patch by Amber Brown.

- bpo-29235: The `cProfile.Profile` class can now be used as a context manager. Patch by Scott Sanderson.

- bpo-33495: Change dataclasses.Fields repr to use the repr of each of its members, instead of str. This makes it more clear what each field actually represents. This is especially true for the ‘type’ member.

- bpo-26103: Correct `inspect.isdatadescriptor` to look for `__set__` or `__delete__`. Patch by Aaron Hall.

- bpo-29209: Removed the `doctype()` method and the html parameter of the constructor of `XMLParser`. The `doctype()` method defined in a subclass will no longer be called. Deprecated methods `getchildren()` and `getiterator()` in the `ElementTree` module emit now a `DeprecationWarning` instead of `PendingDeprecationWarning`.

- bpo-33453: Fix dataclasses to work if using literal string type annotations or if using PEP 563 “Postponed Evaluation of Annotations”. Only specific string prefixes are detected for both ClassVar (“ClassVar” and “typing.ClassVar”) and InitVar (“InitVar” and “dataclasses.InitVar”).

- bpo-28556: Minor fixes in typing module: add annotations to `NamedTuple.__new__`, pass `*args` and `**kwds` in `Generic.__new__`. Original PRs by Paulius Šarka and Chad Dombrova.

- bpo-33365: Print the header values besides the header keys instead just the header keys if debuglevel is set to >0 in `http.client`. Patch by Marco Strigl.

- bpo-20087: Updated alias mapping with glibc 2.27 supported locales.

- bpo-33422: Fix trailing quotation marks getting deleted when looking up byte/string literals on pydoc. Patch by Andrés Delfino.

- bpo-28167: The function `platform.linux_distribution` and `platform.dist` now trigger a `DeprecationWarning` and have been marked for removal in Python 3.8

- bpo-33281: Fix ctypes.util.find_library regression on macOS.

- bpo-33311: Text and html output generated by cgitb does not display parentheses if the current call is done directly in the module. Patch by Stéphane Blondon.

- bpo-27300: The file classes in tempfile now accept an errors parameter that complements the already existing encoding. Patch by Stephan Hohe.

- bpo-32933: `unittest.mock.mock_open()` now supports iteration over the file contents. Patch by Tony Flury.

- bpo-33217: Raise `TypeError` when looking up non-Enum objects in Enum classes and Enum members.

- bpo-33197: Update error message when constructing invalid inspect.Parameters Patch by Donghee Na.

- bpo-33383: Fixed crash in the get() method of the `dbm.ndbm` database object when it is called with a single argument.

- bpo-33375: The warnings module now finds the Python file associated with a warning from the code object, rather than the frame’s global namespace. This is consistent with how tracebacks and pdb find filenames, and should work better for dynamically executed code.

- bpo-33336: `imaplib` now allows `MOVE` command in `IMAP4.uid()` (RFC 6851: IMAP MOVE Extension) and potentially as a name of supported method of `IMAP4` object.

- bpo-32455: Added jump parameter to `dis.stack_effect()`.

- bpo-27485: Rename and deprecate undocumented functions in `urllib.parse()`.

- bpo-33332: Add `signal.valid_signals()` to expose the POSIX sigfillset() functionality.

- bpo-33251: `ConfigParser.items()` was fixed so that key-value pairs passed in via `vars()` are not included in the resulting output.

- bpo-33329: Fix multiprocessing regression on newer glibcs

- bpo-33334: `dis.stack_effect()` now supports all defined opcodes including NOP and EXTENDED_ARG.

- bpo-991266: Fix quoting of the `Comment` attribute of `http.cookies.SimpleCookie`.

- bpo-33131: Upgrade bundled version of pip to 10.0.1.

- bpo-33308: Fixed a crash in the `parser` module when converting an ST object to a tree of tuples or lists with `line_info=False` and `col_info=True`.

- bpo-23403: lib2to3 now uses pickle protocol 4 for pre-computed grammars.

- bpo-33266: lib2to3 now recognizes `rf'...'` strings.

- bpo-11594: Ensure line-endings are respected when using lib2to3.

- bpo-33254: Have `importlib.resources.contents()` and `importlib.abc.ResourceReader.contents()` return an iterable instead of an iterator.

- bpo-33265: `contextlib.ExitStack` and `contextlib.AsyncExitStack` now use a method instead of a wrapper function for exit callbacks.

- bpo-33263: Fix FD leak in `_SelectorSocketTransport` Patch by Vlad Starostin.

- bpo-33256: Fix display of `<module>` call in the html produced by `cgitb.html()`. Patch by Stéphane Blondon.

- bpo-33144: `random.Random()` and its subclassing mechanism got optimized to check only once at class/subclass instantiation time whether its `getrandbits()` method can be relied on by other methods, including `randrange()`, for the generation of arbitrarily large random integers. Patch by Wolfgang Maier.

- bpo-33185: Fixed regression when running pydoc with the `-m` switch. (The regression was introduced in 3.7.0b3 by the resolution of bpo-33053)

  This fix also changed pydoc to add `os.getcwd()` to `sys.path` when necessary, rather than adding `"."`.

- bpo-29613: Added support for the `SameSite` cookie flag to the `http.cookies` module.

- bpo-33169: Delete entries of `None` in `sys.path_importer_cache` when `importlib.machinery.invalidate_caches()` is called.

- bpo-33203: `random.Random.choice()` now raises `IndexError` for empty sequences consistently even when called from subclasses without a `getrandbits()` implementation.

- bpo-33224: Update difflib.mdiff() for PEP 479. Convert an uncaught StopIteration in a generator into a return-statement.

- bpo-33209: End framing at the end of C implementation of `pickle.Pickler.dump()`.

- bpo-32861: The urllib.robotparser’s `__str__` representation now includes wildcard entries and the “Crawl-delay” and “Request-rate” fields. Also removes extra newlines that were being appended to the end of the string. Patch by Michael Lazar.

- bpo-23403: `DEFAULT_PROTOCOL` in `pickle` was bumped to 4. Protocol 4 is described in PEP 3154 and available since Python 3.4. It offers better performance and smaller size compared to protocol 3 introduced in Python 3.0.

- bpo-20104: Improved error handling and fixed a reference leak in `os.posix_spawn()`.

- bpo-33106: Deleting a key from a read-only dbm database raises module specific error instead of KeyError.

- bpo-33175: In dataclasses, Field.__set_name__ now looks up the __set_name__ special method on the class, not the instance, of the default value.

- bpo-32380: Create functools.singledispatchmethod to support generic single dispatch on descriptors and methods.

- bpo-33141: Have Field objects pass through __set_name__ to their default values, if they have their own __set_name__.

- bpo-33096: Allow ttk.Treeview.insert to insert iid that has a false boolean value. Note iid=0 and iid=False would be same. Patch by Garvit Khatri.

- bpo-32873: Treat type variables and special typing forms as immutable by copy and pickle. This fixes several minor issues and inconsistencies, and improves backwards compatibility with Python 3.6.

- bpo-33134: When computing dataclass’s __hash__, use the lookup table to contain the function which returns the __hash__ value. This is an improvement over looking up a string, and then testing that string to see what to do.

- bpo-33127: The ssl module now compiles with LibreSSL 2.7.1.

- bpo-32505: Raise TypeError if a member variable of a dataclass is of type Field, but doesn’t have a type annotation.

- bpo-33078: Fix the failure on OSX caused by the tests relying on sem_getvalue

- bpo-33116: Add ‘Field’ to dataclasses.__all__.

- bpo-32896: Fix an error where subclassing a dataclass with a field that uses a default_factory would generate an incorrect class.

- bpo-33100: Dataclasses: If a field has a default value that’s a MemberDescriptorType, then it’s from that field being in __slots__, not an actual default value.

- bpo-32953: If a non-dataclass inherits from a frozen dataclass, allow attributes to be added to the derived class. Only attributes from the frozen dataclass cannot be assigned to. Require all dataclasses in a hierarchy to be either all frozen or all non-frozen.

- bpo-33097: Raise RuntimeError when `executor.submit` is called during interpreter shutdown.

- bpo-32968: Modulo and floor division involving Fraction and float should return float.

- bpo-33061: Add missing `NoReturn` to `__all__` in typing.py

- bpo-33078: Fix the size handling in multiprocessing.Queue when a pickling error occurs.

- bpo-33064: lib2to3 now properly supports trailing commas after `*args` and `**kwargs` in function signatures.

- bpo-33056: FIX properly close leaking fds in concurrent.futures.ProcessPoolExecutor.

- bpo-33021: Release the GIL during fstat() calls, avoiding hang of all threads when calling mmap.mmap(), os.urandom(), and random.seed(). Patch by Nir Soffer.

- bpo-31804: Avoid failing in multiprocessing.Process if the standard streams are closed or None at exit.

- bpo-33034: Providing an explicit error message when casting the port property to anything that is not an integer value using `urlparse()` and `urlsplit()`. Patch by Matt Eaton.

- bpo-30249: Improve struct.unpack_from() exception messages for problems with the buffer size and offset.

- bpo-33037: Skip sending/receiving data after SSL transport closing.

- bpo-27683: Fix a regression in `ipaddress` that result of `hosts()` is empty when the network is constructed by a tuple containing an integer mask and only 1 bit left for addresses.

- bpo-22674: Add the strsignal() function in the signal module that returns the system description of the given signal, as returned by strsignal(3).

- bpo-32999: Fix C implementation of `ABC.__subclasscheck__(cls, subclass)` crashed when `subclass` is not a type object.

- bpo-33009: Fix inspect.signature() for single-parameter partialmethods.

- bpo-32969: Expose several missing constants in zlib and fix corresponding documentation.

- bpo-32056: Improved exceptions raised for invalid number of channels and sample width when read an audio file in modules `aifc`, `wave` and `sunau`.

- bpo-32970: Improved disassembly of the MAKE_FUNCTION instruction.

- bpo-32844: Fix wrong redirection of a low descriptor (0 or 1) to stderr in subprocess if another low descriptor is closed.

- bpo-32960: For dataclasses, disallow inheriting frozen from non-frozen classes, and also disallow inheriting non-frozen from frozen classes. This restriction will be relaxed at a future date.

- bpo-32713: Fixed tarfile.itn handling of out-of-bounds float values. Patch by Joffrey Fuhrer.

- bpo-32257: The ssl module now contains OP_NO_RENEGOTIATION constant, available with OpenSSL 1.1.0h or 1.1.1.

- bpo-32951: Direct instantiation of SSLSocket and SSLObject objects is now prohibited. The constructors were never documented, tested, or designed as public constructors. Users were suppose to use ssl.wrap_socket() or SSLContext.

- bpo-32929: Remove the tri-state parameter “hash”, and add the boolean “unsafe_hash”. If unsafe_hash is True, add a __hash__ function, but if a __hash__ exists, raise TypeError. If unsafe_hash is False, add a __hash__ based on the values of eq= and frozen=. The unsafe_hash=False behavior is the same as the old hash=None behavior. unsafe_hash=False is the default, just as hash=None used to be.

- bpo-32947: Add OP_ENABLE_MIDDLEBOX_COMPAT and test workaround for TLSv1.3 for future compatibility with OpenSSL 1.1.1.

- bpo-32146: Document the interaction between frozen executables and the spawn and forkserver start methods in multiprocessing.

- bpo-30622: The ssl module now detects missing NPN support in LibreSSL.

- bpo-32922: dbm.open() now encodes filename with the filesystem encoding rather than default encoding.

- bpo-32759: Free unused arenas in multiprocessing.heap.

- bpo-32859: In `os.dup2`, don’t check every call whether the `dup3` syscall exists or not.

- bpo-32556: nt._getfinalpathname, nt._getvolumepathname and nt._getdiskusage now correctly convert from bytes.

- bpo-21060: Rewrite confusing message from setup.py upload from “No dist file created in earlier command” to the more helpful “Must create and upload files in one command”.

- bpo-32857: In `tkinter`, `after_cancel(None)` now raises a `ValueError` instead of canceling the first scheduled function. Patch by Cheryl Sabella.

- bpo-32852: Make sure sys.argv remains as a list when running trace.

- bpo-31333: `_abc` module is added. It is a speedup module with C implementations for various functions and methods in `abc`. Creating an ABC subclass and calling `isinstance` or `issubclass` with an ABC subclass are up to 1.5x faster. In addition, this makes Python start-up up to 10% faster.

  Note that the new implementation hides internal registry and caches, previously accessible via private attributes `_abc_registry`, `_abc_cache`, and `_abc_negative_cache`. There are three debugging helper methods that can be used instead `_dump_registry`, `_abc_registry_clear`, and `_abc_caches_clear`.

- bpo-32841: Fixed `asyncio.Condition` issue which silently ignored cancellation after notifying and cancelling a conditional lock. Patch by Bar Harel.

- bpo-32819: ssl.match_hostname() has been simplified and no longer depends on re and ipaddress module for wildcard and IP addresses. Error reporting for invalid wildcards has been improved.

- bpo-19675: `multiprocessing.Pool` no longer leaks processes if its initialization fails.

- bpo-32394: socket: Remove TCP_FASTOPEN,TCP_KEEPCNT,TCP_KEEPIDLE,TCP_KEEPINTVL flags on older version Windows during run-time.

- bpo-31787: Fixed refleaks of `__init__()` methods in various modules. (Contributed by Oren Milman)

- bpo-30157: Fixed guessing quote and delimiter in csv.Sniffer.sniff() when only the last field is quoted. Patch by Jake Davis.

- bpo-30688: Added support of `\N{name}` escapes in regular expressions. Based on patch by Jonathan Eunice.

- bpo-32792: collections.ChainMap() preserves the order of the underlying mappings.

- bpo-32775: `fnmatch.translate()` no longer produces patterns which contain set operations. Sets starting with ‘[’ or containing ‘–’, ‘&&’, ‘~~’ or ‘||’ will be interpreted differently in regular expressions in future versions. Currently they emit warnings. fnmatch.translate() now avoids producing patterns containing such sets by accident.

- bpo-32622: Implement native fast sendfile for Windows proactor event loop.

- bpo-32777: Fix a rare but potential pre-exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process. This bug appears to have been introduced in 3.4.

- bpo-32647: The ctypes module used to depend on indirect linking for dlopen. The shared extension is now explicitly linked against libdl on platforms with dl.

- bpo-32749: A `dbm.dumb` database opened with flags ‘r’ is now read-only. `dbm.dumb.open()` with flags ‘r’ and ‘w’ no longer creates a database if it does not exist.

- bpo-32741: Implement `asyncio.TimerHandle.when()` method.

- bpo-32691: Use mod_spec.parent when running modules with pdb

- bpo-32734: Fixed `asyncio.Lock()` safety issue which allowed acquiring and locking the same lock multiple times, without it being free. Patch by Bar Harel.

- bpo-32727: Do not include name field in SMTP envelope from address. Patch by Stéphane Wirtel

- bpo-31453: Add TLSVersion constants and SSLContext.maximum_version / minimum_version attributes. The new API wraps OpenSSL 1.1 https://web.archive.org/web/20180309043602/https://www.openssl.org/docs/man1.1.0/ssl/SSL_CTX_set_min_proto_version.html feature.

- bpo-24334: Internal implementation details of ssl module were cleaned up. The SSLSocket has one less layer of indirection. Owner and session information are now handled by the SSLSocket and SSLObject constructor. Channel binding implementation has been simplified.

- bpo-31848: Fix the error handling in Aifc_read.initfp() when the SSND chunk is not found. Patch by Zackery Spytz.

- bpo-32585: Add Ttk spinbox widget to `tkinter.ttk`. Patch by Alan D Moore.

- bpo-32512: `profile` CLI accepts `-m module_name` as an alternative to script path.

- bpo-8525: help() on a type now displays builtin subclasses. This is intended primarily to help with notification of more specific exception subclasses.

  Patch by Sanyam Khurana.

- bpo-31639: http.server now exposes a ThreadingHTTPServer class and uses it when the module is run with `-m` to cope with web browsers pre-opening sockets.

- bpo-29877: compileall: import ProcessPoolExecutor only when needed, preventing hangs on low resource platforms

- bpo-32221: Various functions returning tuple containing IPv6 addresses now omit `%scope` part since the same information is already encoded in scopeid tuple item. Especially this speeds up `socket.recvfrom()` when it receives multicast packet since useless resolving of network interface name is omitted.

- bpo-32147: `binascii.unhexlify()` is now up to 2 times faster. Patch by Sergey Fedoseev.

- bpo-30693: The TarFile class now recurses directories in a reproducible way.

- bpo-30693: The ZipFile class now recurses directories in a reproducible way.

- bpo-31680: Added `curses.ncurses_version`.

- bpo-31908: Fix output of cover files for `trace` module command-line tool. Previously emitted cover files only when `--missing` option was used. Patch by Michael Selik.

- bpo-31608: Raise a `TypeError` instead of crashing if a `collections.deque` subclass returns a non-deque from `__new__`. Patch by Oren Milman.

- bpo-31425: Add support for sockets of the AF_QIPCRTR address family, supported by the Linux kernel. This is used to communicate with services, such as GPS or radio, running on Qualcomm devices. Patch by Bjorn Andersson.

- bpo-22005: Implemented unpickling instances of `datetime`, `date` and `time` pickled by Python 2. `encoding='latin1'` should be used for successful decoding.

- bpo-27645: `sqlite3.Connection` now exposes a `backup` method, if the underlying SQLite library is at version 3.6.11 or higher. Patch by Lele Gaifax.

- bpo-16865: Support arrays >=2GiB in `ctypes`. Patch by Segev Finer.

- bpo-31508: Removed support of arguments in `tkinter.ttk.Treeview.selection`. It was deprecated in 3.6. Use specialized methods like `selection_set` for changing the selection.

- bpo-29456: Fix bugs in hangul normalization: u1176, u11a7 and u11c3

### Documentation

- bpo-21257: Document `http.client.parse_headers()`.

- bpo-34764: Improve example of iter() with 2nd sentinel argument.

- bpo-35564: Explicitly set master_doc variable in conf.py for compliance with Sphinx 2.0

- bpo-35511: Specified that profile.Profile class doesn’t not support enable or disable methods. Also, elaborated that Profile object as a context manager is only supported in cProfile module.

- bpo-10536: Enhance the gettext docs. Patch by Éric Araujo

- bpo-35089: Remove mention of `typing.io` and `typing.re`. Their types should be imported from `typing` directly.

- bpo-35038: Fix the documentation about an unexisting `f_restricted` attribute in the frame object. Patch by Stéphane Wirtel

- bpo-35042: Replace PEP XYZ by the pep role and allow to use the direct links to the PEPs.

- bpo-35044: Fix the documentation with the role `exc` for the appropriated exception. Patch by Stéphane Wirtel

- bpo-35035: Rename documentation for `email.utils` to `email.utils.rst`.

- bpo-34967: Use app.add_object_type() instead of the deprecated Sphinx function app.description_unit()

- bpo-34913: Add documentation about the new command line interface of the gzip module.

- bpo-32174: chm document displays non-ASCII characters properly on some MBCS Windows systems.

- bpo-11233: Create availability directive for documentation. Original patch by Georg Brandl.

- bpo-34790: Document how passing coroutines to asyncio.wait() can be confusing.

- bpo-34552: Make clear that `==` operator sometimes is equivalent to `is`. The `<`, `<=`, `>` and `>=` operators are only defined where they make sense.

- bpo-28617: Fixed info in the stdtypes docs concerning the types that support membership tests.

- bpo-20177: Migrate datetime.date.fromtimestamp to Argument Clinic. Patch by Tim Hoffmann.

- bpo-34065: Fix wrongly written basicConfig documentation markup syntax

- bpo-33460: replaced ellipsis with correct error codes in tutorial chapter 3.

- bpo-33847: Add ‘@’ operator entry to index.

- bpo-33409: Clarified the relationship between PEP 538’s PYTHONCOERCECLOCALE and PEP 540’s PYTHONUTF8 mode.

- bpo-33197: Add versionadded tag to the documentation of ParameterKind.description

- bpo-17045: Improve the C-API doc for PyTypeObject. This includes adding several quick-reference tables and a lot of missing slot/typedef entries. The existing entries were also cleaned up with a slightly more consistent format.

- bpo-33736: Improve the documentation of `asyncio.open_connection()`, `asyncio.start_server()` and their UNIX socket counterparts.

- bpo-23859: Document that `asyncio.wait()` does not cancel its futures on timeout.

- bpo-32436: Document PEP 567 changes to asyncio.

- bpo-33604: Update HMAC md5 default to a DeprecationWarning, bump removal to 3.8.

- bpo-33594: Document `getargspec`, `from_function` and `from_builtin` as deprecated in their respective docstring, and include version since deprecation in DeprecationWarning message.

- bpo-33503: Fix broken pypi link

- bpo-33421: Add missing documentation for `typing.AsyncContextManager`.

- bpo-33487: BZ2file now emit a DeprecationWarning when buffering=None is passed, the deprecation message and documentation also now explicitly state it is deprecated since 3.0.

- bpo-33378: Add Korean language switcher for https://docs.python.org/3/

- bpo-33276: Clarify that the `__path__` attribute on modules cannot be just any value.

- bpo-33201: Modernize documentation for writing C extension types.

- bpo-33195: Deprecate `Py_UNICODE` usage in `c-api/arg` document. `Py_UNICODE` related APIs are deprecated since Python 3.3, but it is missed in the document.

- bpo-33126: Document PyBuffer_ToContiguous().

- bpo-27212: Modify documentation for the `islice()` recipe to consume initial values up to the start index.

- bpo-28247: Update `zipapp` documentation to describe how to make standalone applications.

- bpo-18802: Documentation changes for ipaddress. Patch by Jon Foster and Berker Peksag.

- bpo-27428: Update documentation to clarify that `WindowsRegistryFinder` implements `MetaPathFinder`. (Patch by Himanshu Lakhara)

- bpo-28124: The ssl module function ssl.wrap_socket() has been de-emphasized and deprecated in favor of the more secure and efficient SSLContext.wrap_socket() method.

- bpo-17232: Clarify docs for -O and -OO. Patch by Terry Reedy.

- bpo-32436: Add documentation for the contextvars module (PEP 567).

- bpo-32800: Update link to w3c doc for xml default namespaces.

- bpo-11015: Update `test.support` documentation.

- bpo-32613: Update the faq/windows.html to use the py command from PEP 397 instead of python.

- bpo-8722: Document `__getattr__()` behavior when property `get()` method raises `AttributeError`.

- bpo-32614: Modify RE examples in documentation to use raw strings to prevent `DeprecationWarning` and add text to REGEX HOWTO to highlight the deprecation.

- bpo-20709: Remove the paragraph where we explain that os.utime() does not support a directory as path under Windows. Patch by Jan-Philip Gehrcke

- bpo-32722: Remove the bad example in the tutorial of the Generator Expression. Patch by Stéphane Wirtel

- bpo-31972: Improve docstrings for `pathlib.PurePath` subclasses.

- bpo-30607: Use the externalized `python-docs-theme` package when building the documentation.

- bpo-8243: Add a note about curses.addch and curses.addstr exception behavior when writing outside a window, or pad.

- bpo-32337: Update documentation related with `dict` order.

- bpo-25041: Document `AF_PACKET` in the `socket` module.

- bpo-31432: Clarify meaning of CERT_NONE, CERT_OPTIONAL, and CERT_REQUIRED flags for ssl.SSLContext.verify_mode.

### Tests

- bpo-35772: Fix sparse file tests of test_tarfile on ppc64 with the tmpfs filesystem. Fix the function testing if the filesystem supports sparse files: create a file which contains data and “holes”, instead of creating a file which contains no data. tmpfs effective block size is a page size (tmpfs lives in the page cache). RHEL uses 64 KiB pages on aarch64, ppc64, ppc64le, only s390x and x86_64 use 4 KiB pages, whereas the test punch holes of 4 KiB.

- bpo-35045: Make ssl tests less strict and also accept TLSv1 as system default. The changes unbreaks test_min_max_version on Fedora 29.

- bpo-32710: `test_asyncio/test_sendfile.py` now resets the event loop policy using `tearDownModule()` as done in other tests, to prevent a warning when running tests on Windows.

- bpo-33717: test.pythoninfo now logs information of all clocks, not only time.time() and time.perf_counter().

- bpo-35488: Add a test to pathlib’s Path.match() to verify it does not support glob-style ** recursive pattern matching.

- bpo-31731: Fix a race condition in `check_interrupted_write()` of test_io: create directly the thread with SIGALRM signal blocked, rather than blocking the signal later from the thread. Previously, it was possible that the thread gets the signal before the signal is blocked.

- bpo-35424: Fix test_multiprocessing_main_handling: use `multiprocessing.Pool` with a context manager and then explicitly join the pool.

- bpo-35519: Rename `test.bisect` module to `test.bisect_cmd` to avoid conflict with `bisect` module when running directly a test like `./python Lib/test/test_xmlrpc.py`.

- bpo-35513: Replace `time.time()` with `time.monotonic()` in tests to measure time delta.

- bpo-34279: `test.support.run_unittest()` no longer raise `TestDidNotRun` if the test result contains skipped tests. The exception is now only raised if no test have been run and no test have been skipped.

- bpo-35412: Add testcase to `test_future4`: check unicode literal.

- bpo-26704: Added test demonstrating double-patching of an instance method. Patch by Anthony Sottile.

- bpo-33725: test_multiprocessing_fork may crash on recent versions of macOS. Until the issue is resolved, skip the test on macOS.

- bpo-35352: Modify test_asyncio to use the certificate set from the test directory.

- bpo-35317: Fix `mktime()` overflow error in `test_email`: run `test_localtime_daylight_true_dst_true()` and `test_localtime_daylight_false_dst_true()` with a specific timezone.

- bpo-21263: After several reports that test_gdb does not work properly on macOS and since gdb is not shipped by default anymore, test_gdb is now skipped on macOS when LLVM Clang has been used to compile Python. Patch by Lysandros Nikolaou

- bpo-34279: regrtest issue a warning when no tests have been executed in a particular test file. Also, a new final result state is issued if no test have been executed across all test files. Patch by Pablo Galindo.

- bpo-34962: make docstest in Doc now passes., and is enforced in CI

- bpo-23596: Use argparse for the command line of the gzip module. Patch by Antony Lee

- bpo-34537: Fix `test_gdb.test_strings()` when `LC_ALL=C` and GDB was compiled with Python 3.6 or earlier.

- bpo-34587: test_socket: Remove RDSTest.testCongestion(). The test tries to fill the receiver’s socket buffer and expects an error. But the RDS protocol doesn’t require that. Moreover, the Linux implementation of RDS expects that the producer of the messages reduces its rate, it’s not the role of the receiver to trigger an error. The test fails on Fedora 28 by design, so just remove it.

- bpo-34661: Fix test_shutil if unzip doesn’t support -t.

- bpo-34200: Fixed non-deterministic flakiness of test_pkg by not using the scary test.support.module_cleanup() logic to save and restore sys.modules contents between test cases.

- bpo-34569: The experimental PEP 554 data channels now correctly pass negative PyLong objects between subinterpreters on 32-bit systems. Patch by Michael Felt.

- bpo-34594: Fix usage of hardcoded `errno` values in the tests.

- bpo-34579: Fix test_embed for AIX Patch by Michael Felt

- bpo-34542: Use 3072 RSA keys and SHA-256 signature for test certs and keys.

- bpo-11193: Remove special condition for AIX in `test_subprocess.test_undecodable_env`

- bpo-34347: Fix `test_utf8_mode.test_cmd_line` for AIX

- bpo-34490: On AIX with AF_UNIX family sockets getsockname() does not provide ‘sockname’, so skip calls to transport.get_extra_info(‘sockname’)

- bpo-34391: Fix ftplib test for TLS 1.3 by reading from data socket.

- bpo-11192: Fix `test_socket` on AIX 6.1 and later IPv6 zone id supports only supported by `inet_pton6_zone()`. Switch to runtime-based `platform.system()` to establish current platform rather than build-time based `sys.platform()`

- bpo-34399: Update all RSA keys and DH params to use at least 2048 bits.

- bpo-34373: Fix `test_mktime` and `test_pthread_getcpuclickid` tests for AIX Add range checking for `_PyTime_localtime` for AIX Patch by Michael Felt

- bpo-11191: Skip the distutils test ‘test_search_cpp’ when using XLC as compiler patch by aixtools (Michael Felt)

- Improved an error message when mock assert_has_calls fails.

- bpo-33746: Fix test_unittest when run in verbose mode.

- bpo-33901: Fix test_dbm_gnu on macOS with gdbm 1.15: add a larger value to make sure that the file size changes.

- bpo-33873: Fix a bug in `regrtest` that caused an extra test to run if –huntrleaks/-R was used. Exit with error in case that invalid parameters are specified to –huntrleaks/-R (at least one warmup run and one repetition must be used).

- bpo-33562: Check that a global asyncio event loop policy is not left behind by any tests.

- bpo-33655: Ignore test_posix_fallocate failures on BSD platforms that might be due to running on ZFS.

- bpo-32962: Fixed test_gdb when Python is compiled with flags -mcet -fcf-protection -O0.

- bpo-33358: Fix `test_embed.test_pre_initialization_sys_options()` when the interpreter is built with `--enable-shared`.

- bpo-32872: Avoid regrtest compatibility issue with namespace packages.

- bpo-32517: Fix failing `test_asyncio` on macOS 10.12.2+ due to transport of `KqueueSelector` loop was not being closed.

- bpo-32663: Making sure the `SMTPUTF8SimTests` class of tests gets run in `test_smtplib.py`.

- bpo-27643: Test_C test case needs “signed short” bitfields, but the IBM XLC compiler (on AIX) does not support this Skip the code and test when AIX and XLC are used

  Applicable to Python2-2.7 and later

- bpo-19417: Add test_bdb.py.

- bpo-31809: Add tests to verify connection with secp ECDH curves.

### Build

- bpo-34691: The _contextvars module is now built into the core Python library on Windows.

- bpo-35683: Improved Azure Pipelines build steps and now verifying layouts correctly

- bpo-35642: Remove asynciomodule.c from pythoncore.vcxproj

- bpo-35550: Fix incorrect Solaris #ifdef checks to look for __sun && __SVR4 instead of sun when compiling.

- bpo-35499: `make profile-opt` no longer replaces `CFLAGS_NODIST` with `CFLAGS`. It now adds profile-guided optimization (PGO) flags to `CFLAGS_NODIST`: existing `CFLAGS_NODIST` flags are kept.

- bpo-35257: Avoid leaking the linker flags from Link Time Optimizations (LTO) into distutils when compiling C extensions.

- bpo-35351: When building Python with clang and LTO, LTO flags are no longer passed into CFLAGS to build third-party C extensions through distutils.

- bpo-35139: Fix a compiler error when statically linking `pyexpat` in `Modules/Setup`.

- bpo-35059: PCbuild: Set InlineFunctionExpansion to OnlyExplicitInline (“/Ob1” option) in pyproject.props in Debug mode to expand functions marked as inline. This change should make Python compiled in Debug mode a little bit faster on Windows.

- bpo-35011: Restores the use of pyexpatns.h to isolate our embedded copy of the expat C library so that its symbols do not conflict at link or dynamic loading time with an embedding application or other extension modules with their own version of libexpat.

- bpo-28015: Have –with-lto works correctly with clang.

- bpo-34765: Update the outdated install-sh file to the latest revision from automake v1.16.1

- bpo-34585: Check for floating-point byte order in configure.ac using compilation tests instead of executing code, so that these checks work in cross-compiled builds.

- bpo-34710: Fixed SSL module build with OpenSSL & pedantic CFLAGS.

- bpo-34582: Add JUnit XML output for regression tests and update Azure DevOps builds.

- bpo-34081: Make Sphinx warnings as errors in the Docs Makefile.

- bpo-34555: Fix for case where it was not possible to have both `HAVE_LINUX_VM_SOCKETS_H` and `HAVE_SOCKADDR_ALG` be undefined.

- bpo-33015: Fix an undefined behaviour in the pthread implementation of `PyThread_start_new_thread()`: add a function wrapper to always return `NULL`.

- bpo-34245: The Python shared library is now installed with write permission (mode 0755), which is the standard way of installing such libraries.

- bpo-34121: Fix detection of C11 atomic support on clang.

- bpo-32430: Rename Modules/Setup.dist to Modules/Setup, and remove the necessity to copy the former manually to the latter when updating the local source tree.

- bpo-30345: Add -g to LDFLAGS when compiling with LTO to get debug symbols.

- bpo-5755: Move `-Wstrict-prototypes` option to `CFLAGS_NODIST` from `OPT`. This option emitted annoying warnings when building extension modules written in C++.

- bpo-33614: Ensures module definition files for the stable ABI on Windows are correctly regenerated.

- bpo-33648: The –with-c-locale-warning configuration flag has been removed. It has had no effect for about a year.

- bpo-33522: Enable CI builds on Visual Studio Team Services at https://python.visualstudio.com/cpython

- bpo-33512: configure’s check for “long double” has been simplified

- bpo-33483: C compiler is now correctly detected from the standard environment variables. –without-gcc and –with-icc options have been removed.

- bpo-33394: Enable the verbose build for extension modules, when GNU make is passed macros on the command line.

- bpo-33393: Update config.guess and config.sub files.

- bpo-33377: Add new triplets for mips r6 and riscv variants (used in extension suffixes).

- bpo-32232: By default, modules configured in `Modules/Setup` are no longer built with `-DPy_BUILD_CORE`. Instead, modules that specifically need that preprocessor definition include it in their individual entries.

- bpo-33182: The embedding tests can once again be built with clang 6.0

- bpo-33163: Upgrade pip to 9.0.3 and setuptools to v39.0.1.

- bpo-33012: gcc 8 has added a new warning heuristic to detect invalid function casts and a stock python build seems to hit that warning quite often. The most common is the cast of a METH_NOARGS function (that uses just one argument) to a PyCFunction. Fix this by adding a dummy argument to all functions that implement METH_NOARGS.

- bpo-32898: Fix the python debug build when using COUNT_ALLOCS.

- bpo-29442: Replace optparse with argparse in setup.py

### Windows

- bpo-35890: Fix API calling consistency of GetVersionEx and wcstok.

- bpo-32560: The `py` launcher now forwards its `STARTUPINFO` structure to child processes.

- bpo-35854: Fix EnvBuilder and –symlinks in venv on Windows

- bpo-35811: Avoid propagating venv settings when launching via py.exe

- bpo-35797: Fix default executable used by the multiprocessing module

- bpo-35758: Allow building on ARM with MSVC.

- bpo-29734: Fix handle leaks in os.stat on Windows.

- bpo-35596: Use unchecked PYCs for the embeddable distro to avoid zipimport restrictions.

- bpo-35596: Fix vcruntime140.dll being added to embeddable distro multiple times.

- bpo-35402: Update Windows build to use Tcl and Tk 8.6.9

- bpo-35401: Updates Windows build to OpenSSL 1.1.0j

- bpo-34977: venv on Windows will now use a python.exe redirector rather than copying the actual binaries from the base environment.

- bpo-34977: Adds support for building a Windows App Store package

- bpo-35067: Remove _distutils_findvs module and use vswhere.exe instead.

- bpo-32557: Allow shutil.disk_usage to take a file path on Windows

- bpo-34770: Fix a possible null pointer dereference in pyshellext.cpp.

- bpo-34603: Fix returning structs from functions produced by MSVC

- bpo-34581: Guard MSVC-specific code in socketmodule.c with `#ifdef _MSC_VER`.

- bpo-34532: Fixes exit code of list version arguments for py.exe.

- bpo-34062: Fixed the ‘–list’ and ‘–list-paths’ arguments for the py.exe launcher

- bpo-34225: Ensure INCLUDE and LIB directories do not end with a backslash.

- bpo-34011: A suite of code has been changed which copied across DLLs and init.tcl from the running Python location into a venv being created. These copies are needed only when running from a Python source build, and the copying code is now only run when that is the case, rather than whenever a venv is created.

- bpo-34006: Revert line length limit for Windows help docs. The line-length limit is not needed because the pages appear in a separate app rather than on a browser tab. It can also interact badly with the DPI setting.

- bpo-31546: Restore running PyOS_InputHook while waiting for user input at the prompt. The restores integration of interactive GUI windows (such as Matplotlib figures) with the prompt on Windows.

- bpo-30237: Output error when ReadConsole is canceled by CancelSynchronousIo instead of crashing.

- bpo-33895: GIL is released while calling functions that acquire Windows loader lock.

- bpo-33720: Reduces maximum marshal recursion depth on release builds.

- bpo-29097: Fix bug where `datetime.fromtimestamp()` erroneously throws an `OSError` on Windows for values between 0 and 86400. Patch by Ammar Askar.

- bpo-33316: PyThread_release_lock always fails

- bpo-33184: Update Windows installer to use OpenSSL 1.1.0h.

- bpo-32890: Fix usage of GetLastError() instead of errno in os.execve() and os.truncate().

- bpo-33016: Fix potential use of uninitialized memory in nt._getfinalpathname

- bpo-32903: Fix a memory leak in os.chdir() on Windows if the current directory is set to a UNC path.

- bpo-32901: Update Tcl and Tk versions to 8.6.8

- bpo-31966: Fixed WindowsConsoleIO.write() for writing empty data.

- bpo-32409: Ensures activate.bat can handle Unicode contents.

- bpo-32457: Improves handling of denormalized executable path when launching Python.

- bpo-32370: Use the correct encoding for ipconfig output in the uuid module. Patch by Segev Finer.

- bpo-29248: Fix `os.readlink()` on Windows, which was mistakenly treating the `PrintNameOffset` field of the reparse data buffer as a number of characters instead of bytes. Patch by Craig Holmquist and SSE4.

- bpo-1104: Correctly handle string length in `msilib.SummaryInfo.GetProperty()` to prevent it from truncating the last character.

### macOS

- bpo-35401: Update macOS installer to use OpenSSL 1.1.0j.

- bpo-35025: Properly guard the use of the `CLOCK_GETTIME` et al. macros in `timemodule` on macOS.

- bpo-24658: On macOS, fix reading from and writing into a file with a size larger than 2 GiB.

- bpo-34405: Update to OpenSSL 1.1.0i for macOS installer builds.

- bpo-33635: In macOS stat on some file descriptors (/dev/fd/3 f.e) will result in bad file descriptor OSError. Guard against this exception was added in is_dir, is_file and similar methods. DirEntry.is_dir can also throw this exception so _RecursiveWildcardSelector._iterate_directories was also extended with the same error ignoring pattern.

- bpo-13631: The .editrc file in user’s home directory is now processed correctly during the readline initialization through editline emulation on macOS.

- bpo-33184: Update macOS installer build to use OpenSSL 1.1.0h.

- bpo-32726: Build and link with private copy of Tcl/Tk 8.6 for the macOS 10.6+ installer. The 10.9+ installer variant already does this. This means that the Python 3.7 provided by the python.org macOS installers no longer need or use any external versions of Tcl/Tk, either system-provided or user-installed, such as ActiveTcl.

- bpo-32901: Update macOS 10.9+ installer to Tcl/Tk 8.6.8.

- bpo-31903: In `_scproxy`, drop the GIL when calling into `SystemConfiguration` to avoid deadlocks.

### IDLE

- bpo-35770: IDLE macosx deletes Options => Configure IDLE. It previously deleted Window => Zoom Height by mistake. (Zoom Height is now on the Options menu). On Mac, the settings dialog is accessed via Preferences on the IDLE menu.

- bpo-35769: Change IDLE’s new file name from ‘Untitled’ to ‘untitled’

- bpo-35660: Fix imports in idlelib.window.

- bpo-35641: Proper format `calltip` when the function has no docstring.

- bpo-33987: Use ttk Frame for ttk widgets.

- bpo-34055: Fix erroneous ‘smart’ indents and newlines in IDLE Shell.

- bpo-35591: Find Selection now works when selection not found.

- bpo-35196: Speed up squeezer line counting.

- bpo-35598: Update config_key: use PEP 8 names and ttk widgets, make some objects global, and add tests.

- bpo-28097: Add Previous/Next History entries to Shell menu.

- bpo-35208: Squeezer now properly counts wrapped lines before newlines.

- bpo-35555: Gray out Code Context menu entry when it’s not applicable.

- bpo-35521: Document the IDLE editor code context feature. Add some internal references within the IDLE doc.

- bpo-22703: The Code Context menu label now toggles between Show/Hide Code Context. The Zoom Height menu now toggles between Zoom/Restore Height. Zoom Height has moved from the Window menu to the Options menu.

- bpo-35213: Where appropriate, use ‘macOS’ in idlelib.

- bpo-34864: On macOS, warn if the system preference “Prefer tabs when opening documents” is set to “Always”.

- bpo-34864: Document two IDLE on MacOS issues. The System Preferences Dock “prefer tabs always” setting disables some IDLE features. Menus are a bit different than as described for Windows and Linux.

- bpo-35202: Remove unused imports from lib/idlelib

- bpo-33000: Document that IDLE’s shell has no line limit. A program that runs indefinitely can overfill memory.

- bpo-23220: Explain how IDLE’s Shell displays output.

- bpo-35099: Improve the doc about IDLE running user code. The section is renamed from “IDLE – console differences” is renamed “Running user code”. It mostly covers the implications of using custom `sys.stdxxx` objects.

- bpo-35097: Add IDLE doc subsection explaining editor windows. Topics include opening, title and status bar, .py* extension, and running.

- bpo-35093: Document the IDLE document viewer in the IDLE doc. Add a paragraph in “Help and preferences”, “Help sources” subsection.

- bpo-35088: Update idlelib.help.copy_string docstring. We now use git and backporting instead of hg and forward merging.

- bpo-35087: Update idlelib help files for the current doc build. The main change is the elimination of chapter-section numbers.

- bpo-34548: Use configured color theme for read-only text views.

- bpo-1529353: Enable “squeezing” of long outputs in the shell, to avoid performance degradation and to clean up the history without losing it. Squeezed outputs may be copied, viewed in a separate window, and “unsqueezed”.

- bpo-34047: Fixed mousewheel scrolling direction on macOS.

- bpo-34275: Make IDLE calltips always visible on Mac. Some MacOS-tk combinations need .update_idletasks(). Patch by Kevin Walzer.

- bpo-34120: Fix unresponsiveness after closing certain windows and dialogs.

- bpo-33975: Avoid small type when running htests. Since part of the purpose of human-viewed tests is to determine that widgets look right, it is important that they look the same for testing as when running IDLE.

- bpo-33905: Add test for idlelib.stackview.StackBrowser.

- bpo-33924: Change mainmenu.menudefs key ‘windows’ to ‘window’. Every other menudef key is lowercase version of main menu entry.

- bpo-33906: Rename idlelib.windows as window Match Window on the main menu and remove last plural module name.

- bpo-33917: Fix and document idlelib/idle_test/template.py. The revised file compiles, runs, and tests OK. idle_test/README.txt explains how to use it to create new IDLE test files.

- bpo-33904: IDLE: In rstrip, rename class RstripExtension as Rstrip

- bpo-33907: For consistency and clarity, rename an IDLE module and classes. Module calltips and its class CallTips are now calltip and Calltip. In module calltip_w, class CallTip is now CalltipWindow.

- bpo-33856: Add “help” in the welcome message of IDLE

- bpo-33839: IDLE: refactor ToolTip and CallTip and add documentation and tests

- bpo-33855: Minimally test all IDLE modules. Add missing files, import module, instantiate classes, and check coverage. Check existing files.

- bpo-33656: On Windows, add API call saying that tk scales for DPI. On Windows 8.1+ or 10, with DPI compatibility properties of the Python binary unchanged, and a monitor resolution greater than 96 DPI, this should make text and lines sharper. It should otherwise have no effect.

- bpo-33768: Clicking on a context line moves that line to the top of the editor window.

- bpo-33763: IDLE: Use read-only text widget for code context instead of label widget.

- bpo-33664: Scroll IDLE editor text by lines. Previously, the mouse wheel and scrollbar slider moved text by a fixed number of pixels, resulting in partial lines at the top of the editor box. The change also applies to the shell and grep output windows, but not to read-only text views.

- bpo-33679: Enable theme-specific color configuration for Code Context. Use the Highlights tab to see the setting for built-in themes or add settings to custom themes.

- bpo-33642: Display up to maxlines non-blank lines for Code Context. If there is no current context, show a single blank line.

- bpo-33628: IDLE: Cleanup codecontext.py and its test.

- bpo-33564: IDLE’s code context now recognizes async as a block opener.

- bpo-21474: Update word/identifier definition from ascii to unicode. In text and entry boxes, this affects selection by double-click, movement left/right by control-left/right, and deletion left/right by control-BACKSPACE/DEL.

- bpo-33204: IDLE: consistently color invalid string prefixes. A ‘u’ string prefix cannot be paired with either ‘r’ or ‘f’. Consistently color as much of the prefix, starting at the right, as is valid. Revise and extend colorizer test.

- bpo-32984: Set `__file__` while running a startup file. Like Python, IDLE optionally runs one startup file in the Shell window before presenting the first interactive input prompt. For IDLE, `-s` runs a file named in environmental variable `IDLESTARTUP` or `PYTHONSTARTUP`; `-r file` runs `file`. Python sets `__file__` to the startup file name before running the file and unsets it before the first prompt. IDLE now does the same when run normally, without the `-n` option.

- bpo-32940: Simplify and rename StringTranslatePseudoMapping in pyparse.

- bpo-32916: Change `str` to `code` in pyparse.

- bpo-32905: Remove unused code in pyparse module.

- bpo-32874: Add tests for pyparse.

- bpo-32837: Using the system and place-dependent default encoding for open() is a bad idea for IDLE’s system and location-independent files.

- bpo-32826: Add “encoding=utf-8” to open() in IDLE’s test_help_about. GUI test test_file_buttons() only looks at initial ascii-only lines, but failed on systems where open() defaults to ‘ascii’ because readline() internally reads and decodes far enough ahead to encounter a non-ascii character in CREDITS.txt.

- bpo-32831: Add docstrings and tests for codecontext.

- bpo-32765: Update configdialog General tab docstring to add new widgets to the widget list.

### Tools/Demos

- bpo-35884: Add a benchmark script for timing various ways to access variables: `Tools/scripts/var_access_benchmark.py`.

- bpo-34989: python-gdb.py now handles errors on computing the line number of a Python frame.

- bpo-20260: Argument Clinic now has non-bitwise unsigned int converters.

- bpo-32962: python-gdb now catches `UnicodeDecodeError` exceptions when calling `string()`.

- bpo-32962: python-gdb now catches ValueError on read_var(): when Python has no debug symbols for example.

- bpo-33189: pygettext.py now recognizes only literal strings as docstrings and translatable strings, and rejects bytes literals and f-string expressions.

- bpo-31920: Fixed handling directories as arguments in the `pygettext` script. Based on patch by Oleg Krasnikov.

- bpo-29673: Fix pystackv and pystack gdbinit macros.

- bpo-25427: Remove the pyvenv script in favor of `python3 -m venv` in order to lower confusion as to what Python interpreter a virtual environment will be created for.

- bpo-32885: Add an `-n` flag for `Tools/scripts/pathfix.py` to disable automatic backup creation (files with `~` suffix).

- bpo-32222: Fix pygettext not extracting docstrings for functions with type annotated arguments. Patch by Toby Harradine.

- bpo-31583: Fix 2to3 for using with –add-suffix option but without –output-dir option for relative path to files in current directory.

### C API

- bpo-35713: The `PyByteArray_Init()` and `PyByteArray_Fini()` functions have been removed. They did nothing since Python 2.7.4 and Python 3.2.0, were excluded from the limited API (stable ABI), and were not documented.

- bpo-33817: Fixed `_PyBytes_Resize()` for empty bytes objects.

- bpo-35322: Fix memory leak in `PyUnicode_EncodeLocale()` and `PyUnicode_EncodeFSDefault()` on error handling.

- bpo-35059: The following C macros have been converted to static inline functions: `Py_INCREF()`, `Py_DECREF()`, `Py_XINCREF()`, `Py_XDECREF()`, `PyObject_INIT()`, `PyObject_INIT_VAR()`.

- bpo-35296: `make install` now also installs the internal API: `Include/internal/*.h` header files.

- bpo-35081: Internal APIs surrounded by `#ifdef Py_BUILD_CORE` have been moved from `Include/*.h` headers to new header files `Include/internal/pycore_*.h`.

- bpo-35259: Conditionally declare `Py_FinalizeEx()` (new in 3.6) based on Py_LIMITED_API. Patch by Arthur Neufeld.

- bpo-35081: The `_PyObject_GC_TRACK()` and `_PyObject_GC_UNTRACK()` macros have been removed from the public C API.

- bpo-35134: Creation of a new `Include/cpython/` subdirectory.

- bpo-34725: Adds _Py_SetProgramFullPath so embedders may override sys.executable

- bpo-34910: Ensure that `PyObject_Print()` always returns `-1` on error. Patch by Zackery Spytz.

- bpo-34523: Py_DecodeLocale() and Py_EncodeLocale() now use the UTF-8 encoding on Windows if Py_LegacyWindowsFSEncodingFlag is zero.

- bpo-34193: Fix pluralization in TypeError messages in getargs.c and typeobject.c: ‘1 argument’ instead of ‘1 arguments’ and ‘1 element’ instead of ‘1 elements’.

- bpo-34127: Return grammatically correct error message based on argument count. Patch by Karthikeyan Singaravelan.

- bpo-23927: Fixed `SystemError` in `PyArg_ParseTupleAndKeywords()` when the `w*` format unit is used for optional parameter.

- bpo-32455: Added `PyCompile_OpcodeStackEffectWithJump()`.

- bpo-34008: Py_Main() can again be called after Py_Initialize(), as in Python 3.6.

- bpo-32500: Fixed error messages for `PySequence_Size()`, `PySequence_GetItem()`, `PySequence_SetItem()` and `PySequence_DelItem()` called with a mapping and `PyMapping_Size()` called with a sequence.

- bpo-33818: `PyExceptionClass_Name()` will now return `const char *` instead of `char *`.

- bpo-33042: Embedding applications may once again call PySys_ResetWarnOptions, PySys_AddWarnOption, and PySys_AddXOption prior to calling Py_Initialize.

- bpo-32374: Document that m_traverse for multi-phase initialized modules can be called with m_state=NULL, and add a sanity check

- bpo-30863: `PyUnicode_AsWideChar()` and `PyUnicode_AsWideCharString()` no longer cache the `wchar_t*` representation of string objects.

## Python 3.7.0 final

Release date: 2018-06-27

### Library

- bpo-33851: Fix `ast.get_docstring()` for a node that lacks a docstring.

### C API

- bpo-33932: Calling Py_Initialize() twice does nothing, instead of failing with a fatal error: restore the Python 3.6 behaviour.

## Python 3.7.0 release candidate 1

Release date: 2018-06-12

### Core and Builtins

- bpo-33803: Fix a crash in hamt.c caused by enabling GC tracking for an object that hadn’t all of its fields set to NULL.

- bpo-33706: Fix a crash in Python initialization when parsing the command line options. Thanks Christoph Gohlke for the bug report and the fix!

- bpo-30654: Fixed reset of the SIGINT handler to SIG_DFL on interpreter shutdown even when there was a custom handler set previously. Patch by Philipp Kerling.

- bpo-31849: Fix signed/unsigned comparison warning in pyhash.c.

### Library

- bpo-30167: Prevent site.main() exception if PYTHONSTARTUP is set. Patch by Steve Weber.

- bpo-33812: Datetime instance d with non-None tzinfo, but with d.tzinfo.utcoffset(d) returning None is now treated as naive by the astimezone() method.

- bpo-30805: Avoid race condition with debug logging

- bpo-33694: asyncio: Fix a race condition causing data loss on pause_reading()/resume_reading() when using the ProactorEventLoop.

- bpo-32493: Correct test for `uuid_enc_be` availability in `configure.ac`. Patch by Michael Felt.

- bpo-33792: Add asyncio.WindowsSelectorEventLoopPolicy and asyncio.WindowsProactorEventLoopPolicy.

- bpo-33778: Update `unicodedata`’s database to Unicode version 11.0.0.

- bpo-33770: improve base64 exception message for encoded inputs of invalid length

- bpo-33769: asyncio/start_tls: Fix error message; cancel callbacks in case of an unhandled error; mark SSLTransport as closed if it is aborted.

- bpo-33767: The concatenation (`+`) and repetition (`*`) sequence operations now raise `TypeError` instead of `SystemError` when performed on `mmap.mmap` objects. Patch by Zackery Spytz.

- bpo-33734: asyncio/ssl: Fix AttributeError, increase default handshake timeout

- bpo-11874: Use a better regex when breaking usage into wrappable parts. Avoids bogus assertion errors from custom metavar strings.

- bpo-33582: Emit a deprecation warning for inspect.formatargspec

### Documentation

- bpo-33409: Clarified the relationship between PEP 538’s PYTHONCOERCECLOCALE and PEP 540’s PYTHONUTF8 mode.

- bpo-33736: Improve the documentation of `asyncio.open_connection()`, `asyncio.start_server()` and their UNIX socket counterparts.

- bpo-31432: Clarify meaning of CERT_NONE, CERT_OPTIONAL, and CERT_REQUIRED flags for ssl.SSLContext.verify_mode.

### Build

- bpo-5755: Move `-Wstrict-prototypes` option to `CFLAGS_NODIST` from `OPT`. This option emitted annoying warnings when building extension modules written in C++.

### Windows

- bpo-33720: Reduces maximum marshal recursion depth on release builds.

### IDLE

- bpo-33656: On Windows, add API call saying that tk scales for DPI. On Windows 8.1+ or 10, with DPI compatibility properties of the Python binary unchanged, and a monitor resolution greater than 96 DPI, this should make text and lines sharper. It should otherwise have no effect.

- bpo-33768: Clicking on a context line moves that line to the top of the editor window.

- bpo-33763: IDLE: Use read-only text widget for code context instead of label widget.

- bpo-33664: Scroll IDLE editor text by lines. Previously, the mouse wheel and scrollbar slider moved text by a fixed number of pixels, resulting in partial lines at the top of the editor box. The change also applies to the shell and grep output windows, but not to read-only text views.

- bpo-33679: Enable theme-specific color configuration for Code Context. Use the Highlights tab to see the setting for built-in themes or add settings to custom themes.

- bpo-33642: Display up to maxlines non-blank lines for Code Context. If there is no current context, show a single blank line.

## Python 3.7.0 beta 5

Release date: 2018-05-30

### Core and Builtins

- bpo-33622: Fixed a leak when the garbage collector fails to add an object with the `__del__` method or referenced by it into the `gc.garbage` list. `PyGC_Collect()` can now be called when an exception is set and preserves it.

- bpo-33509: Fix module_globals parameter of warnings.warn_explicit(): don’t crash if module_globals is not a dict.

- bpo-20104: The new `os.posix_spawn` added in 3.7.0b1 was removed as we are still working on what the API should look like. Expect this in 3.8 instead.

- bpo-33475: Fixed miscellaneous bugs in converting annotations to strings and optimized parentheses in the string representation.

- bpo-33391: Fix a leak in set_symmetric_difference().

- bpo-28055: Fix unaligned accesses in siphash24(). Patch by Rolf Eike Beer.

- bpo-32911: Due to unexpected compatibility issues discovered during downstream beta testing, reverted bpo-29463. `docstring` field is removed from Module, ClassDef, FunctionDef, and AsyncFunctionDef ast nodes which was added in 3.7a1. Docstring expression is restored as a first statement in their body. Based on patch by Inada Naoki.

- bpo-21983: Fix a crash in `ctypes.cast()` in case the type argument is a ctypes structured data type. Patch by Eryk Sun and Oren Milman.

### Library

- bpo-32751: When cancelling the task due to a timeout, `asyncio.wait_for()` will now wait until the cancellation is complete.

- bpo-32684: Fix gather to propagate cancellation of itself even with return_exceptions.

- bpo-33654: Support protocol type switching in SSLTransport.set_protocol().

- bpo-33674: Pause the transport as early as possible to further reduce the risk of data_received() being called before connection_made().

- bpo-33674: Fix a race condition in SSLProtocol.connection_made() of asyncio.sslproto: start immediately the handshake instead of using call_soon(). Previously, data_received() could be called before the handshake started, causing the handshake to hang or fail.

- bpo-31647: Fixed bug where calling write_eof() on a _SelectorSocketTransport after it’s already closed raises AttributeError.

- bpo-32610: Make asyncio.all_tasks() return only pending tasks.

- bpo-32410: Avoid blocking on file IO in sendfile fallback code

- bpo-33469: Fix RuntimeError after closing loop that used run_in_executor

- bpo-33672: Fix Task.__repr__ crash with Cython’s bogus coroutines

- bpo-33654: Fix transport.set_protocol() to support switching between asyncio.Protocol and asyncio.BufferedProtocol. Fix loop.start_tls() to work with asyncio.BufferedProtocols.

- bpo-33652: Pickles of type variables and subscripted generics are now future-proof and compatible with older Python versions.

- bpo-32493: Fixed `uuid.uuid1()` on FreeBSD.

- bpo-33618: Finalize and document preliminary and experimental TLS 1.3 support with OpenSSL 1.1.1

- bpo-33623: Fix possible SIGSGV when asyncio.Future is created in __del__

- bpo-30877: Fixed a bug in the Python implementation of the JSON decoder that prevented the cache of parsed strings from clearing after finishing the decoding. Based on patch by c-fos.

- bpo-33570: Change TLS 1.3 cipher suite settings for compatibility with OpenSSL 1.1.1-pre6 and newer. OpenSSL 1.1.1 will have TLS 1.3 ciphers enabled by default.

- bpo-28556: Do not simplify arguments to `typing.Union`. Now `Union[Manager, Employee]` is not simplified to `Employee` at runtime. Such simplification previously caused several bugs and limited possibilities for introspection.

- bpo-33540: Add a new `block_on_close` class attribute to `ForkingMixIn` and `ThreadingMixIn` classes of `socketserver`.

- bpo-33548: tempfile._candidate_tempdir_list should consider common TEMP locations

- bpo-33109: argparse subparsers are once again not required by default, reverting the change in behavior introduced by bpo-26510 in 3.7.0a2.

- bpo-33536: dataclasses.make_dataclass now checks for invalid field names and duplicate fields. Also, added a check for invalid field specifications.

- bpo-33542: Prevent `uuid.get_node` from using a DUID instead of a MAC on Windows. Patch by Zvi Effron

- bpo-26819: Fix race condition with `ReadTransport.resume_reading` in Windows proactor event loop.

- Fix failure in `typing.get_type_hints()` when ClassVar was provided as a string forward reference.

- bpo-33505: Optimize asyncio.ensure_future() by reordering if checks: 1.17x faster.

- bpo-33497: Add errors param to cgi.parse_multipart and make an encoding in FieldStorage use the given errors (needed for Twisted). Patch by Amber Brown.

- bpo-33495: Change dataclasses.Fields repr to use the repr of each of its members, instead of str. This makes it more clear what each field actually represents. This is especially true for the ‘type’ member.

- bpo-33453: Fix dataclasses to work if using literal string type annotations or if using PEP 563 “Postponed Evaluation of Annotations”. Only specific string prefixes are detected for both ClassVar (“ClassVar” and “typing.ClassVar”) and InitVar (“InitVar” and “dataclasses.InitVar”).

- bpo-28556: Minor fixes in typing module: add annotations to `NamedTuple.__new__`, pass `*args` and `**kwds` in `Generic.__new__`. Original PRs by Paulius Šarka and Chad Dombrova.

- bpo-20087: Updated alias mapping with glibc 2.27 supported locales.

- bpo-33422: Fix trailing quotation marks getting deleted when looking up byte/string literals on pydoc. Patch by Andrés Delfino.

- bpo-28167: The function `platform.linux_distribution` and `platform.dist` now trigger a `DeprecationWarning` and have been marked for removal in Python 3.8

- bpo-33197: Update error message when constructing invalid inspect.Parameters Patch by Donghee Na.

- bpo-33263: Fix FD leak in `_SelectorSocketTransport` Patch by Vlad Starostin.

- bpo-32861: The urllib.robotparser’s `__str__` representation now includes wildcard entries and the “Crawl-delay” and “Request-rate” fields. Patch by Michael Lazar.

- bpo-32257: The ssl module now contains OP_NO_RENEGOTIATION constant, available with OpenSSL 1.1.0h or 1.1.1.

- bpo-16865: Support arrays >=2GiB in `ctypes`. Patch by Segev Finer.

### Documentation

- bpo-23859: Document that `asyncio.wait()` does not cancel its futures on timeout.

- bpo-32436: Document PEP 567 changes to asyncio.

- bpo-33604: Update HMAC md5 default to a DeprecationWarning, bump removal to 3.8.

- bpo-33503: Fix broken pypi link

- bpo-33421: Add missing documentation for `typing.AsyncContextManager`.

### Tests

- bpo-33655: Ignore test_posix_fallocate failures on BSD platforms that might be due to running on ZFS.

- bpo-32604: Remove the _xxsubinterpreters module (meant for testing) and associated helpers. This module was originally added recently in 3.7b1.

### Build

- bpo-33614: Ensures module definition files for the stable ABI on Windows are correctly regenerated.

- bpo-33522: Enable CI builds on Visual Studio Team Services at https://python.visualstudio.com/cpython

- bpo-33012: Add `-Wno-cast-function-type` for gcc 8 for silencing warnings about function casts like casting to PyCFunction in method definition lists.

### macOS

- bpo-13631: The .editrc file in user’s home directory is now processed correctly during the readline initialization through editline emulation on macOS.

### IDLE

- bpo-33628: IDLE: Cleanup codecontext.py and its test.

- bpo-33564: IDLE’s code context now recognizes async as a block opener.

- bpo-32831: Add docstrings and tests for codecontext.

## Python 3.7.0 beta 4

Release date: 2018-05-02

### Core and Builtins

- bpo-33363: Raise a SyntaxError for `async with` and `async for` statements outside of async functions.

- bpo-33128: Fix a bug that causes PathFinder to appear twice on sys.meta_path. Patch by Pablo Galindo Salgado.

- bpo-33312: Fixed clang ubsan (undefined behavior sanitizer) warnings in dictobject.c by adjusting how the internal struct _dictkeysobject shared keys structure is declared.

- bpo-33231: Fix potential memory leak in `normalizestring()`.

- bpo-33205: Change dict growth function from `round_up_to_power_2(used*2+hashtable_size/2)` to `round_up_to_power_2(used*3)`. Previously, dict is shrinked only when `used == 0`. Now dict has more chance to be shrinked.

- bpo-29922: Improved error messages in ‘async with’ when `__aenter__()` or `__aexit__()` return non-awaitable object.

- bpo-33199: Fix `ma_version_tag` in dict implementation is uninitialized when copying from key-sharing dict.

### Library

- bpo-33281: Fix ctypes.util.find_library regression on macOS.

- bpo-33383: Fixed crash in the get() method of the `dbm.ndbm` database object when it is called with a single argument.

- bpo-33329: Fix multiprocessing regression on newer glibcs

- bpo-991266: Fix quoting of the `Comment` attribute of `http.cookies.SimpleCookie`.

- bpo-33131: Upgrade bundled version of pip to 10.0.1.

- bpo-33308: Fixed a crash in the `parser` module when converting an ST object to a tree of tuples or lists with `line_info=False` and `col_info=True`.

- bpo-33266: lib2to3 now recognizes `rf'...'` strings.

- bpo-11594: Ensure line-endings are respected when using lib2to3.

- bpo-33254: Have `importlib.resources.contents()` and `importlib.abc.ResourceReader.contents()` return an iterable instead of an iterator.

- bpo-33256: Fix display of `<module>` call in the html produced by `cgitb.html()`. Patch by Stéphane Blondon.

- bpo-33185: Fixed regression when running pydoc with the `-m` switch. (The regression was introduced in 3.7.0b3 by the resolution of bpo-33053) This fix also changed pydoc to add `os.getcwd()` to `sys.path` when necessary, rather than adding `"."`.

- bpo-33169: Delete entries of `None` in `sys.path_importer_cache` when `importlib.machinery.invalidate_caches()` is called.

- bpo-33217: Deprecate looking up non-Enum objects in Enum classes and Enum members (will raise `TypeError` in 3.8+).

- bpo-33203: `random.Random.choice()` now raises `IndexError` for empty sequences consistently even when called from subclasses without a `getrandbits()` implementation.

- bpo-33224: Update difflib.mdiff() for PEP 479. Convert an uncaught StopIteration in a generator into a return-statement.

- bpo-33209: End framing at the end of C implementation of `pickle.Pickler.dump()`.

- bpo-20104: Improved error handling and fixed a reference leak in `os.posix_spawn()`.

- bpo-33175: In dataclasses, Field.__set_name__ now looks up the __set_name__ special method on the class, not the instance, of the default value.

- bpo-33097: Raise RuntimeError when `executor.submit` is called during interpreter shutdown.

- bpo-31908: Fix output of cover files for `trace` module command-line tool. Previously emitted cover files only when `--missing` option was used. Patch by Michael Selik.

### Documentation

- bpo-33378: Add Korean language switcher for https://docs.python.org/3/

- bpo-33276: Clarify that the `__path__` attribute on modules cannot be just any value.

- bpo-33201: Modernize documentation for writing C extension types.

- bpo-33195: Deprecate `Py_UNICODE` usage in `c-api/arg` document. `Py_UNICODE` related APIs are deprecated since Python 3.3, but it is missed in the document.

- bpo-8243: Add a note about curses.addch and curses.addstr exception behavior when writing outside a window, or pad.

- bpo-32337: Update documentation related with `dict` order.

### Tests

- bpo-33358: Fix `test_embed.test_pre_initialization_sys_options()` when the interpreter is built with `--enable-shared`.

### Build

- bpo-33394: Enable the verbose build for extension modules, when GNU make is passed macros on the command line.

- bpo-33393: Update config.guess and config.sub files.

- bpo-33377: Add new triplets for mips r6 and riscv variants (used in extension suffixes).

- bpo-32232: By default, modules configured in `Modules/Setup` are no longer built with `-DPy_BUILD_CORE`. Instead, modules that specifically need that preprocessor definition include it in their individual entries.

- bpo-33182: The embedding tests can once again be built with clang 6.0

### Windows

- bpo-33184: Update Windows installer to use OpenSSL 1.1.0h.

### macOS

- bpo-33184: Update macOS installer build to use OpenSSL 1.1.0h.

### IDLE

- bpo-21474: Update word/identifier definition from ascii to unicode. In text and entry boxes, this affects selection by double-click, movement left/right by control-left/right, and deletion left/right by control-BACKSPACE/DEL.

- bpo-33204: IDLE: consistently color invalid string prefixes. A ‘u’ string prefix cannot be paired with either ‘r’ or ‘f’. Consistently color as much of the prefix, starting at the right, as is valid. Revise and extend colorizer test.

### Tools/Demos

- bpo-33189: pygettext.py now recognizes only literal strings as docstrings and translatable strings, and rejects bytes literals and f-string expressions.

- bpo-31920: Fixed handling directories as arguments in the `pygettext` script. Based on patch by Oleg Krasnikov.

- bpo-29673: Fix pystackv and pystack gdbinit macros.

- bpo-31583: Fix 2to3 for using with –add-suffix option but without –output-dir option for relative path to files in current directory.

## Python 3.7.0 beta 3

Release date: 2018-03-29

### Security

- bpo-33136: Harden ssl module against LibreSSL CVE 2018-8970. X509_VERIFY_PARAM_set1_host() is called with an explicit namelen. A new test ensures that NULL bytes are not allowed.

- bpo-33001: Minimal fix to prevent buffer overrun in os.symlink on Windows

- bpo-32981: Regexes in difflib and poplib were vulnerable to catastrophic backtracking. These regexes formed potential DOS vectors (REDOS). They have been refactored. This resolves CVE 2018-1060 and CVE 2018-1061. Patch by Jamie Davis.

### Core and Builtins

- bpo-33053: When using the -m switch, sys.path[0] is now explicitly expanded as the starting working directory, rather than being left as the empty path (which allows imports from the current working directory at the time of the import)

- bpo-33018: Improve consistency of errors raised by `issubclass()` when called with a non-class and an abstract base class as the first and second arguments, respectively. Patch by Josh Bronson.

- bpo-33041: Fixed jumping when the function contains an `async for` loop.

- bpo-33026: Fixed jumping out of “with” block by setting f_lineno.

- bpo-33005: Fix a crash on fork when using a custom memory allocator (ex: using PYTHONMALLOC env var). _PyGILState_Reinit() and _PyInterpreterState_Enable() now use the default RAW memory allocator to allocate a new interpreters mutex on fork.

- bpo-17288: Prevent jumps from ‘return’ and ‘exception’ trace events.

- bpo-32836: Don’t use temporary variables in cases of list/dict/set comprehensions

### Library

- bpo-33141: Have Field objects pass through __set_name__ to their default values, if they have their own __set_name__.

- bpo-33096: Allow ttk.Treeview.insert to insert iid that has a false boolean value. Note iid=0 and iid=False would be same. Patch by Garvit Khatri.

- bpo-32873: Treat type variables and special typing forms as immutable by copy and pickle. This fixes several minor issues and inconsistencies, and improves backwards compatibility with Python 3.6.

- bpo-33134: When computing dataclass’s __hash__, use the lookup table to contain the function which returns the __hash__ value. This is an improvement over looking up a string, and then testing that string to see what to do.

- bpo-33127: The ssl module now compiles with LibreSSL 2.7.1.

- bpo-32505: Raise TypeError if a member variable of a dataclass is of type Field, but doesn’t have a type annotation.

- bpo-33078: Fix the failure on OSX caused by the tests relying on sem_getvalue

- bpo-33116: Add ‘Field’ to dataclasses.__all__.

- bpo-32896: Fix an error where subclassing a dataclass with a field that uses a default_factory would generate an incorrect class.

- bpo-33100: Dataclasses: If a field has a default value that’s a MemberDescriptorType, then it’s from that field being in __slots__, not an actual default value.

- bpo-32953: If a non-dataclass inherits from a frozen dataclass, allow attributes to be added to the derived class. Only attributes from the frozen dataclass cannot be assigned to. Require all dataclasses in a hierarchy to be either all frozen or all non-frozen.

- bpo-33061: Add missing `NoReturn` to `__all__` in typing.py

- bpo-33078: Fix the size handling in multiprocessing.Queue when a pickling error occurs.

- bpo-33064: lib2to3 now properly supports trailing commas after `*args` and `**kwargs` in function signatures.

- bpo-33056: FIX properly close leaking fds in concurrent.futures.ProcessPoolExecutor.

- bpo-33021: Release the GIL during fstat() calls, avoiding hang of all threads when calling mmap.mmap(), os.urandom(), and random.seed(). Patch by Nir Soffer.

- bpo-31804: Avoid failing in multiprocessing.Process if the standard streams are closed or None at exit.

- bpo-33037: Skip sending/receiving data after SSL transport closing.

- bpo-27683: Fix a regression in `ipaddress` that result of `hosts()` is empty when the network is constructed by a tuple containing an integer mask and only 1 bit left for addresses.

- bpo-32999: Fix C implementation of `ABC.__subclasscheck__(cls, subclass)` crashed when `subclass` is not a type object.

- bpo-33009: Fix inspect.signature() for single-parameter partialmethods.

- bpo-32969: Expose several missing constants in zlib and fix corresponding documentation.

- bpo-32056: Improved exceptions raised for invalid number of channels and sample width when read an audio file in modules `aifc`, `wave` and `sunau`.

- bpo-32844: Fix wrong redirection of a low descriptor (0 or 1) to stderr in subprocess if another low descriptor is closed.

- bpo-32857: In `tkinter`, `after_cancel(None)` now raises a `ValueError` instead of canceling the first scheduled function. Patch by Cheryl Sabella.

- bpo-31639: http.server now exposes a ThreadedHTTPServer class and uses it when the module is run with `-m` to cope with web browsers pre-opening sockets.

- bpo-27645: `sqlite3.Connection` now exposes a `backup` method, if the underlying SQLite library is at version 3.6.11 or higher. Patch by Lele Gaifax.

### Documentation

- bpo-33126: Document PyBuffer_ToContiguous().

- bpo-27212: Modify documentation for the `islice()` recipe to consume initial values up to the start index.

- bpo-28247: Update `zipapp` documentation to describe how to make standalone applications.

- bpo-18802: Documentation changes for ipaddress. Patch by Jon Foster and Berker Peksag.

- bpo-27428: Update documentation to clarify that `WindowsRegistryFinder` implements `MetaPathFinder`. (Patch by Himanshu Lakhara)

### Tests

- bpo-32872: Avoid regrtest compatibility issue with namespace packages.

- bpo-32517: Fix failing `test_asyncio` on macOS 10.12.2+ due to transport of `KqueueSelector` loop was not being closed.

- bpo-19417: Add test_bdb.py.

### Build

- bpo-33163: Upgrade pip to 9.0.3 and setuptools to v39.0.1.

### Windows

- bpo-33016: Fix potential use of uninitialized memory in nt._getfinalpathname

- bpo-32903: Fix a memory leak in os.chdir() on Windows if the current directory is set to a UNC path.

### macOS

- bpo-32726: Build and link with private copy of Tcl/Tk 8.6 for the macOS 10.6+ installer. The 10.9+ installer variant already does this. This means that the Python 3.7 provided by the python.org macOS installers no longer need or use any external versions of Tcl/Tk, either system-provided or user-installed, such as ActiveTcl.

### IDLE

- bpo-32984: Set `__file__` while running a startup file. Like Python, IDLE optionally runs one startup file in the Shell window before presenting the first interactive input prompt. For IDLE, `-s` runs a file named in environmental variable `IDLESTARTUP` or `PYTHONSTARTUP`; `-r file` runs `file`. Python sets `__file__` to the startup file name before running the file and unsets it before the first prompt. IDLE now does the same when run normally, without the `-n` option.

- bpo-32940: Simplify and rename StringTranslatePseudoMapping in pyparse.

### Tools/Demos

- bpo-32885: Add an `-n` flag for `Tools/scripts/pathfix.py` to disable automatic backup creation (files with `~` suffix).

### C API

- bpo-33042: Embedding applications may once again call PySys_ResetWarnOptions, PySys_AddWarnOption, and PySys_AddXOption prior to calling Py_Initialize.

- bpo-32374: Document that m_traverse for multi-phase initialized modules can be called with m_state=NULL, and add a sanity check

## Python 3.7.0 beta 2

Release date: 2018-02-27

### Security

- bpo-28414: The ssl module now allows users to perform their own IDN en/decoding when using SNI.

### Core and Builtins

- bpo-32889: Update Valgrind suppression list to account for the rename of `Py_ADDRESS_IN_RANG` to `address_in_range`.

- bpo-31356: Remove the new API added in bpo-31356 (gc.ensure_disabled() context manager).

- bpo-32305: For namespace packages, ensure that both `__file__` and `__spec__.origin` are set to None.

- bpo-32303: Make sure `__spec__.loader` matches `__loader__` for namespace packages.

- bpo-32711: Fix the warning messages for Python/ast_unparse.c. Patch by Stéphane Wirtel

- bpo-32583: Fix possible crashing in builtin Unicode decoders caused by write out-of-bound errors when using customized decode error handlers.

### Library

- bpo-32960: For dataclasses, disallow inheriting frozen from non-frozen classes, and also disallow inheriting non-frozen from frozen classes. This restriction will be relaxed at a future date.

- bpo-32713: Fixed tarfile.itn handling of out-of-bounds float values. Patch by Joffrey Fuhrer.

- bpo-32951: Direct instantiation of SSLSocket and SSLObject objects is now prohibited. The constructors were never documented, tested, or designed as public constructors. Users were suppose to use ssl.wrap_socket() or SSLContext.

- bpo-32929: Remove the tri-state parameter “hash”, and add the boolean “unsafe_hash”. If unsafe_hash is True, add a __hash__ function, but if a __hash__ exists, raise TypeError. If unsafe_hash is False, add a __hash__ based on the values of eq= and frozen=. The unsafe_hash=False behavior is the same as the old hash=None behavior. unsafe_hash=False is the default, just as hash=None used to be.

- bpo-32947: Add OP_ENABLE_MIDDLEBOX_COMPAT and test workaround for TLSv1.3 for future compatibility with OpenSSL 1.1.1.

- bpo-30622: The ssl module now detects missing NPN support in LibreSSL.

- bpo-32922: dbm.open() now encodes filename with the filesystem encoding rather than default encoding.

- bpo-32859: In `os.dup2`, don’t check every call whether the `dup3` syscall exists or not.

- bpo-32556: nt._getfinalpathname, nt._getvolumepathname and nt._getdiskusage now correctly convert from bytes.

- bpo-25988: Emit a `DeprecationWarning` when using or importing an ABC directly from `collections` rather than from `collections.abc`.

- bpo-21060: Rewrite confusing message from setup.py upload from “No dist file created in earlier command” to the more helpful “Must create and upload files in one command”.

- bpo-32852: Make sure sys.argv remains as a list when running trace.

- bpo-31333: `_abc` module is added. It is a speedup module with C implementations for various functions and methods in `abc`. Creating an ABC subclass and calling `isinstance` or `issubclass` with an ABC subclass are up to 1.5x faster. In addition, this makes Python start-up up to 10% faster. Note that the new implementation hides internal registry and caches, previously accessible via private attributes `_abc_registry`, `_abc_cache`, and `_abc_negative_cache`. There are three debugging helper methods that can be used instead `_dump_registry`, `_abc_registry_clear`, and `_abc_caches_clear`.

- bpo-32841: Fixed `asyncio.Condition` issue which silently ignored cancellation after notifying and cancelling a conditional lock. Patch by Bar Harel.

- bpo-32819: ssl.match_hostname() has been simplified and no longer depends on re and ipaddress module for wildcard and IP addresses. Error reporting for invalid wildcards has been improved.

- bpo-32394: socket: Remove TCP_FASTOPEN,TCP_KEEPCNT,TCP_KEEPIDLE,TCP_KEEPINTVL flags on older version Windows during run-time.

- bpo-31787: Fixed refleaks of `__init__()` methods in various modules. (Contributed by Oren Milman)

- bpo-30157: Fixed guessing quote and delimiter in csv.Sniffer.sniff() when only the last field is quoted. Patch by Jake Davis.

- bpo-32792: collections.ChainMap() preserves the order of the underlying mappings.

- bpo-32775: `fnmatch.translate()` no longer produces patterns which contain set operations. Sets starting with ‘[’ or containing ‘–’, ‘&&’, ‘~~’ or ‘||’ will be interpreted differently in regular expressions in future versions. Currently they emit warnings. fnmatch.translate() now avoids producing patterns containing such sets by accident.

- bpo-32622: Implement native fast sendfile for Windows proactor event loop.

- bpo-32777: Fix a rare but potential pre-exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process. This bug appears to have been introduced in 3.4.

- bpo-32647: The ctypes module used to depend on indirect linking for dlopen. The shared extension is now explicitly linked against libdl on platforms with dl.

- bpo-32741: Implement `asyncio.TimerHandle.when()` method.

- bpo-32691: Use mod_spec.parent when running modules with pdb

- bpo-32734: Fixed `asyncio.Lock()` safety issue which allowed acquiring and locking the same lock multiple times, without it being free. Patch by Bar Harel.

- bpo-32727: Do not include name field in SMTP envelope from address. Patch by Stéphane Wirtel

- bpo-31453: Add TLSVersion constants and SSLContext.maximum_version / minimum_version attributes. The new API wraps OpenSSL 1.1 https://web.archive.org/web/20180309043602/https://www.openssl.org/docs/man1.1.0/ssl/SSL_CTX_set_min_proto_version.html feature.

- bpo-24334: Internal implementation details of ssl module were cleaned up. The SSLSocket has one less layer of indirection. Owner and session information are now handled by the SSLSocket and SSLObject constructor. Channel binding implementation has been simplified.

- bpo-31848: Fix the error handling in Aifc_read.initfp() when the SSND chunk is not found. Patch by Zackery Spytz.

- bpo-32585: Add Ttk spinbox widget to `tkinter.ttk`. Patch by Alan D Moore.

- bpo-32221: Various functions returning tuple containing IPv6 addresses now omit `%scope` part since the same information is already encoded in scopeid tuple item. Especially this speeds up `socket.recvfrom()` when it receives multicast packet since useless resolving of network interface name is omitted.

- bpo-30693: The TarFile class now recurses directories in a reproducible way.

- bpo-30693: The ZipFile class now recurses directories in a reproducible way.

### Documentation

- bpo-28124: The ssl module function ssl.wrap_socket() has been de-emphasized and deprecated in favor of the more secure and efficient SSLContext.wrap_socket() method.

- bpo-17232: Clarify docs for -O and -OO. Patch by Terry Reedy.

- bpo-32436: Add documentation for the contextvars module (PEP 567).

- bpo-32800: Update link to w3c doc for xml default namespaces.

- bpo-11015: Update `test.support` documentation.

- bpo-8722: Document `__getattr__()` behavior when property `get()` method raises `AttributeError`.

- bpo-32614: Modify RE examples in documentation to use raw strings to prevent `DeprecationWarning` and add text to REGEX HOWTO to highlight the deprecation.

- bpo-31972: Improve docstrings for `pathlib.PurePath` subclasses.

### Tests

- bpo-31809: Add tests to verify connection with secp ECDH curves.

### Build

- bpo-32898: Fix the python debug build when using COUNT_ALLOCS.

### Windows

- bpo-32901: Update Tcl and Tk versions to 8.6.8

- bpo-31966: Fixed WindowsConsoleIO.write() for writing empty data.

- bpo-32409: Ensures activate.bat can handle Unicode contents.

- bpo-32457: Improves handling of denormalized executable path when launching Python.

- bpo-32370: Use the correct encoding for ipconfig output in the uuid module. Patch by Segev Finer.

- bpo-29248: Fix `os.readlink()` on Windows, which was mistakenly treating the `PrintNameOffset` field of the reparse data buffer as a number of characters instead of bytes. Patch by Craig Holmquist and SSE4.

### macOS

- bpo-32901: Update macOS 10.9+ installer to Tcl/Tk 8.6.8.

### IDLE

- bpo-32916: Change `str` to `code` in pyparse.

- bpo-32905: Remove unused code in pyparse module.

- bpo-32874: Add tests for pyparse.

- bpo-32837: Using the system and place-dependent default encoding for open() is a bad idea for IDLE’s system and location-independent files.

- bpo-32826: Add “encoding=utf-8” to open() in IDLE’s test_help_about. GUI test test_file_buttons() only looks at initial ascii-only lines, but failed on systems where open() defaults to ‘ascii’ because readline() internally reads and decodes far enough ahead to encounter a non-ascii character in CREDITS.txt.

- bpo-32765: Update configdialog General tab docstring to add new widgets to the widget list.

### Tools/Demos

- bpo-32222: Fix pygettext not extracting docstrings for functions with type annotated arguments. Patch by Toby Harradine.

## Python 3.7.0 beta 1

Release date: 2018-01-30

### Core and Builtins

- bpo-32703: Fix coroutine’s ResourceWarning when there’s an active error set when it’s being finalized.

- bpo-32650: Pdb and other debuggers dependent on bdb.py will correctly step over (next command) native coroutines. Patch by Pablo Galindo.

- bpo-28685: Optimize list.sort() and sorted() by using type specialized comparisons when possible.

- bpo-32685: Improve suggestion when the Python 2 form of print statement is either present on the same line as the header of a compound statement or else terminated by a semi-colon instead of a newline. Patch by Nitish Chandra.

- bpo-32697: Python now explicitly preserves the definition order of keyword-only parameters. It’s always preserved their order, but this behavior was never guaranteed before; this behavior is now guaranteed and tested.

- bpo-32690: The locals() dictionary now displays in the lexical order that variables were defined. Previously, the order was reversed.

- bpo-32677: Add `.isascii()` method to `str`, `bytes` and `bytearray`. It can be used to test that string contains only ASCII characters.

- bpo-32670: Enforce PEP 479 for all code. This means that manually raising a StopIteration exception from a generator is prohibited for all code, regardless of whether ‘from __future__ import generator_stop’ was used or not.

- bpo-32591: Added built-in support for tracking the origin of coroutine objects; see sys.set_coroutine_origin_tracking_depth and CoroutineType.cr_origin. This replaces the asyncio debug mode’s use of coroutine wrapping for native coroutine objects.

- bpo-31368: Expose preadv and pwritev system calls in the os module. Patch by Pablo Galindo

- bpo-32544: `hasattr(obj, name)` and `getattr(obj, name, default)` are about 4 times faster than before when `name` is not found and `obj` doesn’t override `__getattr__` or `__getattribute__`.

- bpo-26163: Improved frozenset() hash to create more distinct hash values when faced with datasets containing many similar values.

- bpo-32550: Remove the STORE_ANNOTATION bytecode.

- bpo-20104: Expose posix_spawn as a low level API in the os module. (removed before 3.7.0rc1)

- bpo-24340: Fixed estimation of the code stack size.

- bpo-32436: Implement PEP 567 Context Variables.

- bpo-18533: `repr()` on a dict containing its own `values()` or `items()` no longer raises `RecursionError`; OrderedDict similarly. Instead, use `...`, as for other recursive structures. Patch by Ben North.

- bpo-20891: Py_Initialize() now creates the GIL. The GIL is no longer created “on demand” to fix a race condition when PyGILState_Ensure() is called in a non-Python thread.

- bpo-32028: Leading whitespace is now correctly ignored when generating suggestions for converting Py2 print statements to Py3 builtin print function calls. Patch by Sanyam Khurana.

- bpo-31179: Make dict.copy() up to 5.5 times faster.

- bpo-31113: Get rid of recursion in the compiler for normal control flow.

### Library

- bpo-25988: Deprecate exposing the contents of collections.abc in the regular collections module.

- bpo-31429: The default cipher suite selection of the ssl module now uses a blacklist approach rather than a hard-coded whitelist. Python no longer re-enables ciphers that have been blocked by OpenSSL security update. Default cipher suite selection can be configured on compile time.

- bpo-30306: contextlib.contextmanager now releases the arguments passed to the underlying generator as soon as the context manager is entered. Previously it would keep them alive for as long as the context manager was alive, even when not being used as a function decorator. Patch by Martin Teichmann.

- bpo-21417: Added support for setting the compression level for zipfile.ZipFile.

- bpo-32251: Implement asyncio.BufferedProtocol (provisional API).

- bpo-32513: In dataclasses, allow easier overriding of dunder methods without specifying decorator parameters.

- bpo-32660: `termios` makes available `FIONREAD`, `FIONCLEX`, `FIOCLEX`, `FIOASYNC` and `FIONBIO` also under Solaris/derivatives.

- bpo-27931: Fix email address header parsing error when the username is an empty quoted string. Patch by Xiang Zhang.

- bpo-32659: Under Solaris and derivatives, `os.stat_result` provides a st_fstype attribute.

- bpo-32662: Implement Server.start_serving(), Server.serve_forever(), and Server.is_serving() methods. Add ‘start_serving’ keyword parameter to loop.create_server() and loop.create_unix_server().

- bpo-32391: Implement `asyncio.StreamWriter.wait_closed()` and `asyncio.StreamWriter.is_closing()` methods

- bpo-32643: Make Task._step, Task._wakeup and Future._schedule_callbacks methods private.

- bpo-32630: Refactor decimal module to use contextvars to store decimal context.

- bpo-32622: Add `asyncio.AbstractEventLoop.sendfile()` method.

- bpo-32304: distutils’ upload command no longer corrupts tar files ending with a CR byte, and no longer tries to convert CR to CRLF in any of the upload text fields.

- bpo-32502: uuid.uuid1 no longer raises an exception if a 64-bit hardware address is encountered.

- bpo-32596: `concurrent.futures` imports `ThreadPoolExecutor` and `ProcessPoolExecutor` lazily (using PEP 562). It makes `import asyncio` about 15% faster because asyncio uses only `ThreadPoolExecutor` by default.

- bpo-31801: Add `_ignore_` to `Enum` so temporary variables can be used during class construction without being turned into members.

- bpo-32576: Use queue.SimpleQueue() in places where it can be invoked from a weakref callback.

- bpo-32574: Fix memory leak in asyncio.Queue, when the queue has limited size and it is full, the cancelation of queue.put() can cause a memory leak. Patch by: José Melero.

- bpo-32521: The nis module is now compatible with new libnsl and headers location.

- bpo-32467: collections.abc.ValuesView now inherits from collections.abc.Collection.

- bpo-32473: Improve ABCMeta._dump_registry() output readability

- bpo-32102: New argument `capture_output` for subprocess.run

- bpo-32521: glibc has removed Sun RPC. Use replacement libtirpc headers and library in nis module.

- bpo-32493: UUID module fixes build for FreeBSD/OpenBSD

- bpo-32503: Pickling with protocol 4 no longer creates too small frames.

- bpo-29237: Create enum for pstats sorting options

- bpo-32454: Add close(fd) function to the socket module.

- bpo-25942: The subprocess module is now more graceful when handling a Ctrl-C KeyboardInterrupt during subprocess.call, subprocess.run, or a Popen context manager. It now waits a short amount of time for the child (presumed to have also gotten the SIGINT) to exit, before continuing the KeyboardInterrupt exception handling. This still includes a SIGKILL in the call() and run() APIs, but at least the child had a chance first.

- bpo-32433: The hmac module now has hmac.digest(), which provides an optimized HMAC digest.

- bpo-28134: Sockets now auto-detect family, type and protocol from file descriptor by default.

- bpo-32404: Fix bug where `datetime.datetime.fromtimestamp()` did not call __new__ in `datetime.datetime` subclasses.

- bpo-32403: Improved speed of `datetime.date` and `datetime.datetime` alternate constructors.

- bpo-32228: Ensure that `truncate()` preserves the file position (as reported by `tell()`) after writes longer than the buffer size.

- bpo-32410: Implement `loop.sock_sendfile` for asyncio event loop.

- bpo-22908: Added seek and tell to the ZipExtFile class. This only works if the file object used to open the zipfile is seekable.

- bpo-32373: Add socket.getblocking() method.

- bpo-32248: Add `importlib.resources` and `importlib.abc.ResourceReader` as the unified API for reading resources contained within packages. Loaders wishing to support resource reading must implement the `get_resource_reader()` method. File-based and zipimport-based loaders both implement these APIs. `importlib.abc.ResourceLoader` is deprecated in favor of these new APIs.

- bpo-32320: collections.namedtuple() now supports default values.

- bpo-29302: Add contextlib.AsyncExitStack. Patch by Alexander Mohr and Ilya Kulakov.

- bpo-31961: Removed in Python 3.7.0b2. The args argument of subprocess.Popen can now be a path-like object. If args is given as a sequence, it’s first element can now be a path-like object as well.

- bpo-31900: The `locale.localeconv()` function now sets temporarily the `LC_CTYPE` locale to the `LC_NUMERIC` locale to decode `decimal_point` and `thousands_sep` byte strings if they are non-ASCII or longer than 1 byte, and the `LC_NUMERIC` locale is different than the `LC_CTYPE` locale. This temporary change affects other threads. Same change for the `str.format()` method when formatting a number (`int`, `float`, `float` and subclasses) with the `n` type (ex: `'{:n}'.format(1234)`).

- bpo-31853: Use super().method instead of socket.method in SSLSocket. They were there most likely for legacy reasons.

- bpo-31399: The ssl module now uses OpenSSL’s X509_VERIFY_PARAM_set1_host() and X509_VERIFY_PARAM_set1_ip() API to verify hostname and IP addresses. Subject common name fallback can be disabled with SSLContext.hostname_checks_common_name.

- bpo-14976: Add a queue.SimpleQueue class, an unbounded FIFO queue with a reentrant C implementation of put().

### Documentation

- bpo-32724: Add references to some commands in the documentation of Pdb. Patch by Stéphane Wirtel

- bpo-32649: Complete the C API documentation, profiling and tracing part with the newly added per-opcode events.

- bpo-17799: Explain real behaviour of sys.settrace and sys.setprofile and their C-API counterparts regarding which type of events are received in each function. Patch by Pablo Galindo Salgado.

### Tests

- bpo-32721: Fix test_hashlib to not fail if the _md5 module is not built.

- bpo-28414: Add test cases for IDNA 2003 and 2008 host names. IDNA 2003 internationalized host names are working since bpo-31399 has landed. IDNA 2008 are still broken.

- bpo-32604: Add a new “_xxsubinterpreters” extension module that exposes the existing subinterpreter C-API and a new cross-interpreter data sharing mechanism. The module is primarily intended for more thorough testing of the existing subinterpreter support. Note that the _xxsubinterpreters module has been removed in 3.7.0rc1.

- bpo-32602: Add test certs and test for ECDSA cert and EC/RSA dual mode.

- bpo-32549: On Travis CI, Python now Compiles and uses a local copy of OpenSSL 1.1.0g for testing.

### Build

- bpo-32635: Fix segfault of the crypt module when libxcrypt is provided instead of libcrypt at the system.

- bpo-32598: Use autoconf to detect OpenSSL libs, headers and supported features. The ax_check_openssl M4 macro uses pkg-config to locate OpenSSL and falls back to manual search.

- bpo-32593: Drop support of FreeBSD 9 and older.

- bpo-29708: If the `SOURCE_DATE_EPOCH` environment variable is set, `py_compile` will always create hash-based `.pyc` files.

### Windows

- bpo-32588: Create standalone _distutils_findvs module and add missing _queue module to installer.

- bpo-29911: Ensure separate Modify and Uninstall buttons are displayed.

- bpo-32507: Use app-local UCRT install rather than the proper update for old versions of Windows.

### macOS

- bpo-32726: Provide an additional, more modern macOS installer variant that supports macOS 10.9+ systems in 64-bit mode only. Upgrade the supplied third-party libraries to OpenSSL 1.1.0g and to SQLite 3.22.0. The 10.9+ installer now links with and supplies its own copy of Tcl/Tk 8.6.

- bpo-28440: No longer add /Library/Python/3.x/site-packages to sys.path for macOS framework builds to avoid future conflicts.

### C API

- bpo-32681: Fix uninitialized variable ‘res’ in the C implementation of os.dup2. Patch by Stéphane Wirtel

- bpo-10381: Add C API access to the `datetime.timezone` constructor and `datetime.timzone.UTC` singleton.

## Python 3.7.0 alpha 4

Release date: 2018-01-08

### Core and Builtins

- bpo-31975: The default warning filter list now starts with a “default::DeprecationWarning:__main__” entry, so deprecation warnings are once again shown by default in single-file scripts and at the interactive prompt.

- bpo-32226: `__class_getitem__` is now an automatic class method.

- bpo-32399: Add AIX uuid library support for RFC4122 using uuid_create() in libc.a

- bpo-32390: Fix the compilation failure on AIX after the f_fsid field has been added to the object returned by os.statvfs() (bpo-32143). Original patch by Michael Felt.

- bpo-32379: Make MRO computation faster when a class inherits from a single base.

- bpo-32259: The error message of a TypeError raised when unpack non-iterable is now more specific.

- bpo-27169: The `__debug__` constant is now optimized out at compile time. This fixes also bpo-22091.

- bpo-32329: The `-R` option now turns on hash randomization when the `PYTHONHASHSEED` environment variable is set to `0`. Previously, the option was ignored. Moreover, `sys.flags.hash_randomization` is now properly set to 0 when hash randomization is turned off by `PYTHONHASHSEED=0`.

- bpo-30416: The optimizer is now protected from spending much time doing complex calculations and consuming much memory for creating large constants in constant folding. Increased limits for constants that can be produced in constant folding.

- bpo-32282: Fix an unnecessary ifdef in the include of VersionHelpers.h in socketmodule on Windows.

- bpo-30579: Implement TracebackType.__new__ to allow Python-level creation of traceback objects, and make TracebackType.tb_next mutable.

- bpo-32260: Don’t byte swap the input keys to the SipHash algorithm on big-endian platforms. This should ensure siphash gives consistent results across platforms.

- bpo-31506: Improve the error message logic for object.__new__ and object.__init__. Patch by Sanyam Khurana.

- bpo-20361: `-b` and `-bb` now inject `'default::BytesWarning'` and `error::BytesWarning` entries into `sys.warnoptions`, ensuring that they take precedence over any other warning filters configured via the `-W` option or the `PYTHONWARNINGS` environment variable.

- bpo-32230: `-X dev` now injects a `'default'` entry into sys.warnoptions, ensuring that it behaves identically to actually passing `-Wdefault` at the command line.

- bpo-29240: Add a new UTF-8 mode: implementation of the PEP 540.

- bpo-32226: PEP 560: Add support for `__mro_entries__` and `__class_getitem__`. Implemented by Ivan Levkivskyi.

- bpo-32225: PEP 562: Add support for module `__getattr__` and `__dir__`. Implemented by Ivan Levkivskyi.

- bpo-31901: The `atexit` module now has its callback stored per interpreter.

- bpo-31650: Implement PEP 552 (Deterministic pycs). Python now supports invalidating bytecode cache files bashed on a source content hash rather than source last-modified time.

- bpo-29469: Move constant folding from bytecode layer to AST layer. Original patch by Eugene Toder.

### Library

- bpo-32506: Now that dict is defined as keeping insertion order, drop OrderedDict and just use plain dict.

- bpo-32279: Add params to dataclasses.make_dataclasses(): init, repr, eq, order, hash, and frozen. Pass them through to dataclass().

- bpo-32278: Make type information optional on dataclasses.make_dataclass(). If omitted, the string ‘typing.Any’ is used.

- bpo-32499: Add dataclasses.is_dataclass(obj), which returns True if obj is a dataclass or an instance of one.

- bpo-32468: Improve frame repr() to mention filename, code name and current line number.

- bpo-23749: asyncio: Implement loop.start_tls()

- bpo-32441: Return the new file descriptor (i.e., the second argument) from `os.dup2`. Previously, `None` was always returned.

- bpo-32422: `functools.lru_cache` uses less memory (3 words for each cached key) and takes about 1/3 time for cyclic GC.

- bpo-31721: Prevent Python crash from happening when Future._log_traceback is set to True manually. Now it can only be set to False, or a ValueError is raised.

- bpo-32415: asyncio: Add Task.get_loop() and Future.get_loop()

- bpo-26133: Don’t unsubscribe signals in asyncio UNIX event loop on interpreter shutdown.

- bpo-32363: Make asyncio.Task.set_exception() and set_result() raise NotImplementedError. Task._step() and Future.__await__() raise proper exceptions when they are in an invalid state, instead of raising an AssertionError.

- bpo-32357: Optimize asyncio.iscoroutine() and loop.create_task() for non-native coroutines (e.g. async/await compiled with Cython). ‘loop.create_task(python_coroutine)’ used to be 20% faster than ‘loop.create_task(cython_coroutine)’. Now, the latter is as fast.

- bpo-32356: asyncio.transport.resume_reading() and pause_reading() are now idempotent. New transport.is_reading() method is added.

- bpo-32355: Optimize asyncio.gather(); now up to 15% faster.

- bpo-32351: Use fastpath in asyncio.sleep if delay<0 (2x boost)

- bpo-32348: Optimize asyncio.Future schedule/add/remove callback. The optimization shows 3-6% performance improvements of async/await code.

- bpo-32331: Fix socket.settimeout() and socket.setblocking() to keep socket.type as is. Fix socket.socket() constructor to reset any bit flags applied to socket’s type. This change only affects OSes that have SOCK_NONBLOCK and/or SOCK_CLOEXEC.

- bpo-32248: Add `importlib.abc.ResourceReader` as an ABC for loaders to provide a unified API for reading resources contained within packages. Also add `importlib.resources` as the port of `importlib_resources`.

- bpo-32311: Implement asyncio.create_task(coro) shortcut

- bpo-32327: Convert asyncio functions that were documented as coroutines to coroutines. Affected functions: loop.sock_sendall, loop.sock_recv, loop.sock_accept, loop.getaddrinfo, loop.getnameinfo.

- bpo-32323: `urllib.parse.urlsplit()` does not convert zone-id (scope) to lower case for scoped IPv6 addresses in hostnames now.

- bpo-32302: Fix bdist_wininst of distutils for CRT v142: it binary compatible with CRT v140.

- bpo-29711: Fix `stop_serving` in asyncio proactor loop kill all listening servers

- bpo-32308: `re.sub()` now replaces empty matches adjacent to a previous non-empty match.

- bpo-29970: Abort asyncio SSLProtocol connection if handshake not complete within 10 seconds.

- bpo-32314: Implement asyncio.run().

- bpo-17852: Revert incorrect fix based on misunderstanding of _Py_PyAtExit() semantics.

- bpo-32296: Implement asyncio._get_running_loop() and get_event_loop() in C. This makes them 4x faster.

- bpo-32250: Implement `asyncio.current_task()` and `asyncio.all_tasks()`. Add helpers intended to be used by alternative task implementations: `asyncio._register_task`, `asyncio._enter_task`, `asyncio._leave_task` and `asyncio._unregister_task`. Deprecate `asyncio.Task.current_task()` and `asyncio.Task.all_tasks()`.

- bpo-32255: A single empty field is now always quoted when written into a CSV file. This allows to distinguish an empty row from a row consisting of a single empty field. Patch by Licht Takeuchi.

- bpo-32277: Raise `NotImplementedError` instead of `SystemError` on platforms where `chmod(..., follow_symlinks=False)` is not supported. Patch by Anthony Sottile.

- bpo-30050: New argument warn_on_full_buffer to signal.set_wakeup_fd lets you control whether Python prints a warning on stderr when the wakeup fd buffer overflows.

- bpo-29137: The `fpectl` library has been removed. It was never enabled by default, never worked correctly on x86-64, and it changed the Python ABI in ways that caused unexpected breakage of C extensions.

- bpo-32273: Move asyncio.test_utils to test.test_asyncio.

- bpo-32272: Remove asyncio.async() function.

- bpo-32269: Add asyncio.get_running_loop() function.

- bpo-32265: All class and static methods of builtin types now are correctly classified by inspect.classify_class_attrs() and grouped in pydoc ouput. Added types.ClassMethodDescriptorType for unbound class methods of builtin types.

- bpo-32253: Deprecate `yield from lock`, `await lock`, `with (yield from lock)` and `with await lock` for asyncio synchronization primitives.

- bpo-22589: Changed MIME type of .bmp from ‘image/x-ms-bmp’ to ‘image/bmp’

- bpo-32193: Convert asyncio to use async/await syntax. Old styled `yield from` is still supported too.

- bpo-32206: Add support to run modules with pdb

- bpo-32227: `functools.singledispatch` now supports registering implementations using type annotations.

- bpo-15873: Added new alternate constructors `datetime.datetime.fromisoformat()`, `datetime.time.fromisoformat()` and `datetime.date.fromisoformat()` as the inverse operation of each classes’s respective `isoformat` methods.

- bpo-32199: The getnode() ip getter now uses ‘ip link’ instead of ‘ip link list’.

- bpo-32143: os.statvfs() includes the f_fsid field from statvfs(2)

- bpo-26439: Fix ctypes.util.find_library() for AIX by implementing ctypes._aix.find_library() Patch by: Michael Felt

- bpo-31993: The pickler now uses less memory when serializing large bytes and str objects into a file. Pickles created with protocol 4 will require less memory for unpickling large bytes and str objects.

- bpo-27456: Ensure TCP_NODELAY is set on Linux. Tests by Victor Stinner.

- bpo-31778: ast.literal_eval() is now more strict. Addition and subtraction of arbitrary numbers no longer allowed.

- bpo-31802: Importing native path module (`posixpath`, `ntpath`) now works even if the `os` module still is not imported.

- bpo-30241: Add contextlib.AbstractAsyncContextManager. Patch by Jelle Zijlstra.

- bpo-31699: Fix deadlocks in `concurrent.futures.ProcessPoolExecutor` when task arguments or results cause pickling or unpickling errors. This should make sure that calls to the `ProcessPoolExecutor` API always eventually return.

- bpo-15216: `TextIOWrapper.reconfigure()` supports changing encoding, errors, and newline.

### Documentation

- bpo-32418: Add get_loop() method to Server and AbstractServer classes.

### Tests

- bpo-32252: Fix faulthandler_suppress_crash_report() used to prevent core dump files when testing crashes. getrlimit() returns zero on success.

- bpo-32002: Adjust C locale coercion testing for the empty locale and POSIX locale cases to more readily adjust to platform dependent behaviour.

### Windows

- bpo-19764: Implement support for `subprocess.Popen(close_fds=True)` on Windows. Patch by Segev Finer.

### Tools/Demos

- bpo-24960: 2to3 and lib2to3 can now read pickled grammar files using pkgutil.get_data() rather than probing the filesystem. This lets 2to3 and lib2to3 work when run from a zipfile.

### C API

- bpo-32030: Py_Initialize() doesn’t reset the memory allocators to default if the `PYTHONMALLOC` environment variable is not set.

- bpo-29084: Undocumented C API for OrderedDict has been excluded from the limited C API. It was added by mistake and actually never worked in the limited C API.

- bpo-32264: Moved the pygetopt.h header into internal/, since it has no public APIs.

- bpo-32241: `Py_SetProgramName()` and `Py_SetPythonHome()` now take the `const wchar *` arguments instead of `wchar *`.

## Python 3.7.0 alpha 3

Release date: 2017-12-05

### Core and Builtins

- bpo-32176: co_flags.CO_NOFREE is now always set correctly by the code object constructor based on freevars and cellvars, rather than needing to be set correctly by the caller. This ensures it will be cleared automatically when additional cell references are injected into a modified code object and function.

- bpo-10544: Yield expressions are now deprecated in comprehensions and generator expressions. They are still permitted in the definition of the outermost iterable, as that is evaluated directly in the enclosing scope.

- bpo-32137: The repr of deeply nested dict now raises a RecursionError instead of crashing due to a stack overflow.

- bpo-32096: Revert memory allocator changes in the C API: move structures back from _PyRuntime to Objects/obmalloc.c. The memory allocators are once again initialized statically, and so PyMem_RawMalloc() and Py_DecodeLocale() can be called before _PyRuntime_Initialize().

- bpo-32043: Add a new “developer mode”: new “-X dev” command line option to enable debug checks at runtime.

- bpo-32023: SyntaxError is now correctly raised when a generator expression without parenthesis is used instead of an inheritance list in a class definition. The duplication of the parentheses can be omitted only on calls.

- bpo-32012: SyntaxError is now correctly raised when a generator expression without parenthesis is passed as an argument, but followed by a trailing comma. A generator expression always needs to be directly inside a set of parentheses and cannot have a comma on either side.

- bpo-28180: A new internal `_Py_SetLocaleFromEnv(category)` helper function has been added in order to improve the consistency of behaviour across different `libc` implementations (e.g. Android doesn’t support setting the locale from the environment by default).

- bpo-31949: Fixed several issues in printing tracebacks (PyTraceBack_Print()). Setting sys.tracebacklimit to 0 or less now suppresses printing tracebacks. Setting sys.tracebacklimit to None now causes using the default limit. Setting sys.tracebacklimit to an integer larger than LONG_MAX now means using the limit LONG_MAX rather than the default limit. Fixed integer overflows in the case of more than `2**31` traceback items on Windows. Fixed output errors handling.

- bpo-30696: Fix the interactive interpreter looping endlessly when no memory.

- bpo-20047: Bytearray methods partition() and rpartition() now accept only bytes-like objects as separator, as documented. In particular they now raise TypeError rather of returning a bogus result when an integer is passed as a separator.

- bpo-21720: BytesWarning no longer emitted when the fromlist argument of `__import__()` or the `__all__` attribute of the module contain bytes instances.

- bpo-31845: Environment variables are once more read correctly at interpreter startup.

- bpo-28936: Ensure that lexically first syntax error involving a parameter and `global` or `nonlocal` is detected first at a given scope. Patch by Ivan Levkivskyi.

- bpo-31825: Fixed OverflowError in the ‘unicode-escape’ codec and in codecs.escape_decode() when decode an escaped non-ascii byte.

- bpo-31618: The per-frame tracing logic added in 3.7a1 has been altered so that `frame->f_lineno` is updated before either `"line"` or `"opcode"` events are emitted. Previously, opcode events were emitted first, and therefore would occasionally see stale line numbers on the frame. The behavior of this feature has changed slightly as a result: when both `f_trace_lines` and `f_trace_opcodes` are enabled, line events now occur first.

- bpo-28603: Print the full context/cause chain of exceptions on interpreter exit, even if an exception in the chain is unhashable or compares equal to later ones. Patch by Zane Bitter.

- bpo-31786: Fix timeout rounding in the select module to round correctly negative timeouts between -1.0 and 0.0. The functions now block waiting for events as expected. Previously, the call was incorrectly non-blocking. Patch by Pablo Galindo.

- bpo-31781: Prevent crashes when calling methods of an uninitialized `zipimport.zipimporter` object. Patch by Oren Milman.

- bpo-30399: Standard repr() of BaseException with a single argument no longer contains redundant trailing comma.

- bpo-31626: Fixed a bug in debug memory allocator. There was a write to freed memory after shrinking a memory block.

- bpo-30817: `PyErr_PrintEx()` clears now the ignored exception that may be raised by `_PySys_SetObjectId()`, for example when no memory.

### Library

- bpo-28556: Two minor fixes for `typing` module: allow shallow copying instances of generic classes, improve interaction of `__init_subclass__` with generics. Original PRs by Ivan Levkivskyi.

- bpo-32214: PEP 557, Data Classes. Provides a decorator which adds boilerplate methods to classes which use type annotations so specify fields.

- bpo-27240: The header folding algorithm for the new email policies has been rewritten, which also fixes bpo-30788, bpo-31831, and bpo-32182. In particular, RFC2231 folding is now done correctly.

- bpo-32186: io.FileIO.readall() and io.FileIO.read() now release the GIL when getting the file size. Fixed hang of all threads with inaccessible NFS server. Patch by Nir Soffer.

- bpo-32101: Add `sys.flags.dev_mode` flag

- bpo-32154: The `asyncio.windows_utils.socketpair()` function has been removed: use directly `socket.socketpair()` which is available on all platforms since Python 3.5 (before, it wasn’t available on Windows). `asyncio.windows_utils.socketpair()` was just an alias to `socket.socketpair` on Python 3.5 and newer.

- bpo-32089: warnings: In development (-X dev) and debug mode (pydebug build), use the “default” action for ResourceWarning, rather than the “always” action, in the default warnings filters.

- bpo-32107: `uuid.getnode()` now preferentially returns universally administered MAC addresses if available, over locally administered MAC addresses. This makes a better guarantee for global uniqueness of UUIDs returned from `uuid.uuid1()`. If only locally administered MAC addresses are available, the first such one found is returned.

- bpo-23033: Wildcard is now supported in hostname when it is one and only character in the left most segment of hostname in second argument of `ssl.match_hostname()`. Patch by Mandeep Singh.

- bpo-12239: Make `msilib.SummaryInformation.GetProperty()` return `None` when the value of property is `VT_EMPTY`. Initial patch by Mark Mc Mahon.

- bpo-28334: Use `os.path.expanduser()` to find the `~/.netrc` file in `netrc.netrc`. If it does not exist, `FileNotFoundError` is raised. Patch by Dimitri Merejkowsky.

- bpo-32121: Made `tracemalloc.Traceback` behave more like the traceback module, sorting the frames from oldest to most recent. `Traceback.format()` now accepts negative limit, truncating the result to the `abs(limit)` oldest frames. To get the old behaviour, one can use the new most_recent_first argument to `Traceback.format()`. (Patch by Jesse Bakker.)

- bpo-31325: Fix wrong usage of `collections.namedtuple()` in the `RobotFileParser.parse()` method. Initial patch by Robin Wellner.

- bpo-12382: `msilib.OpenDatabase()` now raises a better exception message when it couldn’t open or create an MSI file. Initial patch by William Tisäter.

- bpo-19610: `setup()` now warns about invalid types for some fields. The `distutils.dist.Distribution` class now warns when `classifiers`, `keywords` and `platforms` fields are not specified as a list or a string.

- bpo-32071: Added the `-k` command-line option to `python -m unittest` to run only tests that match the given pattern(s).

- bpo-10049: Added nullcontext no-op context manager to contextlib. This provides a simpler and faster alternative to ExitStack() when handling optional context managers.

- bpo-28684: The new test.support.skip_unless_bind_unix_socket() decorator is used here to skip asyncio tests that fail because the platform lacks a functional bind() function for unix domain sockets (as it is the case for non root users on the recent Android versions that run now SELinux in enforcing mode).

- bpo-32110: `codecs.StreamReader.read(n)` now returns not more than n characters/bytes for non-negative n. This makes it compatible with `read()` methods of other file-like objects.

- bpo-27535: The warnings module doesn’t leak memory anymore in the hidden warnings registry for the “ignore” action of warnings filters. warn_explicit() function doesn’t add the warning key to the registry anymore for the “ignore” action.

- bpo-32088: warnings: When Python is build is debug mode (`Py_DEBUG`), `DeprecationWarning`, `PendingDeprecationWarning` and `ImportWarning` warnings are now displayed by default.

- bpo-1647489: Fixed searching regular expression patterns that could match an empty string. Non-empty string can now be correctly found after matching an empty string.

- bpo-25054: Added support of splitting on a pattern that could match an empty string.

- bpo-32072: Fixed issues with binary plists: Fixed saving bytearrays. Identical objects will be saved only once. Equal references will be load as identical objects. Added support for saving and loading recursive data structures.

- bpo-32069: Drop legacy SSL transport from asyncio, ssl.MemoryBIO is always used anyway.

- bpo-32066: asyncio: Support pathlib.Path in create_unix_connection; sock arg should be optional

- bpo-32046: Updates 2to3 to convert from operator.isCallable(obj) to callable(obj). Patch by Donghee Na.

- bpo-32018: inspect.signature should follow PEP 8, if the parameter has an annotation and a default value. Patch by Donghee Na.

- bpo-32025: Add time.thread_time() and time.thread_time_ns()

- bpo-32037: Integers that fit in a signed 32-bit integer will be now pickled with protocol 0 using the INT opcode. This will decrease the size of a pickle, speed up pickling and unpickling, and make these integers be unpickled as int instances in Python 2.

- bpo-32034: Make asyncio.IncompleteReadError and LimitOverrunError pickleable.

- bpo-32015: Fixed the looping of asyncio in the case of reconnection the socket during waiting async read/write from/to the socket.

- bpo-32011: Restored support of loading marshal files with the TYPE_INT64 code. These files can be produced in Python 2.7.

- bpo-28369: Enhance add_reader/writer check that socket is not used by some transport. Before, only cases when add_reader/writer were called with an int FD were supported. Now the check is implemented correctly for all file-like objects.

- bpo-31976: Fix race condition when flushing a file is slow, which can cause a segfault if closing the file from another thread.

- bpo-31985: Formally deprecated aifc.openfp, sunau.openfp, and wave.openfp. Since change 7bc817d5ba917528e8bd07ec461c635291e7b06a in 1993, openfp in each of the three modules had been pointing to that module’s open function as a matter of backwards compatibility, though it had been both untested and undocumented.

- bpo-21862: cProfile command line now accepts `-m module_name` as an alternative to script path. Patch by Sanyam Khurana.

- bpo-31970: Reduce performance overhead of asyncio debug mode.

- bpo-31843: database argument of sqlite3.connect() now accepts a path-like object, instead of just a string.

- bpo-31945: Add Configurable blocksize to `HTTPConnection` and `HTTPSConnection` for improved upload throughput. Patch by Nir Soffer.

- bpo-31943: Add a `cancelled()` method to `asyncio.Handle`. Patch by Marat Sharafutdinov.

- bpo-9678: Fixed determining the MAC address in the uuid module: Using ifconfig on NetBSD and OpenBSD. Using arp on Linux, FreeBSD, NetBSD and OpenBSD. Based on patch by Takayuki Shimizukawa.

- bpo-30057: Fix potential missed signal in signal.signal().

- bpo-31933: Fix Blake2 params leaf_size and node_offset on big endian platforms. Patch by Jack O’Connor.

- bpo-21423: Add an initializer argument to {Process,Thread}PoolExecutor

- bpo-31927: Fixed compilation of the socket module on NetBSD 8. Fixed assertion failure or reading arbitrary data when parse a AF_BLUETOOTH address on NetBSD and DragonFly BSD.

- bpo-27666: Fixed stack corruption in curses.box() and curses.ungetmouse() when the size of types chtype or mmask_t is less than the size of C long. curses.box() now accepts characters as arguments. Based on patch by Steve Fink.

- bpo-31917: Add 3 new clock identifiers: `time.CLOCK_BOOTTIME`, `time.CLOCK_PROF` and `time.CLOCK_UPTIME`.

- bpo-31897: plistlib now catches more errors when read binary plists and raises InvalidFileException instead of unexpected exceptions.

- bpo-25720: Fix the method for checking pad state of curses WINDOW. Patch by Masayuki Yamamoto.

- bpo-31893: Fixed the layout of the kqueue_event structure on OpenBSD and NetBSD. Fixed the comparison of the kqueue_event objects.

- bpo-31891: Fixed building the curses module on NetBSD.

- bpo-31884: added required constants to subprocess module for setting priority on windows

- bpo-28281: Remove year (1-9999) limits on the Calendar.weekday() function. Patch by Mark Gollahon.

- bpo-31702: crypt.mksalt() now allows to specify the number of rounds for SHA-256 and SHA-512 hashing.

- bpo-30639: `inspect.getfile()` no longer computes the repr of unknown objects to display in an error message, to protect against badly behaved custom reprs.

- bpo-30768: Fix the pthread+semaphore implementation of PyThread_acquire_lock_timed() when called with timeout > 0 and intr_flag=0: recompute the timeout if sem_timedwait() is interrupted by a signal (EINTR). See also the PEP 475.

- bpo-31854: Add `mmap.ACCESS_DEFAULT` constant.

- bpo-31834: Use optimized code for BLAKE2 only with SSSE3+. The pure SSE2 implementation is slower than the pure C reference implementation.

- bpo-28292: Calendar.itermonthdates() will now consistently raise an exception when a date falls outside of the 0001-01-01 through 9999-12-31 range. To support applications that cannot tolerate such exceptions, the new methods itermonthdays3() and itermonthdays4() are added. The new methods return tuples and are not restricted by the range supported by datetime.date.

- bpo-28564: The shutil.rmtree() function has been sped up to 20–40%. This was done using the os.scandir() function.

- bpo-28416: Instances of pickle.Pickler subclass with the persistent_id() method and pickle.Unpickler subclass with the persistent_load() method no longer create reference cycles.

- bpo-31653: Don’t release the GIL if we can acquire a multiprocessing semaphore immediately.

- bpo-28326: Fix multiprocessing.Process when stdout and/or stderr is closed or None.

- bpo-20825: Add `subnet_of` and `superset_of` containment tests to `ipaddress.IPv6Network` and `ipaddress.IPv4Network`. Patch by Michel Albert and Cheryl Sabella.

- bpo-31827: Remove the os.stat_float_times() function. It was introduced in Python 2.3 for backward compatibility with Python 2.2, and was deprecated since Python 3.1.

- bpo-31756: Add a `subprocess.Popen(text=False)` keyword argument to `subprocess` functions to be more explicit about when the library should attempt to decode outputs into text. Patch by Andrew Clegg.

- bpo-31819: Add AbstractEventLoop.sock_recv_into().

- bpo-31457: If nested log adapters are used, the inner `process()` methods are no longer omitted.

- bpo-31457: The `manager` property on LoggerAdapter objects is now properly settable.

- bpo-31806: Fix timeout rounding in time.sleep(), threading.Lock.acquire() and socket.socket.settimeout() to round correctly negative timeouts between -1.0 and 0.0. The functions now block waiting for events as expected. Previously, the call was incorrectly non-blocking. Patch by Pablo Galindo.

- bpo-31803: time.clock() and time.get_clock_info(‘clock’) now emit a DeprecationWarning warning.

- bpo-31800: Extended support for parsing UTC offsets. strptime ‘%z’ can now parse the output generated by datetime.isoformat, including seconds and microseconds.

- bpo-28603: traceback: Fix a TypeError that occurred during printing of exception tracebacks when either the current exception or an exception in its context/cause chain is unhashable. Patch by Zane Bitter.

- bpo-30541: Add new function to seal a mock and prevent the automatically creation of child mocks. Patch by Mario Corchero.

- bpo-31784: Implement the PEP 564, add new 6 new functions with nanosecond resolution to the `time` module: `clock_gettime_ns()`, `clock_settime_ns()`, `monotonic_ns()`, `perf_counter_ns()`, `process_time_ns()`, `time_ns()`.

- bpo-30143: 2to3 now generates a code that uses abstract collection classes from collections.abc rather than collections.

- bpo-31770: Prevent a crash when calling the `__init__()` method of a `sqlite3.Cursor` object more than once. Patch by Oren Milman.

- bpo-31764: Prevent a crash in `sqlite3.Cursor.close()` in case the `Cursor` object is uninitialized. Patch by Oren Milman.

- bpo-31752: Fix possible crash in timedelta constructor called with custom integers.

- bpo-31620: an empty asyncio.Queue now doesn’t leak memory when queue.get pollers timeout

- bpo-31690: Allow the flags re.ASCII, re.LOCALE, and re.UNICODE to be used as group flags for regular expressions.

- bpo-30349: FutureWarning is now emitted if a regular expression contains character set constructs that will change semantically in the future (nested sets and set operations).

- bpo-31664: Added support for the Blowfish hashing in the crypt module.

- bpo-31632: Fix method set_protocol() of class _SSLProtocolTransport in asyncio module. This method was previously modifying a wrong reference to the protocol.

- bpo-15037: Added a workaround for getkey() in curses for ncurses 5.7 and earlier.

- bpo-31307: Allow use of bytes objects for arguments to `configparser.ConfigParser.read()`. Patch by Vincent Michel.

- bpo-31334: Fix `poll.poll([timeout])` in the `select` module for arbitrary negative timeouts on all OSes where it can only be a non-negative integer or -1. Patch by Riccardo Coccioli.

- bpo-31310: multiprocessing’s semaphore tracker should be launched again if crashed.

- bpo-31308: Make multiprocessing’s forkserver process immune to Ctrl-C and other user interruptions. If it crashes, restart it when necessary.

- bpo-31245: Added support for AF_UNIX socket in asyncio `create_datagram_endpoint`.

- bpo-30553: Add HTTP/2 status code 421 (Misdirected Request) to `http.HTTPStatus`. Patch by Vitor Pereira.

### Documentation

- bpo-32105: Added asyncio.BaseEventLoop.connect_accepted_socket versionadded marker.

### Tests

- bpo-31380: Skip test_httpservers test_undecodable_file on macOS: fails on APFS.

- bpo-31705: Skip test_socket.test_sha256() on Linux kernel older than 4.5. The test fails with ENOKEY on kernel 3.10 (on ppc64le). A fix was merged into the kernel 4.5.

- bpo-32138: Skip on Android test_faulthandler tests that raise SIGSEGV and remove the test.support.requires_android_level decorator.

- bpo-32136: The runtime embedding tests have been split out from `Lib/test/test_capi.py` into a new `Lib/test/test_embed.py` file.

- bpo-28668: test.support.requires_multiprocessing_queue is removed. Skip tests with test.support.import_module(‘multiprocessing.synchronize’) instead when the semaphore implementation is broken or missing.

- bpo-32126: Skip test_get_event_loop_new_process in test.test_asyncio.test_events when sem_open() is not functional.

- bpo-31174: Fix test_tools.test_unparse: DirectoryTestCase now stores the names sample to always test the same files. It prevents false alarms when hunting reference leaks.

### Build

- bpo-28538: Revert the previous changes, the if_nameindex structure is defined by Unified Headers.

- bpo-28762: Revert the last commit, the F_LOCK macro is defined by Android Unified Headers.

- bpo-29040: Support building Android with Unified Headers. The first NDK release to support Unified Headers is android-ndk-r14.

- bpo-32059: `detect_modules()` in `setup.py` now also searches the sysroot paths when cross-compiling.

- bpo-31957: Fixes Windows SDK version detection when building for Windows.

- bpo-31609: Fixes quotes in PCbuild/clean.bat

- bpo-31934: Abort the build when building out of a not clean source tree.

- bpo-31926: Fixed Argument Clinic sometimes causing compilation errors when there was more than one function and/or method in a .c file with the same name.

- bpo-28791: Update Windows builds to use SQLite 3.21.0.

- bpo-28791: Update OS X installer to use SQLite 3.21.0.

- bpo-28643: Record profile-opt build progress with stamp files.

- bpo-31866: Finish removing support for AtheOS.

### Windows

- bpo-1102: Return `None` when `View.Fetch()` returns `ERROR_NO_MORE_ITEMS` instead of raising `MSIError`. Initial patch by Anthony Tuininga.

- bpo-31944: Fixes Modify button in Apps and Features dialog.

- bpo-20486: Implement the `Database.Close()` method to help closing MSI database objects.

- bpo-31857: Make the behavior of USE_STACKCHECK deterministic in a multi-threaded environment.

### macOS

- bpo-31392: Update macOS installer to use OpenSSL 1.0.2m

### IDLE

- bpo-32207: Improve tk event exception tracebacks in IDLE. When tk event handling is driven by IDLE’s run loop, a confusing and distracting queue.EMPTY traceback context is no longer added to tk event exception tracebacks. The traceback is now the same as when event handling is driven by user code. Patch based on a suggestion by Serhiy Storchaka.

- bpo-32164: Delete unused file idlelib/tabbedpages.py. Use of TabbedPageSet in configdialog was replaced by ttk.Notebook.

- bpo-32100: IDLE: Fix old and new bugs in pathbrowser; improve tests. Patch mostly by Cheryl Sabella.

- bpo-31858: IDLE – Restrict shell prompt manipulation to the shell. Editor and output windows only see an empty last prompt line. This simplifies the code and fixes a minor bug when newline is inserted. Sys.ps1, if present, is read on Shell start-up, but is not set or changed.

- bpo-31860: The font sample in the IDLE configuration dialog is now editable. Changes persist while IDLE remains open

- bpo-31836: Test_code_module now passes if run after test_idle, which sets ps1. The code module uses sys.ps1 if present or sets it to ‘>>> ‘ if not. Test_code_module now properly tests both behaviors. Ditto for ps2.

- bpo-28603: Fix a TypeError that caused a shell restart when printing a traceback that includes an exception that is unhashable. Patch by Zane Bitter.

- bpo-13802: Use non-Latin characters in the IDLE’s Font settings sample. Even if one selects a font that defines a limited subset of the unicode Basic Multilingual Plane, tcl/tk will use other fonts that define a character. The expanded example give users of non-Latin characters a better idea of what they might see in IDLE’s shell and editors. To make room for the expanded sample, frames on the Font tab are re-arranged. The Font/Tabs help explains a bit about the additions.

### Tools/Demos

- bpo-32159: Remove CVS and Subversion tools: remove svneol.py and treesync.py scripts. CPython migrated from CVS to Subversion, to Mercurial, and then to Git. CVS and Subversion are no longer used to develop CPython.

- bpo-30722: Make redemo work with Python 3.6 and newer versions. Also, remove the `LOCALE` option since it doesn’t work with string patterns in Python 3. Patch by Christoph Sarnowski.

### C API

- bpo-20891: Fix PyGILState_Ensure(). When PyGILState_Ensure() is called in a non-Python thread before PyEval_InitThreads(), only call PyEval_InitThreads() after calling PyThreadState_New() to fix a crash.

- bpo-32125: The `Py_UseClassExceptionsFlag` flag has been removed. It was deprecated and wasn’t used anymore since Python 2.0.

- bpo-25612: Move the current exception state from the frame object to the co-routine. This simplifies the interpreter and fixes a couple of obscure bugs caused by having swap exception state when entering or exiting a generator.

- bpo-23699: Add Py_RETURN_RICHCOMPARE macro to reduce boilerplate code in rich comparison functions.

- bpo-30697: The `PyExc_RecursionErrorInst` singleton is removed and `PyErr_NormalizeException()` does not use it anymore. This singleton is persistent and its members being never cleared may cause a segfault during finalization of the interpreter. See also bpo-22898.

## Python 3.7.0 alpha 2

Release date: 2017-10-16

### Core and Builtins

- bpo-31558: `gc.freeze()` is a new API that allows for moving all objects currently tracked by the garbage collector to a permanent generation, effectively removing them from future collection events. This can be used to protect those objects from having their PyGC_Head mutated. In effect, this enables great copy-on-write stability at fork().

- bpo-31642: Restored blocking “from package import module” by setting sys.modules[“package.module”] to None.

- bpo-31708: Allow use of asynchronous generator expressions in synchronous functions.

- bpo-31709: Drop support of asynchronous __aiter__.

- bpo-30404: The -u option now makes the stdout and stderr streams unbuffered rather than line-buffered.

- bpo-31619: Fixed a ValueError when convert a string with large number of underscores to integer with binary base.

- bpo-31602: Fix an assertion failure in `zipimporter.get_source()` in case of a bad `zlib.decompress()`. Patch by Oren Milman.

- bpo-31592: Fixed an assertion failure in Python parser in case of a bad `unicodedata.normalize()`. Patch by Oren Milman.

- bpo-31588: Raise a `TypeError` with a helpful error message when class creation fails due to a metaclass with a bad `__prepare__()` method. Patch by Oren Milman.

- bpo-31574: Importlib was instrumented with two dtrace probes to profile import timing.

- bpo-31566: Fix an assertion failure in `_warnings.warn()` in case of a bad `__name__` global. Patch by Oren Milman.

- bpo-31506: Improved the error message logic for `object.__new__` and `object.__init__`.

- bpo-31505: Fix an assertion failure in `json`, in case `_json.make_encoder()` received a bad `encoder()` argument. Patch by Oren Milman.

- bpo-31492: Fix assertion failures in case of failing to import from a module with a bad `__name__` attribute, and in case of failing to access an attribute of such a module. Patch by Oren Milman.

- bpo-31478: Fix an assertion failure in `_random.Random.seed()` in case the argument has a bad `__abs__()` method. Patch by Oren Milman.

- bpo-31336: Speed up class creation by 10-20% by reducing the overhead in the necessary special method lookups. Patch by Stefan Behnel.

- bpo-31415: Add `-X importtime` option to show how long each import takes. It can be used to optimize application’s startup time. Support the `PYTHONPROFILEIMPORTTIME` as an equivalent way to enable this.

- bpo-31410: Optimized calling wrapper and classmethod descriptors.

- bpo-31353: PEP 553 - Add a new built-in called `breakpoint()` which calls `sys.breakpointhook()`. By default this imports `pdb` and calls `pdb.set_trace()`, but users may override `sys.breakpointhook()` to call whatever debugger they want. The original value of the hook is saved in `sys.__breakpointhook__`.

- bpo-17852: Maintain a list of open buffered files, flush them before exiting the interpreter. Based on a patch from Armin Rigo.

- bpo-31315: Fix an assertion failure in imp.create_dynamic(), when spec.name is not a string. Patch by Oren Milman.

- bpo-31311: Fix a crash in the `__setstate__()` method of `ctypes._CData`, in case of a bad `__dict__`. Patch by Oren Milman.

- bpo-31293: Fix crashes in true division and multiplication of a timedelta object by a float with a bad as_integer_ratio() method. Patch by Oren Milman.

- bpo-31285: Fix an assertion failure in `warnings.warn_explicit`, when the return value of the received loader’s `get_source()` has a bad `splitlines()` method. Patch by Oren Milman.

- bpo-30406: Make `async` and `await` proper keywords, as specified in PEP 492.

### Library

- bpo-30058: Fixed buffer overflow in select.kqueue.control().

- bpo-31672: `idpattern` in `string.Template` matched some non-ASCII characters. Now it uses `-i` regular expression local flag to avoid non-ASCII characters.

- bpo-31701: On Windows, faulthandler.enable() now ignores MSC and COM exceptions.

- bpo-31728: Prevent crashes in `_elementtree` due to unsafe cleanup of `Element.text` and `Element.tail`. Patch by Oren Milman.

- bpo-31671: Now `re.compile()` converts passed RegexFlag to normal int object before compiling. bm_regex_compile benchmark shows 14% performance improvements.

- bpo-30397: The types of compiled regular objects and match objects are now exposed as `re.Pattern` and `re.Match`. This adds information in pydoc output for the `re` module.

- bpo-31675: Fixed memory leaks in Tkinter’s methods splitlist() and split() when pass a string larger than 2 GiB.

- bpo-31673: Fixed typo in the name of Tkinter’s method adderrorinfo().

- bpo-31648: Improvements to path predicates in ElementTree: Allow whitespace around predicate parts, i.e. “[a = ‘text’]” instead of requiring the less readable “[a=’text’]”. Add support for text comparison of the current node, like “[.=’text’]”. Patch by Stefan Behnel.

- bpo-30806: Fix the string representation of a netrc object.

- bpo-31638: Add optional argument `compressed` to `zipapp.create_archive`, and add option `--compress` to the command line interface of `zipapp`.

- bpo-25351: Avoid venv activate failures with undefined variables

- bpo-20519: Avoid ctypes use (if possible) and improve import time for uuid.

- bpo-28293: The regular expression cache is no longer completely dumped when it is full.

- bpo-31596: Added pthread_getcpuclockid() to the time module

- bpo-27494: Make 2to3 accept a trailing comma in generator expressions. For example, `set(x for x in [],)` is now allowed.

- bpo-30347: Stop crashes when concurrently iterate over itertools.groupby() iterators.

- bpo-30346: An iterator produced by itertools.groupby() iterator now becomes exhausted after advancing the groupby iterator.

- bpo-31556: Cancel asyncio.wait_for future faster if timeout <= 0

- bpo-31540: Allow passing a context object in `concurrent.futures.ProcessPoolExecutor` constructor. Also, free job resources in `concurrent.futures.ProcessPoolExecutor` earlier to improve memory usage when a worker waits for new jobs.

- bpo-31516: `threading.current_thread()` should not return a dummy thread at shutdown.

- bpo-31525: In the sqlite module, require the sqlite3_prepare_v2 API. Thus, the sqlite module now requires sqlite version at least 3.3.9.

- bpo-26510: argparse subparsers are now required by default. This matches behaviour in Python 2. For optional subparsers, use the new parameter `add_subparsers(required=False)`. Patch by Anthony Sottile. (As of 3.7.0rc1, the default was changed to not required as had been the case since Python 3.3.)

- bpo-27541: Reprs of subclasses of some collection and iterator classes (`bytearray`, `array.array`, `collections.deque`, `collections.defaultdict`, `itertools.count`, `itertools.repeat`) now contain actual type name instead of hardcoded names of the base class.

- bpo-31351: python -m ensurepip now exits with non-zero exit code if pip bootstrapping has failed.

- bpo-31389: `pdb.set_trace()` now takes an optional keyword-only argument `header`. If given, this is printed to the console just before debugging begins.

### Documentation

- bpo-31537: Fix incorrect usage of `get_history_length` in readline documentation example code. Patch by Brad Smith.

- bpo-30085: The operator functions without double underscores are preferred for clarity. The one with underscores are only kept for back-compatibility.

### Build

- bpo-31696: Improve compiler version information in `sys.version` when Python is built with Clang.

- bpo-31625: Stop using ranlib on static libraries. Instead, we assume ar supports the ‘s’ flag.

- bpo-31624: Remove support for BSD/OS.

- bpo-22140: Prevent double substitution of prefix in python-config.sh.

- bpo-31569: Correct PCBuild/ case to PCbuild/ in build scripts and documentation.

- bpo-31536: Avoid wholesale rebuild after `make regen-all` if nothing changed.

### IDLE

- bpo-31460: Simplify the API of IDLE’s Module Browser. Passing a widget instead of an flist with a root widget opens the option of creating a browser frame that is only part of a window. Passing a full file name instead of pieces assumed to come from a .py file opens the possibility of browsing python files that do not end in .py.

- bpo-31649: IDLE - Make _htest, _utest parameters keyword only.

- bpo-31559: Remove test order dependence in idle_test.test_browser.

- bpo-31459: Rename IDLE’s module browser from Class Browser to Module Browser. The original module-level class and method browser became a module browser, with the addition of module-level functions, years ago. Nested classes and functions were added yesterday. For back-compatibility, the virtual event <<open-class-browser>>, which appears on the Keys tab of the Settings dialog, is not changed. Patch by Cheryl Sabella.

- bpo-31500: Default fonts now are scaled on HiDPI displays.

- bpo-1612262: IDLE module browser now shows nested classes and functions. Original patches for code and tests by Guilherme Polo and Cheryl Sabella, respectively.

### C API

- bpo-28280: Make `PyMapping_Keys()`, `PyMapping_Values()` and `PyMapping_Items()` always return a `list` (rather than a `list` or a `tuple`). Patch by Oren Milman.

- bpo-31532: Fix memory corruption due to allocator mix in getpath.c between Py_GetPath() and Py_SetPath()

- bpo-25658: Implement PEP 539 for Thread Specific Storage (TSS) API: it is a new Thread Local Storage (TLS) API to CPython which would supersede use of the existing TLS API within the CPython interpreter, while deprecating the existing API. PEP written by Erik M. Bray, patch by Masayuki Yamamoto.

## Python 3.7.0 alpha 1

Release date: 2017-09-19

### Security

- bpo-29781: SSLObject.version() now correctly returns None when handshake over BIO has not been performed yet.

- bpo-29505: Add fuzz tests for float(str), int(str), unicode(str); for oss-fuzz.

- bpo-30947: Upgrade libexpat embedded copy from version 2.2.1 to 2.2.3 to get security fixes.

- bpo-30730: Prevent environment variables injection in subprocess on Windows. Prevent passing other environment variables and command arguments.

- bpo-30694: Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes of multiple security vulnerabilities including: CVE 2017-9233 (External entity infinite loop DoS), CVE 2016-9063 (Integer overflow, re-fix), CVE 2016-0718 (Fix regression bugs from 2.2.0’s fix to CVE 2016-0718) and CVE 2012-0876 (Counter hash flooding with SipHash). Note: the CVE 2016-5300 (Use os-specific entropy sources like getrandom) doesn’t impact Python, since Python already gets entropy from the OS to set the expat secret using `XML_SetHashSalt()`.

- bpo-30500: Fix urllib.parse.splithost() to correctly parse fragments. For example, `splithost('//127.0.0.1#@evil.com/')` now correctly returns the `127.0.0.1` host, instead of treating `@evil.com` as the host in an authentication (`login@host`).

- bpo-29591: Update expat copy from 2.1.1 to 2.2.0 to get fixes of CVE 2016-0718 and CVE 2016-4472. See https://sourceforge.net/p/expat/bugs/537/ for more information.

### Core and Builtins

- bpo-31490: Fix an assertion failure in `ctypes` class definition, in case the class has an attribute whose name is specified in `_anonymous_` but not in `_fields_`. Patch by Oren Milman.

- bpo-31471: Fix an assertion failure in `subprocess.Popen()` on Windows, in case the env argument has a bad `keys()` method. Patch by Oren Milman.

- bpo-31418: Fix an assertion failure in `PyErr_WriteUnraisable()` in case of an exception with a bad `__module__` attribute. Patch by Oren Milman.

- bpo-31416: Fix assertion failures in case of a bad warnings.filters or warnings.defaultaction. Patch by Oren Milman.

- bpo-28411: Change direct usage of PyInterpreterState.modules to PyImport_GetModuleDict(). Also introduce more uniformity in other code that deals with sys.modules. This helps reduce complications when working on sys.modules.

- bpo-28411: Switch to the abstract API when dealing with `PyInterpreterState.modules`. This allows later support for all dict subclasses and other Mapping implementations. Also add a `PyImport_GetModule()` function to reduce a bunch of duplicated code.

- bpo-31411: Raise a TypeError instead of SystemError in case warnings.onceregistry is not a dictionary. Patch by Oren Milman.

- bpo-31344: For finer control of tracing behaviour when testing the interpreter, two new frame attributes have been added to control the emission of particular trace events: `f_trace_lines` (`True` by default) to turn off per-line trace events; and `f_trace_opcodes` (`False` by default) to turn on per-opcode trace events.

- bpo-31373: Fix several possible instances of undefined behavior due to floating-point demotions.

- bpo-30465: Location information (`lineno` and `col_offset`) in f-strings is now (mostly) correct. This fixes tools like flake8 from showing warnings on the wrong line (typically the first line of the file).

- bpo-30860: Consolidate CPython’s global runtime state under a single struct. This improves discoverability of the runtime state.

- bpo-31347: Fix possible undefined behavior in _PyObject_FastCall_Prepend.

- bpo-31343: Include sys/sysmacros.h for major(), minor(), and makedev(). GNU C libray plans to remove the functions from sys/types.h.

- bpo-31291: Fix an assertion failure in `zipimport.zipimporter.get_data` on Windows, when the return value of `pathname.replace('/','\\')` isn’t a string. Patch by Oren Milman.

- bpo-31271: Fix an assertion failure in the `write()` method of `io.TextIOWrapper`, when the encoder doesn’t return a bytes object. Patch by Oren Milman.

- bpo-31243: Fix a crash in some methods of `io.TextIOWrapper`, when the decoder’s state is invalid. Patch by Oren Milman.

- bpo-30721: `print` now shows correct usage hint for using Python 2 redirection syntax. Patch by Sanyam Khurana.

- bpo-31070: Fix a race condition in importlib _get_module_lock().

- bpo-30747: Add a non-dummy implementation of _Py_atomic_store and _Py_atomic_load on MSVC.

- bpo-31095: Fix potential crash during GC caused by `tp_dealloc` which doesn’t call `PyObject_GC_UnTrack()`.

- bpo-31071: Avoid masking original TypeError in call with * unpacking when other arguments are passed.

- bpo-30978: str.format_map() now passes key lookup exceptions through. Previously any exception was replaced with a KeyError exception.

- bpo-30808: Use _Py_atomic API for concurrency-sensitive signal state.

- bpo-30876: Relative import from unloaded package now reimports the package instead of failing with SystemError. Relative import from non-package now fails with ImportError rather than SystemError.

- bpo-30703: Improve signal delivery. Avoid using Py_AddPendingCall from signal handler, to avoid calling signal-unsafe functions. The tests I’m adding here fail without the rest of the patch, on Linux and OS X. This means our signal delivery logic had defects (some signals could be lost).

- bpo-30765: Avoid blocking in pthread_mutex_lock() when PyThread_acquire_lock() is asked not to block.

- bpo-31161: Make sure the ‘Missing parentheses’ syntax error message is only applied to SyntaxError, not to subclasses. Patch by Martijn Pieters.

- bpo-30814: Fixed a race condition when import a submodule from a package.

- bpo-30736: The internal unicodedata database has been upgraded to Unicode 10.0.

- bpo-30604: Move co_extra_freefuncs from per-thread to per-interpreter to avoid crashes.

- bpo-30597: `print` now shows expected input in custom error message when used as a Python 2 statement. Patch by Sanyam Khurana.

- bpo-30682: Removed a too-strict assertion that failed for certain f-strings, such as eval(“f’\n’”) and eval(“f’\r’”).

- bpo-30501: The compiler now produces more optimal code for complex condition expressions in the “if”, “while” and “assert” statement, the “if” expression, and generator expressions and comprehensions.

- bpo-28180: Implement PEP 538 (legacy C locale coercion). This means that when a suitable coercion target locale is available, both the core interpreter and locale-aware C extensions will assume the use of UTF-8 as the default text encoding, rather than ASCII.

- bpo-30486: Allows setting cell values for __closure__. Patch by Lisa Roach.

- bpo-30537: itertools.islice now accepts integer-like objects (having an __index__ method) as start, stop, and slice arguments

- bpo-25324: Tokens needed for parsing in Python moved to C. `COMMENT`, `NL` and `ENCODING`. This way the tokens and tok_names in the token module don’t get changed when you import the tokenize module.

- bpo-29104: Fixed parsing backslashes in f-strings.

- bpo-27945: Fixed various segfaults with dict when input collections are mutated during searching, inserting or comparing. Based on patches by Duane Griffin and Tim Mitchell.

- bpo-25794: Fixed type.__setattr__() and type.__delattr__() for non-interned attribute names. Based on patch by Eryk Sun.

- bpo-30039: If a KeyboardInterrupt happens when the interpreter is in the middle of resuming a chain of nested ‘yield from’ or ‘await’ calls, it’s now correctly delivered to the innermost frame.

- bpo-28974: `object.__format__(x, '')` is now equivalent to `str(x)` rather than `format(str(self), '')`.

- bpo-30024: Circular imports involving absolute imports with binding a submodule to a name are now supported.

- bpo-12414: sys.getsizeof() on a code object now returns the sizes which includes the code struct and sizes of objects which it references. Patch by Donghee Na.

- bpo-29839: len() now raises ValueError rather than OverflowError if __len__() returned a large negative integer.

- bpo-11913: README.rst is now included in the list of distutils standard READMEs and therefore included in source distributions.

- bpo-29914: Fixed default implementations of __reduce__ and __reduce_ex__(). object.__reduce__() no longer takes arguments, object.__reduce_ex__() now requires one argument.

- bpo-29949: Fix memory usage regression of set and frozenset object.

- bpo-29935: Fixed error messages in the index() method of tuple, list and deque when pass indices of wrong type.

- bpo-29816: Shift operation now has less opportunity to raise OverflowError. ValueError always is raised rather than OverflowError for negative counts. Shifting zero with non-negative count always returns zero.

- bpo-24821: Fixed the slowing down to 25 times in the searching of some unlucky Unicode characters.

- bpo-29102: Add a unique ID to PyInterpreterState. This makes it easier to identify each subinterpreter.

- bpo-29894: The deprecation warning is emitted if __complex__ returns an instance of a strict subclass of complex. In a future versions of Python this can be an error.

- bpo-29859: Show correct error messages when any of the pthread_* calls in thread_pthread.h fails.

- bpo-29849: Fix a memory leak when an ImportError is raised during from import.

- bpo-28856: Fix an oversight that %b format for bytes should support objects follow the buffer protocol.

- bpo-29723: The `sys.path[0]` initialization change for bpo-29139 caused a regression by revealing an inconsistency in how sys.path is initialized when executing `__main__` from a zipfile, directory, or other import location. The interpreter now consistently avoids ever adding the import location’s parent directory to `sys.path`, and ensures no other `sys.path` entries are inadvertently modified when inserting the import location named on the command line.

- bpo-29568: Escaped percent “%%” in the format string for classic string formatting no longer allows any characters between two percents.

- bpo-29714: Fix a regression that bytes format may fail when containing zero bytes inside.

- bpo-29695: bool(), float(), list() and tuple() no longer take keyword arguments. The first argument of int() can now be passes only as positional argument.

- bpo-28893: Set correct __cause__ for errors about invalid awaitables returned from __aiter__ and __anext__.

- bpo-28876: `bool(range)` works even if `len(range)` raises `OverflowError`.

- bpo-29683: Fixes to memory allocation in _PyCode_SetExtra. Patch by Brian Coleman.

- bpo-29684: Fix minor regression of PyEval_CallObjectWithKeywords. It should raise TypeError when kwargs is not a dict. But it might cause segv when args=NULL and kwargs is not a dict.

- bpo-28598: Support __rmod__ for subclasses of str being called before str.__mod__. Patch by Martijn Pieters.

- bpo-29607: Fix stack_effect computation for CALL_FUNCTION_EX. Patch by Matthieu Dartiailh.

- bpo-29602: Fix incorrect handling of signed zeros in complex constructor for complex subclasses and for inputs having a __complex__ method. Patch by Serhiy Storchaka.

- bpo-29347: Fixed possibly dereferencing undefined pointers when creating weakref objects.

- bpo-29463: Add `docstring` field to Module, ClassDef, FunctionDef, and AsyncFunctionDef ast nodes. docstring is not first stmt in their body anymore. It affects `co_firstlineno` and `co_lnotab` of code object for module and class. (Reverted in bpo-32911.)

- bpo-29438: Fixed use-after-free problem in key sharing dict.

- bpo-29546: Set the ‘path’ and ‘name’ attribute on ImportError for `from ... import ...`.

- bpo-29546: Improve from-import error message with location

- bpo-29478: If max_line_length=None is specified while using the Compat32 policy, it is no longer ignored. Patch by Mircea Cosbuc.

- bpo-29319: Prevent RunMainFromImporter overwriting sys.path[0].

- bpo-29337: Fixed possible BytesWarning when compare the code objects. Warnings could be emitted at compile time.

- bpo-29327: Fixed a crash when pass the iterable keyword argument to sorted().

- bpo-29034: Fix memory leak and use-after-free in os module (path_converter).

- bpo-29159: Fix regression in bytes(x) when x.__index__() raises Exception.

- bpo-29049: Call _PyObject_GC_TRACK() lazily when calling Python function. Calling function is up to 5% faster.

- bpo-28927: bytes.fromhex() and bytearray.fromhex() now ignore all ASCII whitespace, not only spaces. Patch by Robert Xiao.

- bpo-28932: Do not include <sys/random.h> if it does not exist.

- bpo-25677: Correct the positioning of the syntax error caret for indented blocks. Based on patch by Michael Layzell.

- bpo-29000: Fixed bytes formatting of octals with zero padding in alternate form.

- bpo-18896: Python function can now have more than 255 parameters. collections.namedtuple() now supports tuples with more than 255 elements.

- bpo-28596: The preferred encoding is UTF-8 on Android. Patch written by Chi Hsuan Yen.

- bpo-22257: Clean up interpreter startup (see PEP 432).

- bpo-26919: On Android, operating system data is now always encoded/decoded to/from UTF-8, instead of the locale encoding to avoid inconsistencies with os.fsencode() and os.fsdecode() which are already using UTF-8.

- bpo-28991: functools.lru_cache() was susceptible to an obscure reentrancy bug triggerable by a monkey-patched len() function.

- bpo-28147: Fix a memory leak in split-table dictionaries: setattr() must not convert combined table into split table. Patch written by INADA Naoki.

- bpo-28739: f-string expressions are no longer accepted as docstrings and by ast.literal_eval() even if they do not include expressions.

- bpo-28512: Fixed setting the offset attribute of SyntaxError by PyErr_SyntaxLocationEx() and PyErr_SyntaxLocationObject().

- bpo-28918: Fix the cross compilation of xxlimited when Python has been built with Py_DEBUG defined.

- bpo-23722: Rather than silently producing a class that doesn’t support zero-argument `super()` in methods, failing to pass the new `__classcell__` namespace entry up to `type.__new__` now results in a `DeprecationWarning` and a class that supports zero-argument `super()`.

- bpo-28797: Modifying the class __dict__ inside the __set_name__ method of a descriptor that is used inside that class no longer prevents calling the __set_name__ method of other descriptors.

- bpo-28799: Remove the `PyEval_GetCallStats()` function and deprecate the untested and undocumented `sys.callstats()` function. Remove the `CALL_PROFILE` special build: use the `sys.setprofile()` function, `cProfile` or `profile` to profile function calls.

- bpo-12844: More than 255 arguments can now be passed to a function.

- bpo-28782: Fix a bug in the implementation `yield from` when checking if the next instruction is YIELD_FROM. Regression introduced by WORDCODE (bpo-26647).

- bpo-28774: Fix error position of the unicode error in ASCII and Latin1 encoders when a string returned by the error handler contains multiple non-encodable characters (non-ASCII for the ASCII codec, characters out of the U+0000-U+00FF range for Latin1).

- bpo-28731: Optimize _PyDict_NewPresized() to create correct size dict. Improve speed of dict literal with constant keys up to 30%.

- bpo-28532: Show sys.version when -V option is supplied twice.

- bpo-27100: The with-statement now checks for __enter__ before it checks for __exit__. This gives less confusing error messages when both methods are missing. Patch by Jonathan Ellington.

- bpo-28746: Fix the set_inheritable() file descriptor method on platforms that do not have the ioctl FIOCLEX and FIONCLEX commands.

- bpo-26920: Fix not getting the locale’s charset upon initializing the interpreter, on platforms that do not have langinfo.

- bpo-28648: Fixed crash in Py_DecodeLocale() in debug build on Mac OS X when decode astral characters. Patch by Xiang Zhang.

- bpo-28665: Improve speed of the STORE_DEREF opcode by 40%.

- bpo-19398: Extra slash no longer added to sys.path components in case of empty compile-time PYTHONPATH components.

- bpo-28621: Sped up converting int to float by reusing faster bits counting implementation. Patch by Adrian Wielgosik.

- bpo-28580: Optimize iterating split table values. Patch by Xiang Zhang.

- bpo-28583: PyDict_SetDefault didn’t combine split table when needed. Patch by Xiang Zhang.

- bpo-28128: Deprecation warning for invalid str and byte escape sequences now prints better information about where the error occurs. Patch by Serhiy Storchaka and Eric Smith.

- bpo-28509: dict.update() no longer allocate unnecessary large memory.

- bpo-28426: Fixed potential crash in PyUnicode_AsDecodedObject() in debug build.

- bpo-28517: Fixed of-by-one error in the peephole optimizer that caused keeping unreachable code.

- bpo-28214: Improved exception reporting for problematic __set_name__ attributes.

- bpo-23782: Fixed possible memory leak in _PyTraceback_Add() and exception loss in PyTraceBack_Here().

- bpo-28183: Optimize and cleanup dict iteration.

- bpo-26081: Added C implementation of asyncio.Future. Original patch by Yury Selivanov.

- bpo-28379: Added sanity checks and tests for PyUnicode_CopyCharacters(). Patch by Xiang Zhang.

- bpo-28376: The type of long range iterator is now registered as Iterator. Patch by Oren Milman.

- bpo-28376: Creating instances of range_iterator by calling range_iterator type now is disallowed. Calling iter() on range instance is the only way. Patch by Oren Milman.

- bpo-26906: Resolving special methods of uninitialized type now causes implicit initialization of the type instead of a fail.

- bpo-18287: PyType_Ready() now checks that tp_name is not NULL. Original patch by Niklas Koep.

- bpo-24098: Fixed possible crash when AST is changed in process of compiling it.

- bpo-28201: Dict reduces possibility of 2nd conflict in hash table when hashes have same lower bits.

- bpo-28350: String constants with null character no longer interned.

- bpo-26617: Fix crash when GC runs during weakref callbacks.

- bpo-27942: String constants now interned recursively in tuples and frozensets.

- bpo-28289: ImportError.__init__ now resets not specified attributes.

- bpo-21578: Fixed misleading error message when ImportError called with invalid keyword args.

- bpo-28203: Fix incorrect type in complex(1.0, {2:3}) error message. Patch by Soumya Sharma.

- bpo-28086: Single var-positional argument of tuple subtype was passed unscathed to the C-defined function. Now it is converted to exact tuple.

- bpo-28214: Now __set_name__ is looked up on the class instead of the instance.

- bpo-27955: Fallback on reading /dev/urandom device when the getrandom() syscall fails with EPERM, for example when blocked by SECCOMP.

- bpo-28192: Don’t import readline in isolated mode.

- bpo-27441: Remove some redundant assignments to ob_size in longobject.c. Thanks Oren Milman.

- bpo-27222: Clean up redundant code in long_rshift function. Thanks Oren Milman.

- Upgrade internal unicode databases to Unicode version 9.0.0.

- bpo-28131: Fix a regression in zipimport’s compile_source(). zipimport should use the same optimization level as the interpreter.

- bpo-28126: Replace Py_MEMCPY with memcpy(). Visual Studio can properly optimize memcpy().

- bpo-28120: Fix dict.pop() for splitted dictionary when trying to remove a “pending key” (Not yet inserted in split-table). Patch by Xiang Zhang.

- bpo-26182: Raise DeprecationWarning when async and await keywords are used as variable/attribute/class/function name.

- bpo-26182: Fix a refleak in code that raises DeprecationWarning.

- bpo-28721: Fix asynchronous generators aclose() and athrow() to handle StopAsyncIteration propagation properly.

- bpo-26110: Speed-up method calls: add LOAD_METHOD and CALL_METHOD opcodes.

### Library

- bpo-31499: xml.etree: Fix a crash when a parser is part of a reference cycle.

- bpo-31482: `random.seed()` now works with bytes in version=1

- bpo-28556: typing.get_type_hints now finds the right globalns for classes and modules by default (when no `globalns` was specified by the caller).

- bpo-28556: Speed improvements to the `typing` module. Original PRs by Ivan Levkivskyi and Mitar.

- bpo-31544: The C accelerator module of ElementTree ignored exceptions raised when looking up TreeBuilder target methods in XMLParser().

- bpo-31234: socket.create_connection() now fixes manually a reference cycle: clear the variable storing the last exception on success.

- bpo-31457: LoggerAdapter objects can now be nested.

- bpo-31431: SSLContext.check_hostname now automatically sets SSLContext.verify_mode to ssl.CERT_REQUIRED instead of failing with a ValueError.

- bpo-31233: socketserver.ThreadingMixIn now keeps a list of non-daemonic threads to wait until all these threads complete in server_close().

- bpo-28638: Changed the implementation strategy for collections.namedtuple() to substantially reduce the use of exec() in favor of precomputed methods. As a result, the verbose parameter and _source attribute are no longer supported. The benefits include 1) having a smaller memory footprint for applications using multiple named tuples, 2) faster creation of the named tuple class (approx 4x to 6x depending on how it is measured), and 3) minor speed-ups for instance creation using __new__, _make, and _replace. (The primary patch contributor is Jelle Zijlstra with further improvements by INADA Naoki, Serhiy Storchaka, and Raymond Hettinger.)

- bpo-31400: Improves SSL error handling to avoid losing error numbers.

- bpo-27629: Make return types of SSLContext.wrap_bio() and SSLContext.wrap_socket() customizable.

- bpo-28958: ssl.SSLContext() now uses OpenSSL error information when a context cannot be instantiated.

- bpo-28182: The SSL module now raises SSLCertVerificationError when OpenSSL fails to verify the peer’s certificate. The exception contains more information about the error.

- bpo-27340: SSLSocket.sendall() now uses memoryview to create slices of data. This fixes support for all bytes-like object. It is also more efficient and avoids costly copies.

- bpo-14191: A new function `argparse.ArgumentParser.parse_intermixed_args` provides the ability to parse command lines where there user intermixes options and positional arguments.

- bpo-31178: Fix string concatenation bug in rare error path in the subprocess module

- bpo-31350: Micro-optimize `asyncio._get_running_loop()` to become up to 10% faster.

- bpo-31170: expat: Update libexpat from 2.2.3 to 2.2.4. Fix copying of partial characters for UTF-8 input (libexpat bug 115): https://github.com/libexpat/libexpat/issues/115

- bpo-29136: Add TLS 1.3 cipher suites and OP_NO_TLSv1_3.

- bpo-1198569: `string.Template` subclasses can optionally define `braceidpattern` if they want to specify different placeholder patterns inside and outside the braces. If None (the default) it falls back to `idpattern`.

- bpo-31326: concurrent.futures.ProcessPoolExecutor.shutdown() now explicitly closes the call queue. Moreover, shutdown(wait=True) now also join the call queue thread, to prevent leaking a dangling thread.

- bpo-27144: The `map()` and `as_completed()` iterators in `concurrent.futures` now avoid keeping a reference to yielded objects.

- bpo-31281: Fix `fileinput.FileInput(files, inplace=True)` when `files` contain `pathlib.Path` objects.

- bpo-10746: Fix ctypes producing wrong PEP 3118 type codes for integer types.

- bpo-27584: `AF_VSOCK` has been added to the socket interface which allows communication between virtual machines and their host.

- bpo-22536: The subprocess module now sets the filename when FileNotFoundError is raised on POSIX systems due to the executable or cwd not being found.

- bpo-29741: Update some methods in the _pyio module to also accept integer types. Patch by Oren Milman.

- bpo-31249: concurrent.futures: WorkItem.run() used by ThreadPoolExecutor now breaks a reference cycle between an exception object and the WorkItem object.

- bpo-31247: xmlrpc.server now explicitly breaks reference cycles when using sys.exc_info() in code handling exceptions.

- bpo-23835: configparser: reading defaults in the `ConfigParser()` constructor is now using `read_dict()`, making its behavior consistent with the rest of the parser. Non-string keys and values in the defaults dictionary are now being implicitly converted to strings. Patch by James Tocknell.

- bpo-31238: pydoc: the stop() method of the private ServerThread class now waits until DocServer.serve_until_quit() completes and then explicitly sets its docserver attribute to None to break a reference cycle.

- bpo-5001: Many asserts in `multiprocessing` are now more informative, and some error types have been changed to more specific ones.

- bpo-31109: Convert zipimport to use Argument Clinic.

- bpo-30102: The ssl and hashlib modules now call OPENSSL_add_all_algorithms_noconf() on OpenSSL < 1.1.0. The function detects CPU features and enables optimizations on some CPU architectures such as POWER8. Patch is based on research from Gustavo Serra Scalet.

- bpo-18966: Non-daemonic threads created by a multiprocessing.Process are now joined on child exit.

- bpo-31183: `dis` now works with asynchronous generator and coroutine objects. Patch by George Collins based on diagnosis by Luciano Ramalho.

- bpo-5001: There are a number of uninformative asserts in the `multiprocessing` module, as noted in issue 5001. This change fixes two of the most potentially problematic ones, since they are in error-reporting code, in the `multiprocessing.managers.convert_to_error` function. (It also makes more informative a ValueError message.) The only potentially problematic change is that the AssertionError is now a TypeError; however, this should also help distinguish it from an AssertionError being reported by the function/its caller (such as in issue 31169). - Patch by Allen W. Smith (drallensmith on github).

- bpo-31185: Fixed miscellaneous errors in asyncio speedup module.

- bpo-31151: socketserver.ForkingMixIn.server_close() now waits until all child processes completed to prevent leaking zombie processes.

- bpo-31072: Add an `include_file` parameter to `zipapp.create_archive()`

- bpo-24700: Optimize array.array comparison. It is now from 10x up to 70x faster when comparing arrays holding values of the same integer type.

- bpo-31135: ttk: fix the destroy() method of LabeledScale and OptionMenu classes. Call the parent destroy() method even if the used attribute doesn’t exist. The LabeledScale.destroy() method now also explicitly clears label and scale attributes to help the garbage collector to destroy all widgets.

- bpo-31107: Fix `copyreg._slotnames()` mangled attribute calculation for classes whose name begins with an underscore. Patch by Shane Harvey.

- bpo-31080: Allow `logging.config.fileConfig` to accept kwargs and/or args.

- bpo-30897: `pathlib.Path` objects now include an `is_mount()` method (only implemented on POSIX). This is similar to `os.path.ismount(p)`. Patch by Cooper Ry Lees.

- bpo-31061: Fixed a crash when using asyncio and threads.

- bpo-30987: Added support for CAN ISO-TP protocol in the socket module.

- bpo-30522: Added a `setStream` method to `logging.StreamHandler` to allow the stream to be set after creation.

- bpo-30502: Fix handling of long oids in ssl. Based on patch by Christian Heimes.

- bpo-5288: Support tzinfo objects with sub-minute offsets.

- bpo-30919: Fix shared memory performance regression in multiprocessing in 3.x. Shared memory used anonymous memory mappings in 2.x, while 3.x mmaps actual files. Try to be careful to do as little disk I/O as possible.

- bpo-26732: Fix too many fds in processes started with the “forkserver” method. A child process would inherit as many fds as the number of still-running children.

- bpo-29403: Fix `unittest.mock`’s autospec to not fail on method-bound builtin functions. Patch by Aaron Gallagher.

- bpo-30961: Fix decrementing a borrowed reference in tracemalloc.

- bpo-19896: Fix multiprocessing.sharedctypes to recognize typecodes `'q'` and `'Q'`.

- bpo-30946: Remove obsolete code in readline module for platforms where GNU readline is older than 2.1 or where select() is not available.

- bpo-25684: Change `ttk.OptionMenu` radiobuttons to be unique across instances of `OptionMenu`.

- bpo-30886: Fix multiprocessing.Queue.join_thread(): it now waits until the thread completes, even if the thread was started by the same process which created the queue.

- bpo-29854: Fix segfault in readline when using readline’s history-size option. Patch by Nir Soffer.

- bpo-30794: Added multiprocessing.Process.kill method to terminate using the SIGKILL signal on Unix.

- bpo-30319: socket.close() now ignores ECONNRESET error.

- bpo-30828: Fix out of bounds write in `asyncio.CFuture.remove_done_callback()`.

- bpo-30302: Use keywords in the `repr` of `datetime.timedelta`.

- bpo-30807: signal.setitimer() may disable the timer when passed a tiny value. Tiny values (such as 1e-6) are valid non-zero values for setitimer(), which is specified as taking microsecond-resolution intervals. However, on some platform, our conversion routine could convert 1e-6 into a zero interval, therefore disabling the timer instead of (re-)scheduling it.

- bpo-30441: Fix bug when modifying os.environ while iterating over it

- bpo-29585: Avoid importing `sysconfig` from `site` to improve startup speed. Python startup is about 5% faster on Linux and 30% faster on macOS.

- bpo-29293: Add missing parameter “n” on multiprocessing.Condition.notify(). The doc claims multiprocessing.Condition behaves like threading.Condition, but its notify() method lacked the optional “n” argument (to specify the number of sleepers to wake up) that threading.Condition.notify() accepts.

- bpo-30532: Fix email header value parser dropping folding white space in certain cases.

- bpo-30596: Add a `close()` method to `multiprocessing.Process`.

- bpo-9146: Fix a segmentation fault in _hashopenssl when standard hash functions such as md5 are not available in the linked OpenSSL library. As in some special FIPS-140 build environments.

- bpo-29169: Update zlib to 1.2.11.

- bpo-30119: ftplib.FTP.putline() now throws ValueError on commands that contains CR or LF. Patch by Donghee Na.

- bpo-30879: os.listdir() and os.scandir() now emit bytes names when called with bytes-like argument.

- bpo-30746: Prohibited the ‘=’ character in environment variable names in `os.putenv()` and `os.spawn*()`.

- bpo-30664: The description of a unittest subtest now preserves the order of keyword arguments of TestCase.subTest().

- bpo-21071: struct.Struct.format type is now `str` instead of `bytes`.

- bpo-29212: Fix concurrent.futures.thread.ThreadPoolExecutor threads to have a non repr() based thread name by default when no thread_name_prefix is supplied. They will now identify themselves as “ThreadPoolExecutor-y_n”.

- bpo-29755: Fixed the lgettext() family of functions in the gettext module. They now always return bytes.

- bpo-30616: Functional API of enum allows to create empty enums. Patched by Donghee Na

- bpo-30038: Fix race condition between signal delivery and wakeup file descriptor. Patch by Nathaniel Smith.

- bpo-23894: lib2to3 now recognizes `rb'...'` and `f'...'` strings.

- bpo-24744: pkgutil.walk_packages function now raises ValueError if path is a string. Patch by Sanyam Khurana.

- bpo-24484: Avoid race condition in multiprocessing cleanup.

- bpo-30589: Fix multiprocessing.Process.exitcode to return the opposite of the signal number when the process is killed by a signal (instead of 255) when using the “forkserver” method.

- bpo-28994: The traceback no longer displayed for SystemExit raised in a callback registered by atexit.

- bpo-30508: Don’t log exceptions if Task/Future “cancel()” method was called.

- bpo-30645: Fix path calculation in `imp.load_package()`, fixing it for cases when a package is only shipped with bytecodes. Patch by Alexandru Ardelean.

- bpo-11822: The dis.dis() function now is able to disassemble nested code objects.

- bpo-30624: selectors does not take KeyboardInterrupt and SystemExit into account, leaving a fd in a bad state in case of error. Patch by Giampaolo Rodola’.

- bpo-30595: multiprocessing.Queue.get() with a timeout now polls its reader in non-blocking mode if it succeeded to acquire the lock but the acquire took longer than the timeout.

- bpo-28556: Updates to typing module: Add generic AsyncContextManager, add support for ContextManager on all versions. Original PRs by Jelle Zijlstra and Ivan Levkivskyi

- bpo-30605: re.compile() no longer raises a BytesWarning when compiling a bytes instance with misplaced inline modifier. Patch by Roy Williams.

- bpo-29870: Fix ssl sockets leaks when connection is aborted in asyncio/ssl implementation. Patch by Michaël Sghaïer.

- bpo-29743: Closing transport during handshake process leaks open socket. Patch by Nikolay Kim

- bpo-27585: Fix waiter cancellation in asyncio.Lock. Patch by Mathieu Sornay.

- bpo-30014: modify() method of poll(), epoll() and devpoll() based classes of selectors module is around 10% faster. Patch by Giampaolo Rodola’.

- bpo-30418: On Windows, subprocess.Popen.communicate() now also ignore EINVAL on stdin.write() if the child process is still running but closed the pipe.

- bpo-30463: Addded empty __slots__ to abc.ABC. This allows subclassers to deny __dict__ and __weakref__ creation. Patch by Aaron Hall.

- bpo-30520: Loggers are now pickleable.

- bpo-30557: faulthandler now correctly filters and displays exception codes on Windows

- bpo-30526: Add TextIOWrapper.reconfigure() and a TextIOWrapper.write_through attribute.

- bpo-30245: Fix possible overflow when organize struct.pack_into error message. Patch by Yuan Liu.

- bpo-30378: Fix the problem that logging.handlers.SysLogHandler cannot handle IPv6 addresses.

- bpo-16500: Allow registering at-fork handlers.

- bpo-30470: Deprecate invalid ctypes call protection on Windows. Patch by Mariatta Wijaya.

- bpo-30414: multiprocessing.Queue._feed background running thread do not break from main loop on exception.

- bpo-30003: Fix handling escape characters in HZ codec. Based on patch by Ma Lin.

- bpo-30149: inspect.signature() now supports callables with variable-argument parameters wrapped with partialmethod. Patch by Donghee Na.

- bpo-30436: importlib.find_spec() raises ModuleNotFoundError instead of AttributeError if the specified parent module is not a package (i.e. lacks a __path__ attribute).

- bpo-30301: Fix AttributeError when using SimpleQueue.empty() under spawn and forkserver start methods.

- bpo-30375: Warnings emitted when compile a regular expression now always point to the line in the user code. Previously they could point into inners of the re module if emitted from inside of groups or conditionals.

- bpo-30329: imaplib and poplib now catch the Windows socket WSAEINVAL error (code 10022) on shutdown(SHUT_RDWR): An invalid operation was attempted. This error occurs sometimes on SSL connections.

- bpo-29196: Removed previously deprecated in Python 2.4 classes Plist, Dict and _InternalDict in the plistlib module. Dict values in the result of functions readPlist() and readPlistFromBytes() are now normal dicts. You no longer can use attribute access to access items of these dictionaries.

- bpo-9850: The `macpath` is now deprecated and will be removed in Python 3.8.

- bpo-30299: Compiling regular expression in debug mode on CPython now displays the compiled bytecode in human readable form.

- bpo-30048: Fixed `Task.cancel()` can be ignored when the task is running coroutine and the coroutine returned without any more `await`.

- bpo-30266: contextlib.AbstractContextManager now supports anti-registration by setting __enter__ = None or __exit__ = None, following the pattern introduced in bpo-25958. Patch by Jelle Zijlstra.

- bpo-30340: Enhanced regular expressions optimization. This increased the performance of matching some patterns up to 25 times.

- bpo-30298: Weaken the condition of deprecation warnings for inline modifiers. Now allowed several subsequential inline modifiers at the start of the pattern (e.g. `'(?i)(?s)...'`). In verbose mode whitespaces and comments now are allowed before and between inline modifiers (e.g. `'(?x) (?i) (?s)...'`).

- bpo-30285: Optimized case-insensitive matching and searching of regular expressions.

- bpo-29990: Fix range checking in GB18030 decoder. Original patch by Ma Lin.

- bpo-29979: rewrite cgi.parse_multipart, reusing the FieldStorage class and making its results consistent with those of FieldStorage for multipart/form-data requests. Patch by Pierre Quentel.

- bpo-30243: Removed the __init__ methods of _json’s scanner and encoder. Misusing them could cause memory leaks or crashes. Now scanner and encoder objects are completely initialized in the __new__ methods.

- bpo-30215: Compiled regular expression objects with the re.LOCALE flag no longer depend on the locale at compile time. Only the locale at matching time affects the result of matching.

- bpo-30185: Avoid KeyboardInterrupt tracebacks in forkserver helper process when Ctrl-C is received.

- bpo-30103: binascii.b2a_uu() and uu.encode() now support using `'`'` as zero instead of space.

- bpo-28556: Various updates to typing module: add typing.NoReturn type, use WrapperDescriptorType, minor bug-fixes. Original PRs by Jim Fasarakis-Hilliard and Ivan Levkivskyi.

- bpo-30205: Fix getsockname() for unbound AF_UNIX sockets on Linux.

- bpo-30228: The seek() and tell() methods of io.FileIO now set the internal seekable attribute to avoid one syscall on open() (in buffered or text mode).

- bpo-30190: unittest’s assertAlmostEqual and assertNotAlmostEqual provide a better message in case of failure which includes the difference between left and right arguments. (patch by Giampaolo Rodola’)

- bpo-30101: Add support for curses.A_ITALIC.

- bpo-29822: inspect.isabstract() now works during __init_subclass__. Patch by Nate Soares.

- bpo-29960: Preserve generator state when _random.Random.setstate() raises an exception. Patch by Bryan Olson.

- bpo-30070: Fixed leaks and crashes in errors handling in the parser module.

- bpo-22352: Column widths in the output of dis.dis() are now adjusted for large line numbers and instruction offsets.

- bpo-30061: Fixed crashes in IOBase methods __next__() and readlines() when readline() or __next__() respectively return non-sizeable object. Fixed possible other errors caused by not checking results of PyObject_Size(), PySequence_Size(), or PyMapping_Size().

- bpo-30218: Fix PathLike support for shutil.unpack_archive. Patch by Jelle Zijlstra.

- bpo-10076: Compiled regular expression and match objects in the re module now support copy.copy() and copy.deepcopy() (they are considered atomic).

- bpo-30068: _io._IOBase.readlines will check if it’s closed first when hint is present.

- bpo-29694: Fixed race condition in pathlib mkdir with flags parents=True. Patch by Armin Rigo.

- bpo-29692: Fixed arbitrary unchaining of RuntimeError exceptions in contextlib.contextmanager. Patch by Siddharth Velankar.

- bpo-26187: Test that sqlite3 trace callback is not called multiple times when schema is changing. Indirectly fixed by switching to use sqlite3_prepare_v2() in bpo-9303. Patch by Aviv Palivoda.

- bpo-30017: Allowed calling the close() method of the zip entry writer object multiple times. Writing to a closed writer now always produces a ValueError.

- bpo-29998: Pickling and copying ImportError now preserves name and path attributes.

- bpo-29995: re.escape() now escapes only regex special characters.

- bpo-29962: Add math.remainder operation, implementing remainder as specified in IEEE 754.

- bpo-29649: Improve struct.pack_into() exception messages for problems with the buffer size and offset. Patch by Andrew Nester.

- bpo-29654: Support If-Modified-Since HTTP header (browser cache). Patch by Pierre Quentel.

- bpo-29931: Fixed comparison check for ipaddress.ip_interface objects. Patch by Sanjay Sundaresan.

- bpo-29953: Fixed memory leaks in the replace() method of datetime and time objects when pass out of bound fold argument.

- bpo-29942: Fix a crash in itertools.chain.from_iterable when encountering long runs of empty iterables.

- bpo-10030: Sped up reading encrypted ZIP files by 2 times.

- bpo-29204: Element.getiterator() and the html parameter of XMLParser() were deprecated only in the documentation (since Python 3.2 and 3.4 correspondingly). Now using them emits a deprecation warning.

- bpo-27863: Fixed multiple crashes in ElementTree caused by race conditions and wrong types.

- bpo-25996: Added support of file descriptors in os.scandir() on Unix. os.fwalk() is sped up by 2 times by using os.scandir().

- bpo-28699: Fixed a bug in pools in multiprocessing.pool that raising an exception at the very first of an iterable may swallow the exception or make the program hang. Patch by Davin Potts and Xiang Zhang.

- bpo-23890: unittest.TestCase.assertRaises() now manually breaks a reference cycle to not keep objects alive longer than expected.

- bpo-29901: The zipapp module now supports general path-like objects, not just pathlib.Path.

- bpo-25803: Avoid incorrect errors raised by Path.mkdir(exist_ok=True) when the OS gives priority to errors such as EACCES over EEXIST.

- bpo-29861: Release references to tasks, their arguments and their results as soon as they are finished in multiprocessing.Pool.

- bpo-19930: The mode argument of os.makedirs() no longer affects the file permission bits of newly created intermediate-level directories.

- bpo-29884: faulthandler: Restore the old sigaltstack during teardown. Patch by Christophe Zeitouny.

- bpo-25455: Fixed crashes in repr of recursive buffered file-like objects.

- bpo-29800: Fix crashes in partial.__repr__ if the keys of partial.keywords are not strings. Patch by Michael Seifert.

- bpo-8256: Fixed possible failing or crashing input() if attributes “encoding” or “errors” of sys.stdin or sys.stdout are not set or are not strings.

- bpo-28692: Using non-integer value for selecting a plural form in gettext is now deprecated.

- bpo-26121: Use C library implementation for math functions erf() and erfc().

- bpo-29619: os.stat() and os.DirEntry.inode() now convert inode (st_ino) using unsigned integers.

- bpo-28298: Fix a bug that prevented array ‘Q’, ‘L’ and ‘I’ from accepting big intables (objects that have __int__) as elements.

- bpo-29645: Speed up importing the webbrowser module. webbrowser.register() is now thread-safe.

- bpo-28231: The zipfile module now accepts path-like objects for external paths.

- bpo-26915: index() and count() methods of collections.abc.Sequence now check identity before checking equality when do comparisons.

- bpo-28682: Added support for bytes paths in os.fwalk().

- bpo-29728: Add new `socket.TCP_NOTSENT_LOWAT` (Linux 3.12) constant. Patch by Nathaniel J. Smith.

- bpo-29623: Allow use of path-like object as a single argument in ConfigParser.read(). Patch by David Ellis.

- bpo-9303: Migrate sqlite3 module to _v2 API. Patch by Aviv Palivoda.

- bpo-28963: Fix out of bound iteration in asyncio.Future.remove_done_callback implemented in C.

- bpo-29704: asyncio.subprocess.SubprocessStreamProtocol no longer closes before all pipes are closed.

- bpo-29271: Fix Task.current_task and Task.all_tasks implemented in C to accept None argument as their pure Python implementation.

- bpo-29703: Fix asyncio to support instantiation of new event loops in child processes.

- bpo-29615: SimpleXMLRPCDispatcher no longer chains KeyError (or any other exception) to exception(s) raised in the dispatched methods. Patch by Petr Motejlek.

- bpo-7769: Method register_function() of xmlrpc.server.SimpleXMLRPCDispatcher and its subclasses can now be used as a decorator.

- bpo-29376: Fix assertion error in threading._DummyThread.is_alive().

- bpo-28624: Add a test that checks that cwd parameter of Popen() accepts PathLike objects. Patch by Sayan Chowdhury.

- bpo-28518: Start a transaction implicitly before a DML statement. Patch by Aviv Palivoda.

- bpo-29742: get_extra_info() raises exception if get called on closed ssl transport. Patch by Nikolay Kim.

- bpo-16285: urllib.parse.quote is now based on RFC 3986 and hence includes ‘~’ in the set of characters that is not quoted by default. Patch by Christian Theune and Ratnadeep Debnath.

- bpo-29532: Altering a kwarg dictionary passed to functools.partial() no longer affects a partial object after creation.

- bpo-29110: Fix file object leak in aifc.open() when file is given as a filesystem path and is not in valid AIFF format. Patch by Anthony Zhang.

- bpo-22807: Add uuid.SafeUUID and uuid.UUID.is_safe to relay information from the platform about whether generated UUIDs are generated with a multiprocessing safe method.

- bpo-29576: Improve some deprecations in importlib. Some deprecated methods now emit DeprecationWarnings and have better descriptive messages.

- bpo-29534: Fixed different behaviour of Decimal.from_float() for _decimal and _pydecimal. Thanks Andrew Nester.

- bpo-10379: locale.format_string now supports the ‘monetary’ keyword argument, and locale.format is deprecated.

- bpo-29851: importlib.reload() now raises ModuleNotFoundError if the module lacks a spec.

- bpo-28556: Various updates to typing module: typing.Counter, typing.ChainMap, improved ABC caching, etc. Original PRs by Jelle Zijlstra, Ivan Levkivskyi, Manuel Krebber, and Łukasz Langa.

- bpo-29100: Fix datetime.fromtimestamp() regression introduced in Python 3.6.0: check minimum and maximum years.

- bpo-29416: Prevent infinite loop in pathlib.Path.mkdir

- bpo-29444: Fixed out-of-bounds buffer access in the group() method of the match object. Based on patch by WGH.

- bpo-29377: Add WrapperDescriptorType, MethodWrapperType, and MethodDescriptorType built-in types to types module. Original patch by Manuel Krebber.

- bpo-29218: Unused install_misc command is now removed. It has been documented as unused since 2000. Patch by Eric N. Vander Weele.

- bpo-29368: The extend() method is now called instead of the append() method when unpickle collections.deque and other list-like objects. This can speed up unpickling to 2 times.

- bpo-29338: The help of a builtin or extension class now includes the constructor signature if __text_signature__ is provided for the class.

- bpo-29335: Fix subprocess.Popen.wait() when the child process has exited to a stopped instead of terminated state (ex: when under ptrace).

- bpo-29290: Fix a regression in argparse that help messages would wrap at non-breaking spaces.

- bpo-28735: Fixed the comparison of mock.MagickMock with mock.ANY.

- bpo-29197: Removed deprecated function ntpath.splitunc().

- bpo-29210: Removed support of deprecated argument “exclude” in tarfile.TarFile.add().

- bpo-29219: Fixed infinite recursion in the repr of uninitialized ctypes.CDLL instances.

- bpo-29192: Removed deprecated features in the http.cookies module.

- bpo-29193: A format string argument for string.Formatter.format() is now positional-only.

- bpo-29195: Removed support of deprecated undocumented keyword arguments in methods of regular expression objects.

- bpo-28969: Fixed race condition in C implementation of functools.lru_cache. KeyError could be raised when cached function with full cache was simultaneously called from different threads with the same uncached arguments.

- bpo-20804: The unittest.mock.sentinel attributes now preserve their identity when they are copied or pickled.

- bpo-29142: In urllib.request, suffixes in no_proxy environment variable with leading dots could match related hostnames again (e.g. .b.c matches a.b.c). Patch by Milan Oberkirch.

- bpo-28961: Fix unittest.mock._Call helper: don’t ignore the name parameter anymore. Patch written by Jiajun Huang.

- bpo-15812: inspect.getframeinfo() now correctly shows the first line of a context. Patch by Sam Breese.

- bpo-28985: Update authorizer constants in sqlite3 module. Patch by Dingyuan Wang.

- bpo-29079: Prevent infinite loop in pathlib.resolve() on Windows

- bpo-13051: Fixed recursion errors in large or resized curses.textpad.Textbox. Based on patch by Tycho Andersen.

- bpo-9770: curses.ascii predicates now work correctly with negative integers.

- bpo-28427: old keys should not remove new values from WeakValueDictionary when collecting from another thread.

- bpo-28923: Remove editor artifacts from Tix.py.

- bpo-28871: Fixed a crash when deallocate deep ElementTree.

- bpo-19542: Fix bugs in WeakValueDictionary.setdefault() and WeakValueDictionary.pop() when a GC collection happens in another thread.

- bpo-20191: Fixed a crash in resource.prlimit() when passing a sequence that doesn’t own its elements as limits.

- bpo-16255: subprocess.Popen uses /system/bin/sh on Android as the shell, instead of /bin/sh.

- bpo-28779: multiprocessing.set_forkserver_preload() would crash the forkserver process if a preloaded module instantiated some multiprocessing objects such as locks.

- bpo-26937: The chown() method of the tarfile.TarFile class does not fail now when the grp module cannot be imported, as for example on Android platforms.

- bpo-28847: dbm.dumb now supports reading read-only files and no longer writes the index file when it is not changed. A deprecation warning is now emitted if the index file is missed and recreated in the ‘r’ and ‘w’ modes (will be an error in future Python releases).

- bpo-27030: Unknown escapes consisting of `'\'` and an ASCII letter in re.sub() replacement templates regular expressions now are errors.

- bpo-28835: Fix a regression introduced in warnings.catch_warnings(): call warnings.showwarning() if it was overridden inside the context manager.

- bpo-27172: To assist with upgrades from 2.7, the previously documented deprecation of `inspect.getfullargspec()` has been reversed. This decision may be revisited again after the Python 2.7 branch is no longer officially supported.

- bpo-28740: Add sys.getandroidapilevel(): return the build time API version of Android as an integer. Function only available on Android.

- bpo-26273: Add new `socket.TCP_CONGESTION` (Linux 2.6.13) and `socket.TCP_USER_TIMEOUT` (Linux 2.6.37) constants. Patch written by Omar Sandoval.

- bpo-28752: Restored the __reduce__() methods of datetime objects.

- bpo-28727: Regular expression patterns, _sre.SRE_Pattern objects created by re.compile(), become comparable (only x==y and x!=y operators). This change should fix the bpo-18383: don’t duplicate warning filters when the warnings module is reloaded (thing usually only done in unit tests).

- bpo-20572: Remove the subprocess.Popen.wait endtime parameter. It was deprecated in 3.4 and undocumented prior to that.

- bpo-25659: In ctypes, prevent a crash calling the from_buffer() and from_buffer_copy() methods on abstract classes like Array.

- bpo-28548: In the “http.server” module, parse the protocol version if possible, to avoid using HTTP 0.9 in some error responses.

- bpo-19717: Makes Path.resolve() succeed on paths that do not exist. Patch by Vajrasky Kok

- bpo-28563: Fixed possible DoS and arbitrary code execution when handle plural form selections in the gettext module. The expression parser now supports exact syntax supported by GNU gettext.

- bpo-28387: Fixed possible crash in _io.TextIOWrapper deallocator when the garbage collector is invoked in other thread. Based on patch by Sebastian Cufre.

- bpo-27517: LZMA compressor and decompressor no longer raise exceptions if given empty data twice. Patch by Benjamin Fogle.

- bpo-28549: Fixed segfault in curses’s addch() with ncurses6.

- bpo-28449: tarfile.open() with mode “r” or “r:” now tries to open a tar file with compression before trying to open it without compression. Otherwise it had 50% chance failed with ignore_zeros=True.

- bpo-23262: The webbrowser module now supports Firefox 36+ and derived browsers. Based on patch by Oleg Broytman.

- bpo-24241: The webbrowser in an X environment now prefers using the default browser directly. Also, the webbrowser register() function now has a documented ‘preferred’ argument, to specify browsers to be returned by get() with no arguments. Patch by David Steele

- bpo-27939: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused by representing the scale as float value internally in Tk. tkinter.IntVar now works if float value is set to underlying Tk variable.

- bpo-28255: calendar.TextCalendar.prweek() no longer prints a space after a weeks’s calendar. calendar.TextCalendar.pryear() no longer prints redundant newline after a year’s calendar. Based on patch by Xiang Zhang.

- bpo-28255: calendar.TextCalendar.prmonth() no longer prints a space at the start of new line after printing a month’s calendar. Patch by Xiang Zhang.

- bpo-20491: The textwrap.TextWrapper class now honors non-breaking spaces. Based on patch by Kaarle Ritvanen.

- bpo-28353: os.fwalk() no longer fails on broken links.

- bpo-28430: Fix iterator of C implemented asyncio.Future doesn’t accept non-None value is passed to it.send(val).

- bpo-27025: Generated names for Tkinter widgets now start by the “!” prefix for readability.

- bpo-25464: Fixed HList.header_exists() in tkinter.tix module by addin a workaround to Tix library bug.

- bpo-28488: shutil.make_archive() no longer adds entry “./” to ZIP archive.

- bpo-25953: re.sub() now raises an error for invalid numerical group reference in replacement template even if the pattern is not found in the string. Error message for invalid group reference now includes the group index and the position of the reference. Based on patch by SilentGhost.

- bpo-28469: timeit now uses the sequence 1, 2, 5, 10, 20, 50,… instead of 1, 10, 100,… for autoranging.

- bpo-28115: Command-line interface of the zipfile module now uses argparse. Added support of long options.

- bpo-18219: Optimize csv.DictWriter for large number of columns. Patch by Mariatta Wijaya.

- bpo-28448: Fix C implemented asyncio.Future didn’t work on Windows.

- bpo-23214: In the “io” module, the argument to BufferedReader and BytesIO’s read1() methods is now optional and can be -1, matching the BufferedIOBase specification.

- bpo-28480: Fix error building socket module when multithreading is disabled.

- bpo-28240: timeit: remove `-c/--clock` and `-t/--time` command line options which were deprecated since Python 3.3.

- bpo-28240: timeit now repeats the benchmarks 5 times instead of only 3 to make benchmarks more reliable.

- bpo-28240: timeit autorange now uses a single loop iteration if the benchmark takes less than 10 seconds, instead of 10 iterations. “python3 -m timeit -s ‘import time’ ‘time.sleep(1)’” now takes 4 seconds instead of 40 seconds.

- Distutils.sdist now looks for README and setup.py files with case sensitivity. This behavior matches that found in Setuptools 6.0 and later. See setuptools 100 for rationale.

- bpo-24452: Make webbrowser support Chrome on Mac OS X. Patch by Ned Batchelder.

- bpo-20766: Fix references leaked by pdb in the handling of SIGINT handlers.

- bpo-27998: Fixed bytes path support in os.scandir() on Windows. Patch by Eryk Sun.

- bpo-28317: The disassembler now decodes FORMAT_VALUE argument.

- bpo-28380: unittest.mock Mock autospec functions now properly support assert_called, assert_not_called, and assert_called_once.

- bpo-28229: lzma module now supports pathlib.

- bpo-28321: Fixed writing non-BMP characters with binary format in plistlib.

- bpo-28225: bz2 module now supports pathlib. Initial patch by Ethan Furman.

- bpo-28227: gzip now supports pathlib. Patch by Ethan Furman.

- bpo-28332: Deprecated silent truncations in socket.htons and socket.ntohs. Original patch by Oren Milman.

- bpo-27358: Optimized merging var-keyword arguments and improved error message when passing a non-mapping as a var-keyword argument.

- bpo-28257: Improved error message when passing a non-iterable as a var-positional argument. Added opcode BUILD_TUPLE_UNPACK_WITH_CALL.

- bpo-28322: Fixed possible crashes when unpickle itertools objects from incorrect pickle data. Based on patch by John Leitch.

- bpo-28228: imghdr now supports pathlib.

- bpo-28226: compileall now supports pathlib.

- bpo-28314: Fix function declaration (C flags) for the getiterator() method of xml.etree.ElementTree.Element.

- bpo-28148: Stop using localtime() and gmtime() in the time module. Introduced platform independent _PyTime_localtime API that is similar to POSIX localtime_r, but available on all platforms. Patch by Ed Schouten.

- bpo-28253: Fixed calendar functions for extreme months: 0001-01 and 9999-12. Methods itermonthdays() and itermonthdays2() are reimplemented so that they don’t call itermonthdates() which can cause datetime.date under/overflow.

- bpo-28275: Fixed possible use after free in the decompress() methods of the LZMADecompressor and BZ2Decompressor classes. Original patch by John Leitch.

- bpo-27897: Fixed possible crash in sqlite3.Connection.create_collation() if pass invalid string-like object as a name. Patch by Xiang Zhang.

- bpo-18844: random.choices() now has k as a keyword-only argument to improve the readability of common cases and come into line with the signature used in other languages.

- bpo-18893: Fix invalid exception handling in Lib/ctypes/macholib/dyld.py. Patch by Madison May.

- bpo-27611: Fixed support of default root window in the tkinter.tix module. Added the master parameter in the DisplayStyle constructor.

- bpo-27348: In the traceback module, restore the formatting of exception messages like “Exception: None”. This fixes a regression introduced in 3.5a2.

- bpo-25651: Allow false values to be used for msg parameter of subTest().

- bpo-27778: Fix a memory leak in os.getrandom() when the getrandom() is interrupted by a signal and a signal handler raises a Python exception.

- bpo-28200: Fix memory leak on Windows in the os module (fix path_converter() function).

- bpo-25400: RobotFileParser now correctly returns default values for crawl_delay and request_rate. Initial patch by Peter Wirtz.

- bpo-27932: Prevent memory leak in win32_ver().

- Fix UnboundLocalError in socket._sendfile_use_sendfile.

- bpo-28075: Check for ERROR_ACCESS_DENIED in Windows implementation of os.stat(). Patch by Eryk Sun.

- bpo-22493: Warning message emitted by using inline flags in the middle of regular expression now contains a (truncated) regex pattern. Patch by Tim Graham.

- bpo-25270: Prevent codecs.escape_encode() from raising SystemError when an empty bytestring is passed.

- bpo-28181: Get antigravity over HTTPS. Patch by Kaartic Sivaraam.

- bpo-25895: Enable WebSocket URL schemes in urllib.parse.urljoin. Patch by Gergely Imreh and Markus Holtermann.

- bpo-28114: Fix a crash in parse_envlist() when env contains byte strings. Patch by Eryk Sun.

- bpo-27599: Fixed buffer overrun in binascii.b2a_qp() and binascii.a2b_qp().

- bpo-27906: Fix socket accept exhaustion during high TCP traffic. Patch by Kevin Conway.

- bpo-28174: Handle when SO_REUSEPORT isn’t properly supported. Patch by Seth Michael Larson.

- bpo-26654: Inspect functools.partial in asyncio.Handle.__repr__. Patch by iceboy.

- bpo-26909: Fix slow pipes IO in asyncio. Patch by INADA Naoki.

- bpo-28176: Fix callbacks race in asyncio.SelectorLoop.sock_connect.

- bpo-27759: Fix selectors incorrectly retain invalid file descriptors. Patch by Mark Williams.

- bpo-28325: Remove vestigial MacOS 9 macurl2path module and its tests.

- bpo-28368: Refuse monitoring processes if the child watcher has no loop attached. Patch by Vincent Michel.

- bpo-28369: Raise RuntimeError when transport’s FD is used with add_reader, add_writer, etc.

- bpo-28370: Speedup asyncio.StreamReader.readexactly. Patch by Коренберг Марк.

- bpo-28371: Deprecate passing asyncio.Handles to run_in_executor.

- bpo-28372: Fix asyncio to support formatting of non-python coroutines.

- bpo-28399: Remove UNIX socket from FS before binding. Patch by Коренберг Марк.

- bpo-27972: Prohibit Tasks to await on themselves.

- bpo-24142: Reading a corrupt config file left configparser in an invalid state. Original patch by Florian Höch.

- bpo-29581: ABCMeta.__new__ now accepts `**kwargs`, allowing abstract base classes to use keyword parameters in __init_subclass__. Patch by Nate Soares.

- bpo-25532: inspect.unwrap() will now only try to unwrap an object sys.getrecursionlimit() times, to protect against objects which create a new object on every attribute access.

- bpo-30177: path.resolve(strict=False) no longer cuts the path after the first element not present in the filesystem. Patch by Antoine Pietri.

### Documentation

- bpo-31294: Fix incomplete code snippet in the ZeroMQSocketListener and ZeroMQSocketHandler examples and adapt them to Python 3.

- bpo-21649: Add RFC 7525 and Mozilla server side TLS links to SSL documentation.

- bpo-31128: Allow the pydoc server to bind to arbitrary hostnames.

- bpo-30803: Clarify doc on truth value testing. Original patch by Peter Thomassen.

- bpo-30176: Add missing attribute related constants in curses documentation.

- bpo-30052: the link targets for `bytes()` and `bytearray()` are now their respective type definitions, rather than the corresponding builtin function entries. Use bytes and bytearray to reference the latter. In order to ensure this and future cross-reference updates are applied automatically, the daily documentation builds now disable the default output caching features in Sphinx.

- bpo-26985: Add missing info of code object in inspect documentation.

- bpo-19824: Improve the documentation for, and links to, template strings by emphasizing their utility for internationalization, and by clarifying some usage constraints. (See also: bpo-20314, bpo-12518)

- bpo-28929: Link the documentation to its source file on GitHub.

- bpo-25008: Document smtpd.py as effectively deprecated and add a pointer to aiosmtpd, a third-party asyncio-based replacement.

- bpo-26355: Add canonical header link on each page to corresponding major version of the documentation. Patch by Matthias Bussonnier.

- bpo-29349: Fix Python 2 syntax in code for building the documentation.

- bpo-23722: The data model reference and the porting section in the 3.6 What’s New guide now cover the additional `__classcell__` handling needed for custom metaclasses to fully support PEP 487 and zero-argument `super()`.

- bpo-28513: Documented command-line interface of zipfile.

### Tests

- bpo-29639: test.support.HOST is now “localhost”, a new HOSTv4 constant has been added for your `127.0.0.1` needs, similar to the existing HOSTv6 constant.

- bpo-31320: Silence traceback in test_ssl

- bpo-31346: Prefer PROTOCOL_TLS_CLIENT and PROTOCOL_TLS_SERVER protocols for SSLContext.

- bpo-25674: Remove sha256.tbs-internet.com ssl test

- bpo-30715: Address ALPN callback changes for OpenSSL 1.1.0f. The latest version behaves like OpenSSL 1.0.2 and no longer aborts handshake.

- bpo-30822: regrtest: Exclude tzdata from regrtest –all. When running the test suite using –use=all / -u all, exclude tzdata since it makes test_datetime too slow (15-20 min on some buildbots) which then times out on some buildbots. Fix also regrtest command line parser to allow passing -u extralargefile to run test_zipfile64.

- bpo-30695: Add the `set_nomemory(start, stop)` and `remove_mem_hooks()` functions to the `_testcapi` module.

- bpo-30357: test_thread: setUp() now uses support.threading_setup() and support.threading_cleanup() to wait until threads complete to avoid random side effects on following tests. Initial patch written by Grzegorz Grzywacz.

- bpo-30197: Enhanced functions swap_attr() and swap_item() in the test.support module. They now work when delete replaced attribute or item inside the with statement. The old value of the attribute or item (or None if it doesn’t exist) now will be assigned to the target of the “as” clause, if there is one.

- bpo-24932: Use proper command line parsing in _testembed

- bpo-28950: Disallow -j0 to be combined with -T/-l in regrtest command line arguments.

- bpo-28683: Fix the tests that bind() a unix socket and raise PermissionError on Android for a non-root user.

- bpo-26936: Fix the test_socket failures on Android - getservbyname(), getservbyport() and getaddrinfo() are broken on some Android API levels.

- bpo-28666: Now test.support.rmtree is able to remove unwritable or unreadable directories.

- bpo-23839: Various caches now are cleared before running every test file.

- bpo-26944: Fix test_posix for Android where ‘id -G’ is entirely wrong or missing the effective gid.

- bpo-28409: regrtest: fix the parser of command line arguments.

- bpo-28217: Adds _testconsole module to test console input.

- bpo-26939: Add the support.setswitchinterval() function to fix test_functools hanging on the Android armv7 qemu emulator.

### Build

- bpo-31354: Allow `--with-lto` to be used on all builds, not just `make profile-opt`.

- bpo-31370: Remove support for building –without-threads. This option is not really useful anymore in the 21st century. Removing lots of conditional paths allows us to simplify the code base, including in difficult to maintain low-level internal code.

- bpo-31341: Per PEP 11, support for the IRIX operating system was removed.

- bpo-30854: Fix compile error when compiling –without-threads. Patch by Masayuki Yamamoto.

- bpo-30687: Locate msbuild.exe on Windows when building rather than vcvarsall.bat

- bpo-20210: Support the disabled marker in Setup files. Extension modules listed after this marker are not built at all, neither by the Makefile nor by setup.py.

- bpo-29941: Add `--with-assertions` configure flag to explicitly enable C `assert()` checks. Defaults to off. `--with-pydebug` implies `--with-assertions`.

- bpo-28787: Fix out-of-tree builds of Python when configured with `--with--dtrace`.

- bpo-29243: Prevent unnecessary rebuilding of Python during `make test`, `make install` and some other make targets when configured with `--enable-optimizations`.

- bpo-23404: Don’t regenerate generated files based on file modification time anymore: the action is now explicit. Replace `make touch` with `make regen-all`.

- bpo-29643: Fix `--enable-optimization` didn’t work.

- bpo-27593: sys.version and the platform module python_build(), python_branch(), and python_revision() functions now use git information rather than hg when building from a repo.

- bpo-29572: Update Windows build and OS X installers to use OpenSSL 1.0.2k.

- bpo-27659: Prohibit implicit C function declarations: use `-Werror=implicit-function-declaration` when possible (GCC and Clang, but it depends on the compiler version). Patch written by Chi Hsuan Yen.

- bpo-29384: Remove old Be OS helper scripts.

- bpo-26851: Set Android compilation and link flags.

- bpo-28768: Fix implicit declaration of function _setmode. Patch by Masayuki Yamamoto

- bpo-29080: Removes hard dependency on hg.exe from PCBuild/build.bat

- bpo-23903: Added missed names to PC/python3.def.

- bpo-28762: lockf() is available on Android API level 24, but the F_LOCK macro is not defined in android-ndk-r13.

- bpo-28538: Fix the compilation error that occurs because if_nameindex() is available on Android API level 24, but the if_nameindex structure is not defined.

- bpo-20211: Do not add the directory for installing C header files and the directory for installing object code libraries to the cross compilation search paths. Original patch by Thomas Petazzoni.

- bpo-28849: Do not define sys.implementation._multiarch on Android.

- bpo-10656: Fix out-of-tree building on AIX. Patch by Tristan Carel and Michael Haubenwallner.

- bpo-26359: Rename –with-optimiations to –enable-optimizations.

- bpo-28444: Fix missing extensions modules when cross compiling.

- bpo-28208: Update Windows build and OS X installers to use SQLite 3.14.2.

- bpo-28248: Update Windows build and OS X installers to use OpenSSL 1.0.2j.

- bpo-21124: Fix building the _struct module on Cygwin by passing `NULL` instead of `&PyType_Type` to PyVarObject_HEAD_INIT. Patch by Masayuki Yamamoto.

- bpo-13756: Fix building extensions modules on Cygwin. Patch by Roumen Petrov, based on original patch by Jason Tishler.

- bpo-21085: Add configure check for siginfo_t.si_band, which Cygwin does not provide. Patch by Masayuki Yamamoto with review and rebase by Erik Bray.

- bpo-28258: Fixed build with Estonian locale (python-config and distclean targets in Makefile). Patch by Arfrever Frehtes Taifersar Arahesis.

- bpo-26661: setup.py now detects system libffi with multiarch wrapper.

- bpo-27979: A full copy of libffi is no longer bundled for use when building _ctypes on non-OSX UNIX platforms. An installed copy of libffi is now required when building _ctypes on such platforms.

- bpo-15819: Remove redundant include search directory option for building outside the source tree.

- bpo-28676: Prevent missing ‘getentropy’ declaration warning on macOS. Patch by Gareth Rees.

### Windows

- bpo-31392: Update Windows build to use OpenSSL 1.1.0f

- bpo-30389: Adds detection of Visual Studio 2017 to distutils on Windows.

- bpo-31358: zlib is no longer bundled in the CPython source, instead it is downloaded on demand just like bz2, lzma, OpenSSL, Tcl/Tk, and SQLite.

- bpo-31340: Change to building with MSVC v141 (included with Visual Studio 2017)

- bpo-30581: os.cpu_count() now returns the correct number of processors on Windows when the number of logical processors is greater than 64.

- bpo-30916: Pre-build OpenSSL, Tcl and Tk and include the binaries in the build.

- bpo-30731: Add a missing xmlns to python.manifest so that it matches the schema.

- bpo-30291: Allow requiring 64-bit interpreters from py.exe using -64 suffix. Contributed by Steve (Gadget) Barnes.

- bpo-30362: Adds list options (-0, -0p) to py.exe launcher. Contributed by Steve Barnes.

- bpo-23451: Fix socket deprecation warnings in socketmodule.c. Patch by Segev Finer.

- bpo-30450: The build process on Windows no longer depends on Subversion, instead pulling external code from GitHub via a Python script. If Python 3.6 is not found on the system (via `py -3.6`), NuGet is used to download a copy of 32-bit Python.

- bpo-29579: Removes readme.txt from the installer.

- bpo-25778: winreg does not truncate string correctly (Patch by Eryk Sun)

- bpo-28896: Deprecate WindowsRegistryFinder and disable it by default

- bpo-28522: Fixes mishandled buffer reallocation in getpathp.c

- bpo-28402: Adds signed catalog files for stdlib on Windows.

- bpo-28333: Enables Unicode for ps1/ps2 and input() prompts. (Patch by Eryk Sun)

- bpo-28251: Improvements to help manuals on Windows.

- bpo-28110: launcher.msi has different product codes between 32-bit and 64-bit

- bpo-28161: Opening CON for write access fails

- bpo-28162: WindowsConsoleIO readall() fails if first line starts with Ctrl+Z

- bpo-28163: WindowsConsoleIO fileno() passes wrong flags to _open_osfhandle

- bpo-28164: _PyIO_get_console_type fails for various paths

- bpo-28137: Renames Windows path file to ._pth

- bpo-28138: Windows ._pth file should allow import site

### IDLE

- bpo-31493: IDLE code context – fix code update and font update timers. Canceling timers prevents a warning message when test_idle completes.

- bpo-31488: IDLE - Update non-key options in former extension classes. When applying configdialog changes, call .reload for each feature class. Change ParenMatch so updated options affect existing instances attached to existing editor windows.

- bpo-31477: IDLE - Improve rstrip entry in doc. Strip trailing whitespace strips more than blank spaces. Multiline string literals are not skipped.

- bpo-31480: IDLE - make tests pass with zzdummy extension disabled by default.

- bpo-31421: Document how IDLE runs tkinter programs. IDLE calls tcl/tk update in the background in order to make live interaction and experimentation with tkinter applications much easier.

- bpo-31414: IDLE – fix tk entry box tests by deleting first. Adding to an int entry is not the same as deleting and inserting because int(‘’) will fail.

- bpo-31051: Rearrange IDLE configdialog GenPage into Window, Editor, and Help sections.

- bpo-30617: IDLE - Add docstrings and tests for outwin subclass of editor. Move some data and functions from the class to module level. Patch by Cheryl Sabella.

- bpo-31287: IDLE - Do not modify tkinter.message in test_configdialog.

- bpo-27099: Convert IDLE’s built-in ‘extensions’ to regular features. About 10 IDLE features were implemented as supposedly optional extensions. Their different behavior could be confusing or worse for users and not good for maintenance. Hence the conversion. The main difference for users is that user configurable key bindings for builtin features are now handled uniformly. Now, editing a binding in a keyset only affects its value in the keyset. All bindings are defined together in the system-specific default keysets in config-extensions.def. All custom keysets are saved as a whole in config-extension.cfg. All take effect as soon as one clicks Apply or Ok. The affected events are ‘<<force-open-completions>>’, ‘<<expand-word>>’, ‘<<force-open-calltip>>’, ‘<<flash-paren>>’, ‘<<format-paragraph>>’, ‘<<run-module>>’, ‘<<check-module>>’, and ‘<<zoom-height>>’. Any (global) customizations made before 3.6.3 will not affect their keyset-specific customization after 3.6.3. and vice versa. Initial patch by Charles Wohlganger.

- bpo-31206: IDLE: Factor HighPage(Frame) class from ConfigDialog. Patch by Cheryl Sabella.

- bpo-31001: Add tests for configdialog highlight tab. Patch by Cheryl Sabella.

- bpo-31205: IDLE: Factor KeysPage(Frame) class from ConfigDialog. The slightly modified tests continue to pass. Patch by Cheryl Sabella.

- bpo-31130: IDLE – stop leaks in test_configdialog. Initial patch by Victor Stinner.

- bpo-31002: Add tests for configdialog keys tab. Patch by Cheryl Sabella.

- bpo-19903: IDLE: Calltips use `inspect.signature` instead of `inspect.getfullargspec`. This improves calltips for builtins converted to use Argument Clinic. Patch by Louie Lu.

- bpo-31083: IDLE - Add an outline of a TabPage class in configdialog. Update existing classes to match outline. Initial patch by Cheryl Sabella.

- bpo-31050: Factor GenPage(Frame) class from ConfigDialog. The slightly modified tests continue to pass. Patch by Cheryl Sabella.

- bpo-31004: IDLE - Factor FontPage(Frame) class from ConfigDialog. Slightly modified tests continue to pass. Fix General tests. Patch mostly by Cheryl Sabella.

- bpo-30781: IDLE - Use ttk widgets in ConfigDialog. Patches by Terry Jan Reedy and Cheryl Sabella.

- bpo-31060: IDLE - Finish rearranging methods of ConfigDialog Grouping methods pertaining to each tab and the buttons will aid writing tests and improving the tabs and will enable splitting the groups into classes.

- bpo-30853: IDLE – Factor a VarTrace class out of ConfigDialog. Instance tracers manages pairs consisting of a tk variable and a callback function. When tracing is turned on, setting the variable calls the function. Test coverage for the new class is 100%.

- bpo-31003: IDLE: Add more tests for General tab.

- bpo-30993: IDLE - Improve configdialog font page and tests. In configdialog: Document causal pathways in create_font_tab docstring. Simplify some attribute names. Move set_samples calls to var_changed_font (idea from Cheryl Sabella). Move related functions to positions after the create widgets function. In test_configdialog: Fix test_font_set so not order dependent. Fix renamed test_indent_scale so it tests the widget. Adjust tests for movement of set_samples call. Add tests for load functions. Put all font tests in one class and tab indent tests in another. Except for two lines, these tests completely cover the related functions.

- bpo-30981: IDLE – Add more configdialog font page tests.

- bpo-28523: IDLE: replace ‘colour’ with ‘color’ in configdialog.

- bpo-30917: Add tests for idlelib.config.IdleConf. Increase coverage from 46% to 96%. Patch by Louie Lu.

- bpo-30934: Document coverage details for idlelib tests. Add section to idlelib/idle-test/README.txt. Include check that branches are taken both ways. Exclude IDLE-specific code that does not run during unit tests.

- bpo-30913: IDLE: Document ConfigDialog tk Vars, methods, and widgets in docstrings This will facilitate improving the dialog and splitting up the class. Original patch by Cheryl Sabella.

- bpo-30899: IDLE: Add tests for ConfigParser subclasses in config. Patch by Louie Lu.

- bpo-30881: IDLE: Add docstrings to browser.py. Patch by Cheryl Sabella.

- bpo-30851: IDLE: Remove unused variables in configdialog. One is a duplicate, one is set but cannot be altered by users. Patch by Cheryl Sabella.

- bpo-30870: IDLE: In Settings dialog, select font with Up, Down keys as well as mouse. Initial patch by Louie Lu.

- bpo-8231: IDLE: call config.IdleConf.GetUserCfgDir only once.

- bpo-30779: IDLE: Factor ConfigChanges class from configdialog, put in config; test. * In config, put dump test code in a function; run it and unittest in ‘if __name__ == ‘__main__’. * Add class config.ConfigChanges based on changes_class_v4.py on bpo issue. * Add class test_config.ChangesTest, partly using configdialog_tests_v1.py. * Revise configdialog to use ConfigChanges; see tracker msg297804. * Revise test_configdialog to match configdialog changes. * Remove configdialog functions unused or moved to ConfigChanges. Cheryl Sabella contributed parts of the patch.

- bpo-30777: IDLE: configdialog - Add docstrings and fix comments. Patch by Cheryl Sabella.

- bpo-30495: IDLE: Improve textview with docstrings, PEP8 names, and more tests. Patch by Cheryl Sabella.

- bpo-30723: IDLE: Make several improvements to parenmatch. Add ‘parens’ style to highlight both opener and closer. Make ‘default’ style, which is not default, a synonym for ‘opener’. Make time-delay work the same with all styles. Add help for config dialog extensions tab, including help for parenmatch. Add new tests. Original patch by Charles Wohlganger.

- bpo-30674: IDLE: add docstrings to grep module. Patch by Cheryl Sabella

- bpo-21519: IDLE’s basic custom key entry dialog now detects duplicates properly. Original patch by Saimadhav Heblikar.

- bpo-29910: IDLE no longer deletes a character after commenting out a region by a key shortcut. Add `return 'break'` for this and other potential conflicts between IDLE and default key bindings.

- bpo-30728: Review and change idlelib.configdialog names. Lowercase method and attribute names. Replace ‘colour’ with ‘color’, expand overly cryptic names, delete unneeded underscores. Replace `import *` with specific imports. Patches by Cheryl Sabella.

- bpo-6739: IDLE: Verify user-entered key sequences by trying to bind them with tk. Add tests for all 3 validation functions. Original patch by G Polo. Tests added by Cheryl Sabella.

- bpo-15786: Fix several problems with IDLE’s autocompletion box. The following should now work: clicking on selection box items; using the scrollbar; selecting an item by hitting Return. Hangs on MacOSX should no longer happen. Patch by Louie Lu.

- bpo-25514: Add doc subsubsection about IDLE failure to start. Popup no-connection message directs users to this section.

- bpo-30642: Fix reference leaks in IDLE tests. Patches by Louie Lu and Terry Jan Reedy.

- bpo-30495: Add docstrings for textview.py and use PEP8 names. Patches by Cheryl Sabella and Terry Jan Reedy.

- bpo-30290: Help-about: use pep8 names and add tests. Increase coverage to 100%. Patches by Louie Lu, Cheryl Sabella, and Terry Jan Reedy.

- bpo-30303: Add _utest option to textview; add new tests. Increase coverage to 100%. Patches by Louie Lu and Terry Jan Reedy.

- bpo-29071: IDLE colors f-string prefixes (but not invalid ur prefixes).

- bpo-28572: Add 10% to coverage of IDLE’s test_configdialog. Update and augment description of the configuration system.

### Tools/Demos

- bpo-30983: gdb integration commands (py-bt, etc.) work on optimized shared builds now, too. PEP 523 introduced _PyEval_EvalFrameDefault which inlines PyEval_EvalFrameEx on non-debug shared builds. This broke the ability to use py-bt, py-up, and a few other Python-specific gdb integrations. The problem is fixed by only looking for _PyEval_EvalFrameDefault frames in python-gdb.py. Original patch by Bruno “Polaco” Penteado.

- bpo-29748: Added the slice index converter in Argument Clinic.

- bpo-24037: Argument Clinic now uses the converter `bool(accept={int})` rather than `int` for semantical booleans. This avoids repeating the default value for Python and C and will help in converting to `bool` in future.

- bpo-29367: python-gdb.py now supports also `method-wrapper` (`wrapperobject`) objects.

- bpo-28023: Fix python-gdb.py didn’t support new dict implementation.

- bpo-15369: The pybench and pystone microbenchmark have been removed from Tools. Please use the new Python benchmark suite https://github.com/python/pyperformance which is more reliable and includes a portable version of pybench working on Python 2 and Python 3.

- bpo-28102: The zipfile module CLI now prints usage to stderr. Patch by Stephen J. Turnbull.

### C API

- bpo-31338: Added the `Py_UNREACHABLE()` macro for code paths which are never expected to be reached. This and a few other useful macros are now documented in the C API manual.

- bpo-30832: Remove own implementation for thread-local storage. CPython has provided the own implementation for thread-local storage (TLS) on Python/thread.c, it’s used in the case which a platform has not supplied native TLS. However, currently all supported platforms (Windows and pthreads) have provided native TLS and defined the Py_HAVE_NATIVE_TLS macro with unconditional in any case.

- bpo-30708: PyUnicode_AsWideCharString() now raises a ValueError if the second argument is NULL and the wchar_t* string contains null characters.

- bpo-16500: Deprecate PyOS_AfterFork() and add PyOS_BeforeFork(), PyOS_AfterFork_Parent() and PyOS_AfterFork_Child().

- bpo-6532: The type of results of PyThread_start_new_thread() and PyThread_get_thread_ident(), and the id parameter of PyThreadState_SetAsyncExc() changed from “long” to “unsigned long”.

- bpo-27867: Function PySlice_GetIndicesEx() is deprecated and replaced with a macro if Py_LIMITED_API is not set or set to the value between 0x03050400 and 0x03060000 (not including) or 0x03060100 or higher. Added functions PySlice_Unpack() and PySlice_AdjustIndices().

- bpo-29083: Fixed the declaration of some public API functions. PyArg_VaParse() and PyArg_VaParseTupleAndKeywords() were not available in limited API. PyArg_ValidateKeywordArguments(), PyArg_UnpackTuple() and Py_BuildValue() were not available in limited API of version < 3.3 when PY_SSIZE_T_CLEAN is defined.

- bpo-28769: The result of PyUnicode_AsUTF8AndSize() and PyUnicode_AsUTF8() is now of type `const char *` rather of `char *`.

- bpo-29058: All stable API extensions added after Python 3.2 are now available only when Py_LIMITED_API is set to the PY_VERSION_HEX value of the minimum Python version supporting this API.

- bpo-28822: The index parameters start and end of PyUnicode_FindChar() are now adjusted to behave like `str[start:end]`.

- bpo-28808: PyUnicode_CompareWithASCIIString() now never raises exceptions.

- bpo-28761: The fields name and doc of structures PyMemberDef, PyGetSetDef, PyStructSequence_Field, PyStructSequence_Desc, and wrapperbase are now of type `const char *` rather of `char *`.

- bpo-28748: Private variable _Py_PackageContext is now of type `const char *` rather of `char *`.

- bpo-19569: Compiler warnings are now emitted if use most of deprecated functions.

- bpo-28426: Deprecated undocumented functions PyUnicode_AsEncodedObject(), PyUnicode_AsDecodedObject(), PyUnicode_AsDecodedUnicode() and PyUnicode_AsEncodedUnicode().

## Python 3.6.6 final

Release date: 2018-06-27

There were no new changes in version 3.6.6.

## Python 3.6.6 release candidate 1

Release date: 2018-06-11

### Core and Builtins

- bpo-33786: Fix asynchronous generators to handle GeneratorExit in athrow() correctly

- bpo-30654: Fixed reset of the SIGINT handler to SIG_DFL on interpreter shutdown even when there was a custom handler set previously. Patch by Philipp Kerling.

- bpo-33622: Fixed a leak when the garbage collector fails to add an object with the `__del__` method or referenced by it into the `gc.garbage` list. `PyGC_Collect()` can now be called when an exception is set and preserves it.

- bpo-31849: Fix signed/unsigned comparison warning in pyhash.c.

- bpo-33391: Fix a leak in set_symmetric_difference().

- bpo-28055: Fix unaligned accesses in siphash24(). Patch by Rolf Eike Beer.

- bpo-33231: Fix potential memory leak in `normalizestring()`.

- bpo-29922: Improved error messages in ‘async with’ when `__aenter__()` or `__aexit__()` return non-awaitable object.

- bpo-33199: Fix `ma_version_tag` in dict implementation is uninitialized when copying from key-sharing dict.

- bpo-33041: Fixed jumping when the function contains an `async for` loop.

- bpo-32282: Fix an unnecessary ifdef in the include of VersionHelpers.h in socketmodule on Windows.

- bpo-21983: Fix a crash in `ctypes.cast()` in case the type argument is a ctypes structured data type. Patch by Eryk Sun and Oren Milman.

### Library

- bpo-30167: Prevent site.main() exception if PYTHONSTARTUP is set. Patch by Steve Weber.

- bpo-33812: Datetime instance d with non-None tzinfo, but with d.tzinfo.utcoffset(d) returning None is now treated as naive by the astimezone() method.

- bpo-30805: Avoid race condition with debug logging

- bpo-33767: The concatenation (`+`) and repetition (`*`) sequence operations now raise `TypeError` instead of `SystemError` when performed on `mmap.mmap` objects. Patch by Zackery Spytz.

- bpo-32684: Fix gather to propagate cancellation of itself even with return_exceptions.

- bpo-33674: Fix a race condition in SSLProtocol.connection_made() of asyncio.sslproto: start immediately the handshake instead of using call_soon(). Previously, data_received() could be called before the handshake started, causing the handshake to hang or fail.

- bpo-31647: Fixed bug where calling write_eof() on a _SelectorSocketTransport after it’s already closed raises AttributeError.

- bpo-33672: Fix Task.__repr__ crash with Cython’s bogus coroutines

- bpo-33469: Fix RuntimeError after closing loop that used run_in_executor

- bpo-11874: Use a better regex when breaking usage into wrappable parts. Avoids bogus assertion errors from custom metavar strings.

- bpo-30877: Fixed a bug in the Python implementation of the JSON decoder that prevented the cache of parsed strings from clearing after finishing the decoding. Based on patch by c-fos.

- bpo-33548: tempfile._candidate_tempdir_list should consider common TEMP locations

- bpo-33542: Prevent `uuid.get_node` from using a DUID instead of a MAC on Windows. Patch by Zvi Effron

- bpo-26819: Fix race condition with `ReadTransport.resume_reading` in Windows proactor event loop.

- bpo-28556: Minor fixes in typing module: add annotations to `NamedTuple.__new__`, pass `*args` and `**kwds` in `Generic.__new__`. Original PRs by Paulius Šarka and Chad Dombrova.

- bpo-20087: Updated alias mapping with glibc 2.27 supported locales.

- bpo-33422: Fix trailing quotation marks getting deleted when looking up byte/string literals on pydoc. Patch by Andrés Delfino.

- bpo-33197: Update error message when constructing invalid inspect.Parameters Patch by Donghee Na.

- bpo-33383: Fixed crash in the get() method of the `dbm.ndbm` database object when it is called with a single argument.

- bpo-33329: Fix multiprocessing regression on newer glibcs

- bpo-991266: Fix quoting of the `Comment` attribute of `http.cookies.SimpleCookie`.

- bpo-33131: Upgrade bundled version of pip to 10.0.1.

- bpo-33308: Fixed a crash in the `parser` module when converting an ST object to a tree of tuples or lists with `line_info=False` and `col_info=True`.

- bpo-33263: Fix FD leak in `_SelectorSocketTransport` Patch by Vlad Starostin.

- bpo-33256: Fix display of `<module>` call in the html produced by `cgitb.html()`. Patch by Stéphane Blondon.

- bpo-33203: `random.Random.choice()` now raises `IndexError` for empty sequences consistently even when called from subclasses without a `getrandbits()` implementation.

- bpo-33224: Update difflib.mdiff() for PEP 479. Convert an uncaught StopIteration in a generator into a return-statement.

- bpo-33209: End framing at the end of C implementation of `pickle.Pickler.dump()`.

- bpo-32861: The urllib.robotparser’s `__str__` representation now includes wildcard entries and the “Crawl-delay” and “Request-rate” fields. Patch by Michael Lazar.

- bpo-33096: Allow ttk.Treeview.insert to insert iid that has a false boolean value. Note iid=0 and iid=False would be same. Patch by Garvit Khatri.

- bpo-33127: The ssl module now compiles with LibreSSL 2.7.1.

- bpo-33021: Release the GIL during fstat() calls, avoiding hang of all threads when calling mmap.mmap(), os.urandom(), and random.seed(). Patch by Nir Soffer.

- bpo-27683: Fix a regression in `ipaddress` that result of `hosts()` is empty when the network is constructed by a tuple containing an integer mask and only 1 bit left for addresses.

- bpo-32844: Fix wrong redirection of a low descriptor (0 or 1) to stderr in subprocess if another low descriptor is closed.

- bpo-31908: Fix output of cover files for `trace` module command-line tool. Previously emitted cover files only when `--missing` option was used. Patch by Michael Selik.

- bpo-31457: If nested log adapters are used, the inner `process()` methods are no longer omitted.

- bpo-16865: Support arrays >=2GiB in `ctypes`. Patch by Segev Finer.

- bpo-31238: pydoc: the stop() method of the private ServerThread class now waits until DocServer.serve_until_quit() completes and then explicitly sets its docserver attribute to None to break a reference cycle.

### Documentation

- bpo-33503: Fix broken pypi link

- bpo-33421: Add missing documentation for `typing.AsyncContextManager`.

- bpo-33378: Add Korean language switcher for https://docs.python.org/3/

- bpo-33276: Clarify that the `__path__` attribute on modules cannot be just any value.

- bpo-33201: Modernize documentation for writing C extension types.

- bpo-33195: Deprecate `Py_UNICODE` usage in `c-api/arg` document. `Py_UNICODE` related APIs are deprecated since Python 3.3, but it is missed in the document.

- bpo-33126: Document PyBuffer_ToContiguous().

- bpo-27212: Modify documentation for the `islice()` recipe to consume initial values up to the start index.

- bpo-28247: Update `zipapp` documentation to describe how to make standalone applications.

- bpo-18802: Documentation changes for ipaddress. Patch by Jon Foster and Berker Peksag.

- bpo-27428: Update documentation to clarify that `WindowsRegistryFinder` implements `MetaPathFinder`. (Patch by Himanshu Lakhara)

- bpo-8243: Add a note about curses.addch and curses.addstr exception behavior when writing outside a window, or pad.

- bpo-31432: Clarify meaning of CERT_NONE, CERT_OPTIONAL, and CERT_REQUIRED flags for ssl.SSLContext.verify_mode.

### Tests

- bpo-33655: Ignore test_posix_fallocate failures on BSD platforms that might be due to running on ZFS.

- bpo-19417: Add test_bdb.py.

### Build

- bpo-5755: Move `-Wstrict-prototypes` option to `CFLAGS_NODIST` from `OPT`. This option emitted annoying warnings when building extension modules written in C++.

- bpo-33614: Ensures module definition files for the stable ABI on Windows are correctly regenerated.

- bpo-33522: Enable CI builds on Visual Studio Team Services at https://python.visualstudio.com/cpython

- bpo-33012: Add `-Wno-cast-function-type` for gcc 8 for silencing warnings about function casts like casting to PyCFunction in method definition lists.

- bpo-33394: Enable the verbose build for extension modules, when GNU make is passed macros on the command line.

### Windows

- bpo-33184: Update Windows installer to OpenSSL 1.0.2o.

### macOS

- bpo-33184: Update macOS installer build to use OpenSSL 1.0.2o.

### IDLE

- bpo-33656: On Windows, add API call saying that tk scales for DPI. On Windows 8.1+ or 10, with DPI compatibility properties of the Python binary unchanged, and a monitor resolution greater than 96 DPI, this should make text and lines sharper. It should otherwise have no effect.

- bpo-33768: Clicking on a context line moves that line to the top of the editor window.

- bpo-33763: IDLE: Use read-only text widget for code context instead of label widget.

- bpo-33664: Scroll IDLE editor text by lines. Previously, the mouse wheel and scrollbar slider moved text by a fixed number of pixels, resulting in partial lines at the top of the editor box. The change also applies to the shell and grep output windows, but not to read-only text views.

- bpo-33679: Enable theme-specific color configuration for Code Context. Use the Highlights tab to see the setting for built-in themes or add settings to custom themes.

- bpo-33642: Display up to maxlines non-blank lines for Code Context. If there is no current context, show a single blank line.

- bpo-33628: IDLE: Cleanup codecontext.py and its test.

- bpo-33564: IDLE’s code context now recognizes async as a block opener.

- bpo-29706: IDLE now colors async and await as keywords in 3.6. They become full keywords in 3.7.

- bpo-21474: Update word/identifier definition from ascii to unicode. In text and entry boxes, this affects selection by double-click, movement left/right by control-left/right, and deletion left/right by control-BACKSPACE/DEL.

- bpo-33204: IDLE: consistently color invalid string prefixes. A ‘u’ string prefix cannot be paired with either ‘r’ or ‘f’. Consistently color as much of the prefix, starting at the right, as is valid. Revise and extend colorizer test.

- bpo-32831: Add docstrings and tests for codecontext.

### Tools/Demos

- bpo-33189: pygettext.py now recognizes only literal strings as docstrings and translatable strings, and rejects bytes literals and f-string expressions.

- bpo-31920: Fixed handling directories as arguments in the `pygettext` script. Based on patch by Oleg Krasnikov.

- bpo-29673: Fix pystackv and pystack gdbinit macros.

- bpo-32885: Add an `-n` flag for `Tools/scripts/pathfix.py` to disable automatic backup creation (files with `~` suffix).

- bpo-31583: Fix 2to3 for using with –add-suffix option but without –output-dir option for relative path to files in current directory.

### C API

- bpo-32374: Document that m_traverse for multi-phase initialized modules can be called with m_state=NULL, and add a sanity check

## Python 3.6.5 final

Release date: 2018-03-28

### Tests

- bpo-32872: Avoid regrtest compatibility issue with namespace packages.

### Build

- bpo-33163: Upgrade pip to 9.0.3 and setuptools to v39.0.1.

## Python 3.6.5 release candidate 1

Release date: 2018-03-13

### Security

- bpo-33001: Minimal fix to prevent buffer overrun in os.symlink on Windows

- bpo-32981: Regexes in difflib and poplib were vulnerable to catastrophic backtracking. These regexes formed potential DOS vectors (REDOS). They have been refactored. This resolves CVE 2018-1060 and CVE 2018-1061. Patch by Jamie Davis.

### Core and Builtins

- bpo-33026: Fixed jumping out of “with” block by setting f_lineno.

- bpo-17288: Prevent jumps from ‘return’ and ‘exception’ trace events.

- bpo-32889: Update Valgrind suppression list to account for the rename of `Py_ADDRESS_IN_RANG` to `address_in_range`.

- bpo-32650: Pdb and other debuggers dependent on bdb.py will correctly step over (next command) native coroutines. Patch by Pablo Galindo.

- bpo-32685: Improve suggestion when the Python 2 form of print statement is either present on the same line as the header of a compound statement or else terminated by a semi-colon instead of a newline. Patch by Nitish Chandra.

- bpo-32583: Fix possible crashing in builtin Unicode decoders caused by write out-of-bound errors when using customized decode error handlers.

- bpo-26163: Improved frozenset() hash to create more distinct hash values when faced with datasets containing many similar values.

- bpo-27169: The `__debug__` constant is now optimized out at compile time. This fixes also bpo-22091.

- bpo-32329: `sys.flags.hash_randomization` is now properly set to 0 when hash randomization is turned off by `PYTHONHASHSEED=0`.

- bpo-30416: The optimizer is now protected from spending much time doing complex calculations and consuming much memory for creating large constants in constant folding.

- bpo-18533: `repr()` on a dict containing its own `values()` or `items()` no longer raises `RecursionError`; OrderedDict similarly. Instead, use `...`, as for other recursive structures. Patch by Ben North.

- bpo-32028: Leading whitespace is now correctly ignored when generating suggestions for converting Py2 print statements to Py3 builtin print function calls. Patch by Sanyam Khurana.

- bpo-32137: The repr of deeply nested dict now raises a RecursionError instead of crashing due to a stack overflow.

### Library

- bpo-33064: lib2to3 now properly supports trailing commas after `*args` and `**kwargs` in function signatures.

- bpo-31804: Avoid failing in multiprocessing.Process if the standard streams are closed or None at exit.

- bpo-33037: Skip sending/receiving data after SSL transport closing.

- bpo-30353: Fix ctypes pass-by-value for structs on 64-bit Cygwin/MinGW.

- bpo-33009: Fix inspect.signature() for single-parameter partialmethods.

- bpo-32969: Expose several missing constants in zlib and fix corresponding documentation.

- bpo-32713: Fixed tarfile.itn handling of out-of-bounds float values. Patch by Joffrey Fuhrer.

- bpo-30622: The ssl module now detects missing NPN support in LibreSSL.

- bpo-32922: dbm.open() now encodes filename with the filesystem encoding rather than default encoding.

- bpo-32859: In `os.dup2`, don’t check every call whether the `dup3` syscall exists or not.

- bpo-21060: Rewrite confusing message from setup.py upload from “No dist file created in earlier command” to the more helpful “Must create and upload files in one command”.

- bpo-32857: In `tkinter`, `after_cancel(None)` now raises a `ValueError` instead of canceling the first scheduled function. Patch by Cheryl Sabella.

- bpo-32852: Make sure sys.argv remains as a list when running trace.

- bpo-32841: Fixed `asyncio.Condition` issue which silently ignored cancellation after notifying and cancelling a conditional lock. Patch by Bar Harel.

- bpo-31787: Fixed refleaks of `__init__()` methods in various modules. (Contributed by Oren Milman)

- bpo-30157: Fixed guessing quote and delimiter in csv.Sniffer.sniff() when only the last field is quoted. Patch by Jake Davis.

- bpo-32394: socket: Remove TCP_FASTOPEN, TCP_KEEPCNT flags on older version Windows during run-time.

- bpo-32777: Fix a rare but potential pre-exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process. This bug appears to have been introduced in 3.4.

- bpo-32647: The ctypes module used to depend on indirect linking for dlopen. The shared extension is now explicitly linked against libdl on platforms with dl.

- bpo-32734: Fixed `asyncio.Lock()` safety issue which allowed acquiring and locking the same lock multiple times, without it being free. Patch by Bar Harel.

- bpo-32727: Do not include name field in SMTP envelope from address. Patch by Stéphane Wirtel

- bpo-27931: Fix email address header parsing error when the username is an empty quoted string. Patch by Xiang Zhang.

- bpo-32304: distutils’ upload command no longer corrupts tar files ending with a CR byte, and no longer tries to convert CR to CRLF in any of the upload text fields.

- bpo-32502: uuid.uuid1 no longer raises an exception if a 64-bit hardware address is encountered.

- bpo-31848: Fix the error handling in Aifc_read.initfp() when the SSND chunk is not found. Patch by Zackery Spytz.

- bpo-32555: On FreeBSD and Solaris, os.strerror() now always decode the byte string from the current locale encoding, rather than using ASCII/surrogateescape in some cases.

- bpo-32521: The nis module is now compatible with new libnsl and headers location.

- bpo-32473: Improve ABCMeta._dump_registry() output readability

- bpo-32521: glibc has removed Sun RPC. Use replacement libtirpc headers and library in nis module.

- bpo-32228: Ensure that `truncate()` preserves the file position (as reported by `tell()`) after writes longer than the buffer size.

- bpo-26133: Don’t unsubscribe signals in asyncio UNIX event loop on interpreter shutdown.

- bpo-32185: The SSL module no longer sends IP addresses in SNI TLS extension on platforms with OpenSSL 1.0.2+ or inet_pton.

- bpo-32323: `urllib.parse.urlsplit()` does not convert zone-id (scope) to lower case for scoped IPv6 addresses in hostnames now.

- bpo-32302: Fix bdist_wininst of distutils for CRT v142: it binary compatible with CRT v140.

- bpo-32255: A single empty field is now always quoted when written into a CSV file. This allows to distinguish an empty row from a row consisting of a single empty field. Patch by Licht Takeuchi.

- bpo-32277: Raise `NotImplementedError` instead of `SystemError` on platforms where `chmod(..., follow_symlinks=False)` is not supported. Patch by Anthony Sottile.

- bpo-32199: The getnode() ip getter now uses ‘ip link’ instead of ‘ip link list’.

- bpo-27456: Ensure TCP_NODELAY is set on Linux. Tests by Victor Stinner.

- bpo-31900: The `locale.localeconv()` function now sets temporarily the `LC_CTYPE` locale to the `LC_NUMERIC` locale to decode `decimal_point` and `thousands_sep` byte strings if they are non-ASCII or longer than 1 byte, and the `LC_NUMERIC` locale is different than the `LC_CTYPE` locale. This temporary change affects other threads. Same change for the `str.format()` method when formatting a number (`int`, `float`, `float` and subclasses) with the `n` type (ex: `'{:n}'.format(1234)`).

- bpo-31802: Importing native path module (`posixpath`, `ntpath`) now works even if the `os` module still is not imported.

### Documentation

- bpo-17232: Clarify docs for -O and -OO. Patch by Terry Reedy.

- bpo-32800: Update link to w3c doc for xml default namespaces.

- bpo-8722: Document `__getattr__()` behavior when property `get()` method raises `AttributeError`.

- bpo-32614: Modify RE examples in documentation to use raw strings to prevent `DeprecationWarning` and add text to REGEX HOWTO to highlight the deprecation.

- bpo-31972: Improve docstrings for `pathlib.PurePath` subclasses.

- bpo-17799: Explain real behaviour of sys.settrace and sys.setprofile and their C-API counterparts regarding which type of events are received in each function. Patch by Pablo Galindo Salgado.

### Tests

- bpo-32517: Fix failing `test_asyncio` on macOS 10.12.2+ due to transport of `KqueueSelector` loop was not being closed.

- bpo-32721: Fix test_hashlib to not fail if the _md5 module is not built.

- bpo-32252: Fix faulthandler_suppress_crash_report() used to prevent core dump files when testing crashes. getrlimit() returns zero on success.

- bpo-31518: Debian Unstable has disabled TLS 1.0 and 1.1 for SSLv23_METHOD(). Change TLS/SSL protocol of some tests to PROTOCOL_TLS or PROTOCOL_TLSv1_2 to make them pass on Debian.

### Build

- bpo-32635: Fix segfault of the crypt module when libxcrypt is provided instead of libcrypt at the system.

### Windows

- bpo-33016: Fix potential use of uninitialized memory in nt._getfinalpathname

- bpo-32903: Fix a memory leak in os.chdir() on Windows if the current directory is set to a UNC path.

- bpo-31966: Fixed WindowsConsoleIO.write() for writing empty data.

- bpo-32409: Ensures activate.bat can handle Unicode contents.

- bpo-32457: Improves handling of denormalized executable path when launching Python.

- bpo-32370: Use the correct encoding for ipconfig output in the uuid module. Patch by Segev Finer.

- bpo-29248: Fix `os.readlink()` on Windows, which was mistakenly treating the `PrintNameOffset` field of the reparse data buffer as a number of characters instead of bytes. Patch by Craig Holmquist and SSE4.

- bpo-32588: Create standalone _distutils_findvs module.

### macOS

- bpo-32726: Provide an additional, more modern macOS installer variant that supports macOS 10.9+ systems in 64-bit mode only. Upgrade the supplied third-party libraries to OpenSSL 1.0.2n, XZ 5.2.3, and SQLite 3.22.0. The 10.9+ installer now links with and supplies its own copy of Tcl/Tk 8.6.8.

### IDLE

- bpo-32984: Set `__file__` while running a startup file. Like Python, IDLE optionally runs one startup file in the Shell window before presenting the first interactive input prompt. For IDLE, `-s` runs a file named in environmental variable `IDLESTARTUP` or `PYTHONSTARTUP`; `-r file` runs `file`. Python sets `__file__` to the startup file name before running the file and unsets it before the first prompt. IDLE now does the same when run normally, without the `-n` option.

- bpo-32940: Simplify and rename StringTranslatePseudoMapping in pyparse.

- bpo-32916: Change `str` to `code` in pyparse.

- bpo-32905: Remove unused code in pyparse module.

- bpo-32874: Add tests for pyparse.

- bpo-32837: Using the system and place-dependent default encoding for open() is a bad idea for IDLE’s system and location-independent files.

- bpo-32826: Add “encoding=utf-8” to open() in IDLE’s test_help_about. GUI test test_file_buttons() only looks at initial ascii-only lines, but failed on systems where open() defaults to ‘ascii’ because readline() internally reads and decodes far enough ahead to encounter a non-ascii character in CREDITS.txt.

- bpo-32765: Update configdialog General tab docstring to add new widgets to the widget list.

### Tools/Demos

- bpo-24960: 2to3 and lib2to3 can now read pickled grammar files using pkgutil.get_data() rather than probing the filesystem. This lets 2to3 and lib2to3 work when run from a zipfile.

- bpo-32222: Fix pygettext not extracting docstrings for functions with type annotated arguments. Patch by Toby Harradine.

### C API

- bpo-29084: Undocumented C API for OrderedDict has been excluded from the limited C API. It was added by mistake and actually never worked in the limited C API.

## Python 3.6.4 final

Release date: 2017-12-18

There were no new code changes in version 3.6.4 since v3.6.4rc1.

## Python 3.6.4 release candidate 1

Release date: 2017-12-05

### Core and Builtins

- bpo-32176: co_flags.CO_NOFREE is now always set correctly by the code object constructor based on freevars and cellvars, rather than needing to be set correctly by the caller. This ensures it will be cleared automatically when additional cell references are injected into a modified code object and function.

- bpo-31949: Fixed several issues in printing tracebacks (PyTraceBack_Print()). Setting sys.tracebacklimit to 0 or less now suppresses printing tracebacks. Setting sys.tracebacklimit to None now causes using the default limit. Setting sys.tracebacklimit to an integer larger than LONG_MAX now means using the limit LONG_MAX rather than the default limit. Fixed integer overflows in the case of more than `2**31` traceback items on Windows. Fixed output errors handling.

- bpo-30696: Fix the interactive interpreter looping endlessly when no memory.

- bpo-20047: Bytearray methods partition() and rpartition() now accept only bytes-like objects as separator, as documented. In particular they now raise TypeError rather of returning a bogus result when an integer is passed as a separator.

- bpo-31852: Fix a segmentation fault caused by a combination of the async soft keyword and continuation lines.

- bpo-21720: BytesWarning no longer emitted when the fromlist argument of `__import__()` or the `__all__` attribute of the module contain bytes instances.

- bpo-31825: Fixed OverflowError in the ‘unicode-escape’ codec and in codecs.escape_decode() when decode an escaped non-ascii byte.

- bpo-28603: Print the full context/cause chain of exceptions on interpreter exit, even if an exception in the chain is unhashable or compares equal to later ones. Patch by Zane Bitter.

- bpo-31786: Fix timeout rounding in the select module to round correctly negative timeouts between -1.0 and 0.0. The functions now block waiting for events as expected. Previously, the call was incorrectly non-blocking. Patch by Pablo Galindo.

- bpo-31642: Restored blocking “from package import module” by setting sys.modules[“package.module”] to None.

- bpo-31626: Fixed a bug in debug memory allocator. There was a write to freed memory after shrinking a memory block.

- bpo-31619: Fixed a ValueError when convert a string with large number of underscores to integer with binary base.

- bpo-31592: Fixed an assertion failure in Python parser in case of a bad `unicodedata.normalize()`. Patch by Oren Milman.

- bpo-31588: Raise a `TypeError` with a helpful error message when class creation fails due to a metaclass with a bad `__prepare__()` method. Patch by Oren Milman.

- bpo-31566: Fix an assertion failure in `_warnings.warn()` in case of a bad `__name__` global. Patch by Oren Milman.

- bpo-31505: Fix an assertion failure in `json`, in case `_json.make_encoder()` received a bad `encoder()` argument. Patch by Oren Milman.

- bpo-31492: Fix assertion failures in case of failing to import from a module with a bad `__name__` attribute, and in case of failing to access an attribute of such a module. Patch by Oren Milman.

- bpo-31490: Fix an assertion failure in `ctypes` class definition, in case the class has an attribute whose name is specified in `_anonymous_` but not in `_fields_`. Patch by Oren Milman.

- bpo-31478: Fix an assertion failure in `_random.Random.seed()` in case the argument has a bad `__abs__()` method. Patch by Oren Milman.

- bpo-31315: Fix an assertion failure in imp.create_dynamic(), when spec.name is not a string. Patch by Oren Milman.

- bpo-31311: Fix a crash in the `__setstate__()` method of `ctypes._CData`, in case of a bad `__dict__`. Patch by Oren Milman.

- bpo-31293: Fix crashes in true division and multiplication of a timedelta object by a float with a bad as_integer_ratio() method. Patch by Oren Milman.

- bpo-31285: Fix an assertion failure in `warnings.warn_explicit`, when the return value of the received loader’s `get_source()` has a bad `splitlines()` method. Patch by Oren Milman.

- bpo-30817: `PyErr_PrintEx()` clears now the ignored exception that may be raised by `_PySys_SetObjectId()`, for example when no memory.

### Library

- bpo-28556: Two minor fixes for `typing` module: allow shallow copying instances of generic classes, improve interaction of `__init_subclass__` with generics. Original PRs by Ivan Levkivskyi.

- bpo-27240: The header folding algorithm for the new email policies has been rewritten, which also fixes bpo-30788, bpo-31831, and bpo-32182. In particular, RFC2231 folding is now done correctly.

- bpo-32186: io.FileIO.readall() and io.FileIO.read() now release the GIL when getting the file size. Fixed hang of all threads with inaccessible NFS server. Patch by Nir Soffer.

- bpo-12239: Make `msilib.SummaryInformation.GetProperty()` return `None` when the value of property is `VT_EMPTY`. Initial patch by Mark Mc Mahon.

- bpo-31325: Fix wrong usage of `collections.namedtuple()` in the `RobotFileParser.parse()` method. Initial patch by Robin Wellner.

- bpo-12382: `msilib.OpenDatabase()` now raises a better exception message when it couldn’t open or create an MSI file. Initial patch by William Tisäter.

- bpo-32110: `codecs.StreamReader.read(n)` now returns not more than n characters/bytes for non-negative n. This makes it compatible with `read()` methods of other file-like objects.

- bpo-32072: Fixed issues with binary plists: Fixed saving bytearrays. Identical objects will be saved only once. Equal references will be load as identical objects. Added support for saving and loading recursive data structures.

- bpo-32034: Make asyncio.IncompleteReadError and LimitOverrunError pickleable.

- bpo-32015: Fixed the looping of asyncio in the case of reconnection the socket during waiting async read/write from/to the socket.

- bpo-32011: Restored support of loading marshal files with the TYPE_INT64 code. These files can be produced in Python 2.7.

- bpo-31970: Reduce performance overhead of asyncio debug mode.

- bpo-9678: Fixed determining the MAC address in the uuid module: Using ifconfig on NetBSD and OpenBSD. Using arp on Linux, FreeBSD, NetBSD and OpenBSD. Based on patch by Takayuki Shimizukawa.

- bpo-30057: Fix potential missed signal in signal.signal().

- bpo-31933: Fix Blake2 params leaf_size and node_offset on big endian platforms. Patch by Jack O’Connor.

- bpo-31927: Fixed compilation of the socket module on NetBSD 8. Fixed assertion failure or reading arbitrary data when parse a AF_BLUETOOTH address on NetBSD and DragonFly BSD.

- bpo-27666: Fixed stack corruption in curses.box() and curses.ungetmouse() when the size of types chtype or mmask_t is less than the size of C long. curses.box() now accepts characters as arguments. Based on patch by Steve Fink.

- bpo-31897: plistlib now catches more errors when read binary plists and raises InvalidFileException instead of unexpected exceptions.

- bpo-25720: Fix the method for checking pad state of curses WINDOW. Patch by Masayuki Yamamoto.

- bpo-31893: Fixed the layout of the kqueue_event structure on OpenBSD and NetBSD. Fixed the comparison of the kqueue_event objects.

- bpo-31891: Fixed building the curses module on NetBSD.

- bpo-28416: Instances of pickle.Pickler subclass with the persistent_id() method and pickle.Unpickler subclass with the persistent_load() method no longer create reference cycles.

- bpo-28326: Fix multiprocessing.Process when stdout and/or stderr is closed or None.

- bpo-31457: If nested log adapters are used, the inner `process()` methods are no longer omitted.

- bpo-31457: The `manager` property on LoggerAdapter objects is now properly settable.

- bpo-31806: Fix timeout rounding in time.sleep(), threading.Lock.acquire() and socket.socket.settimeout() to round correctly negative timeouts between -1.0 and 0.0. The functions now block waiting for events as expected. Previously, the call was incorrectly non-blocking. Patch by Pablo Galindo.

- bpo-28603: traceback: Fix a TypeError that occurred during printing of exception tracebacks when either the current exception or an exception in its context/cause chain is unhashable. Patch by Zane Bitter.

- bpo-30058: Fixed buffer overflow in select.kqueue.control().

- bpo-31770: Prevent a crash when calling the `__init__()` method of a `sqlite3.Cursor` object more than once. Patch by Oren Milman.

- bpo-31672: `idpattern` in `string.Template` matched some non-ASCII characters. Now it uses `-i` regular expression local flag to avoid non-ASCII characters.

- bpo-31764: Prevent a crash in `sqlite3.Cursor.close()` in case the `Cursor` object is uninitialized. Patch by Oren Milman.

- bpo-31752: Fix possible crash in timedelta constructor called with custom integers.

- bpo-31701: On Windows, faulthandler.enable() now ignores MSC and COM exceptions.

- bpo-31728: Prevent crashes in `_elementtree` due to unsafe cleanup of `Element.text` and `Element.tail`. Patch by Oren Milman.

- bpo-31620: an empty asyncio.Queue now doesn’t leak memory when queue.get pollers timeout

- bpo-31632: Fix method set_protocol() of class _SSLProtocolTransport in asyncio module. This method was previously modifying a wrong reference to the protocol.

- bpo-31675: Fixed memory leaks in Tkinter’s methods splitlist() and split() when pass a string larger than 2 GiB.

- bpo-31673: Fixed typo in the name of Tkinter’s method adderrorinfo().

- bpo-30806: Fix the string representation of a netrc object.

- bpo-15037: Added a workaround for getkey() in curses for ncurses 5.7 and earlier.

- bpo-25351: Avoid venv activate failures with undefined variables

- bpo-25532: inspect.unwrap() will now only try to unwrap an object sys.getrecursionlimit() times, to protect against objects which create a new object on every attribute access.

- bpo-30347: Stop crashes when concurrently iterate over itertools.groupby() iterators.

- bpo-31516: `threading.current_thread()` should not return a dummy thread at shutdown.

- bpo-31351: python -m ensurepip now exits with non-zero exit code if pip bootstrapping has failed.

- bpo-31482: `random.seed()` now works with bytes in version=1

- bpo-31334: Fix `poll.poll([timeout])` in the `select` module for arbitrary negative timeouts on all OSes where it can only be a non-negative integer or -1. Patch by Riccardo Coccioli.

- bpo-31310: multiprocessing’s semaphore tracker should be launched again if crashed.

- bpo-31308: Make multiprocessing’s forkserver process immune to Ctrl-C and other user interruptions. If it crashes, restart it when necessary.

### Documentation

- bpo-32105: Added asyncio.BaseEventLoop.connect_accepted_socket versionadded marker.

- bpo-31537: Fix incorrect usage of `get_history_length` in readline documentation example code. Patch by Brad Smith.

- bpo-30085: The operator functions without double underscores are preferred for clarity. The one with underscores are only kept for back-compatibility.

### Tests

- bpo-31380: Skip test_httpservers test_undecodable_file on macOS: fails on APFS.

- bpo-31705: Skip test_socket.test_sha256() on Linux kernel older than 4.5. The test fails with ENOKEY on kernel 3.10 (on ppc64le). A fix was merged into the kernel 4.5.

- bpo-31174: Fix test_tools.test_unparse: DirectoryTestCase now stores the names sample to always test the same files. It prevents false alarms when hunting reference leaks.

- bpo-30695: Add the `set_nomemory(start, stop)` and `remove_mem_hooks()` functions to the `_testcapi` module.

### Build

- bpo-32059: `detect_modules()` in `setup.py` now also searches the sysroot paths when cross-compiling.

- bpo-31957: Fixes Windows SDK version detection when building for Windows.

- bpo-31609: Fixes quotes in PCbuild/clean.bat

- bpo-31934: Abort the build when building out of a not clean source tree.

- bpo-31926: Fixed Argument Clinic sometimes causing compilation errors when there was more than one function and/or method in a .c file with the same name.

- bpo-28791: Update Windows builds to use SQLite 3.21.0.

- bpo-28791: Update OS X installer to use SQLite 3.21.0.

- bpo-22140: Prevent double substitution of prefix in python-config.sh.

- bpo-31536: Avoid wholesale rebuild after `make regen-all` if nothing changed.

### Windows

- bpo-1102: Return `None` when `View.Fetch()` returns `ERROR_NO_MORE_ITEMS` instead of raising `MSIError`. Initial patch by Anthony Tuininga.

- bpo-31944: Fixes Modify button in Apps and Features dialog.

### macOS

- bpo-31392: Update macOS installer to use OpenSSL 1.0.2m

### IDLE

- bpo-32207: Improve tk event exception tracebacks in IDLE. When tk event handling is driven by IDLE’s run loop, a confusing and distracting queue.EMPTY traceback context is no longer added to tk event exception tracebacks. The traceback is now the same as when event handling is driven by user code. Patch based on a suggestion by Serhiy Storchaka.

- bpo-32164: Delete unused file idlelib/tabbedpages.py. Use of TabbedPageSet in configdialog was replaced by ttk.Notebook.

- bpo-32100: IDLE: Fix old and new bugs in pathbrowser; improve tests. Patch mostly by Cheryl Sabella.

- bpo-31858: IDLE – Restrict shell prompt manipulation to the shell. Editor and output windows only see an empty last prompt line. This simplifies the code and fixes a minor bug when newline is inserted. Sys.ps1, if present, is read on Shell start-up, but is not set or changed.

- bpo-31860: The font sample in the IDLE configuration dialog is now editable. Changes persist while IDLE remains open

- bpo-31836: Test_code_module now passes if run after test_idle, which sets ps1. The code module uses sys.ps1 if present or sets it to ‘>>> ‘ if not. Test_code_module now properly tests both behaviors. Ditto for ps2.

- bpo-28603: Fix a TypeError that caused a shell restart when printing a traceback that includes an exception that is unhashable. Patch by Zane Bitter.

- bpo-13802: Use non-Latin characters in the IDLE’s Font settings sample. Even if one selects a font that defines a limited subset of the unicode Basic Multilingual Plane, tcl/tk will use other fonts that define a character. The expanded example give users of non-Latin characters a better idea of what they might see in IDLE’s shell and editors. To make room for the expanded sample, frames on the Font tab are re-arranged. The Font/Tabs help explains a bit about the additions.

- bpo-31460: Simplify the API of IDLE’s Module Browser. Passing a widget instead of an flist with a root widget opens the option of creating a browser frame that is only part of a window. Passing a full file name instead of pieces assumed to come from a .py file opens the possibility of browsing python files that do not end in .py.

- bpo-31649: IDLE - Make _htest, _utest parameters keyword only.

- bpo-31559: Remove test order dependence in idle_test.test_browser.

- bpo-31459: Rename IDLE’s module browser from Class Browser to Module Browser. The original module-level class and method browser became a module browser, with the addition of module-level functions, years ago. Nested classes and functions were added yesterday. For back-compatibility, the virtual event <<open-class-browser>>, which appears on the Keys tab of the Settings dialog, is not changed. Patch by Cheryl Sabella.

- bpo-31500: Default fonts now are scaled on HiDPI displays.

- bpo-1612262: IDLE module browser now shows nested classes and functions. Original patches for code and tests by Guilherme Polo and Cheryl Sabella, respectively.

### Tools/Demos

- bpo-30722: Make redemo work with Python 3.6 and newer versions. Also, remove the `LOCALE` option since it doesn’t work with string patterns in Python 3. Patch by Christoph Sarnowski.

### C API

- bpo-20891: Fix PyGILState_Ensure(). When PyGILState_Ensure() is called in a non-Python thread before PyEval_InitThreads(), only call PyEval_InitThreads() after calling PyThreadState_New() to fix a crash.

- bpo-31532: Fix memory corruption due to allocator mix in getpath.c between Py_GetPath() and Py_SetPath()

- bpo-30697: The `PyExc_RecursionErrorInst` singleton is removed and `PyErr_NormalizeException()` does not use it anymore. This singleton is persistent and its members being never cleared may cause a segfault during finalization of the interpreter. See also bpo-22898.

## Python 3.6.3 final

Release date: 2017-10-03

### Library

- bpo-31641: Re-allow arbitrary iterables in `concurrent.futures.as_completed()`. Fixes regression in 3.6.3rc1.

### Build

- bpo-31662: Fix typos in Windows `uploadrelease.bat` script. Fix Windows Doc build issues in `Doc/make.bat`.

- bpo-31423: Fix building the PDF documentation with newer versions of Sphinx.

## Python 3.6.3 release candidate 1

Release date: 2017-09-18

### Security

- bpo-29781: SSLObject.version() now correctly returns None when handshake over BIO has not been performed yet.

- bpo-30947: Upgrade libexpat embedded copy from version 2.2.1 to 2.2.3 to get security fixes.

### Core and Builtins

- bpo-31471: Fix an assertion failure in `subprocess.Popen()` on Windows, in case the env argument has a bad `keys()` method. Patch by Oren Milman.

- bpo-31418: Fix an assertion failure in `PyErr_WriteUnraisable()` in case of an exception with a bad `__module__` attribute. Patch by Oren Milman.

- bpo-31416: Fix assertion failures in case of a bad warnings.filters or warnings.defaultaction. Patch by Oren Milman.

- bpo-31411: Raise a TypeError instead of SystemError in case warnings.onceregistry is not a dictionary. Patch by Oren Milman.

- bpo-31373: Fix several possible instances of undefined behavior due to floating-point demotions.

- bpo-30465: Location information (`lineno` and `col_offset`) in f-strings is now (mostly) correct. This fixes tools like flake8 from showing warnings on the wrong line (typically the first line of the file).

- bpo-31343: Include sys/sysmacros.h for major(), minor(), and makedev(). GNU C libray plans to remove the functions from sys/types.h.

- bpo-31291: Fix an assertion failure in `zipimport.zipimporter.get_data` on Windows, when the return value of `pathname.replace('/','\\')` isn’t a string. Patch by Oren Milman.

- bpo-31271: Fix an assertion failure in the `write()` method of `io.TextIOWrapper`, when the encoder doesn’t return a bytes object. Patch by Oren Milman.

- bpo-31243: Fix a crash in some methods of `io.TextIOWrapper`, when the decoder’s state is invalid. Patch by Oren Milman.

- bpo-30721: `print` now shows correct usage hint for using Python 2 redirection syntax. Patch by Sanyam Khurana.

- bpo-31070: Fix a race condition in importlib _get_module_lock().

- bpo-31095: Fix potential crash during GC caused by `tp_dealloc` which doesn’t call `PyObject_GC_UnTrack()`.

- bpo-31071: Avoid masking original TypeError in call with * unpacking when other arguments are passed.

- bpo-30978: str.format_map() now passes key lookup exceptions through. Previously any exception was replaced with a KeyError exception.

- bpo-30808: Use _Py_atomic API for concurrency-sensitive signal state.

- bpo-30876: Relative import from unloaded package now reimports the package instead of failing with SystemError. Relative import from non-package now fails with ImportError rather than SystemError.

- bpo-30703: Improve signal delivery. Avoid using Py_AddPendingCall from signal handler, to avoid calling signal-unsafe functions. The tests I’m adding here fail without the rest of the patch, on Linux and OS X. This means our signal delivery logic had defects (some signals could be lost).

- bpo-30765: Avoid blocking in pthread_mutex_lock() when PyThread_acquire_lock() is asked not to block.

- bpo-31161: Make sure the ‘Missing parentheses’ syntax error message is only applied to SyntaxError, not to subclasses. Patch by Martijn Pieters.

- bpo-30814: Fixed a race condition when import a submodule from a package.

- bpo-30597: `print` now shows expected input in custom error message when used as a Python 2 statement. Patch by Sanyam Khurana.

### Library

- bpo-31499: xml.etree: Fix a crash when a parser is part of a reference cycle.

- bpo-28556: typing.get_type_hints now finds the right globalns for classes and modules by default (when no `globalns` was specified by the caller).

- bpo-28556: Speed improvements to the `typing` module. Original PRs by Ivan Levkivskyi and Mitar.

- bpo-31544: The C accelerator module of ElementTree ignored exceptions raised when looking up TreeBuilder target methods in XMLParser().

- bpo-31234: socket.create_connection() now fixes manually a reference cycle: clear the variable storing the last exception on success.

- bpo-31457: LoggerAdapter objects can now be nested.

- bpo-31400: Improves SSL error handling to avoid losing error numbers.

- bpo-28958: ssl.SSLContext() now uses OpenSSL error information when a context cannot be instantiated.

- bpo-27340: SSLSocket.sendall() now uses memoryview to create slices of data. This fixes support for all bytes-like object. It is also more efficient and avoids costly copies.

- bpo-31178: Fix string concatenation bug in rare error path in the subprocess module

- bpo-31350: Micro-optimize `asyncio._get_running_loop()` to become up to 10% faster.

- bpo-31170: expat: Update libexpat from 2.2.3 to 2.2.4. Fix copying of partial characters for UTF-8 input (libexpat bug 115): https://github.com/libexpat/libexpat/issues/115

- bpo-29136: Add TLS 1.3 cipher suites and OP_NO_TLSv1_3.

- bpo-29212: Fix concurrent.futures.thread.ThreadPoolExecutor threads to have a non repr() based thread name by default when no thread_name_prefix is supplied. They will now identify themselves as “ThreadPoolExecutor-y_n”.

- bpo-9146: Fix a segmentation fault in _hashopenssl when standard hash functions such as md5 are not available in the linked OpenSSL library. As in some special FIPS-140 build environments.

- bpo-27144: The `map()` and `as_completed()` iterators in `concurrent.futures` now avoid keeping a reference to yielded objects.

- bpo-10746: Fix ctypes producing wrong PEP 3118 type codes for integer types.

- bpo-22536: The subprocess module now sets the filename when FileNotFoundError is raised on POSIX systems due to the executable or cwd not being found.

- bpo-31249: concurrent.futures: WorkItem.run() used by ThreadPoolExecutor now breaks a reference cycle between an exception object and the WorkItem object.

- bpo-31247: xmlrpc.server now explicitly breaks reference cycles when using sys.exc_info() in code handling exceptions.

- bpo-30102: The ssl and hashlib modules now call OPENSSL_add_all_algorithms_noconf() on OpenSSL < 1.1.0. The function detects CPU features and enables optimizations on some CPU architectures such as POWER8. Patch is based on research from Gustavo Serra Scalet.

- bpo-31185: Fixed miscellaneous errors in asyncio speedup module.

- bpo-31135: ttk: fix the destroy() method of LabeledScale and OptionMenu classes. Call the parent destroy() method even if the used attribute doesn’t exist. The LabeledScale.destroy() method now also explicitly clears label and scale attributes to help the garbage collector to destroy all widgets.

- bpo-31107: Fix `copyreg._slotnames()` mangled attribute calculation for classes whose name begins with an underscore. Patch by Shane Harvey.

- bpo-31061: Fixed a crash when using asyncio and threads.

- bpo-30502: Fix handling of long oids in ssl. Based on patch by Christian Heimes.

- bpo-30119: ftplib.FTP.putline() now throws ValueError on commands that contains CR or LF. Patch by Donghee Na.

- bpo-30595: multiprocessing.Queue.get() with a timeout now polls its reader in non-blocking mode if it succeeded to acquire the lock but the acquire took longer than the timeout.

- bpo-29403: Fix `unittest.mock`’s autospec to not fail on method-bound builtin functions. Patch by Aaron Gallagher.

- bpo-30961: Fix decrementing a borrowed reference in tracemalloc.

- bpo-25684: Change `ttk.OptionMenu` radiobuttons to be unique across instances of `OptionMenu`.

- bpo-30886: Fix multiprocessing.Queue.join_thread(): it now waits until the thread completes, even if the thread was started by the same process which created the queue.

- bpo-29854: Fix segfault in readline when using readline’s history-size option. Patch by Nir Soffer.

- bpo-30319: socket.close() now ignores ECONNRESET error.

- bpo-30828: Fix out of bounds write in `asyncio.CFuture.remove_done_callback()`.

- bpo-30807: signal.setitimer() may disable the timer when passed a tiny value. Tiny values (such as 1e-6) are valid non-zero values for setitimer(), which is specified as taking microsecond-resolution intervals. However, on some platform, our conversion routine could convert 1e-6 into a zero interval, therefore disabling the timer instead of (re-)scheduling it.

- bpo-30441: Fix bug when modifying os.environ while iterating over it

- bpo-30532: Fix email header value parser dropping folding white space in certain cases.

- bpo-30879: os.listdir() and os.scandir() now emit bytes names when called with bytes-like argument.

- bpo-30746: Prohibited the ‘=’ character in environment variable names in `os.putenv()` and `os.spawn*()`.

- bpo-29755: Fixed the lgettext() family of functions in the gettext module. They now always return bytes.

### Documentation

- bpo-31294: Fix incomplete code snippet in the ZeroMQSocketListener and ZeroMQSocketHandler examples and adapt them to Python 3.

- bpo-21649: Add RFC 7525 and Mozilla server side TLS links to SSL documentation.

- bpo-30803: Clarify doc on truth value testing. Original patch by Peter Thomassen.

### Tests

- bpo-31320: Silence traceback in test_ssl

- bpo-25674: Remove sha256.tbs-internet.com ssl test

- bpo-30715: Address ALPN callback changes for OpenSSL 1.1.0f. The latest version behaves like OpenSSL 1.0.2 and no longer aborts handshake.

- bpo-30822: regrtest: Exclude tzdata from regrtest –all. When running the test suite using –use=all / -u all, exclude tzdata since it makes test_datetime too slow (15-20 min on some buildbots) which then times out on some buildbots. Fix also regrtest command line parser to allow passing -u extralargefile to run test_zipfile64.

### Build

- bpo-30854: Fix compile error when compiling –without-threads. Patch by Masayuki Yamamoto.

### Windows

- bpo-30389: Adds detection of Visual Studio 2017 to distutils on Windows.

- bpo-31340: Change to building with MSVC v141 (included with Visual Studio 2017)

- bpo-30581: os.cpu_count() now returns the correct number of processors on Windows when the number of logical processors is greater than 64.

- bpo-30731: Add a missing xmlns to python.manifest so that it matches the schema.

### IDLE

- bpo-31493: IDLE code context – fix code update and font update timers. Canceling timers prevents a warning message when test_idle completes.

- bpo-31488: IDLE - Update non-key options in former extension classes. When applying configdialog changes, call .reload for each feature class. Change ParenMatch so updated options affect existing instances attached to existing editor windows.

- bpo-31477: IDLE - Improve rstrip entry in doc. Strip trailing whitespace strips more than blank spaces. Multiline string literals are not skipped.

- bpo-31480: IDLE - make tests pass with zzdummy extension disabled by default.

- bpo-31421: Document how IDLE runs tkinter programs. IDLE calls tcl/tk update in the background in order to make live interaction and experimentation with tkinter applications much easier.

- bpo-31414: IDLE – fix tk entry box tests by deleting first. Adding to an int entry is not the same as deleting and inserting because int(‘’) will fail.

- bpo-31051: Rearrange IDLE configdialog GenPage into Window, Editor, and Help sections.

- bpo-30617: IDLE - Add docstrings and tests for outwin subclass of editor. Move some data and functions from the class to module level. Patch by Cheryl Sabella.

- bpo-31287: IDLE - Do not modify tkinter.message in test_configdialog.

- bpo-27099: Convert IDLE’s built-in ‘extensions’ to regular features. About 10 IDLE features were implemented as supposedly optional extensions. Their different behavior could be confusing or worse for users and not good for maintenance. Hence the conversion. The main difference for users is that user configurable key bindings for builtin features are now handled uniformly. Now, editing a binding in a keyset only affects its value in the keyset. All bindings are defined together in the system-specific default keysets in config-extensions.def. All custom keysets are saved as a whole in config-extension.cfg. All take effect as soon as one clicks Apply or Ok. The affected events are ‘<<force-open-completions>>’, ‘<<expand-word>>’, ‘<<force-open-calltip>>’, ‘<<flash-paren>>’, ‘<<format-paragraph>>’, ‘<<run-module>>’, ‘<<check-module>>’, and ‘<<zoom-height>>’. Any (global) customizations made before 3.6.3 will not affect their keyset-specific customization after 3.6.3. and vice versa. Initial patch by Charles Wohlganger.

- bpo-31206: IDLE: Factor HighPage(Frame) class from ConfigDialog. Patch by Cheryl Sabella.

- bpo-31001: Add tests for configdialog highlight tab. Patch by Cheryl Sabella.

- bpo-31205: IDLE: Factor KeysPage(Frame) class from ConfigDialog. The slightly modified tests continue to pass. Patch by Cheryl Sabella.

- bpo-31130: IDLE – stop leaks in test_configdialog. Initial patch by Victor Stinner.

- bpo-31002: Add tests for configdialog keys tab. Patch by Cheryl Sabella.

- bpo-19903: IDLE: Calltips use `inspect.signature` instead of `inspect.getfullargspec`. This improves calltips for builtins converted to use Argument Clinic. Patch by Louie Lu.

- bpo-31083: IDLE - Add an outline of a TabPage class in configdialog. Update existing classes to match outline. Initial patch by Cheryl Sabella.

- bpo-31050: Factor GenPage(Frame) class from ConfigDialog. The slightly modified tests continue to pass. Patch by Cheryl Sabella.

- bpo-31004: IDLE - Factor FontPage(Frame) class from ConfigDialog. Slightly modified tests continue to pass. Fix General tests. Patch mostly by Cheryl Sabella.

- bpo-30781: IDLE - Use ttk widgets in ConfigDialog. Patches by Terry Jan Reedy and Cheryl Sabella.

- bpo-31060: IDLE - Finish rearranging methods of ConfigDialog Grouping methods pertaining to each tab and the buttons will aid writing tests and improving the tabs and will enable splitting the groups into classes.

- bpo-30853: IDLE – Factor a VarTrace class out of ConfigDialog. Instance tracers manages pairs consisting of a tk variable and a callback function. When tracing is turned on, setting the variable calls the function. Test coverage for the new class is 100%.

- bpo-31003: IDLE: Add more tests for General tab.

- bpo-30993: IDLE - Improve configdialog font page and tests. In configdialog: Document causal pathways in create_font_tab docstring. Simplify some attribute names. Move set_samples calls to var_changed_font (idea from Cheryl Sabella). Move related functions to positions after the create widgets function. In test_configdialog: Fix test_font_set so not order dependent. Fix renamed test_indent_scale so it tests the widget. Adjust tests for movement of set_samples call. Add tests for load functions. Put all font tests in one class and tab indent tests in another. Except for two lines, these tests completely cover the related functions.

- bpo-30981: IDLE – Add more configdialog font page tests.

- bpo-28523: IDLE: replace ‘colour’ with ‘color’ in configdialog.

- bpo-30917: Add tests for idlelib.config.IdleConf. Increase coverage from 46% to 96%. Patch by Louie Lu.

- bpo-30934: Document coverage details for idlelib tests. Add section to idlelib/idle-test/README.txt. Include check that branches are taken both ways. Exclude IDLE-specific code that does not run during unit tests.

- bpo-30913: IDLE: Document ConfigDialog tk Vars, methods, and widgets in docstrings This will facilitate improving the dialog and splitting up the class. Original patch by Cheryl Sabella.

- bpo-30899: IDLE: Add tests for ConfigParser subclasses in config. Patch by Louie Lu.

- bpo-30881: IDLE: Add docstrings to browser.py. Patch by Cheryl Sabella.

- bpo-30851: IDLE: Remove unused variables in configdialog. One is a duplicate, one is set but cannot be altered by users. Patch by Cheryl Sabella.

- bpo-30870: IDLE: In Settings dialog, select font with Up, Down keys as well as mouse. Initial patch by Louie Lu.

- bpo-8231: IDLE: call config.IdleConf.GetUserCfgDir only once.

- bpo-30779: IDLE: Factor ConfigChanges class from configdialog, put in config; test. * In config, put dump test code in a function; run it and unittest in ‘if __name__ == ‘__main__’. * Add class config.ConfigChanges based on changes_class_v4.py on bpo issue. * Add class test_config.ChangesTest, partly using configdialog_tests_v1.py. * Revise configdialog to use ConfigChanges; see tracker msg297804. * Revise test_configdialog to match configdialog changes. * Remove configdialog functions unused or moved to ConfigChanges. Cheryl Sabella contributed parts of the patch.

- bpo-30777: IDLE: configdialog - Add docstrings and fix comments. Patch by Cheryl Sabella.

- bpo-30495: IDLE: Improve textview with docstrings, PEP8 names, and more tests. Patch by Cheryl Sabella.

- bpo-30723: IDLE: Make several improvements to parenmatch. Add ‘parens’ style to highlight both opener and closer. Make ‘default’ style, which is not default, a synonym for ‘opener’. Make time-delay work the same with all styles. Add help for config dialog extensions tab, including help for parenmatch. Add new tests. Original patch by Charles Wohlganger.

- bpo-30674: IDLE: add docstrings to grep module. Patch by Cheryl Sabella

- bpo-21519: IDLE’s basic custom key entry dialog now detects duplicates properly. Original patch by Saimadhav Heblikar.

- bpo-29910: IDLE no longer deletes a character after commenting out a region by a key shortcut. Add `return 'break'` for this and other potential conflicts between IDLE and default key bindings.

- bpo-30728: Review and change idlelib.configdialog names. Lowercase method and attribute names. Replace ‘colour’ with ‘color’, expand overly cryptic names, delete unneeded underscores. Replace `import *` with specific imports. Patches by Cheryl Sabella.

- bpo-6739: IDLE: Verify user-entered key sequences by trying to bind them with tk. Add tests for all 3 validation functions. Original patch by G Polo. Tests added by Cheryl Sabella.

### Tools/Demos

- bpo-30983: gdb integration commands (py-bt, etc.) work on optimized shared builds now, too. PEP 523 introduced _PyEval_EvalFrameDefault which inlines PyEval_EvalFrameEx on non-debug shared builds. This broke the ability to use py-bt, py-up, and a few other Python-specific gdb integrations. The problem is fixed by only looking for _PyEval_EvalFrameDefault frames in python-gdb.py. Original patch by Bruno “Polaco” Penteado.

## Python 3.6.2 final

Release date: 2017-07-17

No changes since release candidate 2

## Python 3.6.2 release candidate 2

Release date: 2017-07-07

### Security

- bpo-30730: Prevent environment variables injection in subprocess on Windows. Prevent passing other environment variables and command arguments.

- bpo-30694: Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes of multiple security vulnerabilities including: CVE 2017-9233 (External entity infinite loop DoS), CVE 2016-9063 (Integer overflow, re-fix), CVE 2016-0718 (Fix regression bugs from 2.2.0’s fix to CVE 2016-0718) and CVE 2012-0876 (Counter hash flooding with SipHash). Note: the CVE 2016-5300 (Use os-specific entropy sources like getrandom) doesn’t impact Python, since Python already gets entropy from the OS to set the expat secret using `XML_SetHashSalt()`.

- bpo-30500: Fix urllib.parse.splithost() to correctly parse fragments. For example, `splithost('//127.0.0.1#@evil.com/')` now correctly returns the `127.0.0.1` host, instead of treating `@evil.com` as the host in an authentication (`login@host`).

## Python 3.6.2 release candidate 1

Release date: 2017-06-17

### Security

- bpo-29591: Update expat copy from 2.1.1 to 2.2.0 to get fixes of CVE 2016-0718 and CVE 2016-4472. See https://sourceforge.net/p/expat/bugs/537/ for more information.

### Core and Builtins

- bpo-30682: Removed a too-strict assertion that failed for certain f-strings, such as eval(“f’\n’”) and eval(“f’\r’”).

- bpo-30604: Move co_extra_freefuncs to not be per-thread to avoid crashes

- bpo-29104: Fixed parsing backslashes in f-strings.

- bpo-27945: Fixed various segfaults with dict when input collections are mutated during searching, inserting or comparing. Based on patches by Duane Griffin and Tim Mitchell.

- bpo-25794: Fixed type.__setattr__() and type.__delattr__() for non-interned attribute names. Based on patch by Eryk Sun.

- bpo-30039: If a KeyboardInterrupt happens when the interpreter is in the middle of resuming a chain of nested ‘yield from’ or ‘await’ calls, it’s now correctly delivered to the innermost frame.

- bpo-12414: sys.getsizeof() on a code object now returns the sizes which includes the code struct and sizes of objects which it references. Patch by Donghee Na.

- bpo-29949: Fix memory usage regression of set and frozenset object.

- bpo-29935: Fixed error messages in the index() method of tuple, list and deque when pass indices of wrong type.

- bpo-29859: Show correct error messages when any of the pthread_* calls in thread_pthread.h fails.

- bpo-28876: `bool(range)` works even if `len(range)` raises `OverflowError`.

- bpo-29600: Fix wrapping coroutine return values in StopIteration.

- bpo-28856: Fix an oversight that %b format for bytes should support objects follow the buffer protocol.

- bpo-29714: Fix a regression that bytes format may fail when containing zero bytes inside.

- bpo-29478: If max_line_length=None is specified while using the Compat32 policy, it is no longer ignored. Patch by Mircea Cosbuc.

### Library

- bpo-30616: Functional API of enum allows to create empty enums. Patched by Donghee Na

- bpo-30038: Fix race condition between signal delivery and wakeup file descriptor. Patch by Nathaniel Smith.

- bpo-23894: lib2to3 now recognizes `rb'...'` and `f'...'` strings.

- bpo-23890: unittest.TestCase.assertRaises() now manually breaks a reference cycle to not keep objects alive longer than expected.

- bpo-30149: inspect.signature() now supports callables with variable-argument parameters wrapped with partialmethod. Patch by Donghee Na.

- bpo-30645: Fix path calculation in imp.load_package(), fixing it for cases when a package is only shipped with bytecodes. Patch by Alexandru Ardelean.

- bpo-29931: Fixed comparison check for ipaddress.ip_interface objects. Patch by Sanjay Sundaresan.

- bpo-30605: re.compile() no longer raises a BytesWarning when compiling a bytes instance with misplaced inline modifier. Patch by Roy Williams.

- bpo-24484: Avoid race condition in multiprocessing cleanup (#2159)

- bpo-28994: The traceback no longer displayed for SystemExit raised in a callback registered by atexit.

- bpo-30508: Don’t log exceptions if Task/Future “cancel()” method was called.

- bpo-28556: Updates to typing module: Add generic AsyncContextManager, add support for ContextManager on all versions. Original PRs by Jelle Zijlstra and Ivan Levkivskyi

- bpo-29870: Fix ssl sockets leaks when connection is aborted in asyncio/ssl implementation. Patch by Michaël Sghaïer.

- bpo-29743: Closing transport during handshake process leaks open socket. Patch by Nikolay Kim

- bpo-27585: Fix waiter cancellation in asyncio.Lock. Patch by Mathieu Sornay.

- bpo-30418: On Windows, subprocess.Popen.communicate() now also ignore EINVAL on stdin.write() if the child process is still running but closed the pipe.

- bpo-29822: inspect.isabstract() now works during __init_subclass__. Patch by Nate Soares.

- bpo-29581: ABCMeta.__new__ now accepts `**kwargs`, allowing abstract base classes to use keyword parameters in __init_subclass__. Patch by Nate Soares.

- bpo-30557: faulthandler now correctly filters and displays exception codes on Windows

- bpo-30378: Fix the problem that logging.handlers.SysLogHandler cannot handle IPv6 addresses.

- bpo-29960: Preserve generator state when _random.Random.setstate() raises an exception. Patch by Bryan Olson.

- bpo-30414: multiprocessing.Queue._feed background running thread do not break from main loop on exception.

- bpo-30003: Fix handling escape characters in HZ codec. Based on patch by Ma Lin.

- bpo-30301: Fix AttributeError when using SimpleQueue.empty() under spawn and forkserver start methods.

- bpo-30329: imaplib and poplib now catch the Windows socket WSAEINVAL error (code 10022) on shutdown(SHUT_RDWR): An invalid operation was attempted. This error occurs sometimes on SSL connections.

- bpo-30375: Warnings emitted when compile a regular expression now always point to the line in the user code. Previously they could point into inners of the re module if emitted from inside of groups or conditionals.

- bpo-30048: Fixed `Task.cancel()` can be ignored when the task is running coroutine and the coroutine returned without any more `await`.

- bpo-30266: contextlib.AbstractContextManager now supports anti-registration by setting __enter__ = None or __exit__ = None, following the pattern introduced in bpo-25958. Patch by Jelle Zijlstra.

- bpo-30298: Weaken the condition of deprecation warnings for inline modifiers. Now allowed several subsequential inline modifiers at the start of the pattern (e.g. `'(?i)(?s)...'`). In verbose mode whitespaces and comments now are allowed before and between inline modifiers (e.g. `'(?x) (?i) (?s)...'`).

- bpo-29990: Fix range checking in GB18030 decoder. Original patch by Ma Lin.

- bpo-26293: Change resulted because of zipfile breakage. (See also: bpo-29094)

- bpo-30243: Removed the __init__ methods of _json’s scanner and encoder. Misusing them could cause memory leaks or crashes. Now scanner and encoder objects are completely initialized in the __new__ methods.

- bpo-30185: Avoid KeyboardInterrupt tracebacks in forkserver helper process when Ctrl-C is received.

- bpo-28556: Various updates to typing module: add typing.NoReturn type, use WrapperDescriptorType, minor bug-fixes. Original PRs by Jim Fasarakis-Hilliard and Ivan Levkivskyi.

- bpo-30205: Fix getsockname() for unbound AF_UNIX sockets on Linux.

- bpo-30070: Fixed leaks and crashes in errors handling in the parser module.

- bpo-30061: Fixed crashes in IOBase methods __next__() and readlines() when readline() or __next__() respectively return non-sizeable object. Fixed possible other errors caused by not checking results of PyObject_Size(), PySequence_Size(), or PyMapping_Size().

- bpo-30017: Allowed calling the close() method of the zip entry writer object multiple times. Writing to a closed writer now always produces a ValueError.

- bpo-30068: _io._IOBase.readlines will check if it’s closed first when hint is present.

- bpo-29694: Fixed race condition in pathlib mkdir with flags parents=True. Patch by Armin Rigo.

- bpo-29692: Fixed arbitrary unchaining of RuntimeError exceptions in contextlib.contextmanager. Patch by Siddharth Velankar.

- bpo-29998: Pickling and copying ImportError now preserves name and path attributes.

- bpo-29953: Fixed memory leaks in the replace() method of datetime and time objects when pass out of bound fold argument.

- bpo-29942: Fix a crash in itertools.chain.from_iterable when encountering long runs of empty iterables.

- bpo-27863: Fixed multiple crashes in ElementTree caused by race conditions and wrong types.

- bpo-28699: Fixed a bug in pools in multiprocessing.pool that raising an exception at the very first of an iterable may swallow the exception or make the program hang. Patch by Davin Potts and Xiang Zhang.

- bpo-25803: Avoid incorrect errors raised by Path.mkdir(exist_ok=True) when the OS gives priority to errors such as EACCES over EEXIST.

- bpo-29861: Release references to tasks, their arguments and their results as soon as they are finished in multiprocessing.Pool.

- bpo-29884: faulthandler: Restore the old sigaltstack during teardown. Patch by Christophe Zeitouny.

- bpo-25455: Fixed crashes in repr of recursive buffered file-like objects.

- bpo-29800: Fix crashes in partial.__repr__ if the keys of partial.keywords are not strings. Patch by Michael Seifert.

- bpo-29742: get_extra_info() raises exception if get called on closed ssl transport. Patch by Nikolay Kim.

- bpo-8256: Fixed possible failing or crashing input() if attributes “encoding” or “errors” of sys.stdin or sys.stdout are not set or are not strings.

- bpo-28298: Fix a bug that prevented array ‘Q’, ‘L’ and ‘I’ from accepting big intables (objects that have __int__) as elements. Patch by Oren Milman.

- bpo-28231: The zipfile module now accepts path-like objects for external paths.

- bpo-26915: index() and count() methods of collections.abc.Sequence now check identity before checking equality when do comparisons.

- bpo-29615: SimpleXMLRPCDispatcher no longer chains KeyError (or any other exception) to exception(s) raised in the dispatched methods. Patch by Petr Motejlek.

- bpo-30177: path.resolve(strict=False) no longer cuts the path after the first element not present in the filesystem. Patch by Antoine Pietri.

### IDLE

- bpo-15786: Fix several problems with IDLE’s autocompletion box. The following should now work: clicking on selection box items; using the scrollbar; selecting an item by hitting Return. Hangs on MacOSX should no longer happen. Patch by Louie Lu.

- bpo-25514: Add doc subsubsection about IDLE failure to start. Popup no-connection message directs users to this section.

- bpo-30642: Fix reference leaks in IDLE tests. Patches by Louie Lu and Terry Jan Reedy.

- bpo-30495: Add docstrings for textview.py and use PEP8 names. Patches by Cheryl Sabella and Terry Jan Reedy.

- bpo-30290: Help-about: use pep8 names and add tests. Increase coverage to 100%. Patches by Louie Lu, Cheryl Sabella, and Terry Jan Reedy.

- bpo-30303: Add _utest option to textview; add new tests. Increase coverage to 100%. Patches by Louie Lu and Terry Jan Reedy.

### C API

- bpo-27867: Function PySlice_GetIndicesEx() no longer replaced with a macro if Py_LIMITED_API is not set.

### Build

- bpo-29941: Add `--with-assertions` configure flag to explicitly enable C `assert()` checks. Defaults to off. `--with-pydebug` implies `--with-assertions`.

- bpo-28787: Fix out-of-tree builds of Python when configured with `--with--dtrace`.

- bpo-29243: Prevent unnecessary rebuilding of Python during `make test`, `make install` and some other make targets when configured with `--enable-optimizations`.

- bpo-23404: Don’t regenerate generated files based on file modification time anymore: the action is now explicit. Replace `make touch` with `make regen-all`.

- bpo-29643: Fix `--enable-optimization` didn’t work.

### Documentation

- bpo-30176: Add missing attribute related constants in curses documentation.

- bpo-30052: the link targets for `bytes()` and `bytearray()` are now their respective type definitions, rather than the corresponding builtin function entries. Use bytes and bytearray to reference the latter. In order to ensure this and future cross-reference updates are applied automatically, the daily documentation builds now disable the default output caching features in Sphinx.

- bpo-26985: Add missing info of code object in inspect documentation.

### Tools/Demos

- bpo-29367: python-gdb.py now supports also `method-wrapper` (`wrapperobject`) objects.

### Tests

- bpo-30357: test_thread: setUp() now uses support.threading_setup() and support.threading_cleanup() to wait until threads complete to avoid random side effects on following tests. Initial patch written by Grzegorz Grzywacz.

- bpo-30197: Enhanced functions swap_attr() and swap_item() in the test.support module. They now work when delete replaced attribute or item inside the with statement. The old value of the attribute or item (or None if it doesn’t exist) now will be assigned to the target of the “as” clause, if there is one.

### Windows

- bpo-30687: Locate msbuild.exe on Windows when building rather than vcvarsall.bat

- bpo-30450: The build process on Windows no longer depends on Subversion, instead pulling external code from GitHub via a Python script. If Python 3.6 is not found on the system (via `py -3.6`), NuGet is used to download a copy of 32-bit Python.

## Python 3.6.1 final

Release date: 2017-03-21

### Core and Builtins

- bpo-29723: The `sys.path[0]` initialization change for bpo-29139 caused a regression by revealing an inconsistency in how sys.path is initialized when executing `__main__` from a zipfile, directory, or other import location. The interpreter now consistently avoids ever adding the import location’s parent directory to `sys.path`, and ensures no other `sys.path` entries are inadvertently modified when inserting the import location named on the command line.

### Build

- bpo-27593: fix format of git information used in sys.version

- Fix incompatible comment in python.h

## Python 3.6.1 release candidate 1

Release date: 2017-03-04

### Core and Builtins

- bpo-28893: Set correct __cause__ for errors about invalid awaitables returned from __aiter__ and __anext__.

- bpo-29683: Fixes to memory allocation in _PyCode_SetExtra. Patch by Brian Coleman.

- bpo-29684: Fix minor regression of PyEval_CallObjectWithKeywords. It should raise TypeError when kwargs is not a dict. But it might cause segv when args=NULL and kwargs is not a dict.

- bpo-28598: Support __rmod__ for subclasses of str being called before str.__mod__. Patch by Martijn Pieters.

- bpo-29607: Fix stack_effect computation for CALL_FUNCTION_EX. Patch by Matthieu Dartiailh.

- bpo-29602: Fix incorrect handling of signed zeros in complex constructor for complex subclasses and for inputs having a __complex__ method. Patch by Serhiy Storchaka.

- bpo-29347: Fixed possibly dereferencing undefined pointers when creating weakref objects.

- bpo-29438: Fixed use-after-free problem in key sharing dict.

- bpo-29319: Prevent RunMainFromImporter overwriting sys.path[0].

- bpo-29337: Fixed possible BytesWarning when compare the code objects. Warnings could be emitted at compile time.

- bpo-29327: Fixed a crash when pass the iterable keyword argument to sorted().

- bpo-29034: Fix memory leak and use-after-free in os module (path_converter).

- bpo-29159: Fix regression in bytes(x) when x.__index__() raises Exception.

- bpo-28932: Do not include <sys/random.h> if it does not exist.

- bpo-25677: Correct the positioning of the syntax error caret for indented blocks. Based on patch by Michael Layzell.

- bpo-29000: Fixed bytes formatting of octals with zero padding in alternate form.

- bpo-26919: On Android, operating system data is now always encoded/decoded to/from UTF-8, instead of the locale encoding to avoid inconsistencies with os.fsencode() and os.fsdecode() which are already using UTF-8.

- bpo-28991: functools.lru_cache() was susceptible to an obscure reentrancy bug triggerable by a monkey-patched len() function.

- bpo-28739: f-string expressions are no longer accepted as docstrings and by ast.literal_eval() even if they do not include expressions.

- bpo-28512: Fixed setting the offset attribute of SyntaxError by PyErr_SyntaxLocationEx() and PyErr_SyntaxLocationObject().

- bpo-28918: Fix the cross compilation of xxlimited when Python has been built with Py_DEBUG defined.

- bpo-28731: Optimize _PyDict_NewPresized() to create correct size dict. Improve speed of dict literal with constant keys up to 30%.

### Library

- bpo-29169: Update zlib to 1.2.11.

- bpo-29623: Allow use of path-like object as a single argument in ConfigParser.read(). Patch by David Ellis.

- bpo-28963: Fix out of bound iteration in asyncio.Future.remove_done_callback implemented in C.

- bpo-29704: asyncio.subprocess.SubprocessStreamProtocol no longer closes before all pipes are closed.

- bpo-29271: Fix Task.current_task and Task.all_tasks implemented in C to accept None argument as their pure Python implementation.

- bpo-29703: Fix asyncio to support instantiation of new event loops in child processes.

- bpo-29376: Fix assertion error in threading._DummyThread.is_alive().

- bpo-28624: Add a test that checks that cwd parameter of Popen() accepts PathLike objects. Patch by Sayan Chowdhury.

- bpo-28518: Start a transaction implicitly before a DML statement. Patch by Aviv Palivoda.

- bpo-29532: Altering a kwarg dictionary passed to functools.partial() no longer affects a partial object after creation.

- bpo-29110: Fix file object leak in aifc.open() when file is given as a filesystem path and is not in valid AIFF format. Patch by Anthony Zhang.

- bpo-28556: Various updates to typing module: typing.Counter, typing.ChainMap, improved ABC caching, etc. Original PRs by Jelle Zijlstra, Ivan Levkivskyi, Manuel Krebber, and Łukasz Langa.

- bpo-29100: Fix datetime.fromtimestamp() regression introduced in Python 3.6.0: check minimum and maximum years.

- bpo-29519: Fix weakref spewing exceptions during interpreter shutdown when used with a rare combination of multiprocessing and custom codecs.

- bpo-29416: Prevent infinite loop in pathlib.Path.mkdir

- bpo-29444: Fixed out-of-bounds buffer access in the group() method of the match object. Based on patch by WGH.

- bpo-29335: Fix subprocess.Popen.wait() when the child process has exited to a stopped instead of terminated state (ex: when under ptrace).

- bpo-29290: Fix a regression in argparse that help messages would wrap at non-breaking spaces.

- bpo-28735: Fixed the comparison of mock.MagickMock with mock.ANY.

- bpo-29316: Restore the provisional status of typing module, add corresponding note to documentation. Patch by Ivan L.

- bpo-29219: Fixed infinite recursion in the repr of uninitialized ctypes.CDLL instances.

- bpo-29011: Fix an important omission by adding Deque to the typing module.

- bpo-28969: Fixed race condition in C implementation of functools.lru_cache. KeyError could be raised when cached function with full cache was simultaneously called from different threads with the same uncached arguments.

- bpo-29142: In urllib.request, suffixes in no_proxy environment variable with leading dots could match related hostnames again (e.g. .b.c matches a.b.c). Patch by Milan Oberkirch.

- bpo-28961: Fix unittest.mock._Call helper: don’t ignore the name parameter anymore. Patch written by Jiajun Huang.

- bpo-29203: functools.lru_cache() now respects PEP 468 and preserves the order of keyword arguments. f(a=1, b=2) is now cached separately from f(b=2, a=1) since both calls could potentially give different results.

- bpo-15812: inspect.getframeinfo() now correctly shows the first line of a context. Patch by Sam Breese.

- bpo-29094: Offsets in a ZIP file created with extern file object and modes “w” and “x” now are relative to the start of the file.

- bpo-29085: Allow random.Random.seed() to use high quality OS randomness rather than the pid and time.

- bpo-29061: Fixed bug in secrets.randbelow() which would hang when given a negative input. Patch by Brendan Donegan.

- bpo-29079: Prevent infinite loop in pathlib.resolve() on Windows

- bpo-13051: Fixed recursion errors in large or resized curses.textpad.Textbox. Based on patch by Tycho Andersen.

- bpo-29119: Fix weakrefs in the pure python version of collections.OrderedDict move_to_end() method. Contributed by Andra Bogildea.

- bpo-9770: curses.ascii predicates now work correctly with negative integers.

- bpo-28427: old keys should not remove new values from WeakValueDictionary when collecting from another thread.

- bpo-28923: Remove editor artifacts from Tix.py.

- bpo-29055: Neaten-up empty population error on random.choice() by suppressing the upstream exception.

- bpo-28871: Fixed a crash when deallocate deep ElementTree.

- bpo-19542: Fix bugs in WeakValueDictionary.setdefault() and WeakValueDictionary.pop() when a GC collection happens in another thread.

- bpo-20191: Fixed a crash in resource.prlimit() when passing a sequence that doesn’t own its elements as limits.

- bpo-28779: multiprocessing.set_forkserver_preload() would crash the forkserver process if a preloaded module instantiated some multiprocessing objects such as locks.

- bpo-28847: dbm.dumb now supports reading read-only files and no longer writes the index file when it is not changed.

- bpo-26937: The chown() method of the tarfile.TarFile class does not fail now when the grp module cannot be imported, as for example on Android platforms.

### IDLE

- bpo-29071: IDLE colors f-string prefixes (but not invalid ur prefixes).

- bpo-28572: Add 10% to coverage of IDLE’s test_configdialog. Update and augment description of the configuration system.

### Windows

- bpo-29579: Removes readme.txt from the installer

- bpo-29326: Ignores blank lines in ._pth files (Patch by Alexey Izbyshev)

- bpo-28164: Correctly handle special console filenames (patch by Eryk Sun)

- bpo-29409: Implement PEP 529 for io.FileIO (Patch by Eryk Sun)

- bpo-29392: Prevent crash when passing invalid arguments into msvcrt module.

- bpo-25778: winreg does not truncate string correctly (Patch by Eryk Sun)

- bpo-28896: Deprecate WindowsRegistryFinder and disable it by default.

### C API

- bpo-27867: Function PySlice_GetIndicesEx() is replaced with a macro if Py_LIMITED_API is not set or set to the value between 0x03050400 and 0x03060000 (not including) or 0x03060100 or higher.

- bpo-29083: Fixed the declaration of some public API functions. PyArg_VaParse() and PyArg_VaParseTupleAndKeywords() were not available in limited API. PyArg_ValidateKeywordArguments(), PyArg_UnpackTuple() and Py_BuildValue() were not available in limited API of version < 3.3 when PY_SSIZE_T_CLEAN is defined.

- bpo-29058: All stable API extensions added after Python 3.2 are now available only when Py_LIMITED_API is set to the PY_VERSION_HEX value of the minimum Python version supporting this API.

### Documentation

- bpo-28929: Link the documentation to its source file on GitHub.

- bpo-25008: Document smtpd.py as effectively deprecated and add a pointer to aiosmtpd, a third-party asyncio-based replacement.

- bpo-26355: Add canonical header link on each page to corresponding major version of the documentation. Patch by Matthias Bussonnier.

- bpo-29349: Fix Python 2 syntax in code for building the documentation.

### Tests

- bpo-28087: Skip test_asyncore and test_eintr poll failures on macOS. Skip some tests of select.poll when running on macOS due to unresolved issues with the underlying system poll function on some macOS versions.

- bpo-29571: to match the behaviour of the `re.LOCALE` flag, test_re.test_locale_flag now uses `locale.getpreferredencoding(False)` to determine the candidate encoding for the test regex (allowing it to correctly skip the test when the default locale encoding is a multi-byte encoding)

- bpo-28950: Disallow -j0 to be combined with -T/-l in regrtest command line arguments.

- bpo-28683: Fix the tests that bind() a unix socket and raise PermissionError on Android for a non-root user.

- bpo-26939: Add the support.setswitchinterval() function to fix test_functools hanging on the Android armv7 qemu emulator.

### Build

- bpo-27593: sys.version and the platform module python_build(), python_branch(), and python_revision() functions now use git information rather than hg when building from a repo.

- bpo-29572: Update Windows build and OS X installers to use OpenSSL 1.0.2k.

- bpo-26851: Set Android compilation and link flags.

- bpo-28768: Fix implicit declaration of function _setmode. Patch by Masayuki Yamamoto

- bpo-29080: Removes hard dependency on hg.exe from PCBuild/build.bat

- bpo-23903: Added missed names to PC/python3.def.

- bpo-28762: lockf() is available on Android API level 24, but the F_LOCK macro is not defined in android-ndk-r13.

- bpo-28538: Fix the compilation error that occurs because if_nameindex() is available on Android API level 24, but the if_nameindex structure is not defined.

- bpo-20211: Do not add the directory for installing C header files and the directory for installing object code libraries to the cross compilation search paths. Original patch by Thomas Petazzoni.

- bpo-28849: Do not define sys.implementation._multiarch on Android.

## Python 3.6.0 final

Release date: 2016-12-23

No changes since release candidate 2

## Python 3.6.0 release candidate 2

Release date: 2016-12-16

### Core and Builtins

- bpo-28147: Fix a memory leak in split-table dictionaries: setattr() must not convert combined table into split table. Patch written by INADA Naoki.

- bpo-28990: Fix asyncio SSL hanging if connection is closed before handshake is completed. (Patch by HoHo-Ho)

### Tools/Demos

- bpo-28770: Fix python-gdb.py for fastcalls.

### Windows

- bpo-28896: Deprecate WindowsRegistryFinder.

### Build

- bpo-28898: Prevent gdb build errors due to HAVE_LONG_LONG redefinition.

## Python 3.6.0 release candidate 1

Release date: 2016-12-06

### Core and Builtins

- bpo-23722: Rather than silently producing a class that doesn’t support zero-argument `super()` in methods, failing to pass the new `__classcell__` namespace entry up to `type.__new__` now results in a `DeprecationWarning` and a class that supports zero-argument `super()`.

- bpo-28797: Modifying the class __dict__ inside the __set_name__ method of a descriptor that is used inside that class no longer prevents calling the __set_name__ method of other descriptors.

- bpo-28782: Fix a bug in the implementation `yield from` when checking if the next instruction is YIELD_FROM. Regression introduced by WORDCODE (bpo-26647).

### Library

- bpo-27030: Unknown escapes in re.sub() replacement template are allowed again. But they still are deprecated and will be disabled in 3.7.

- bpo-28835: Fix a regression introduced in warnings.catch_warnings(): call warnings.showwarning() if it was overridden inside the context manager.

- bpo-27172: To assist with upgrades from 2.7, the previously documented deprecation of `inspect.getfullargspec()` has been reversed. This decision may be revisited again after the Python 2.7 branch is no longer officially supported.

- bpo-26273: Add new `socket.TCP_CONGESTION` (Linux 2.6.13) and `socket.TCP_USER_TIMEOUT` (Linux 2.6.37) constants. Patch written by Omar Sandoval.

- bpo-24142: Reading a corrupt config file left configparser in an invalid state. Original patch by Florian Höch.

- bpo-28843: Fix asyncio C Task to handle exceptions __traceback__.

### C API

- bpo-28808: PyUnicode_CompareWithASCIIString() now never raises exceptions.

### Documentation

- bpo-23722: The data model reference and the porting section in the What’s New guide now cover the additional `__classcell__` handling needed for custom metaclasses to fully support PEP 487 and zero-argument `super()`.

### Tools/Demos

- bpo-28023: Fix python-gdb.py didn’t support new dict implementation.

## Python 3.6.0 beta 4

Release date: 2016-11-21

### Core and Builtins

- bpo-28532: Show sys.version when -V option is supplied twice.

- bpo-27100: The with-statement now checks for __enter__ before it checks for __exit__. This gives less confusing error messages when both methods are missing. Patch by Jonathan Ellington.

- bpo-28746: Fix the set_inheritable() file descriptor method on platforms that do not have the ioctl FIOCLEX and FIONCLEX commands.

- bpo-26920: Fix not getting the locale’s charset upon initializing the interpreter, on platforms that do not have langinfo.

- bpo-28648: Fixed crash in Py_DecodeLocale() in debug build on Mac OS X when decode astral characters. Patch by Xiang Zhang.

- bpo-19398: Extra slash no longer added to sys.path components in case of empty compile-time PYTHONPATH components.

- bpo-28665: Improve speed of the STORE_DEREF opcode by 40%.

- bpo-28583: PyDict_SetDefault didn’t combine split table when needed. Patch by Xiang Zhang.

- bpo-27243: Change PendingDeprecationWarning -> DeprecationWarning. As it was agreed in the issue, __aiter__ returning an awaitable should result in PendingDeprecationWarning in 3.5 and in DeprecationWarning in 3.6.

- bpo-26182: Fix a refleak in code that raises DeprecationWarning.

- bpo-28721: Fix asynchronous generators aclose() and athrow() to handle StopAsyncIteration propagation properly.

### Library

- bpo-28752: Restored the __reduce__() methods of datetime objects.

- bpo-28727: Regular expression patterns, _sre.SRE_Pattern objects created by re.compile(), become comparable (only x==y and x!=y operators). This change should fix the bpo-18383: don’t duplicate warning filters when the warnings module is reloaded (thing usually only done in unit tests).

- bpo-20572: The subprocess.Popen.wait method’s undocumented endtime parameter now raises a DeprecationWarning.

- bpo-25659: In ctypes, prevent a crash calling the from_buffer() and from_buffer_copy() methods on abstract classes like Array.

- bpo-19717: Makes Path.resolve() succeed on paths that do not exist. Patch by Vajrasky Kok

- bpo-28563: Fixed possible DoS and arbitrary code execution when handle plural form selections in the gettext module. The expression parser now supports exact syntax supported by GNU gettext.

- bpo-28387: Fixed possible crash in _io.TextIOWrapper deallocator when the garbage collector is invoked in other thread. Based on patch by Sebastian Cufre.

- bpo-28600: Optimize loop.call_soon.

- bpo-28613: Fix get_event_loop() return the current loop if called from coroutines/callbacks.

- bpo-28634: Fix asyncio.isfuture() to support unittest.Mock.

- bpo-26081: Fix refleak in _asyncio.Future.__iter__().throw.

- bpo-28639: Fix inspect.isawaitable to always return bool Patch by Justin Mayfield.

- bpo-28652: Make loop methods reject socket kinds they do not support.

- bpo-28653: Fix a refleak in functools.lru_cache.

- bpo-28703: Fix asyncio.iscoroutinefunction to handle Mock objects.

- bpo-28704: Fix create_unix_server to support Path-like objects (PEP 519).

- bpo-28720: Add collections.abc.AsyncGenerator.

### Documentation

- bpo-28513: Documented command-line interface of zipfile.

### Tests

- bpo-28666: Now test.support.rmtree is able to remove unwritable or unreadable directories.

- bpo-23839: Various caches now are cleared before running every test file.

### Build

- bpo-10656: Fix out-of-tree building on AIX. Patch by Tristan Carel and Michael Haubenwallner.

- bpo-26359: Rename –with-optimiations to –enable-optimizations.

- bpo-28676: Prevent missing ‘getentropy’ declaration warning on macOS. Patch by Gareth Rees.

## Python 3.6.0 beta 3

Release date: 2016-10-31

### Core and Builtins

- bpo-28128: Deprecation warning for invalid str and byte escape sequences now prints better information about where the error occurs. Patch by Serhiy Storchaka and Eric Smith.

- bpo-28509: dict.update() no longer allocate unnecessary large memory.

- bpo-28426: Fixed potential crash in PyUnicode_AsDecodedObject() in debug build.

- bpo-28517: Fixed of-by-one error in the peephole optimizer that caused keeping unreachable code.

- bpo-28214: Improved exception reporting for problematic __set_name__ attributes.

- bpo-23782: Fixed possible memory leak in _PyTraceback_Add() and exception loss in PyTraceBack_Here().

- bpo-28471: Fix “Python memory allocator called without holding the GIL” crash in socket.setblocking.

### Library

- bpo-27517: LZMA compressor and decompressor no longer raise exceptions if given empty data twice. Patch by Benjamin Fogle.

- bpo-28549: Fixed segfault in curses’s addch() with ncurses6.

- bpo-28449: tarfile.open() with mode “r” or “r:” now tries to open a tar file with compression before trying to open it without compression. Otherwise it had 50% chance failed with ignore_zeros=True.

- bpo-23262: The webbrowser module now supports Firefox 36+ and derived browsers. Based on patch by Oleg Broytman.

- bpo-27939: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused by representing the scale as float value internally in Tk. tkinter.IntVar now works if float value is set to underlying Tk variable.

- bpo-18844: The various ways of specifying weights for random.choices() now produce the same result sequences.

- bpo-28255: calendar.TextCalendar().prmonth() no longer prints a space at the start of new line after printing a month’s calendar. Patch by Xiang Zhang.

- bpo-20491: The textwrap.TextWrapper class now honors non-breaking spaces. Based on patch by Kaarle Ritvanen.

- bpo-28353: os.fwalk() no longer fails on broken links.

- bpo-28430: Fix iterator of C implemented asyncio.Future doesn’t accept non-None value is passed to it.send(val).

- bpo-27025: Generated names for Tkinter widgets now start by the “!” prefix for readability.

- bpo-25464: Fixed HList.header_exists() in tkinter.tix module by addin a workaround to Tix library bug.

- bpo-28488: shutil.make_archive() no longer adds entry “./” to ZIP archive.

- bpo-25953: re.sub() now raises an error for invalid numerical group reference in replacement template even if the pattern is not found in the string. Error message for invalid group reference now includes the group index and the position of the reference. Based on patch by SilentGhost.

- bpo-18219: Optimize csv.DictWriter for large number of columns. Patch by Mariatta Wijaya.

- bpo-28448: Fix C implemented asyncio.Future didn’t work on Windows.

- bpo-28480: Fix error building socket module when multithreading is disabled.

- bpo-24452: Make webbrowser support Chrome on Mac OS X.

- bpo-20766: Fix references leaked by pdb in the handling of SIGINT handlers.

- bpo-28492: Fix how StopIteration exception is raised in _asyncio.Future.

- bpo-28500: Fix asyncio to handle async gens GC from another thread.

- bpo-26923: Fix asyncio.Gather to refuse being cancelled once all children are done. Patch by Johannes Ebke.

- bpo-26796: Don’t configure the number of workers for default threadpool executor. Initial patch by Hans Lawrenz.

- bpo-28544: Implement asyncio.Task in C.

### Windows

- bpo-28522: Fixes mishandled buffer reallocation in getpathp.c

### Build

- bpo-28444: Fix missing extensions modules when cross compiling.

- bpo-28208: Update Windows build and OS X installers to use SQLite 3.14.2.

- bpo-28248: Update Windows build and OS X installers to use OpenSSL 1.0.2j.

### Tests

- bpo-26944: Fix test_posix for Android where ‘id -G’ is entirely wrong or missing the effective gid.

- bpo-28409: regrtest: fix the parser of command line arguments.

## Python 3.6.0 beta 2

Release date: 2016-10-10

### Core and Builtins

- bpo-28183: Optimize and cleanup dict iteration.

- bpo-26081: Added C implementation of asyncio.Future. Original patch by Yury Selivanov.

- bpo-28379: Added sanity checks and tests for PyUnicode_CopyCharacters(). Patch by Xiang Zhang.

- bpo-28376: The type of long range iterator is now registered as Iterator. Patch by Oren Milman.

- bpo-28376: Creating instances of range_iterator by calling range_iterator type now is deprecated. Patch by Oren Milman.

- bpo-28376: The constructor of range_iterator now checks that step is not 0. Patch by Oren Milman.

- bpo-26906: Resolving special methods of uninitialized type now causes implicit initialization of the type instead of a fail.

- bpo-18287: PyType_Ready() now checks that tp_name is not NULL. Original patch by Niklas Koep.

- bpo-24098: Fixed possible crash when AST is changed in process of compiling it.

- bpo-28201: Dict reduces possibility of 2nd conflict in hash table when hashes have same lower bits.

- bpo-28350: String constants with null character no longer interned.

- bpo-26617: Fix crash when GC runs during weakref callbacks.

- bpo-27942: String constants now interned recursively in tuples and frozensets.

- bpo-21578: Fixed misleading error message when ImportError called with invalid keyword args.

- bpo-28203: Fix incorrect type in complex(1.0, {2:3}) error message. Patch by Soumya Sharma.

- bpo-28086: Single var-positional argument of tuple subtype was passed unscathed to the C-defined function. Now it is converted to exact tuple.

- bpo-28214: Now __set_name__ is looked up on the class instead of the instance.

- bpo-27955: Fallback on reading /dev/urandom device when the getrandom() syscall fails with EPERM, for example when blocked by SECCOMP.

- bpo-28192: Don’t import readline in isolated mode.

- Upgrade internal unicode databases to Unicode version 9.0.0.

- bpo-28131: Fix a regression in zipimport’s compile_source(). zipimport should use the same optimization level as the interpreter.

- bpo-28126: Replace Py_MEMCPY with memcpy(). Visual Studio can properly optimize memcpy().

- bpo-28120: Fix dict.pop() for splitted dictionary when trying to remove a “pending key” (Not yet inserted in split-table). Patch by Xiang Zhang.

- bpo-26182: Raise DeprecationWarning when async and await keywords are used as variable/attribute/class/function name.

### Library

- bpo-27998: Fixed bytes path support in os.scandir() on Windows. Patch by Eryk Sun.

- bpo-28317: The disassembler now decodes FORMAT_VALUE argument.

- bpo-26293: Fixed writing ZIP files that starts not from the start of the file. Offsets in ZIP file now are relative to the start of the archive in conforming to the specification.

- bpo-28380: unittest.mock Mock autospec functions now properly support assert_called, assert_not_called, and assert_called_once.

- bpo-27181: remove statistics.geometric_mean and defer until 3.7.

- bpo-28229: lzma module now supports pathlib.

- bpo-28321: Fixed writing non-BMP characters with binary format in plistlib.

- bpo-28225: bz2 module now supports pathlib. Initial patch by Ethan Furman.

- bpo-28227: gzip now supports pathlib. Patch by Ethan Furman.

- bpo-27358: Optimized merging var-keyword arguments and improved error message when passing a non-mapping as a var-keyword argument.

- bpo-28257: Improved error message when passing a non-iterable as a var-positional argument. Added opcode BUILD_TUPLE_UNPACK_WITH_CALL.

- bpo-28322: Fixed possible crashes when unpickle itertools objects from incorrect pickle data. Based on patch by John Leitch.

- bpo-28228: imghdr now supports pathlib.

- bpo-28226: compileall now supports pathlib.

- bpo-28314: Fix function declaration (C flags) for the getiterator() method of xml.etree.ElementTree.Element.

- bpo-28148: Stop using localtime() and gmtime() in the time module. Introduced platform independent _PyTime_localtime API that is similar to POSIX localtime_r, but available on all platforms. Patch by Ed Schouten.

- bpo-28253: Fixed calendar functions for extreme months: 0001-01 and 9999-12. Methods itermonthdays() and itermonthdays2() are reimplemented so that they don’t call itermonthdates() which can cause datetime.date under/overflow.

- bpo-28275: Fixed possible use after free in the decompress() methods of the LZMADecompressor and BZ2Decompressor classes. Original patch by John Leitch.

- bpo-27897: Fixed possible crash in sqlite3.Connection.create_collation() if pass invalid string-like object as a name. Patch by Xiang Zhang.

- bpo-18844: random.choices() now has k as a keyword-only argument to improve the readability of common cases and come into line with the signature used in other languages.

- bpo-18893: Fix invalid exception handling in Lib/ctypes/macholib/dyld.py. Patch by Madison May.

- bpo-27611: Fixed support of default root window in the tkinter.tix module. Added the master parameter in the DisplayStyle constructor.

- bpo-27348: In the traceback module, restore the formatting of exception messages like “Exception: None”. This fixes a regression introduced in 3.5a2.

- bpo-25651: Allow false values to be used for msg parameter of subTest().

- bpo-27778: Fix a memory leak in os.getrandom() when the getrandom() is interrupted by a signal and a signal handler raises a Python exception.

- bpo-28200: Fix memory leak on Windows in the os module (fix path_converter() function).

- bpo-25400: RobotFileParser now correctly returns default values for crawl_delay and request_rate. Initial patch by Peter Wirtz.

- bpo-27932: Prevent memory leak in win32_ver().

- Fix UnboundLocalError in socket._sendfile_use_sendfile.

- bpo-28075: Check for ERROR_ACCESS_DENIED in Windows implementation of os.stat(). Patch by Eryk Sun.

- bpo-22493: Warning message emitted by using inline flags in the middle of regular expression now contains a (truncated) regex pattern. Patch by Tim Graham.

- bpo-25270: Prevent codecs.escape_encode() from raising SystemError when an empty bytestring is passed.

- bpo-28181: Get antigravity over HTTPS. Patch by Kaartic Sivaraam.

- bpo-25895: Enable WebSocket URL schemes in urllib.parse.urljoin. Patch by Gergely Imreh and Markus Holtermann.

- bpo-28114: Fix a crash in parse_envlist() when env contains byte strings. Patch by Eryk Sun.

- bpo-27599: Fixed buffer overrun in binascii.b2a_qp() and binascii.a2b_qp().

- bpo-27906: Fix socket accept exhaustion during high TCP traffic. Patch by Kevin Conway.

- bpo-28174: Handle when SO_REUSEPORT isn’t properly supported. Patch by Seth Michael Larson.

- bpo-26654: Inspect functools.partial in asyncio.Handle.__repr__. Patch by iceboy.

- bpo-26909: Fix slow pipes IO in asyncio. Patch by INADA Naoki.

- bpo-28176: Fix callbacks race in asyncio.SelectorLoop.sock_connect.

- bpo-27759: Fix selectors incorrectly retain invalid file descriptors. Patch by Mark Williams.

- bpo-28368: Refuse monitoring processes if the child watcher has no loop attached. Patch by Vincent Michel.

- bpo-28369: Raise RuntimeError when transport’s FD is used with add_reader, add_writer, etc.

- bpo-28370: Speedup asyncio.StreamReader.readexactly. Patch by Коренберг Марк.

- bpo-28371: Deprecate passing asyncio.Handles to run_in_executor.

- bpo-28372: Fix asyncio to support formatting of non-python coroutines.

- bpo-28399: Remove UNIX socket from FS before binding. Patch by Коренберг Марк.

- bpo-27972: Prohibit Tasks to await on themselves.

### Windows

- bpo-28402: Adds signed catalog files for stdlib on Windows.

- bpo-28333: Enables Unicode for ps1/ps2 and input() prompts. (Patch by Eryk Sun)

- bpo-28251: Improvements to help manuals on Windows.

- bpo-28110: launcher.msi has different product codes between 32-bit and 64-bit

- bpo-28161: Opening CON for write access fails

- bpo-28162: WindowsConsoleIO readall() fails if first line starts with Ctrl+Z

- bpo-28163: WindowsConsoleIO fileno() passes wrong flags to _open_osfhandle

- bpo-28164: _PyIO_get_console_type fails for various paths

- bpo-28137: Renames Windows path file to ._pth

- bpo-28138: Windows ._pth file should allow import site

### C API

- bpo-28426: Deprecated undocumented functions PyUnicode_AsEncodedObject(), PyUnicode_AsDecodedObject(), PyUnicode_AsDecodedUnicode() and PyUnicode_AsEncodedUnicode().

### Build

- bpo-28258: Fixed build with Estonian locale (python-config and distclean targets in Makefile). Patch by Arfrever Frehtes Taifersar Arahesis.

- bpo-26661: setup.py now detects system libffi with multiarch wrapper.

- bpo-15819: Remove redundant include search directory option for building outside the source tree.

### Tests

- bpo-28217: Adds _testconsole module to test console input.

## Python 3.6.0 beta 1

Release date: 2016-09-12

### Core and Builtins

- bpo-23722: The __class__ cell used by zero-argument super() is now initialized from type.__new__ rather than __build_class__, so class methods relying on that will now work correctly when called from metaclass methods during class creation. Patch by Martin Teichmann.

- bpo-25221: Fix corrupted result from PyLong_FromLong(0) when Python is compiled with NSMALLPOSINTS = 0.

- bpo-27080: Implement formatting support for PEP 515. Initial patch by Chris Angelico.

- bpo-27199: In tarfile, expose copyfileobj bufsize to improve throughput. Patch by Jason Fried.

- bpo-27948: In f-strings, only allow backslashes inside the braces (where the expressions are). This is a breaking change from the 3.6 alpha releases, where backslashes are allowed anywhere in an f-string. Also, require that expressions inside f-strings be enclosed within literal braces, and not escapes like `f'\x7b"hi"\x7d'`.

- bpo-28046: Remove platform-specific directories from sys.path.

- bpo-28071: Add early-out for differencing from an empty set.

- bpo-25758: Prevents zipimport from unnecessarily encoding a filename (patch by Eryk Sun)

- bpo-25856: The __module__ attribute of extension classes and functions now is interned. This leads to more compact pickle data with protocol 4.

- bpo-27213: Rework CALL_FUNCTION* opcodes to produce shorter and more efficient bytecode. Patch by Demur Rumed, design by Serhiy Storchaka, reviewed by Serhiy Storchaka and Victor Stinner.

- bpo-26331: Implement tokenizing support for PEP 515. Patch by Georg Brandl.

- bpo-27999: Make “global after use” a SyntaxError, and ditto for nonlocal. Patch by Ivan Levkivskyi.

- bpo-28003: Implement PEP 525 – Asynchronous Generators.

- bpo-27985: Implement PEP 526 – Syntax for Variable Annotations. Patch by Ivan Levkivskyi.

- bpo-26058: Add a new private version to the builtin dict type, incremented at each dictionary creation and at each dictionary change. Implementation of the PEP 509.

- bpo-27364: A backslash-character pair that is not a valid escape sequence now generates a DeprecationWarning. Patch by Emanuel Barry.

- bpo-27350: `dict` implementation is changed like PyPy. It is more compact and preserves insertion order. (Concept developed by Raymond Hettinger and patch by Inada Naoki.)

- bpo-27911: Remove unnecessary error checks in `exec_builtin_or_dynamic()`.

- bpo-27078: Added BUILD_STRING opcode. Optimized f-strings evaluation.

- bpo-17884: Python now requires systems with inttypes.h and stdint.h

- bpo-27961: Require platforms to support `long long`. Python hasn’t compiled without `long long` for years, so this is basically a formality.

- bpo-27355: Removed support for Windows CE. It was never finished, and Windows CE is no longer a relevant platform for Python.

- Implement PEP 523.

- bpo-27870: A left shift of zero by a large integer no longer attempts to allocate large amounts of memory.

- bpo-25402: In int-to-decimal-string conversion, improve the estimate of the intermediate memory required, and remove an unnecessarily strict overflow check. Patch by Serhiy Storchaka.

- bpo-27214: In long_invert, be more careful about modifying object returned by long_add, and remove an unnecessary check for small longs. Thanks Oren Milman for analysis and patch.

- bpo-27506: Support passing the bytes/bytearray.translate() “delete” argument by keyword.

- bpo-27812: Properly clear out a generator’s frame’s backreference to the generator to prevent crashes in frame.clear().

- bpo-27811: Fix a crash when a coroutine that has not been awaited is finalized with warnings-as-errors enabled.

- bpo-27587: Fix another issue found by PVS-Studio: Null pointer check after use of ‘def’ in _PyState_AddModule(). Initial patch by Christian Heimes.

- bpo-27792: The modulo operation applied to `bool` and other `int` subclasses now always returns an `int`. Previously the return type depended on the input values. Patch by Xiang Zhang.

- bpo-26984: int() now always returns an instance of exact int.

- bpo-25604: Fix a minor bug in integer true division; this bug could potentially have caused off-by-one-ulp results on platforms with unreliable ldexp implementations.

- bpo-24254: Make class definition namespace ordered by default.

- bpo-27662: Fix an overflow check in `List_New`: the original code was checking against `Py_SIZE_MAX` instead of the correct upper bound of `Py_SSIZE_T_MAX`. Patch by Xiang Zhang.

- bpo-27782: Multi-phase extension module import now correctly allows the `m_methods` field to be used to add module level functions to instances of non-module types returned from `Py_create_mod`. Patch by Xiang Zhang.

- bpo-27936: The round() function accepted a second None argument for some types but not for others. Fixed the inconsistency by accepting None for all numeric types.

- bpo-27487: Warn if a submodule argument to “python -m” or runpy.run_module() is found in sys.modules after parent packages are imported, but before the submodule is executed.

- bpo-27157: Make only type() itself accept the one-argument form. Patch by Eryk Sun and Emanuel Barry.

- bpo-27558: Fix a SystemError in the implementation of “raise” statement. In a brand new thread, raise a RuntimeError since there is no active exception to reraise. Patch written by Xiang Zhang.

- bpo-28008: Implement PEP 530 – asynchronous comprehensions.

- bpo-27942: Fix memory leak in codeobject.c

### Library

- bpo-28732: Fix crash in os.spawnv() with no elements in args

- bpo-28485: Always raise ValueError for negative compileall.compile_dir(workers=…) parameter, even when multithreading is unavailable.

- bpo-28037: Use sqlite3_get_autocommit() instead of setting Connection->inTransaction manually.

- bpo-25283: Attributes tm_gmtoff and tm_zone are now available on all platforms in the return values of time.localtime() and time.gmtime().

- bpo-24454: Regular expression match object groups are now accessible using __getitem__. “mo[x]” is equivalent to “mo.group(x)”.

- bpo-10740: sqlite3 no longer implicitly commit an open transaction before DDL statements.

- bpo-17941: Add a module parameter to collections.namedtuple().

- bpo-22493: Inline flags now should be used only at the start of the regular expression. Deprecation warning is emitted if uses them in the middle of the regular expression.

- bpo-26885: xmlrpc now supports unmarshalling additional data types used by Apache XML-RPC implementation for numerics and None.

- bpo-28070: Fixed parsing inline verbose flag in regular expressions.

- bpo-19500: Add client-side SSL session resumption to the ssl module.

- bpo-28022: Deprecate ssl-related arguments in favor of SSLContext. The deprecation include manual creation of SSLSocket and certfile/keyfile (or similar) in ftplib, httplib, imaplib, smtplib, poplib and urllib.

- bpo-28043: SSLContext has improved default settings: OP_NO_SSLv2, OP_NO_SSLv3, OP_NO_COMPRESSION, OP_CIPHER_SERVER_PREFERENCE, OP_SINGLE_DH_USE, OP_SINGLE_ECDH_USE and HIGH ciphers without MD5.

- bpo-24693: Changed some RuntimeError’s in the zipfile module to more appropriate types. Improved some error messages and debugging output.

- bpo-17909: `json.load` and `json.loads` now support binary input encoded as UTF-8, UTF-16 or UTF-32. Patch by Serhiy Storchaka.

- bpo-27137: the pure Python fallback implementation of `functools.partial` now matches the behaviour of its accelerated C counterpart for subclassing, pickling and text representation purposes. Patch by Emanuel Barry and Serhiy Storchaka.

- Fix possible integer overflows and crashes in the mmap module with unusual usage patterns.

- bpo-1703178: Fix the ability to pass the –link-objects option to the distutils build_ext command.

- bpo-28019: itertools.count() no longer rounds non-integer step in range between 1.0 and 2.0 to 1.

- bpo-18401: Pdb now supports the ‘readrc’ keyword argument to control whether .pdbrc files should be read. Patch by Martin Matusiak and Sam Kimbrel.

- bpo-25969: Update the lib2to3 grammar to handle the unpacking generalizations added in 3.5.

- bpo-14977: mailcap now respects the order of the lines in the mailcap files (“first match”), as required by RFC 1542. Patch by Michael Lazar.

- bpo-28082: Convert re flag constants to IntFlag.

- bpo-28025: Convert all ssl module constants to IntEnum and IntFlags. SSLContext properties now return flags and enums.

- bpo-23591: Add Flag, IntFlag, and auto() to enum module.

- bpo-433028: Added support of modifier spans in regular expressions.

- bpo-24594: Validates persist parameter when opening MSI database

- bpo-17582: xml.etree.ElementTree nows preserves whitespaces in attributes (Patch by Duane Griffin. Reviewed and approved by Stefan Behnel.)

- bpo-28047: Fixed calculation of line length used for the base64 CTE in the new email policies.

- bpo-27576: Fix call order in OrderedDict.__init__().

- email.generator.DecodedGenerator now supports the policy keyword.

- bpo-28027: Remove undocumented modules from `Lib/plat-*`: IN, CDROM, DLFCN, TYPES, CDIO, and STROPTS.

- bpo-27445: Don’t pass str(_charset) to MIMEText.set_payload(). Patch by Claude Paroz.

- bpo-24277: The new email API is no longer provisional, and the docs have been reorganized and rewritten to emphasize the new API.

- bpo-22450: urllib now includes an `Accept: */*` header among the default headers. This makes the results of REST API requests more consistent and predictable especially when proxy servers are involved.

- lib2to3.pgen3.driver.load_grammar() now creates a stable cache file between runs given the same Grammar.txt input regardless of the hash randomization setting.

- bpo-28005: Allow ImportErrors in encoding implementation to propagate.

- bpo-26667: Support path-like objects in importlib.util.

- bpo-27570: Avoid zero-length memcpy() etc calls with null source pointers in the “ctypes” and “array” modules.

- bpo-22233: Break email header lines only on the RFC specified CR and LF characters, not on arbitrary unicode line breaks. This also fixes a bug in HTTP header parsing.

- bpo-27331: The email.mime classes now all accept an optional policy keyword.

- bpo-27988: Fix email iter_attachments incorrect mutation of payload list.

- bpo-16113: Add SHA-3 and SHAKE support to hashlib module.

- Eliminate a tautological-pointer-compare warning in _scproxy.c.

- bpo-27776: The `os.urandom()` function does now block on Linux 3.17 and newer until the system urandom entropy pool is initialized to increase the security. This change is part of the PEP 524.

- bpo-27778: Expose the Linux `getrandom()` syscall as a new `os.getrandom()` function. This change is part of the PEP 524.

- bpo-27691: Fix ssl module’s parsing of GEN_RID subject alternative name fields in X.509 certs.

- bpo-18844: Add random.choices().

- bpo-25761: Improved error reporting about truncated pickle data in C implementation of unpickler. UnpicklingError is now raised instead of AttributeError and ValueError in some cases.

- bpo-26798: Add BLAKE2 (blake2b and blake2s) to hashlib.

- bpo-26032: Optimized globbing in pathlib by using os.scandir(); it is now about 1.5–4 times faster.

- bpo-25596: Optimized glob() and iglob() functions in the glob module; they are now about 3–6 times faster.

- bpo-27928: Add scrypt (password-based key derivation function) to hashlib module (requires OpenSSL 1.1.0).

- bpo-27850: Remove 3DES from ssl module’s default cipher list to counter measure sweet32 attack (CVE 2016-2183).

- bpo-27766: Add ChaCha20 Poly1305 to ssl module’s default cipher list. (Required OpenSSL 1.1.0 or LibreSSL).

- bpo-25387: Check return value of winsound.MessageBeep.

- bpo-27866: Add SSLContext.get_ciphers() method to get a list of all enabled ciphers.

- bpo-27744: Add AF_ALG (Linux Kernel crypto) to socket module.

- bpo-26470: Port ssl and hashlib module to OpenSSL 1.1.0.

- bpo-11620: Fix support for SND_MEMORY in winsound.PlaySound. Based on a patch by Tim Lesher.

- bpo-11734: Add support for IEEE 754 half-precision floats to the struct module. Based on a patch by Eli Stevens.

- bpo-27919: Deprecated `extra_path` distribution option in distutils packaging.

- bpo-23229: Add new `cmath` constants: `cmath.inf` and `cmath.nan` to match `math.inf` and `math.nan`, and also `cmath.infj` and `cmath.nanj` to match the format used by complex repr.

- bpo-27842: The csv.DictReader now returns rows of type OrderedDict. (Contributed by Steve Holden.)

- Remove support for passing a file descriptor to os.access. It never worked but previously didn’t raise.

- bpo-12885: Fix error when distutils encounters symlink.

- bpo-27881: Fixed possible bugs when setting sqlite3.Connection.isolation_level. Based on patch by Xiang Zhang.

- bpo-27861: Fixed a crash in sqlite3.Connection.cursor() when a factory creates not a cursor. Patch by Xiang Zhang.

- bpo-19884: Avoid spurious output on OS X with Gnu Readline.

- bpo-27706: Restore deterministic behavior of random.Random().seed() for string seeds using seeding version 1. Allows sequences of calls to random() to exactly match those obtained in Python 2. Patch by Nofar Schnider.

- bpo-10513: Fix a regression in Connection.commit(). Statements should not be reset after a commit.

- bpo-12319: Chunked transfer encoding support added to http.client.HTTPConnection requests. The urllib.request.AbstractHTTPHandler class does not enforce a Content-Length header any more. If a HTTP request has a file or iterable body, but no Content-Length header, the library now falls back to use chunked transfer-encoding.

- A new version of typing.py from https://github.com/python/typing: - Collection (only for 3.6) (bpo-27598) - Add FrozenSet to __all__ (upstream #261) - fix crash in _get_type_vars() (upstream #259) - Remove the dict constraint in ForwardRef._eval_type (upstream #252)

- bpo-27832: Make `_normalize` parameter to `Fraction` constructor keyword-only, so that `Fraction(2, 3, 4)` now raises `TypeError`.

- bpo-27539: Fix unnormalised `Fraction.__pow__` result in the case of negative exponent and negative base.

- bpo-21718: cursor.description is now available for queries using CTEs.

- bpo-27819: In distutils sdists, simply produce the “gztar” (gzipped tar format) distributions on all platforms unless “formats” is supplied.

- bpo-2466: posixpath.ismount now correctly recognizes mount points which the user does not have permission to access.

- bpo-9998: On Linux, ctypes.util.find_library now looks in LD_LIBRARY_PATH for shared libraries.

- bpo-27573: exit message for code.interact is now configurable.

- bpo-27930: Improved behaviour of logging.handlers.QueueListener. Thanks to Paulo Andrade and Petr Viktorin for the analysis and patch.

- bpo-6766: Distributed reference counting added to multiprocessing to support nesting of shared values / proxy objects.

- bpo-21201: Improves readability of multiprocessing error message. Thanks to Wojciech Walczak for patch.

- asyncio: Add set_protocol / get_protocol to Transports.

- bpo-27456: asyncio: Set TCP_NODELAY by default.

### IDLE

- bpo-15308: Add ‘interrupt execution’ (^C) to Shell menu. Patch by Roger Serwy, updated by Bayard Randel.

- bpo-27922: Stop IDLE tests from ‘flashing’ gui widgets on the screen.

- bpo-27891: Consistently group and sort imports within idlelib modules.

- bpo-17642: add larger font sizes for classroom projection.

- Add version to title of IDLE help window.

- bpo-25564: In section on IDLE – console differences, mention that using exec means that __builtins__ is defined for each statement.

- bpo-27821: Fix 3.6.0a3 regression that prevented custom key sets from being selected when no custom theme was defined.

### C API

- bpo-26900: Excluded underscored names and other private API from limited API.

- bpo-26027: Add support for path-like objects in PyUnicode_FSConverter() & PyUnicode_FSDecoder().

### Tests

- bpo-27427: Additional tests for the math module. Patch by Francisco Couzo.

- bpo-27953: Skip math and cmath tests that fail on OS X 10.4 due to a poor libm implementation of tan.

- bpo-26040: Improve test_math and test_cmath coverage and rigour. Patch by Jeff Allen.

- bpo-27787: Call gc.collect() before checking each test for “dangling threads”, since the dangling threads are weak references.

### Build

- bpo-27566: Fix clean target in freeze makefile (patch by Lisa Roach)

- bpo-27705: Update message in validate_ucrtbase.py

- bpo-27976: Deprecate building _ctypes with the bundled copy of libffi on non-OSX UNIX platforms.

- bpo-27983: Cause lack of llvm-profdata tool when using clang as required for PGO linking to be a configure time error rather than make time when `--with-optimizations` is enabled. Also improve our ability to find the llvm-profdata tool on MacOS and some Linuxes.

- bpo-21590: Support for DTrace and SystemTap probes.

- bpo-26307: The profile-opt build now applies PGO to the built-in modules.

- bpo-26359: Add the –with-optimizations flag to turn on LTO and PGO build support when available.

- bpo-27917: Set platform triplets for Android builds.

- bpo-25825: Update references to the $(LIBPL) installation path on AIX. This path was changed in 3.2a4.

- Update OS X installer to use SQLite 3.14.1 and XZ 5.2.2.

- bpo-21122: Fix LTO builds on OS X.

- bpo-17128: Build OS X installer with a private copy of OpenSSL. Also provide a sample Install Certificates command script to install a set of root certificates from the third-party certifi module.

### Tools/Demos

- bpo-27952: Get Tools/scripts/fixcid.py working with Python 3 and the current “re” module, avoid invalid Python backslash escapes, and fix a bug parsing escaped C quote signs.

### Windows

- bpo-28065: Update xz dependency to 5.2.2 and build it from source.

- bpo-25144: Ensures TargetDir is set before continuing with custom install.

- bpo-1602: Windows console doesn’t input or print Unicode (PEP 528)

- bpo-27781: Change file system encoding on Windows to UTF-8 (PEP 529)

- bpo-27731: Opt-out of MAX_PATH on Windows 10

- bpo-6135: Adds encoding and errors parameters to subprocess.

- bpo-27959: Adds oem encoding, alias ansi to mbcs, move aliasmbcs to codec lookup.

- bpo-27982: The functions of the winsound module now accept keyword arguments.

- bpo-20366: Build full text search support into SQLite on Windows.

- bpo-27756: Adds new icons for Python files and processes on Windows. Designs by Cherry Wang.

- bpo-27883: Update sqlite to 3.14.1.0 on Windows.

## Python 3.6.0 alpha 4

Release date: 2016-08-15

### Core and Builtins

- bpo-27704: Optimized creating bytes and bytearray from byte-like objects and iterables. Speed up to 3 times for short objects. Original patch by Naoki Inada.

- bpo-26823: Large sections of repeated lines in tracebacks are now abbreviated as “[Previous line repeated {count} more times]” by the builtin traceback rendering. Patch by Emanuel Barry.

- bpo-27574: Decreased an overhead of parsing keyword arguments in functions implemented with using Argument Clinic.

- bpo-22557: Now importing already imported modules is up to 2.5 times faster.

- bpo-17596: Include <wincrypt.h> to help with Min GW building.

- bpo-17599: On Windows, rename the privately defined REPARSE_DATA_BUFFER structure to avoid conflicting with the definition from Min GW.

- bpo-27507: Add integer overflow check in bytearray.extend(). Patch by Xiang Zhang.

- bpo-27581: Don’t rely on wrapping for overflow check in PySequence_Tuple(). Patch by Xiang Zhang.

- bpo-1621: Avoid signed integer overflow in list and tuple operations. Patch by Xiang Zhang.

- bpo-27419: Standard __import__() no longer look up “__import__” in globals or builtins for importing submodules or “from import”. Fixed a crash if raise a warning about unabling to resolve package from __spec__ or __package__.

- bpo-27083: Respect the PYTHONCASEOK environment variable under Windows.

- bpo-27514: Make having too many statically nested blocks a SyntaxError instead of SystemError.

- bpo-27366: Implemented PEP 487 (Simpler customization of class creation). Upon subclassing, the __init_subclass__ classmethod is called on the base class. Descriptors are initialized with __set_name__ after class creation.

### Library

- bpo-26027: Add PEP 519/__fspath__() support to the os and os.path modules. Includes code from Jelle Zijlstra. (See also: bpo-27524)

- bpo-27598: Add Collections to collections.abc. Patch by Ivan Levkivskyi, docs by Neil Girdhar.

- bpo-25958: Support “anti-registration” of special methods from various ABCs, like __hash__, __iter__ or __len__. All these (and several more) can be set to None in an implementation class and the behavior will be as if the method is not defined at all. (Previously, this mechanism existed only for __hash__, to make mutable classes unhashable.) Code contributed by Andrew Barnert and Ivan Levkivskyi.

- bpo-16764: Support keyword arguments to zlib.decompress(). Patch by Xiang Zhang.

- bpo-27736: Prevent segfault after interpreter re-initialization due to ref count problem introduced in code for bpo-27038 in 3.6.0a3. Patch by Xiang Zhang.

- bpo-25628: The verbose and rename parameters for collections.namedtuple are now keyword-only.

- bpo-12345: Add mathematical constant tau to math and cmath. See also PEP 628.

- bpo-26823: traceback.StackSummary.format now abbreviates large sections of repeated lines as “[Previous line repeated {count} more times]” (this change then further affects other traceback display operations in the module). Patch by Emanuel Barry.

- bpo-27664: Add to concurrent.futures.thread.ThreadPoolExecutor() the ability to specify a thread name prefix.

- bpo-27181: Add geometric_mean and harmonic_mean to statistics module.

- bpo-27573: code.interact now prints an message when exiting.

- bpo-6422: Add autorange method to timeit.Timer objects.

- bpo-27773: Correct some memory management errors server_hostname in _ssl.wrap_socket().

- bpo-26750: unittest.mock.create_autospec() now works properly for subclasses of property() and other data descriptors. Removes the never publicly used, never documented unittest.mock.DescriptorTypes tuple.

- bpo-26754: Undocumented support of general bytes-like objects as path in compile() and similar functions is now deprecated.

- bpo-26800: Undocumented support of general bytes-like objects as paths in os functions is now deprecated.

- bpo-26981: Add _order_ compatibility shim to enum.Enum for Python 2/3 code bases.

- bpo-27661: Added tzinfo keyword argument to datetime.combine.

- In the curses module, raise an error if window.getstr() or window.instr() is passed a negative value.

- bpo-27783: Fix possible usage of uninitialized memory in operator.methodcaller.

- bpo-27774: Fix possible Py_DECREF on unowned object in _sre.

- bpo-27760: Fix possible integer overflow in binascii.b2a_qp.

- bpo-27758: Fix possible integer overflow in the _csv module for large record lengths.

- bpo-27568: Prevent HTTPoxy attack (CVE 2016-1000110). Ignore the HTTP_PROXY variable when REQUEST_METHOD environment is set, which indicates that the script is in CGI mode.

- bpo-7063: Remove dead code from the “array” module’s slice handling. Patch by Chuck.

- bpo-27656: Do not assume sched.h defines any SCHED_* constants.

- bpo-27130: In the “zlib” module, fix handling of large buffers (typically 4 GiB) when compressing and decompressing. Previously, inputs were limited to 4 GiB, and compression and decompression operations did not properly handle results of 4 GiB.

- bpo-24773: Implemented PEP 495 (Local Time Disambiguation).

- Expose the EPOLLEXCLUSIVE constant (when it is defined) in the select module.

- bpo-27567: Expose the EPOLLRDHUP and POLLRDHUP constants in the select module.

- bpo-1621: Avoid signed int negation overflow in the “audioop” module.

- bpo-27533: Release GIL in nt._isdir

- bpo-17711: Fixed unpickling by the persistent ID with protocol 0. Original patch by Alexandre Vassalotti.

- bpo-27522: Avoid an unintentional reference cycle in email.feedparser.

- bpo-27512: Fix a segfault when os.fspath() called an __fspath__() method that raised an exception. Patch by Xiang Zhang.

### IDLE

- bpo-27714: text_textview and test_autocomplete now pass when re-run in the same process. This occurs when test_idle fails when run with the -w option but without -jn. Fix warning from test_config.

- bpo-27621: Put query response validation error messages in the query box itself instead of in a separate messagebox. Redo tests to match. Add Mac OSX refinements. Original patch by Mark Roseman.

- bpo-27620: Escape key now closes Query box as cancelled.

- bpo-27609: IDLE: tab after initial whitespace should tab, not autocomplete. This fixes problem with writing docstrings at least twice indented.

- bpo-27609: Explicitly return None when there are also non-None returns. In a few cases, reverse a condition and eliminate a return.

- bpo-25507: IDLE no longer runs buggy code because of its tkinter imports. Users must include the same imports required to run directly in Python.

- bpo-27173: Add ‘IDLE Modern Unix’ to the built-in key sets. Make the default key set depend on the platform. Add tests for the changes to the config module.

- bpo-27452: add line counter and crc to IDLE configHandler test dump.

### Tests

- bpo-25805: Skip a test in test_pkgutil as needed that doesn’t work when `__name__ == __main__`. Patch by SilentGhost.

- bpo-27472: Add test.support.unix_shell as the path to the default shell.

- bpo-27369: In test_pyexpat, avoid testing an error message detail that changed in Expat 2.2.0.

- bpo-27594: Prevent assertion error when running test_ast with coverage enabled: ensure code object has a valid first line number. Patch suggested by Ivan Levkivskyi.

### Windows

- bpo-27647: Update bundled Tcl/Tk to 8.6.6.

- bpo-27610: Adds PEP 514 metadata to Windows installer

- bpo-27469: Adds a shell extension to the launcher so that drag and drop works correctly.

- bpo-27309: Enables proper Windows styles in python[w].exe manifest.

### Build

- bpo-27713: Suppress spurious build warnings when updating importlib’s bootstrap files. Patch by Xiang Zhang

- bpo-25825: Correct the references to Modules/python.exp, which is required on AIX. The references were accidentally changed in 3.5.0a1.

- bpo-27453: CPP invocation in configure must use CPPFLAGS. Patch by Chi Hsuan Yen.

- bpo-27641: The configure script now inserts comments into the makefile to prevent the pgen and _freeze_importlib executables from being cross-compiled.

- bpo-26662: Set PYTHON_FOR_GEN in configure as the Python program to be used for file generation during the build.

- bpo-10910: Avoid C++ compilation errors on FreeBSD and OS X. Also update FreedBSD version checks for the original ctype UTF-8 workaround.

## Python 3.6.0 alpha 3

Release date: 2016-07-11

### Security

- bpo-27278: Fix os.urandom() implementation using getrandom() on Linux. Truncate size to INT_MAX and loop until we collected enough random bytes, instead of casting a directly Py_ssize_t to int.

- bpo-22636: Avoid shell injection problems with ctypes.util.find_library().

### Core and Builtins

- bpo-27473: Fixed possible integer overflow in bytes and bytearray concatenations. Patch by Xiang Zhang.

- bpo-23034: The output of a special Python build with defined COUNT_ALLOCS, SHOW_ALLOC_COUNT or SHOW_TRACK_COUNT macros is now off by default. It can be re-enabled using the “-X showalloccount” option. It now outputs to stderr instead of stdout.

- bpo-27443: __length_hint__() of bytearray iterators no longer return a negative integer for a resized bytearray.

- bpo-27007: The fromhex() class methods of bytes and bytearray subclasses now return an instance of corresponding subclass.

### Library

- bpo-26844: Fix error message for imp.find_module() to refer to ‘path’ instead of ‘name’. Patch by Lev Maximov.

- bpo-23804: Fix SSL zero-length recv() calls to not block and not raise an error about unclean EOF.

- bpo-27466: Change time format returned by http.cookie.time2netscape, confirming the netscape cookie format and making it consistent with documentation.

- bpo-21708: Deprecated dbm.dumb behavior that differs from common dbm behavior: creating a database in ‘r’ and ‘w’ modes and modifying a database in ‘r’ mode.

- bpo-26721: Change the socketserver.StreamRequestHandler.wfile attribute to implement BufferedIOBase. In particular, the write() method no longer does partial writes.

- bpo-22115: Added methods trace_add, trace_remove and trace_info in the tkinter.Variable class. They replace old methods trace_variable, trace, trace_vdelete and trace_vinfo that use obsolete Tcl commands and might not work in future versions of Tcl. Fixed old tracing methods: trace_vdelete() with wrong mode no longer break tracing, trace_vinfo() now always returns a list of pairs of strings, tracing in the “u” mode now works.

- bpo-26243: Only the level argument to zlib.compress() is keyword argument now. The first argument is positional-only.

- bpo-27038: Expose the DirEntry type as os.DirEntry. Code patch by Jelle Zijlstra.

- bpo-27186: Update os.fspath()/PyOS_FSPath() to check the return value of __fspath__() to be either str or bytes.

- bpo-18726: All optional parameters of the dump(), dumps(), load() and loads() functions and JSONEncoder and JSONDecoder class constructors in the json module are now keyword-only.

- bpo-27319: Methods selection_set(), selection_add(), selection_remove() and selection_toggle() of ttk.TreeView now allow passing multiple items as multiple arguments instead of passing them as a tuple. Deprecated undocumented ability of calling the selection() method with arguments.

- bpo-27079: Fixed curses.ascii functions isblank(), iscntrl() and ispunct().

- bpo-27294: Numerical state in the repr for Tkinter event objects is now represented as a combination of known flags.

- bpo-27177: Match objects in the re module now support index-like objects as group indices. Based on patches by Jeroen Demeyer and Xiang Zhang.

- bpo-26754: Some functions (compile() etc) accepted a filename argument encoded as an iterable of integers. Now only strings and byte-like objects are accepted.

- bpo-26536: socket.ioctl now supports SIO_LOOPBACK_FAST_PATH. Patch by Daniel Stokes.

- bpo-27048: Prevents distutils failing on Windows when environment variables contain non-ASCII characters

- bpo-27330: Fixed possible leaks in the ctypes module.

- bpo-27238: Got rid of bare excepts in the turtle module. Original patch by Jelle Zijlstra.

- bpo-27122: When an exception is raised within the context being managed by a contextlib.ExitStack() and one of the exit stack generators catches and raises it in a chain, do not re-raise the original exception when exiting, let the new chained one through. This avoids the PEP 479 bug described in issue25782.

- bpo-16864: sqlite3.Cursor.lastrowid now supports REPLACE statement. Initial patch by Alex LordThorsen.

- bpo-26386: Fixed ttk.TreeView selection operations with item id’s containing spaces.

- bpo-8637: Honor a pager set by the env var MANPAGER (in preference to one set by the env var PAGER).

- bpo-16182: Fix various functions in the “readline” module to use the locale encoding, and fix get_begidx() and get_endidx() to return code point indexes.

- bpo-27392: Add loop.connect_accepted_socket(). Patch by Jim Fulton.

### IDLE

- bpo-27477: IDLE search dialogs now use ttk widgets.

- bpo-27173: Add ‘IDLE Modern Unix’ to the built-in key sets. Make the default key set depend on the platform. Add tests for the changes to the config module.

- bpo-27452: make command line “idle-test> python test_help.py” work. __file__ is relative when python is started in the file’s directory.

- bpo-27452: add line counter and crc to IDLE configHandler test dump.

- bpo-27380: IDLE: add query.py with base Query dialog and ttk widgets. Module had subclasses SectionName, ModuleName, and HelpSource, which are used to get information from users by configdialog and file =>Load Module. Each subclass has itw own validity checks. Using ModuleName allows users to edit bad module names instead of starting over. Add tests and delete the two files combined into the new one.

- bpo-27372: Test_idle no longer changes the locale.

- bpo-27365: Allow non-ascii chars in IDLE NEWS.txt, for contributor names.

- bpo-27245: IDLE: Cleanly delete custom themes and key bindings. Previously, when IDLE was started from a console or by import, a cascade of warnings was emitted. Patch by Serhiy Storchaka.

- bpo-24137: Run IDLE, test_idle, and htest with tkinter default root disabled. Fix code and tests that fail with this restriction. Fix htests to not create a second and redundant root and mainloop.

- bpo-27310: Fix IDLE.app failure to launch on OS X due to vestigial import.

### C API

- bpo-26754: PyUnicode_FSDecoder() accepted a filename argument encoded as an iterable of integers. Now only strings and byte-like objects are accepted.

### Build

- bpo-28066: Fix the logic that searches build directories for generated include files when building outside the source tree.

- bpo-27442: Expose the Android API level that python was built against, in sysconfig.get_config_vars() as ‘ANDROID_API_LEVEL’.

- bpo-27434: The interpreter that runs the cross-build, found in PATH, must now be of the same feature version (e.g. 3.6) as the source being built.

- bpo-26930: Update Windows builds to use OpenSSL 1.0.2h.

- bpo-23968: Rename the platform directory from plat-$(MACHDEP) to plat-$(PLATFORM_TRIPLET). Rename the config directory (LIBPL) from config-$(LDVERSION) to config-$(LDVERSION)-$(PLATFORM_TRIPLET). Install the platform specific _sysconfigdata module into the platform directory and rename it to include the ABIFLAGS.

- Don’t use largefile support for GNU/Hurd.

### Tools/Demos

- bpo-27332: Fixed the type of the first argument of module-level functions generated by Argument Clinic. Patch by Petr Viktorin.

- bpo-27418: Fixed Tools/importbench/importbench.py.

### Documentation

- bpo-19489: Moved the search box from the sidebar to the header and footer of each page. Patch by Ammar Askar.

- bpo-27285: Update documentation to reflect the deprecation of `pyvenv` and normalize on the term “virtual environment”. Patch by Steve Piercy.

### Tests

- bpo-27027: Added test.support.is_android that is True when this is an Android build.

## Python 3.6.0 alpha 2

Release date: 2016-06-13

### Security

- bpo-26556: Update expat to 2.1.1, fixes CVE 2015-1283.

- Fix TLS stripping vulnerability in smtplib, CVE 2016-0772. Reported by Team Oststrom.

- bpo-26839: On Linux, `os.urandom()` now calls `getrandom()` with `GRND_NONBLOCK` to fall back on reading `/dev/urandom` if the urandom entropy pool is not initialized yet. Patch written by Colm Buckley.

### Core and Builtins

- bpo-27095: Simplified MAKE_FUNCTION and removed MAKE_CLOSURE opcodes. Patch by Demur Rumed.

- bpo-27190: Raise NotSupportedError if sqlite3 is older than 3.3.1. Patch by Dave Sawyer.

- bpo-27286: Fixed compiling BUILD_MAP_UNPACK_WITH_CALL opcode. Calling function with generalized unpacking (PEP 448) and conflicting keyword names could cause undefined behavior.

- bpo-27140: Added BUILD_CONST_KEY_MAP opcode.

- bpo-27186: Add support for os.PathLike objects to open() (part of PEP 519).

- bpo-27066: Fixed SystemError if a custom opener (for open()) returns a negative number without setting an exception.

- bpo-26983: float() now always return an instance of exact float. The deprecation warning is emitted if __float__ returns an instance of a strict subclass of float. In a future versions of Python this can be an error.

- bpo-27097: Python interpreter is now about 7% faster due to optimized instruction decoding. Based on patch by Demur Rumed.

- bpo-26647: Python interpreter now uses 16-bit wordcode instead of bytecode. Patch by Demur Rumed.

- bpo-23275: Allow assigning to an empty target list in round brackets: () = iterable.

- bpo-27243: Update the __aiter__ protocol: instead of returning an awaitable that resolves to an asynchronous iterator, the asynchronous iterator should be returned directly. Doing the former will trigger a PendingDeprecationWarning.

### Library

- Comment out socket (SO_REUSEPORT) and posix (O_SHLOCK, O_EXLOCK) constants exposed on the API which are not implemented on GNU/Hurd. They would not work at runtime anyway.

- bpo-27025: Generated names for Tkinter widgets are now more meaningful and recognizable.

- bpo-25455: Fixed crashes in repr of recursive ElementTree.Element and functools.partial objects.

- bpo-27294: Improved repr for Tkinter event objects.

- bpo-20508: Improve exception message of IPv{4,6}Network.__getitem__. Patch by Gareth Rees.

- bpo-21386: Implement missing IPv4Address.is_global property. It was documented since 07a5610bae9d. Initial patch by Roger Luethi.

- bpo-27029: Removed deprecated support of universal newlines mode from ZipFile.open().

- bpo-27030: Unknown escapes consisting of `'\'` and an ASCII letter in regular expressions now are errors. The re.LOCALE flag now can be used only with bytes patterns.

- bpo-27186: Add os.PathLike support to DirEntry (part of PEP 519). Initial patch by Jelle Zijlstra.

- bpo-20900: distutils register command now decodes HTTP responses correctly. Initial patch by ingrid.

- bpo-27186: Add os.PathLike support to pathlib, removing its provisional status (part of PEP 519). Initial patch by Dusty Phillips.

- bpo-27186: Add support for os.PathLike objects to os.fsencode() and os.fsdecode() (part of PEP 519).

- bpo-27186: Introduce os.PathLike and os.fspath() (part of PEP 519).

- A new version of typing.py provides several new classes and features: @overload outside stubs, Reversible, DefaultDict, Text, ContextManager, Type[], NewType(), TYPE_CHECKING, and numerous bug fixes (note that some of the new features are not yet implemented in mypy or other static analyzers). Also classes for PEP 492 (Awaitable, AsyncIterable, AsyncIterator) have been added (in fact they made it into 3.5.1 but were never mentioned).

- bpo-25738: Stop http.server.BaseHTTPRequestHandler.send_error() from sending a message body for 205 Reset Content. Also, don’t send Content header fields in responses that don’t have a body. Patch by Susumu Koshiba.

- bpo-21313: Fix the “platform” module to tolerate when sys.version contains truncated build information.

- bpo-23883: Added missing APIs to __all__ to match the documented APIs for the following modules: cgi, mailbox, mimetypes, plistlib and smtpd. Patches by Jacek Kołodziej.

- bpo-27164: In the zlib module, allow decompressing raw Deflate streams with a predefined zdict. Based on patch by Xiang Zhang.

- bpo-24291: Fix wsgiref.simple_server.WSGIRequestHandler to completely write data to the client. Previously it could do partial writes and truncate data. Also, wsgiref.handler.ServerHandler can now handle stdout doing partial writes, but this is deprecated.

- bpo-21272: Use _sysconfigdata.py to initialize distutils.sysconfig.

- bpo-19611: `inspect` now reports the implicit `.0` parameters generated by the compiler for comprehension and generator expression scopes as if they were positional-only parameters called `implicit0`. Patch by Jelle Zijlstra.

- bpo-26809: Add `__all__` to `string`. Patch by Emanuel Barry.

- bpo-26373: subprocess.Popen.communicate now correctly ignores BrokenPipeError when the child process dies before .communicate() is called in more/all circumstances.

- signal, socket, and ssl module IntEnum constant name lookups now return a consistent name for values having multiple names. Ex: signal.Signals(6) now refers to itself as signal.SIGALRM rather than flipping between that and signal.SIGIOT based on the interpreter’s hash randomization seed.

- bpo-27167: Clarify the subprocess.CalledProcessError error message text when the child process died due to a signal.

- bpo-25931: Don’t define socketserver.Forking* names on platforms such as Windows that do not support os.fork().

- bpo-21776: distutils.upload now correctly handles HTTPError. Initial patch by Claudiu Popa.

- bpo-26526: Replace custom parse tree validation in the parser module with a simple DFA validator.

- bpo-27114: Fix SSLContext._load_windows_store_certs fails with PermissionError

- bpo-18383: Avoid creating duplicate filters when using filterwarnings and simplefilter. Based on patch by Alex Shkop.

- bpo-23026: winreg.QueryValueEx() now return an integer for REG_QWORD type.

- bpo-26741: subprocess.Popen destructor now emits a ResourceWarning warning if the child process is still running.

- bpo-27056: Optimize pickle.load() and pickle.loads(), up to 10% faster to deserialize a lot of small objects.

- bpo-21271: New keyword only parameters in reset_mock call.

### IDLE

- bpo-5124: Paste with text selected now replaces the selection on X11. This matches how paste works on Windows, Mac, most modern Linux apps, and ttk widgets. Original patch by Serhiy Storchaka.

- bpo-24750: Switch all scrollbars in IDLE to ttk versions. Where needed, minimal tests are added to cover changes.

- bpo-24759: IDLE requires tk 8.5 and availability ttk widgets. Delete now unneeded tk version tests and code for older versions. Add test for IDLE syntax colorizer.

- bpo-27239: idlelib.macosx.isXyzTk functions initialize as needed.

- bpo-27262: move Aqua unbinding code, which enable context menus, to macosx.

- bpo-24759: Make clear in idlelib.idle_test.__init__ that the directory is a private implementation of test.test_idle and tool for maintainers.

- bpo-27196: Stop ‘ThemeChanged’ warnings when running IDLE tests. These persisted after other warnings were suppressed in #20567. Apply Serhiy Storchaka’s update_idletasks solution to four test files. Record this additional advice in idle_test/README.txt

- bpo-20567: Revise idle_test/README.txt with advice about avoiding tk warning messages from tests. Apply advice to several IDLE tests.

- bpo-24225: Update idlelib/README.txt with new file names and event handlers.

- bpo-27156: Remove obsolete code not used by IDLE.

- bpo-27117: Make colorizer htest and turtledemo work with dark themes. Move code for configuring text widget colors to a new function.

- bpo-24225: Rename many `idlelib/*.py` and `idle_test/test_*.py` files. Edit files to replace old names with new names when the old name referred to the module rather than the class it contained. See the issue and IDLE section in What’s New in 3.6 for more.

- bpo-26673: When tk reports font size as 0, change to size 10. Such fonts on Linux prevented the configuration dialog from opening.

- bpo-21939: Add test for IDLE’s percolator. Original patch by Saimadhav Heblikar.

- bpo-21676: Add test for IDLE’s replace dialog. Original patch by Saimadhav Heblikar.

- bpo-18410: Add test for IDLE’s search dialog. Original patch by Westley Martínez.

- bpo-21703: Add test for undo delegator. Patch mostly by Saimadhav Heblikar .

- bpo-27044: Add ConfigDialog.remove_var_callbacks to stop memory leaks.

- bpo-23977: Add more asserts to test_delegator.

### Documentation

- bpo-16484: Change the default PYTHONDOCS URL to “https:”, and fix the resulting links to use lowercase. Patch by Sean Rodman, test by Kaushik Nadikuditi.

- bpo-24136: Document the new PEP 448 unpacking syntax of 3.5.

- bpo-22558: Add remaining doc links to source code for Python-coded modules. Patch by Yoni Lavi.

### Tests

- bpo-25285: regrtest now uses subprocesses when the -j1 command line option is used: each test file runs in a fresh child process. Before, the -j1 option was ignored.

- bpo-25285: Tools/buildbot/test.bat script now uses -j1 by default to run each test file in fresh child process.

### Windows

- bpo-27064: The py.exe launcher now defaults to Python 3. The Windows launcher `py.exe` no longer prefers an installed Python 2 version over Python 3 by default when used interactively.

- bpo-17500: Remove unused and outdated icons. (See also: https://github.com/python/pythondotorg/issues/945)

### Build

- bpo-27229: Fix the cross-compiling pgen rule for in-tree builds. Patch by Xavier de Gaye.

- bpo-26930: Update OS X 10.5+ 32-bit-only installer to build and link with OpenSSL 1.0.2h.

### C API

- bpo-27186: Add the PyOS_FSPath() function (part of PEP 519).

- bpo-26282: PyArg_ParseTupleAndKeywords() now supports positional-only parameters.

### Tools/Demos

- bpo-26282: Argument Clinic now supports positional-only and keyword parameters in the same function.

## Python 3.6.0 alpha 1

Release date: 2016-05-16

### Security

- bpo-26657: Fix directory traversal vulnerability with http.server on Windows. This fixes a regression that was introduced in 3.3.4rc1 and 3.4.0rc1. Based on patch by Philipp Hagemeister.

- bpo-26313: ssl.py _load_windows_store_certs fails if windows cert store is empty. Patch by Baji.

- bpo-25939: On Windows open the cert store readonly in ssl.enum_certificates.

### Core and Builtins

- bpo-20041: Fixed TypeError when frame.f_trace is set to None. Patch by Xavier de Gaye.

- bpo-26168: Fixed possible refleaks in failing Py_BuildValue() with the “N” format unit.

- bpo-26991: Fix possible refleak when creating a function with annotations.

- bpo-27039: Fixed bytearray.remove() for values greater than 127. Based on patch by Joe Jevnik.

- bpo-23640: int.from_bytes() no longer bypasses constructors for subclasses.

- bpo-27005: Optimized the float.fromhex() class method for exact float. It is now 2 times faster.

- bpo-18531: Single var-keyword argument of dict subtype was passed unscathed to the C-defined function. Now it is converted to exact dict.

- bpo-26811: gc.get_objects() no longer contains a broken tuple with NULL pointer.

- bpo-20120: Use RawConfigParser for .pypirc parsing, removing support for interpolation unintentionally added with move to Python 3. Behavior no longer does any interpolation in .pypirc files, matching behavior in Python 2.7 and Setuptools 19.0.

- bpo-26249: Memory functions of the `PyMem_Malloc()` domain (`PYMEM_DOMAIN_MEM`) now use the pymalloc allocator rather than system `malloc()`. Applications calling `PyMem_Malloc()` without holding the GIL can now crash: use `PYTHONMALLOC=debug` environment variable to validate the usage of memory allocators in your application.

- bpo-26802: Optimize function calls only using unpacking like `func(*tuple)` (no other positional argument, no keyword): avoid copying the tuple. Patch written by Joe Jevnik.

- bpo-26659: Make the builtin slice type support cycle collection.

- bpo-26718: super.__init__ no longer leaks memory if called multiple times. NOTE: A direct call of super.__init__ is not endorsed!

- bpo-27138: Fix the doc comment for FileFinder.find_spec().

- bpo-27147: Mention PEP 420 in the importlib docs.

- bpo-25339: PYTHONIOENCODING now has priority over locale in setting the error handler for stdin and stdout.

- bpo-26494: Fixed crash on iterating exhausting iterators. Affected classes are generic sequence iterators, iterators of str, bytes, bytearray, list, tuple, set, frozenset, dict, OrderedDict, corresponding views and os.scandir() iterator.

- bpo-26574: Optimize `bytes.replace(b'', b'.')` and `bytearray.replace(b'', b'.')`. Patch written by Josh Snider.

- bpo-26581: If coding cookie is specified multiple times on a line in Python source code file, only the first one is taken to account.

- bpo-19711: Add tests for reloading namespace packages.

- bpo-21099: Switch applicable importlib tests to use PEP 451 API.

- bpo-26563: Debug hooks on Python memory allocators now raise a fatal error if functions of the `PyMem_Malloc()` family are called without holding the GIL.

- bpo-26564: On error, the debug hooks on Python memory allocators now use the `tracemalloc` module to get the traceback where a memory block was allocated.

- bpo-26558: The debug hooks on Python memory allocator `PyObject_Malloc()` now detect when functions are called without holding the GIL.

- bpo-26516: Add `PYTHONMALLOC` environment variable to set the Python memory allocators and/or install debug hooks.

- bpo-26516: The `PyMem_SetupDebugHooks()` function can now also be used on Python compiled in release mode.

- bpo-26516: The `PYTHONMALLOCSTATS` environment variable can now also be used on Python compiled in release mode. It now has no effect if set to an empty string.

- bpo-26516: In debug mode, debug hooks are now also installed on Python memory allocators when Python is configured without pymalloc.

- bpo-26464: Fix str.translate() when string is ASCII and first replacements removes character, but next replacement uses a non-ASCII character or a string longer than 1 character. Regression introduced in Python 3.5.0.

- bpo-22836: Ensure exception reports from PyErr_Display() and PyErr_WriteUnraisable() are sensible even when formatting them produces secondary errors. This affects the reports produced by sys.__excepthook__() and when __del__() raises an exception.

- bpo-26302: Correct behavior to reject comma as a legal character for cookie names.

- bpo-26136: Upgrade the warning when a generator raises StopIteration from PendingDeprecationWarning to DeprecationWarning. Patch by Anish Shah.

- bpo-26204: The compiler now ignores all constant statements: bytes, str, int, float, complex, name constants (None, False, True), Ellipsis and ast.Constant; not only str and int. For example, `1.0` is now ignored in `def f(): 1.0`.

- bpo-4806: Avoid masking the original TypeError exception when using star (`*`) unpacking in function calls. Based on patch by Hagen Fürstenau and Daniel Urban.

- bpo-26146: Add a new kind of AST node: `ast.Constant`. It can be used by external AST optimizers, but the compiler does not emit directly such node.

- bpo-23601: Sped-up allocation of dict key objects by using Python’s small object allocator. (Contributed by Julian Taylor.)

- bpo-18018: Import raises ImportError instead of SystemError if a relative import is attempted without a known parent package.

- bpo-25843: When compiling code, don’t merge constants if they are equal but have a different types. For example, `f1, f2 = lambda: 1, lambda: 1.0` is now correctly compiled to two different functions: `f1()` returns `1` (`int`) and `f2()` returns `1.0` (`float`), even if `1` and `1.0` are equal.

- bpo-26107: The format of the `co_lnotab` attribute of code objects changes to support negative line number delta.

- bpo-26154: Add a new private _PyThreadState_UncheckedGet() function to get the current Python thread state, but don’t issue a fatal error if it is NULL. This new function must be used instead of accessing directly the _PyThreadState_Current variable. The variable is no more exposed since Python 3.5.1 to hide the exact implementation of atomic C types, to avoid compiler issues.

- bpo-25791: If __package__ != __spec__.parent or if neither __package__ or __spec__ are defined then ImportWarning is raised.

- bpo-22995: [UPDATE] Comment out the one of the pickleability tests in _PyObject_GetState() due to regressions observed in Cython-based projects.

- bpo-25961: Disallowed null characters in the type name.

- bpo-25973: Fix segfault when an invalid nonlocal statement binds a name starting with two underscores.

- bpo-22995: Instances of extension types with a state that aren’t subclasses of list or dict and haven’t implemented any pickle-related methods (__reduce__, __reduce_ex__, __getnewargs__, __getnewargs_ex__, or __getstate__), can no longer be pickled. Including memoryview.

- bpo-20440: Massive replacing unsafe attribute setting code with special macro Py_SETREF.

- bpo-25766: Special method __bytes__() now works in str subclasses.

- bpo-25421: __sizeof__ methods of builtin types now use dynamic basic size. This allows sys.getsize() to work correctly with their subclasses with __slots__ defined.

- bpo-25709: Fixed problem with in-place string concatenation and utf-8 cache.

- bpo-5319: New Py_FinalizeEx() API allowing Python to set an exit status of 120 on failure to flush buffered streams.

- bpo-25485: telnetlib.Telnet is now a context manager.

- bpo-24097: Fixed crash in object.__reduce__() if slot name is freed inside __getattr__.

- bpo-24731: Fixed crash on converting objects with special methods __bytes__, __trunc__, and __float__ returning instances of subclasses of bytes, int, and float to subclasses of bytes, int, and float correspondingly.

- bpo-25630: Fix a possible segfault during argument parsing in functions that accept filesystem paths.

- bpo-23564: Fixed a partially broken sanity check in the _posixsubprocess internals regarding how fds_to_pass were passed to the child. The bug had no actual impact as subprocess.py already avoided it.

- bpo-25388: Fixed tokenizer crash when processing undecodable source code with a null byte.

- bpo-25462: The hash of the key now is calculated only once in most operations in C implementation of OrderedDict.

- bpo-22995: Default implementation of __reduce__ and __reduce_ex__ now rejects builtin types with not defined __new__.

- bpo-24802: Avoid buffer overreads when int(), float(), compile(), exec() and eval() are passed bytes-like objects. These objects are not necessarily terminated by a null byte, but the functions assumed they were.

- bpo-25555: Fix parser and AST: fill lineno and col_offset of “arg” node when compiling AST from Python objects.

- bpo-24726: Fixed a crash and leaking NULL in repr() of OrderedDict that was mutated by direct calls of dict methods.

- bpo-25449: Iterating OrderedDict with keys with unstable hash now raises KeyError in C implementations as well as in Python implementation.

- bpo-25395: Fixed crash when highly nested OrderedDict structures were garbage collected.

- bpo-25401: Optimize bytes.fromhex() and bytearray.fromhex(): they are now between 2x and 3.5x faster.

- bpo-25399: Optimize bytearray % args using the new private _PyBytesWriter API. Formatting is now between 2.5 and 5 times faster.

- bpo-25274: sys.setrecursionlimit() now raises a RecursionError if the new recursion limit is too low depending at the current recursion depth. Modify also the “lower-water mark” formula to make it monotonic. This mark is used to decide when the overflowed flag of the thread state is reset.

- bpo-24402: Fix input() to prompt to the redirected stdout when sys.stdout.fileno() fails.

- bpo-25349: Optimize bytes % args using the new private _PyBytesWriter API. Formatting is now up to 2 times faster.

- bpo-24806: Prevent builtin types that are not allowed to be subclassed from being subclassed through multiple inheritance.

- bpo-25301: The UTF-8 decoder is now up to 15 times as fast for error handlers: `ignore`, `replace` and `surrogateescape`.

- bpo-24848: Fixed a number of bugs in UTF-7 decoding of misformed data.

- bpo-25267: The UTF-8 encoder is now up to 75 times as fast for error handlers: `ignore`, `replace`, `surrogateescape`, `surrogatepass`. Patch co-written with Serhiy Storchaka.

- bpo-25280: Import trace messages emitted in verbose (-v) mode are no longer formatted twice.

- bpo-25227: Optimize ASCII and latin1 encoders with the `surrogateescape` error handler: the encoders are now up to 3 times as fast. Initial patch written by Serhiy Storchaka.

- bpo-25003: On Solaris 11.3 or newer, os.urandom() now uses the getrandom() function instead of the getentropy() function. The getentropy() function is blocking to generate very good quality entropy, os.urandom() doesn’t need such high-quality entropy.

- bpo-9232: Modify Python’s grammar to allow trailing commas in the argument list of a function declaration. For example, “def f(*, a = 3,): pass” is now legal. Patch from Mark Dickinson.

- bpo-24965: Implement PEP 498 “Literal String Interpolation”. This allows you to embed expressions inside f-strings, which are converted to normal strings at run time. Given x=3, then f’value={x}’ == ‘value=3’. Patch by Eric V. Smith.

- bpo-26478: Fix semantic bugs when using binary operators with dictionary views and tuples.

- bpo-26171: Fix possible integer overflow and heap corruption in zipimporter.get_data().

- bpo-25660: Fix TAB key behaviour in REPL with readline.

- bpo-26288: Optimize PyLong_AsDouble.

- bpo-26289: Optimize floor and modulo division for single-digit longs. Microbenchmarks show 2-2.5x improvement. Built-in ‘divmod’ function is now also ~10% faster. (See also: bpo-26315)

- bpo-25887: Raise a RuntimeError when a coroutine object is awaited more than once.

### Library

- bpo-27057: Fix os.set_inheritable() on Android, ioctl() is blocked by SELinux and fails with EACCESS. The function now falls back to fcntl(). Patch written by Michał Bednarski.

- bpo-27014: Fix infinite recursion using typing.py. Thanks to Kalle Tuure!

- bpo-27031: Removed dummy methods in Tkinter widget classes: tk_menuBar() and tk_bindForTraversal().

- bpo-14132: Fix urllib.request redirect handling when the target only has a query string. Original fix by Ján Janech.

- bpo-17214: The “urllib.request” module now percent-encodes non-ASCII bytes found in redirect target URLs. Some servers send Location header fields with non-ASCII bytes, but “http.client” requires the request target to be ASCII-encodable, otherwise a UnicodeEncodeError is raised. Based on patch by Christian Heimes.

- bpo-27033: The default value of the decode_data parameter for smtpd.SMTPChannel and smtpd.SMTPServer constructors is changed to False.

- bpo-27034: Removed deprecated class asynchat.fifo.

- bpo-26870: Added readline.set_auto_history(), which can stop entries being automatically added to the history list. Based on patch by Tyler Crompton.

- bpo-26039: zipfile.ZipFile.open() can now be used to write data into a ZIP file, as well as for extracting data. Patch by Thomas Kluyver.

- bpo-26892: Honor debuglevel flag in urllib.request.HTTPHandler. Patch contributed by Chi Hsuan Yen.

- bpo-22274: In the subprocess module, allow stderr to be redirected to stdout even when stdout is not redirected. Patch by Akira Li.

- bpo-26807: mock_open ‘files’ no longer error on readline at end of file. Patch from Yolanda Robla.

- bpo-25745: Fixed leaking a userptr in curses panel destructor.

- bpo-26977: Removed unnecessary, and ignored, call to sum of squares helper in statistics.pvariance.

- bpo-26002: Use bisect in statistics.median instead of a linear search. Patch by Upendra Kuma.

- bpo-25974: Make use of new Decimal.as_integer_ratio() method in statistics module. Patch by Stefan Krah.

- bpo-26996: Add secrets module as described in PEP 506.

- bpo-26881: The modulefinder module now supports extended opcode arguments.

- bpo-23815: Fixed crashes related to directly created instances of types in _tkinter and curses.panel modules.

- bpo-17765: weakref.ref() no longer silently ignores keyword arguments. Patch by Georg Brandl.

- bpo-26873: xmlrpc now raises ResponseError on unsupported type tags instead of silently return incorrect result.

- bpo-26915: The __contains__ methods in the collections ABCs now check for identity before checking equality. This better matches the behavior of the concrete classes, allows sensible handling of NaNs, and makes it easier to reason about container invariants.

- bpo-26711: Fixed the comparison of plistlib.Data with other types.

- bpo-24114: Fix an uninitialized variable in `ctypes.util`. The bug only occurs on SunOS when the ctypes implementation searches for the `crle` program. Patch by Xiang Zhang. Tested on SunOS by Kees Bos.

- bpo-26864: In urllib.request, change the proxy bypass host checking against no_proxy to be case-insensitive, and to not match unrelated host names that happen to have a bypassed hostname as a suffix. Patch by Xiang Zhang.

- bpo-24902: Print server URL on http.server startup. Initial patch by Felix Kaiser.

- bpo-25788: fileinput.hook_encoded() now supports an “errors” argument for passing to open. Original patch by Joseph Hackman.

- bpo-26634: recursive_repr() now sets __qualname__ of wrapper. Patch by Xiang Zhang.

- bpo-26804: urllib.request will prefer lower_case proxy environment variables over UPPER_CASE or Mixed_Case ones. Patch contributed by Hans-Peter Jansen.

- bpo-26837: assertSequenceEqual() now correctly outputs non-stringified differing items (like bytes in the -b mode). This affects assertListEqual() and assertTupleEqual().

- bpo-26041: Remove “will be removed in Python 3.7” from deprecation messages of platform.dist() and platform.linux_distribution(). Patch by Kumaripaba Miyurusara Athukorala.

- bpo-26822: itemgetter, attrgetter and methodcaller objects no longer silently ignore keyword arguments.

- bpo-26733: Disassembling a class now disassembles class and static methods. Patch by Xiang Zhang.

- bpo-26801: Fix error handling in `shutil.get_terminal_size()`, catch `AttributeError` instead of `NameError`. Patch written by Emanuel Barry.

- bpo-24838: tarfile’s ustar and gnu formats now correctly calculate name and link field limits for multibyte character encodings like utf-8.

- bpo-26717: Stop encoding Latin-1-ized WSGI paths with UTF-8. Patch by Anthony Sottile.

- bpo-26782: Add STARTUPINFO to subprocess.__all__ on Windows.

- bpo-26404: Add context manager to socketserver. Patch by Aviv Palivoda.

- bpo-26735: Fix `os.urandom()` on Solaris 11.3 and newer when reading more than 1,024 bytes: call `getrandom()` multiple times with a limit of 1024 bytes per call.

- bpo-26585: Eliminate http.server._quote_html() and use html.escape(quote=False). Patch by Xiang Zhang.

- bpo-26685: Raise OSError if closing a socket fails.

- bpo-16329: Add .webm to mimetypes.types_map. Patch by Giampaolo Rodola’.

- bpo-13952: Add .csv to mimetypes.types_map. Patch by Geoff Wilson.

- bpo-26587: the site module now allows .pth files to specify files to be added to sys.path (e.g. zip files).

- bpo-25609: Introduce contextlib.AbstractContextManager and typing.ContextManager.

- bpo-26709: Fixed Y2038 problem in loading binary PLists.

- bpo-23735: Handle terminal resizing with Readline 6.3+ by installing our own SIGWINCH handler. Patch by Eric Price.

- bpo-25951: Change SSLSocket.sendall() to return None, as explicitly documented for plain socket objects. Patch by Aviv Palivoda.

- bpo-26586: In http.server, respond with “413 Request header fields too large” if there are too many header fields to parse, rather than killing the connection and raising an unhandled exception. Patch by Xiang Zhang.

- bpo-26676: Added missing XMLPullParser to ElementTree.__all__.

- bpo-22854: Change BufferedReader.writable() and BufferedWriter.readable() to always return False.

- bpo-26492: Exhausted iterator of array.array now conforms with the behavior of iterators of other mutable sequences: it lefts exhausted even if iterated array is extended.

- bpo-26641: doctest.DocFileTest and doctest.testfile() now support packages (module splitted into multiple directories) for the package parameter.

- bpo-25195: Fix a regression in mock.MagicMock. _Call is a subclass of tuple (changeset 3603bae63c13 only works for classes) so we need to implement __ne__ ourselves. Patch by Andrew Plummer.

- bpo-26644: Raise ValueError rather than SystemError when a negative length is passed to SSLSocket.recv() or read().

- bpo-23804: Fix SSL recv(0) and read(0) methods to return zero bytes instead of up to 1024.

- bpo-26616: Fixed a bug in datetime.astimezone() method.

- bpo-26637: The `importlib` module now emits an `ImportError` rather than a `TypeError` if `__import__()` is tried during the Python shutdown process but `sys.path` is already cleared (set to `None`).

- bpo-21925: `warnings.formatwarning()` now catches exceptions when calling `linecache.getline()` and `tracemalloc.get_object_traceback()` to be able to log `ResourceWarning` emitted late during the Python shutdown process.

- bpo-23848: On Windows, faulthandler.enable() now also installs an exception handler to dump the traceback of all Python threads on any Windows exception, not only on UNIX signals (SIGSEGV, SIGFPE, SIGABRT).

- bpo-26530: Add C functions `_PyTraceMalloc_Track()` and `_PyTraceMalloc_Untrack()` to track memory blocks using the `tracemalloc` module. Add `_PyTraceMalloc_GetTraceback()` to get the traceback of an object.

- bpo-26588: The _tracemalloc now supports tracing memory allocations of multiple address spaces (domains).

- bpo-24266: Ctrl+C during Readline history search now cancels the search mode when compiled with Readline 7.

- bpo-26590: Implement a safe finalizer for the _socket.socket type. It now releases the GIL to close the socket.

- bpo-18787: spwd.getspnam() now raises a PermissionError if the user doesn’t have privileges.

- bpo-26560: Avoid potential ValueError in BaseHandler.start_response. Initial patch by Peter Inglesby.

- bpo-26567: Add a new function `PyErr_ResourceWarning()` function to pass the destroyed object. Add a source attribute to `warnings.WarningMessage`. Add warnings._showwarnmsg() which uses tracemalloc to get the traceback where source object was allocated.

- bpo-26569: Fix `pyclbr.readmodule()` and `pyclbr.readmodule_ex()` to support importing packages.

- bpo-26499: Account for remaining Content-Length in HTTPResponse.readline() and read1(). Based on patch by Silent Ghost. Also document that HTTPResponse now supports these methods.

- bpo-25320: Handle sockets in directories unittest discovery is scanning. Patch from Victor van den Elzen.

- bpo-16181: cookiejar.http2time() now returns None if year is higher than datetime.MAXYEAR.

- bpo-26513: Fixes platform module detection of Windows Server

- bpo-23718: Fixed parsing time in week 0 before Jan 1. Original patch by Tamás Bence Gedai.

- bpo-26323: Add Mock.assert_called() and Mock.assert_called_once() methods to unittest.mock. Patch written by Amit Saha.

- bpo-20589: Invoking Path.owner() and Path.group() on Windows now raise NotImplementedError instead of ImportError.

- bpo-26177: Fixed the keys() method for Canvas and Scrollbar widgets.

- bpo-15068: Got rid of excessive buffering in fileinput. The bufsize parameter is now deprecated and ignored.

- bpo-19475: Added an optional argument timespec to the datetime isoformat() method to choose the precision of the time component.

- bpo-2202: Fix UnboundLocalError in AbstractDigestAuthHandler.get_algorithm_impls. Initial patch by Mathieu Dupuy.

- bpo-26167: Minimized overhead in copy.copy() and copy.deepcopy(). Optimized copying and deepcopying bytearrays, NotImplemented, slices, short lists, tuples, dicts, sets.

- bpo-25718: Fixed pickling and copying the accumulate() iterator with total is None.

- bpo-26475: Fixed debugging output for regular expressions with the (?x) flag.

- bpo-26482: Allowed pickling recursive dequeues.

- bpo-26335: Make mmap.write() return the number of bytes written like other write methods. Patch by Jakub Stasiak.

- bpo-26457: Fixed the subnets() methods in IP network classes for the case when resulting prefix length is equal to maximal prefix length. Based on patch by Xiang Zhang.

- bpo-26385: Remove the file if the internal open() call in NamedTemporaryFile() fails. Patch by Silent Ghost.

- bpo-26402: Fix XML-RPC client to retry when the server shuts down a persistent connection. This was a regression related to the new http.client.RemoteDisconnected exception in 3.5.0a4.

- bpo-25913: Leading `<~` is optional now in base64.a85decode() with adobe=True. Patch by Swati Jaiswal.

- bpo-26186: Remove an invalid type check in importlib.util.LazyLoader.

- bpo-26367: importlib.__import__() raises ImportError like builtins.__import__() when `level` is specified but without an accompanying package specified.

- bpo-26309: In the “socketserver” module, shut down the request (closing the connected socket) when verify_request() returns false. Patch by Aviv Palivoda.

- bpo-23430: Change the socketserver module to only catch exceptions raised from a request handler that are derived from Exception (instead of BaseException). Therefore SystemExit and KeyboardInterrupt no longer trigger the handle_error() method, and will now to stop a single-threaded server.

- bpo-25995: os.walk() no longer uses FDs proportional to the tree depth.

- bpo-25994: Added the close() method and the support of the context manager protocol for the os.scandir() iterator.

- bpo-23992: multiprocessing: make MapResult not fail-fast upon exception.

- bpo-26243: Support keyword arguments to zlib.compress(). Patch by Aviv Palivoda.

- bpo-26117: The os.scandir() iterator now closes file descriptor not only when the iteration is finished, but when it was failed with error.

- bpo-25949: __dict__ for an OrderedDict instance is now created only when needed.

- bpo-25911: Restored support of bytes paths in os.walk() on Windows.

- bpo-26045: Add UTF-8 suggestion to error message when posting a non-Latin-1 string with http.client.

- bpo-26039: Added zipfile.ZipInfo.from_file() and zipinfo.ZipInfo.is_dir(). Patch by Thomas Kluyver.

- bpo-12923: Reset FancyURLopener’s redirect counter even if there is an exception. Based on patches by Brian Brazil and Daniel Rocco.

- bpo-25945: Fixed a crash when unpickle the functools.partial object with wrong state. Fixed a leak in failed functools.partial constructor. “args” and “keywords” attributes of functools.partial have now always types tuple and dict correspondingly.

- bpo-26202: copy.deepcopy() now correctly copies range() objects with non-atomic attributes.

- bpo-23076: Path.glob() now raises a ValueError if it’s called with an invalid pattern. Patch by Thomas Nyberg.

- bpo-19883: Fixed possible integer overflows in zipimport.

- bpo-26227: On Windows, getnameinfo(), gethostbyaddr() and gethostbyname_ex() functions of the socket module now decode the hostname from the ANSI code page rather than UTF-8.

- bpo-26099: The site module now writes an error into stderr if sitecustomize module can be imported but executing the module raise an ImportError. Same change for usercustomize.

- bpo-26147: xmlrpc now works with strings not encodable with used non-UTF-8 encoding.

- bpo-25935: Garbage collector now breaks reference loops with OrderedDict.

- bpo-16620: Fixed AttributeError in msilib.Directory.glob().

- bpo-26013: Added compatibility with broken protocol 2 pickles created in old Python 3 versions (3.4.3 and lower).

- bpo-26129: Deprecated accepting non-integers in grp.getgrgid().

- bpo-25850: Use cross-compilation by default for 64-bit Windows.

- bpo-25822: Add docstrings to the fields of urllib.parse results. Patch contributed by Swati Jaiswal.

- bpo-22642: Convert trace module option parsing mechanism to argparse. Patch contributed by SilentGhost.

- bpo-24705: Fix sysconfig._parse_makefile not expanding ${} vars appearing before $() vars.

- bpo-26069: Remove the deprecated apis in the trace module.

- bpo-22138: Fix mock.patch behavior when patching descriptors. Restore original values after patching. Patch contributed by Sean McCully.

- bpo-25672: In the ssl module, enable the SSL_MODE_RELEASE_BUFFERS mode option if it is safe to do so.

- bpo-26012: Don’t traverse into symlinks for `**` pattern in pathlib.Path.[r]glob().

- bpo-24120: Ignore PermissionError when traversing a tree with pathlib.Path.[r]glob(). Patch by Ulrich Petri.

- bpo-21815: Accept ] characters in the data portion of imap responses, in order to handle the flags with square brackets accepted and produced by servers such as gmail.

- bpo-25447: fileinput now uses sys.stdin as-is if it does not have a buffer attribute (restores backward compatibility).

- bpo-25971: Optimized creating Fractions from floats by 2 times and from Decimals by 3 times.

- bpo-25802: Document as deprecated the remaining implementations of importlib.abc.Loader.load_module().

- bpo-25928: Add Decimal.as_integer_ratio().

- bpo-25447: Copying the lru_cache() wrapper object now always works, independently from the type of the wrapped object (by returning the original object unchanged).

- bpo-25768: Have the functions in compileall return booleans instead of ints and add proper documentation and tests for the return values.

- bpo-24103: Fixed possible use after free in ElementTree.XMLPullParser.

- bpo-25860: os.fwalk() no longer skips remaining directories when error occurs. Original patch by Samson Lee.

- bpo-25914: Fixed and simplified OrderedDict.__sizeof__.

- bpo-25869: Optimized deepcopying ElementTree; it is now 20 times faster.

- bpo-25873: Optimized iterating ElementTree. Iterating elements Element.iter() is now 40% faster, iterating text Element.itertext() is now up to 2.5 times faster.

- bpo-25902: Fixed various refcount issues in ElementTree iteration.

- bpo-22227: The TarFile iterator is reimplemented using generator. This implementation is simpler that using class.

- bpo-25638: Optimized ElementTree.iterparse(); it is now 2x faster. Optimized ElementTree parsing; it is now 10% faster.

- bpo-25761: Improved detecting errors in broken pickle data.

- bpo-25717: Restore the previous behaviour of tolerating most fstat() errors when opening files. This was a regression in 3.5a1, and stopped anonymous temporary files from working in special cases.

- bpo-24903: Fix regression in number of arguments compileall accepts when ‘-d’ is specified. The check on the number of arguments has been dropped completely as it never worked correctly anyway.

- bpo-25764: In the subprocess module, preserve any exception caused by fork() failure when preexec_fn is used.

- bpo-25771: Tweak the exception message for importlib.util.resolve_name() when ‘package’ isn’t specified but necessary.

- bpo-6478: _strptime’s regexp cache now is reset after changing timezone with time.tzset().

- bpo-14285: When executing a package with the “python -m package” option, and package initialization fails, a proper traceback is now reported. The “runpy” module now lets exceptions from package initialization pass back to the caller, rather than raising ImportError.

- bpo-19771: Also in runpy and the “-m” option, omit the irrelevant message “… is a package and cannot be directly executed” if the package could not even be initialized (e.g. due to a bad `*.pyc` file).

- bpo-25177: Fixed problem with the mean of very small and very large numbers. As a side effect, statistics.mean and statistics.variance should be significantly faster.

- bpo-25718: Fixed copying object with state with boolean value is false.

- bpo-10131: Fixed deep copying of minidom documents. Based on patch by Marian Ganisin.

- bpo-7990: dir() on ElementTree.Element now lists properties: “tag”, “text”, “tail” and “attrib”. Original patch by Santoso Wijaya.

- bpo-25725: Fixed a reference leak in pickle.loads() when unpickling invalid data including tuple instructions.

- bpo-25663: In the Readline completer, avoid listing duplicate global names, and search the global namespace before searching builtins.

- bpo-25688: Fixed file leak in ElementTree.iterparse() raising an error.

- bpo-23914: Fixed SystemError raised by unpickler on broken pickle data.

- bpo-25691: Fixed crash on deleting ElementTree.Element attributes.

- bpo-25624: ZipFile now always writes a ZIP_STORED header for directory entries. Patch by Dingyuan Wang.

- bpo-25626: Change three zlib functions to accept sizes that fit in Py_ssize_t, but internally cap those sizes to UINT_MAX. This resolves a regression in 3.5 where GzipFile.read() failed to read chunks larger than 2 or 4 GiB. The change affects the zlib.Decompress.decompress() max_length parameter, the zlib.decompress() bufsize parameter, and the zlib.Decompress.flush() length parameter.

- bpo-25583: Avoid incorrect errors raised by os.makedirs(exist_ok=True) when the OS gives priority to errors such as EACCES over EEXIST.

- bpo-25593: Change semantics of EventLoop.stop() in asyncio.

- bpo-6973: When we know a subprocess.Popen process has died, do not allow the send_signal(), terminate(), or kill() methods to do anything as they could potentially signal a different process.

- bpo-23883: Added missing APIs to __all__ to match the documented APIs for the following modules: calendar, csv, enum, fileinput, ftplib, logging, optparse, tarfile, threading and wave. Also added a test.support.check__all__() helper. Patches by Jacek Kołodziej, Mauro S. M. Rodrigues and Joel Taddei.

- bpo-25590: In the Readline completer, only call getattr() once per attribute. Also complete names of attributes such as properties and slots which are listed by dir() but not yet created on an instance.

- bpo-25498: Fix a crash when garbage-collecting ctypes objects created by wrapping a memoryview. This was a regression made in 3.5a1. Based on patch by Eryksun.

- bpo-25584: Added “escape” to the __all__ list in the glob module.

- bpo-25584: Fixed recursive glob() with patterns starting with `**`.

- bpo-25446: Fix regression in smtplib’s AUTH LOGIN support.

- bpo-18010: Fix the pydoc web server’s module search function to handle exceptions from importing packages.

- bpo-25554: Got rid of circular references in regular expression parsing.

- bpo-18973: Command-line interface of the calendar module now uses argparse instead of optparse.

- bpo-25510: fileinput.FileInput.readline() now returns b’’ instead of ‘’ at the end if the FileInput was opened with binary mode. Patch by Ryosuke Ito.

- bpo-25503: Fixed inspect.getdoc() for inherited docstrings of properties. Original patch by John Mark Vandenberg.

- bpo-25515: Always use os.urandom as a source of randomness in uuid.uuid4.

- bpo-21827: Fixed textwrap.dedent() for the case when largest common whitespace is a substring of smallest leading whitespace. Based on patch by Robert Li.

- bpo-25447: The lru_cache() wrapper objects now can be copied and pickled (by returning the original object unchanged).

- bpo-25390: typing: Don’t crash on Union[str, Pattern].

- bpo-25441: asyncio: Raise error from drain() when socket is closed.

- bpo-25410: Cleaned up and fixed minor bugs in C implementation of OrderedDict.

- bpo-25411: Improved Unicode support in SMTPHandler through better use of the email package. Thanks to user simon04 for the patch.

- Move the imp module from a PendingDeprecationWarning to DeprecationWarning.

- bpo-25407: Remove mentions of the formatter module being removed in Python 3.6.

- bpo-25406: Fixed a bug in C implementation of OrderedDict.move_to_end() that caused segmentation fault or hang in iterating after moving several items to the start of ordered dict.

- bpo-25382: pickletools.dis() now outputs implicit memo index for the MEMOIZE opcode.

- bpo-25357: Add an optional newline parameter to binascii.b2a_base64(). base64.b64encode() uses it to avoid a memory copy.

- bpo-24164: Objects that need calling `__new__` with keyword arguments, can now be pickled using pickle protocols older than protocol version 4.

- bpo-25364: zipfile now works in threads disabled builds.

- bpo-25328: smtpd’s SMTPChannel now correctly raises a ValueError if both decode_data and enable_SMTPUTF8 are set to true.

- bpo-16099: RobotFileParser now supports Crawl-delay and Request-rate extensions. Patch by Nikolay Bogoychev.

- bpo-25316: distutils raises OSError instead of DistutilsPlatformError when MSVC is not installed.

- bpo-25380: Fixed protocol for the STACK_GLOBAL opcode in pickletools.opcodes.

- bpo-23972: Updates asyncio datagram create method allowing reuseport and reuseaddr socket options to be set prior to binding the socket. Mirroring the existing asyncio create_server method the reuseaddr option for datagram sockets defaults to True if the O/S is ‘posix’ (except if the platform is Cygwin). Patch by Chris Laws.

- bpo-25304: Add asyncio.run_coroutine_threadsafe(). This lets you submit a coroutine to a loop from another thread, returning a concurrent.futures.Future. By Vincent Michel.

- bpo-25232: Fix CGIRequestHandler to split the query from the URL at the first question mark (?) rather than the last. Patch from Xiang Zhang.

- bpo-24657: Prevent CGIRequestHandler from collapsing slashes in the query part of the URL as if it were a path. Patch from Xiang Zhang.

- bpo-25287: Don’t add crypt.METHOD_CRYPT to crypt.methods if it’s not supported. Check if it is supported, it may not be supported on OpenBSD for example.

- bpo-23600: Default implementation of tzinfo.fromutc() was returning wrong results in some cases.

- bpo-25203: Failed readline.set_completer_delims() no longer left the module in inconsistent state.

- bpo-25011: rlcompleter now omits private and special attribute names unless the prefix starts with underscores.

- bpo-25209: rlcompleter now can add a space or a colon after completed keyword.

- bpo-22241: timezone.utc name is now plain ‘UTC’, not ‘UTC-00:00’.

- bpo-23517: fromtimestamp() and utcfromtimestamp() methods of datetime.datetime now round microseconds to nearest with ties going to nearest even integer (ROUND_HALF_EVEN), as round(float), instead of rounding towards -Infinity (ROUND_FLOOR).

- bpo-23552: Timeit now warns when there is substantial (4x) variance between best and worst times. Patch from Serhiy Storchaka.

- bpo-24633: site-packages/README -> README.txt.

- bpo-24879: help() and pydoc can now list named tuple fields in the order they were defined rather than alphabetically. The ordering is determined by the _fields attribute if present.

- bpo-24874: Improve speed of itertools.cycle() and make its pickle more compact.

- Fix crash in itertools.cycle.__setstate__() when the first argument wasn’t a list.

- bpo-20059: urllib.parse raises ValueError on all invalid ports. Patch by Martin Panter.

- bpo-24360: Improve __repr__ of argparse.Namespace() for invalid identifiers. Patch by Matthias Bussonnier.

- bpo-23426: run_setup was broken in distutils. Patch from Alexander Belopolsky.

- bpo-13938: 2to3 converts StringTypes to a tuple. Patch from Mark Hammond.

- bpo-2091: open() accepted a ‘U’ mode string containing ‘+’, but ‘U’ can only be used with ‘r’. Patch from Jeff Balogh and John O’Connor.

- bpo-8585: improved tests for zipimporter2. Patch from Mark Lawrence.

- bpo-18622: unittest.mock.mock_open().reset_mock would recurse infinitely. Patch from Nicola Palumbo and Laurent De Buyst.

- bpo-24426: Fast searching optimization in regular expressions now works for patterns that starts with capturing groups. Fast searching optimization now can’t be disabled at compile time.

- bpo-23661: unittest.mock side_effects can now be exceptions again. This was a regression vs Python 3.4. Patch from Ignacio Rossi

- bpo-13248: Remove deprecated inspect.getmoduleinfo function.

- bpo-25578: Fix (another) memory leak in SSLSocket.getpeercer().

- bpo-25530: Disable the vulnerable SSLv3 protocol by default when creating ssl.SSLContext.

- bpo-25569: Fix memory leak in SSLSocket.getpeercert().

- bpo-25471: Sockets returned from accept() shouldn’t appear to be nonblocking.

- bpo-25319: When threading.Event is reinitialized, the underlying condition should use a regular lock rather than a recursive lock.

- Skip getaddrinfo if host is already resolved. Patch by A. Jesse Jiryu Davis.

- bpo-26050: Add asyncio.StreamReader.readuntil() method. Patch by Марк Коренберг.

- bpo-25924: Avoid unnecessary serialization of getaddrinfo(3) calls on OS X versions 10.5 or higher. Original patch by A. Jesse Jiryu Davis.

- bpo-26406: Avoid unnecessary serialization of getaddrinfo(3) calls on current versions of OpenBSD and NetBSD. Patch by A. Jesse Jiryu Davis.

- bpo-26848: Fix asyncio/subprocess.communicate() to handle empty input. Patch by Jack O’Connor.

- bpo-27040: Add loop.get_exception_handler method

- bpo-27041: asyncio: Add loop.create_future method

### IDLE

- bpo-20640: Add tests for idlelib.configHelpSourceEdit. Patch by Saimadhav Heblikar.

- In the ‘IDLE-console differences’ section of the IDLE doc, clarify how running with IDLE affects sys.modules and the standard streams.

- bpo-25507: fix incorrect change in IOBinding that prevented printing. Augment IOBinding htest to include all major IOBinding functions.

- bpo-25905: Revert unwanted conversion of ‘ to ’ RIGHT SINGLE QUOTATION MARK in README.txt and open this and NEWS.txt with ‘ascii’. Re-encode CREDITS.txt to utf-8 and open it with ‘utf-8’.

- bpo-15348: Stop the debugger engine (normally in a user process) before closing the debugger window (running in the IDLE process). This prevents the RuntimeErrors that were being caught and ignored.

- bpo-24455: Prevent IDLE from hanging when a) closing the shell while the debugger is active (15347); b) closing the debugger with the [X] button (15348); and c) activating the debugger when already active (24455). The patch by Mark Roseman does this by making two changes. 1. Suspend and resume the gui.interaction method with the tcl vwait mechanism intended for this purpose (instead of root.mainloop & .quit). 2. In gui.run, allow any existing interaction to terminate first.

- Change ‘The program’ to ‘Your program’ in an IDLE ‘kill program?’ message to make it clearer that the program referred to is the currently running user program, not IDLE itself.

- bpo-24750: Improve the appearance of the IDLE editor window status bar. Patch by Mark Roseman.

- bpo-25313: Change the handling of new built-in text color themes to better address the compatibility problem introduced by the addition of IDLE Dark. Consistently use the revised idleConf.CurrentTheme everywhere in idlelib.

- bpo-24782: Extension configuration is now a tab in the IDLE Preferences dialog rather than a separate dialog. The former tabs are now a sorted list. Patch by Mark Roseman.

- bpo-22726: Re-activate the config dialog help button with some content about the other buttons and the new IDLE Dark theme.

- bpo-24820: IDLE now has an ‘IDLE Dark’ built-in text color theme. It is more or less IDLE Classic inverted, with a cobalt blue background. Strings, comments, keywords, … are still green, red, orange, … . To use it with IDLEs released before November 2015, hit the ‘Save as New Custom Theme’ button and enter a new name, such as ‘Custom Dark’. The custom theme will work with any IDLE release, and can be modified.

- bpo-25224: README.txt is now an idlelib index for IDLE developers and curious users. The previous user content is now in the IDLE doc chapter. ‘IDLE’ now means ‘Integrated Development and Learning Environment’.

- bpo-24820: Users can now set breakpoint colors in Settings -> Custom Highlighting. Original patch by Mark Roseman.

- bpo-24972: Inactive selection background now matches active selection background, as configured by users, on all systems. Found items are now always highlighted on Windows. Initial patch by Mark Roseman.

- bpo-24570: Idle: make calltip and completion boxes appear on Macs affected by a tk regression. Initial patch by Mark Roseman.

- bpo-24988: Idle ScrolledList context menus (used in debugger) now work on Mac Aqua. Patch by Mark Roseman.

- bpo-24801: Make right-click for context menu work on Mac Aqua. Patch by Mark Roseman.

- bpo-25173: Associate tkinter messageboxes with a specific widget. For Mac OSX, make them a ‘sheet’. Patch by Mark Roseman.

- bpo-25198: Enhance the initial html viewer now used for Idle Help. Properly indent fixed-pitch text (patch by Mark Roseman). Give code snippet a very Sphinx-like light blueish-gray background. Re-use initial width and height set by users for shell and editor. When the Table of Contents (TOC) menu is used, put the section header at the top of the screen.

- bpo-25225: Condense and rewrite Idle doc section on text colors.

- bpo-21995: Explain some differences between IDLE and console Python.

- bpo-22820: Explain need for print when running file from Idle editor.

- bpo-25224: Doc: augment Idle feature list and no-subprocess section.

- bpo-25219: Update doc for Idle command line options. Some were missing and notes were not correct.

- bpo-24861: Most of idlelib is private and subject to change. Use idleib.idle.* to start Idle. See idlelib.__init__.__doc__.

- bpo-25199: Idle: add synchronization comments for future maintainers.

- bpo-16893: Replace help.txt with help.html for Idle doc display. The new idlelib/help.html is rstripped Doc/build/html/library/idle.html. It looks better than help.txt and will better document Idle as released. The tkinter html viewer that works for this file was written by Rose Roseman. The now unused EditorWindow.HelpDialog class and helt.txt file are deprecated.

- bpo-24199: Deprecate unused idlelib.idlever with possible removal in 3.6.

- bpo-24790: Remove extraneous code (which also create 2 & 3 conflicts).

### Documentation

- bpo-26736: Used HTTPS for external links in the documentation if possible.

- bpo-6953: Rework the Readline module documentation to group related functions together, and add more details such as what underlying Readline functions and variables are accessed.

- bpo-23606: Adds note to ctypes documentation regarding cdll.msvcrt.

- bpo-24952: Clarify the default size argument of stack_size() in the “threading” and “_thread” modules. Patch from Mattip.

- bpo-26014: Update 3.x packaging documentation: * “See also” links to the new docs are now provided in the legacy pages * links to setuptools documentation have been updated

### Tests

- bpo-21916: Added tests for the turtle module. Patch by ingrid, Gregory Loyse and Jelle Zijlstra.

- bpo-26295: When using “python3 -m test –testdir=TESTDIR”, regrtest doesn’t add “test.” prefix to test module names.

- bpo-26523: The multiprocessing thread pool (multiprocessing.dummy.Pool) was untested.

- bpo-26015: Added new tests for pickling iterators of mutable sequences.

- bpo-26325: Added test.support.check_no_resource_warning() to check that no ResourceWarning is emitted.

- bpo-25940: Changed test_ssl to use its internal local server more. This avoids relying on svn.python.org, which recently changed root certificate.

- bpo-25616: Tests for OrderedDict are extracted from test_collections into separate file test_ordered_dict.

- bpo-25449: Added tests for OrderedDict subclasses.

- bpo-25188: Add -P/–pgo to test.regrtest to suppress error output when running the test suite for the purposes of a PGO build. Initial patch by Alecsandru Patrascu.

- bpo-22806: Add `python -m test --list-tests` command to list tests.

- bpo-18174: `python -m test --huntrleaks ...` now also checks for leak of file descriptors. Patch written by Richard Oudkerk.

- bpo-25260: Fix `python -m test --coverage` on Windows. Remove the list of ignored directories.

- `PCbuild\rt.bat` now accepts an unlimited number of arguments to pass along to regrtest.py. Previously there was a limit of 9.

- bpo-26583: Skip test_timestamp_overflow in test_import if bytecode files cannot be written.

### Build

- bpo-21277: Don’t try to link _ctypes with a ffi_convenience library.

- bpo-26884: Fix linking extension modules for cross builds. Patch by Xavier de Gaye.

- bpo-26932: Fixed support of RTLD_* constants defined as enum values, not via macros (in particular on Android). Patch by Chi Hsuan Yen.

- bpo-22359: Disable the rules for running _freeze_importlib and pgen when cross-compiling. The output of these programs is normally saved with the source code anyway, and is still regenerated when doing a native build. Patch by Xavier de Gaye.

- bpo-21668: Link audioop, _datetime, _ctypes_test modules to libm, except on Mac OS X. Patch written by Chi Hsuan Yen.

- bpo-25702: A –with-lto configure option has been added that will enable link time optimizations at build time during a make profile-opt. Some compilers and toolchains are known to not produce stable code when using LTO, be sure to test things thoroughly before relying on it. It can provide a few % speed up over profile-opt alone.

- bpo-26624: Adds validation of ucrtbase[d].dll version with warning for old versions.

- bpo-17603: Avoid error about nonexistent fileblocks.o file by using a lower-level check for st_blocks in struct stat.

- bpo-26079: Fixing the build output folder for tix-8.4.3.6. Patch by Bjoern Thiel.

- bpo-26465: Update Windows builds to use OpenSSL 1.0.2g.

- bpo-25348: Added `--pgo` and `--pgo-job` arguments to `PCbuild\build.bat` for building with Profile-Guided Optimization. The old `PCbuild\build_pgo.bat` script is removed.

- bpo-25827: Add support for building with ICC to `configure`, including a new `--with-icc` flag.

- bpo-25696: Fix installation of Python on UNIX with make -j9.

- bpo-24986: It is now possible to build Python on Windows without errors when external libraries are not available.

- bpo-24421: Compile Modules/_math.c once, before building extensions. Previously it could fail to compile properly if the math and cmath builds were concurrent.

- bpo-26465: Update OS X 10.5+ 32-bit-only installer to build and link with OpenSSL 1.0.2g.

- bpo-26268: Update Windows builds to use OpenSSL 1.0.2f.

- bpo-25136: Support Apple Xcode 7’s new textual SDK stub libraries.

- bpo-24324: Do not enable unreachable code warnings when using gcc as the option does not work correctly in older versions of gcc and has been silently removed as of gcc-4.5.

### Windows

- bpo-27053: Updates make_zip.py to correctly generate library ZIP file.

- bpo-26268: Update the prepare_ssl.py script to handle OpenSSL releases that don’t include the contents of the include directory (that is, 1.0.2e and later).

- bpo-26071: bdist_wininst created binaries fail to start and find 32bit Python

- bpo-26073: Update the list of magic numbers in launcher

- bpo-26065: Excludes venv from library when generating embeddable distro.

- bpo-25022: Removed very outdated PC/example_nt/ directory.

### Tools/Demos

- bpo-26799: Fix python-gdb.py: don’t get C types once when the Python code is loaded, but get C types on demand. The C types can change if python-gdb.py is loaded before the Python executable. Patch written by Thomas Ilsche.

- bpo-26271: Fix the Freeze tool to properly use flags passed through configure. Patch by Daniel Shaulov.

- bpo-26489: Add dictionary unpacking support to Tools/parser/unparse.py. Patch by Guo Ci Teo.

- bpo-26316: Fix variable name typo in Argument Clinic.

- bpo-25440: Fix output of python-config –extension-suffix.

- bpo-25154: The pyvenv script has been deprecated in favour of `python3 -m venv`.

### C API

- bpo-26312: SystemError is now raised in all programming bugs with using PyArg_ParseTupleAndKeywords(). RuntimeError did raised before in some programming bugs.

- bpo-26198: ValueError is now raised instead of TypeError on buffer overflow in parsing “es#” and “et#” format units. SystemError is now raised instead of TypeError on programmatical error in parsing format string.

## Python 3.5.5 final

Release date: 2018-02-04

There were no new changes in version 3.5.5.

## Python 3.5.5 release candidate 1

Release date: 2018-01-23

### Security

- bpo-32551: The `sys.path[0]` initialization change for bpo-29139 caused a regression by revealing an inconsistency in how sys.path is initialized when executing `__main__` from a zipfile, directory, or other import location. This is considered a potential security issue, as it may lead to privileged processes unexpectedly loading code from user controlled directories in situations where that was not previously the case. The interpreter now consistently avoids ever adding the import location’s parent directory to `sys.path`, and ensures no other `sys.path` entries are inadvertently modified when inserting the import location named on the command line. (Originally reported as bpo-29723 against Python 3.6rc1, but it was missed at the time that the then upcoming Python 3.5.4 release would also be affected)

- bpo-30657: Fixed possible integer overflow in PyBytes_DecodeEscape, CVE 2017-1000158. Original patch by Jay Bosamiya; rebased to Python 3 by Miro Hrončok.

- bpo-30947: Upgrade libexpat embedded copy from version 2.2.1 to 2.2.3 to get security fixes.

### Core and Builtins

- bpo-31095: Fix potential crash during GC caused by `tp_dealloc` which doesn’t call `PyObject_GC_UnTrack()`.

### Library

- bpo-32072: Fixed issues with binary plists: Fixed saving bytearrays. Identical objects will be saved only once. Equal references will be load as identical objects. Added support for saving and loading recursive data structures.

- bpo-31170: expat: Update libexpat from 2.2.3 to 2.2.4. Fix copying of partial characters for UTF-8 input (libexpat bug 115): https://github.com/libexpat/libexpat/issues/115

## Python 3.5.4 final

Release date: 2017-08-07

### Library

- bpo-30119: ftplib.FTP.putline() now throws ValueError on commands that contains CR or LF. Patch by Donghee Na.

## Python 3.5.4 release candidate 1

Release date: 2017-07-23

### Security

- bpo-30730: Prevent environment variables injection in subprocess on Windows. Prevent passing other environment variables and command arguments.

- bpo-30694: Upgrade expat copy from 2.2.0 to 2.2.1 to get fixes of multiple security vulnerabilities including: CVE 2017-9233 (External entity infinite loop DoS), CVE 2016-9063 (Integer overflow, re-fix), CVE 2016-0718 (Fix regression bugs from 2.2.0’s fix to CVE 2016-0718) and CVE 2012-0876 (Counter hash flooding with SipHash). Note: the CVE 2016-5300 (Use os-specific entropy sources like getrandom) doesn’t impact Python, since Python already gets entropy from the OS to set the expat secret using `XML_SetHashSalt()`.

- bpo-30500: Fix urllib.parse.splithost() to correctly parse fragments. For example, `splithost('//127.0.0.1#@evil.com/')` now correctly returns the `127.0.0.1` host, instead of treating `@evil.com` as the host in an authentication (`login@host`).

- bpo-29591: Update expat copy from 2.1.1 to 2.2.0 to get fixes of CVE 2016-0718 and CVE 2016-4472. See https://sourceforge.net/p/expat/bugs/537/ for more information.

### Core and Builtins

- bpo-30876: Relative import from unloaded package now reimports the package instead of failing with SystemError. Relative import from non-package now fails with ImportError rather than SystemError.

- bpo-30765: Avoid blocking in pthread_mutex_lock() when PyThread_acquire_lock() is asked not to block.

- bpo-27945: Fixed various segfaults with dict when input collections are mutated during searching, inserting or comparing. Based on patches by Duane Griffin and Tim Mitchell.

- bpo-25794: Fixed type.__setattr__() and type.__delattr__() for non-interned attribute names. Based on patch by Eryk Sun.

- bpo-29935: Fixed error messages in the index() method of tuple, list and deque when pass indices of wrong type.

- bpo-28876: `bool(range)` works even if `len(range)` raises `OverflowError`.

- bpo-29600: Fix wrapping coroutine return values in StopIteration.

- bpo-29537: Restore runtime compatibility with bytecode files generated by CPython 3.5.0 to 3.5.2, and adjust the eval loop to avoid the problems that could be caused by the malformed variant of the BUILD_MAP_UNPACK_WITH_CALL opcode that they may contain. Patch by Petr Viktorin, Serhiy Storchaka, and Nick Coghlan.

- bpo-28598: Support __rmod__ for subclasses of str being called before str.__mod__. Patch by Martijn Pieters.

- bpo-29602: Fix incorrect handling of signed zeros in complex constructor for complex subclasses and for inputs having a __complex__ method. Patch by Serhiy Storchaka.

- bpo-29347: Fixed possibly dereferencing undefined pointers when creating weakref objects.

- bpo-29438: Fixed use-after-free problem in key sharing dict.

- bpo-29319: Prevent RunMainFromImporter overwriting sys.path[0].

- bpo-29337: Fixed possible BytesWarning when compare the code objects. Warnings could be emitted at compile time.

- bpo-29478: If max_line_length=None is specified while using the Compat32 policy, it is no longer ignored. Patch by Mircea Cosbuc.

### Library

- bpo-29403: Fix `unittest.mock`’s autospec to not fail on method-bound builtin functions. Patch by Aaron Gallagher.

- bpo-30961: Fix decrementing a borrowed reference in tracemalloc.

- bpo-30886: Fix multiprocessing.Queue.join_thread(): it now waits until the thread completes, even if the thread was started by the same process which created the queue.

- bpo-29854: Fix segfault in readline when using readline’s history-size option. Patch by Nir Soffer.

- bpo-30807: signal.setitimer() may disable the timer when passed a tiny value. Tiny values (such as 1e-6) are valid non-zero values for setitimer(), which is specified as taking microsecond-resolution intervals. However, on some platform, our conversion routine could convert 1e-6 into a zero interval, therefore disabling the timer instead of (re-)scheduling it.

- bpo-30441: Fix bug when modifying os.environ while iterating over it

- bpo-30532: Fix email header value parser dropping folding white space in certain cases.

- bpo-29169: Update zlib to 1.2.11.

- bpo-30879: os.listdir() and os.scandir() now emit bytes names when called with bytes-like argument.

- bpo-30746: Prohibited the ‘=’ character in environment variable names in `os.putenv()` and `os.spawn*()`.

- bpo-29755: Fixed the lgettext() family of functions in the gettext module. They now always return bytes.

- bpo-30645: Fix path calculation in imp.load_package(), fixing it for cases when a package is only shipped with bytecodes. Patch by Alexandru Ardelean.

- bpo-23890: unittest.TestCase.assertRaises() now manually breaks a reference cycle to not keep objects alive longer than expected.

- bpo-30149: inspect.signature() now supports callables with variable-argument parameters wrapped with partialmethod. Patch by Donghee Na.

- bpo-29931: Fixed comparison check for ipaddress.ip_interface objects. Patch by Sanjay Sundaresan.

- bpo-24484: Avoid race condition in multiprocessing cleanup.

- bpo-28994: The traceback no longer displayed for SystemExit raised in a callback registered by atexit.

- bpo-30508: Don’t log exceptions if Task/Future “cancel()” method was called.

- bpo-28556: Updates to typing module: Add generic AsyncContextManager, add support for ContextManager on all versions. Original PRs by Jelle Zijlstra and Ivan Levkivskyi

- bpo-29870: Fix ssl sockets leaks when connection is aborted in asyncio/ssl implementation. Patch by Michaël Sghaïer.

- bpo-29743: Closing transport during handshake process leaks open socket. Patch by Nikolay Kim

- bpo-27585: Fix waiter cancellation in asyncio.Lock. Patch by Mathieu Sornay.

- bpo-30418: On Windows, subprocess.Popen.communicate() now also ignore EINVAL on stdin.write() if the child process is still running but closed the pipe.

- bpo-30378: Fix the problem that logging.handlers.SysLogHandler cannot handle IPv6 addresses.

- bpo-29960: Preserve generator state when _random.Random.setstate() raises an exception. Patch by Bryan Olson.

- bpo-30414: multiprocessing.Queue._feed background running thread do not break from main loop on exception.

- bpo-30003: Fix handling escape characters in HZ codec. Based on patch by Ma Lin.

- bpo-30301: Fix AttributeError when using SimpleQueue.empty() under spawn and forkserver start methods.

- bpo-30329: imaplib and poplib now catch the Windows socket WSAEINVAL error (code 10022) on shutdown(SHUT_RDWR): An invalid operation was attempted. This error occurs sometimes on SSL connections.

- bpo-30375: Warnings emitted when compile a regular expression now always point to the line in the user code. Previously they could point into inners of the re module if emitted from inside of groups or conditionals.

- bpo-30048: Fixed `Task.cancel()` can be ignored when the task is running coroutine and the coroutine returned without any more `await`.

- bpo-29990: Fix range checking in GB18030 decoder. Original patch by Ma Lin.

- bpo-26293: Change resulted because of zipfile breakage. (See also: bpo-29094)

- bpo-30243: Removed the __init__ methods of _json’s scanner and encoder. Misusing them could cause memory leaks or crashes. Now scanner and encoder objects are completely initialized in the __new__ methods.

- bpo-30185: Avoid KeyboardInterrupt tracebacks in forkserver helper process when Ctrl-C is received.

- bpo-28556: Various updates to typing module: add typing.NoReturn type, use WrapperDescriptorType, minor bug-fixes. Original PRs by Jim Fasarakis-Hilliard and Ivan Levkivskyi.

- bpo-30205: Fix getsockname() for unbound AF_UNIX sockets on Linux.

- bpo-30070: Fixed leaks and crashes in errors handling in the parser module.

- bpo-30061: Fixed crashes in IOBase methods __next__() and readlines() when readline() or __next__() respectively return non-sizeable object. Fixed possible other errors caused by not checking results of PyObject_Size(), PySequence_Size(), or PyMapping_Size().

- bpo-30068: _io._IOBase.readlines will check if it’s closed first when hint is present.

- bpo-29694: Fixed race condition in pathlib mkdir with flags parents=True. Patch by Armin Rigo.

- bpo-29692: Fixed arbitrary unchaining of RuntimeError exceptions in contextlib.contextmanager. Patch by Siddharth Velankar.

- bpo-29998: Pickling and copying ImportError now preserves name and path attributes.

- bpo-29942: Fix a crash in itertools.chain.from_iterable when encountering long runs of empty iterables.

- bpo-27863: Fixed multiple crashes in ElementTree caused by race conditions and wrong types.

- bpo-28699: Fixed a bug in pools in multiprocessing.pool that raising an exception at the very first of an iterable may swallow the exception or make the program hang. Patch by Davin Potts and Xiang Zhang.

- bpo-25803: Avoid incorrect errors raised by Path.mkdir(exist_ok=True) when the OS gives priority to errors such as EACCES over EEXIST.

- bpo-29861: Release references to tasks, their arguments and their results as soon as they are finished in multiprocessing.Pool.

- bpo-29884: faulthandler: Restore the old sigaltstack during teardown. Patch by Christophe Zeitouny.

- bpo-25455: Fixed crashes in repr of recursive buffered file-like objects.

- bpo-29800: Fix crashes in partial.__repr__ if the keys of partial.keywords are not strings. Patch by Michael Seifert.

- bpo-29742: get_extra_info() raises exception if get called on closed ssl transport. Patch by Nikolay Kim.

- bpo-8256: Fixed possible failing or crashing input() if attributes “encoding” or “errors” of sys.stdin or sys.stdout are not set or are not strings.

- bpo-28298: Fix a bug that prevented array ‘Q’, ‘L’ and ‘I’ from accepting big intables (objects that have __int__) as elements. Patch by Oren Milman.

- bpo-29615: SimpleXMLRPCDispatcher no longer chains KeyError (or any other exception) to exception(s) raised in the dispatched methods. Patch by Petr Motejlek.

- bpo-29704: asyncio.subprocess.SubprocessStreamProtocol no longer closes before all pipes are closed.

- bpo-29703: Fix asyncio to support instantiation of new event loops in child processes.

- bpo-29376: Fix assertion error in threading._DummyThread.is_alive().

- bpo-29110: Fix file object leak in aifc.open() when file is given as a filesystem path and is not in valid AIFF format. Patch by Anthony Zhang.

- bpo-28961: Fix unittest.mock._Call helper: don’t ignore the name parameter anymore. Patch written by Jiajun Huang.

- bpo-29532: Altering a kwarg dictionary passed to functools.partial() no longer affects a partial object after creation.

- bpo-28556: Various updates to typing module: typing.Counter, typing.ChainMap, improved ABC caching, etc. Original PRs by Jelle Zijlstra, Ivan Levkivskyi, Manuel Krebber, and Łukasz Langa.

- bpo-29100: Fix datetime.fromtimestamp() regression introduced in Python 3.6.0: check minimum and maximum years.

- bpo-29519: Fix weakref spewing exceptions during interpreter shutdown when used with a rare combination of multiprocessing and custom codecs.

- bpo-29416: Prevent infinite loop in pathlib.Path.mkdir

- bpo-29444: Fixed out-of-bounds buffer access in the group() method of the match object. Based on patch by WGH.

- bpo-29335: Fix subprocess.Popen.wait() when the child process has exited to a stopped instead of terminated state (ex: when under ptrace).

- bpo-29290: Fix a regression in argparse that help messages would wrap at non-breaking spaces.

- bpo-28735: Fixed the comparison of mock.MagickMock with mock.ANY.

- bpo-29011: Fix an important omission by adding Deque to the typing module.

- bpo-29219: Fixed infinite recursion in the repr of uninitialized ctypes.CDLL instances.

- bpo-28969: Fixed race condition in C implementation of functools.lru_cache. KeyError could be raised when cached function with full cache was simultaneously called from different threads with the same uncached arguments.

- bpo-29142: In urllib.request, suffixes in no_proxy environment variable with leading dots could match related hostnames again (e.g. .b.c matches a.b.c). Patch by Milan Oberkirch.

### Documentation

- bpo-30176: Add missing attribute related constants in curses documentation.

- bpo-26985: Add missing info of code object in inspect documentation.

- bpo-28929: Link the documentation to its source file on GitHub.

- bpo-25008: Document smtpd.py as effectively deprecated and add a pointer to aiosmtpd, a third-party asyncio-based replacement.

- bpo-26355: Add canonical header link on each page to corresponding major version of the documentation. Patch by Matthias Bussonnier.

- bpo-29349: Fix Python 2 syntax in code for building the documentation.

### Tests

- bpo-30822: Fix regrtest command line parser to allow passing -u extralargefile to run test_zipfile64.

- bpo-30383: regrtest: Enhance regrtest and backport features from the master branch. Add options: –coverage, –testdir, –list-tests (list test files, don’t run them), –list-cases (list test identifiers, don’t run them, bpo-30523), –matchfile (load a list of test filters from a text file, bpo-30540), –slowest (alias to –slow). Enhance output: add timestamp, test result, currently running tests, “Tests result: xxx” summary with total duration, etc. Fix reference leak hunting in regrtest, –huntrleaks: regrtest now warms up caches, create explicitly all internal singletons which are created on demand to prevent false positives when checking for reference leaks. (bpo-30675).

- bpo-30357: test_thread: setUp() now uses support.threading_setup() and support.threading_cleanup() to wait until threads complete to avoid random side effects on following tests. Initial patch written by Grzegorz Grzywacz.

- bpo-28087: Skip test_asyncore and test_eintr poll failures on macOS. Skip some tests of select.poll when running on macOS due to unresolved issues with the underlying system poll function on some macOS versions.

- bpo-30197: Enhanced functions swap_attr() and swap_item() in the test.support module. They now work when delete replaced attribute or item inside the with statement. The old value of the attribute or item (or None if it doesn’t exist) now will be assigned to the target of the “as” clause, if there is one.

- bpo-29571: to match the behaviour of the `re.LOCALE` flag, test_re.test_locale_flag now uses `locale.getpreferredencoding(False)` to determine the candidate encoding for the test regex (allowing it to correctly skip the test when the default locale encoding is a multi-byte encoding)

### Build

- bpo-29243: Prevent unnecessary rebuilding of Python during `make test`, `make install` and some other make targets when configured with `--enable-optimizations`.

- bpo-23404: Don’t regenerate generated files based on file modification time anymore: the action is now explicit. Replace `make touch` with `make regen-all`.

- bpo-29643: Fix `--enable-optimization` didn’t work.

### Windows

- bpo-30687: Locate msbuild.exe on Windows when building rather than vcvarsall.bat

- bpo-29392: Prevent crash when passing invalid arguments into msvcrt module.

### C API

- bpo-27867: Function PySlice_GetIndicesEx() is replaced with a macro if Py_LIMITED_API is set to the value between 0x03050400 and 0x03060000 (not including) or 0x03060100 or higher.

- bpo-29083: Fixed the declaration of some public API functions. PyArg_VaParse() and PyArg_VaParseTupleAndKeywords() were not available in limited API. PyArg_ValidateKeywordArguments(), PyArg_UnpackTuple() and Py_BuildValue() were not available in limited API of version < 3.3 when PY_SSIZE_T_CLEAN is defined.

## Python 3.5.3 final

Release date: 2017-01-17

There were no code changes between 3.5.3rc1 and 3.5.3 final.

## Python 3.5.3 release candidate 1

Release date: 2017-01-02

### Security

- bpo-27278: Fix os.urandom() implementation using getrandom() on Linux. Truncate size to INT_MAX and loop until we collected enough random bytes, instead of casting a directly Py_ssize_t to int.

- bpo-22636: Avoid shell injection problems with ctypes.util.find_library().

### Core and Builtins

- bpo-29073: bytearray formatting no longer truncates on first null byte.

- bpo-28932: Do not include <sys/random.h> if it does not exist.

- bpo-28147: Fix a memory leak in split-table dictionaries: setattr() must not convert combined table into split table.

- bpo-25677: Correct the positioning of the syntax error caret for indented blocks. Based on patch by Michael Layzell.

- bpo-29000: Fixed bytes formatting of octals with zero padding in alternate form.

- bpo-28512: Fixed setting the offset attribute of SyntaxError by PyErr_SyntaxLocationEx() and PyErr_SyntaxLocationObject().

- bpo-28991: functools.lru_cache() was susceptible to an obscure reentrancy bug caused by a monkey-patched len() function.

- bpo-28648: Fixed crash in Py_DecodeLocale() in debug build on Mac OS X when decode astral characters. Patch by Xiang Zhang.

- bpo-19398: Extra slash no longer added to sys.path components in case of empty compile-time PYTHONPATH components.

- bpo-28426: Fixed potential crash in PyUnicode_AsDecodedObject() in debug build.

- bpo-23782: Fixed possible memory leak in _PyTraceback_Add() and exception loss in PyTraceBack_Here().

- bpo-28379: Added sanity checks and tests for PyUnicode_CopyCharacters(). Patch by Xiang Zhang.

- bpo-28376: The type of long range iterator is now registered as Iterator. Patch by Oren Milman.

- bpo-28376: The constructor of range_iterator now checks that step is not 0. Patch by Oren Milman.

- bpo-26906: Resolving special methods of uninitialized type now causes implicit initialization of the type instead of a fail.

- bpo-18287: PyType_Ready() now checks that tp_name is not NULL. Original patch by Niklas Koep.

- bpo-24098: Fixed possible crash when AST is changed in process of compiling it.

- bpo-28350: String constants with null character no longer interned.

- bpo-26617: Fix crash when GC runs during weakref callbacks.

- bpo-27942: String constants now interned recursively in tuples and frozensets.

- bpo-21578: Fixed misleading error message when ImportError called with invalid keyword args.

- bpo-28203: Fix incorrect type in error message from `complex(1.0, {2:3})`. Patch by Soumya Sharma.

- bpo-27955: Fallback on reading /dev/urandom device when the getrandom() syscall fails with EPERM, for example when blocked by SECCOMP.

- bpo-28131: Fix a regression in zipimport’s compile_source(). zipimport should use the same optimization level as the interpreter.

- bpo-25221: Fix corrupted result from PyLong_FromLong(0) when Python is compiled with NSMALLPOSINTS = 0.

- bpo-25758: Prevents zipimport from unnecessarily encoding a filename (patch by Eryk Sun)

- bpo-28189: dictitems_contains no longer swallows compare errors. (Patch by Xiang Zhang)

- bpo-27812: Properly clear out a generator’s frame’s backreference to the generator to prevent crashes in frame.clear().

- bpo-27811: Fix a crash when a coroutine that has not been awaited is finalized with warnings-as-errors enabled.

- bpo-27587: Fix another issue found by PVS-Studio: Null pointer check after use of ‘def’ in _PyState_AddModule(). Initial patch by Christian Heimes.

- bpo-26020: set literal evaluation order did not match documented behaviour.

- bpo-27782: Multi-phase extension module import now correctly allows the `m_methods` field to be used to add module level functions to instances of non-module types returned from `Py_create_mod`. Patch by Xiang Zhang.

- bpo-27936: The round() function accepted a second None argument for some types but not for others. Fixed the inconsistency by accepting None for all numeric types.

- bpo-27487: Warn if a submodule argument to “python -m” or runpy.run_module() is found in sys.modules after parent packages are imported, but before the submodule is executed.

- bpo-27558: Fix a SystemError in the implementation of “raise” statement. In a brand new thread, raise a RuntimeError since there is no active exception to reraise. Patch written by Xiang Zhang.

- bpo-27419: Standard __import__() no longer look up “__import__” in globals or builtins for importing submodules or “from import”. Fixed handling an error of non-string package name.

- bpo-27083: Respect the PYTHONCASEOK environment variable under Windows.

- bpo-27514: Make having too many statically nested blocks a SyntaxError instead of SystemError.

- bpo-27473: Fixed possible integer overflow in bytes and bytearray concatenations. Patch by Xiang Zhang.

- bpo-27507: Add integer overflow check in bytearray.extend(). Patch by Xiang Zhang.

- bpo-27581: Don’t rely on wrapping for overflow check in PySequence_Tuple(). Patch by Xiang Zhang.

- bpo-27443: __length_hint__() of bytearray iterators no longer return a negative integer for a resized bytearray.

- bpo-27942: Fix memory leak in codeobject.c

### Library

- bpo-15812: inspect.getframeinfo() now correctly shows the first line of a context. Patch by Sam Breese.

- bpo-29094: Offsets in a ZIP file created with extern file object and modes “w” and “x” now are relative to the start of the file.

- bpo-13051: Fixed recursion errors in large or resized curses.textpad.Textbox. Based on patch by Tycho Andersen.

- bpo-29119: Fix weakrefs in the pure python version of collections.OrderedDict move_to_end() method. Contributed by Andra Bogildea.

- bpo-9770: curses.ascii predicates now work correctly with negative integers.

- bpo-28427: old keys should not remove new values from WeakValueDictionary when collecting from another thread.

- bpo-28923: Remove editor artifacts from Tix.py.

- bpo-28871: Fixed a crash when deallocate deep ElementTree.

- bpo-19542: Fix bugs in WeakValueDictionary.setdefault() and WeakValueDictionary.pop() when a GC collection happens in another thread.

- bpo-20191: Fixed a crash in resource.prlimit() when pass a sequence that doesn’t own its elements as limits.

- bpo-28779: multiprocessing.set_forkserver_preload() would crash the forkserver process if a preloaded module instantiated some multiprocessing objects such as locks.

- bpo-28847: dbm.dumb now supports reading read-only files and no longer writes the index file when it is not changed.

- bpo-25659: In ctypes, prevent a crash calling the from_buffer() and from_buffer_copy() methods on abstract classes like Array.

- bpo-28732: Fix crash in os.spawnv() with no elements in args

- bpo-28485: Always raise ValueError for negative compileall.compile_dir(workers=…) parameter, even when multithreading is unavailable.

- bpo-28387: Fixed possible crash in _io.TextIOWrapper deallocator when the garbage collector is invoked in other thread. Based on patch by Sebastian Cufre.

- bpo-27517: LZMA compressor and decompressor no longer raise exceptions if given empty data twice. Patch by Benjamin Fogle.

- bpo-28549: Fixed segfault in curses’s addch() with ncurses6.

- bpo-28449: tarfile.open() with mode “r” or “r:” now tries to open a tar file with compression before trying to open it without compression. Otherwise it had 50% chance failed with ignore_zeros=True.

- bpo-23262: The webbrowser module now supports Firefox 36+ and derived browsers. Based on patch by Oleg Broytman.

- bpo-27939: Fixed bugs in tkinter.ttk.LabeledScale and tkinter.Scale caused by representing the scale as float value internally in Tk. tkinter.IntVar now works if float value is set to underlying Tk variable.

- bpo-28255: calendar.TextCalendar().prmonth() no longer prints a space at the start of new line after printing a month’s calendar. Patch by Xiang Zhang.

- bpo-20491: The textwrap.TextWrapper class now honors non-breaking spaces. Based on patch by Kaarle Ritvanen.

- bpo-28353: os.fwalk() no longer fails on broken links.

- bpo-25464: Fixed HList.header_exists() in tkinter.tix module by addin a workaround to Tix library bug.

- bpo-28488: shutil.make_archive() no longer add entry “./” to ZIP archive.

- bpo-24452: Make webbrowser support Chrome on Mac OS X.

- bpo-20766: Fix references leaked by pdb in the handling of SIGINT handlers.

- bpo-26293: Fixed writing ZIP files that starts not from the start of the file. Offsets in ZIP file now are relative to the start of the archive in conforming to the specification.

- bpo-28321: Fixed writing non-BMP characters with binary format in plistlib.

- bpo-28322: Fixed possible crashes when unpickle itertools objects from incorrect pickle data. Based on patch by John Leitch.

- Fix possible integer overflows and crashes in the mmap module with unusual usage patterns.

- bpo-1703178: Fix the ability to pass the –link-objects option to the distutils build_ext command.

- bpo-28253: Fixed calendar functions for extreme months: 0001-01 and 9999-12. Methods itermonthdays() and itermonthdays2() are reimplemented so that they don’t call itermonthdates() which can cause datetime.date under/overflow.

- bpo-28275: Fixed possible use after free in the decompress() methods of the LZMADecompressor and BZ2Decompressor classes. Original patch by John Leitch.

- bpo-27897: Fixed possible crash in sqlite3.Connection.create_collation() if pass invalid string-like object as a name. Patch by Xiang Zhang.

- bpo-18893: Fix invalid exception handling in Lib/ctypes/macholib/dyld.py. Patch by Madison May.

- bpo-27611: Fixed support of default root window in the tkinter.tix module.

- bpo-27348: In the traceback module, restore the formatting of exception messages like “Exception: None”. This fixes a regression introduced in 3.5a2.

- bpo-25651: Allow false values to be used for msg parameter of subTest().

- bpo-27932: Prevent memory leak in win32_ver().

- Fix UnboundLocalError in socket._sendfile_use_sendfile.

- bpo-28075: Check for ERROR_ACCESS_DENIED in Windows implementation of os.stat(). Patch by Eryk Sun.

- bpo-25270: Prevent codecs.escape_encode() from raising SystemError when an empty bytestring is passed.

- bpo-28181: Get antigravity over HTTPS. Patch by Kaartic Sivaraam.

- bpo-25895: Enable WebSocket URL schemes in urllib.parse.urljoin. Patch by Gergely Imreh and Markus Holtermann.

- bpo-27599: Fixed buffer overrun in binascii.b2a_qp() and binascii.a2b_qp().

- bpo-19003: m email.generator now replaces only `\r` and/or `\n` line endings, per the RFC, instead of all unicode line endings.

- bpo-28019: itertools.count() no longer rounds non-integer step in range between 1.0 and 2.0 to 1.

- bpo-25969: Update the lib2to3 grammar to handle the unpacking generalizations added in 3.5.

- bpo-14977: mailcap now respects the order of the lines in the mailcap files (“first match”), as required by RFC 1542. Patch by Michael Lazar.

- bpo-24594: Validates persist parameter when opening MSI database

- bpo-17582: xml.etree.ElementTree nows preserves whitespaces in attributes (Patch by Duane Griffin. Reviewed and approved by Stefan Behnel.)

- bpo-28047: Fixed calculation of line length used for the base64 CTE in the new email policies.

- bpo-27445: Don’t pass str(_charset) to MIMEText.set_payload(). Patch by Claude Paroz.

- bpo-22450: urllib now includes an `Accept: */*` header among the default headers. This makes the results of REST API requests more consistent and predictable especially when proxy servers are involved.

- lib2to3.pgen3.driver.load_grammar() now creates a stable cache file between runs given the same Grammar.txt input regardless of the hash randomization setting.

- bpo-27570: Avoid zero-length memcpy() etc calls with null source pointers in the “ctypes” and “array” modules.

- bpo-22233: Break email header lines only on the RFC specified CR and LF characters, not on arbitrary unicode line breaks. This also fixes a bug in HTTP header parsing.

- bpo-27988: Fix email iter_attachments incorrect mutation of payload list.

- bpo-27691: Fix ssl module’s parsing of GEN_RID subject alternative name fields in X.509 certs.

- bpo-27850: Remove 3DES from ssl module’s default cipher list to counter measure sweet32 attack (CVE 2016-2183).

- bpo-27766: Add ChaCha20 Poly1305 to ssl module’s default cipher list. (Required OpenSSL 1.1.0 or LibreSSL).

- bpo-26470: Port ssl and hashlib module to OpenSSL 1.1.0.

- Remove support for passing a file descriptor to os.access. It never worked but previously didn’t raise.

- bpo-12885: Fix error when distutils encounters symlink.

- bpo-27881: Fixed possible bugs when setting sqlite3.Connection.isolation_level. Based on patch by Xiang Zhang.

- bpo-27861: Fixed a crash in sqlite3.Connection.cursor() when a factory creates not a cursor. Patch by Xiang Zhang.

- bpo-19884: Avoid spurious output on OS X with Gnu Readline.

- bpo-27706: Restore deterministic behavior of random.Random().seed() for string seeds using seeding version 1. Allows sequences of calls to random() to exactly match those obtained in Python 2. Patch by Nofar Schnider.

- bpo-10513: Fix a regression in Connection.commit(). Statements should not be reset after a commit.

- A new version of typing.py from https://github.com/python/typing: Collection (only for 3.6) (bpo-27598). Add FrozenSet to __all__ (upstream #261). Fix crash in _get_type_vars() (upstream #259). Remove the dict constraint in ForwardRef._eval_type (upstream #252).

- bpo-27539: Fix unnormalised `Fraction.__pow__` result in the case of negative exponent and negative base.

- bpo-21718: cursor.description is now available for queries using CTEs.

- bpo-2466: posixpath.ismount now correctly recognizes mount points which the user does not have permission to access.

- bpo-27773: Correct some memory management errors server_hostname in _ssl.wrap_socket().

- bpo-26750: unittest.mock.create_autospec() now works properly for subclasses of property() and other data descriptors.

- In the curses module, raise an error if window.getstr() or window.instr() is passed a negative value.

- bpo-27783: Fix possible usage of uninitialized memory in operator.methodcaller.

- bpo-27774: Fix possible Py_DECREF on unowned object in _sre.

- bpo-27760: Fix possible integer overflow in binascii.b2a_qp.

- bpo-27758: Fix possible integer overflow in the _csv module for large record lengths.

- bpo-27568: Prevent HTTPoxy attack (CVE 2016-1000110). Ignore the HTTP_PROXY variable when REQUEST_METHOD environment is set, which indicates that the script is in CGI mode.

- bpo-27656: Do not assume sched.h defines any SCHED_* constants.

- bpo-27130: In the “zlib” module, fix handling of large buffers (typically 4 GiB) when compressing and decompressing. Previously, inputs were limited to 4 GiB, and compression and decompression operations did not properly handle results of 4 GiB.

- bpo-27533: Release GIL in nt._isdir

- bpo-17711: Fixed unpickling by the persistent ID with protocol 0. Original patch by Alexandre Vassalotti.

- bpo-27522: Avoid an unintentional reference cycle in email.feedparser.

- bpo-26844: Fix error message for imp.find_module() to refer to ‘path’ instead of ‘name’. Patch by Lev Maximov.

- bpo-23804: Fix SSL zero-length recv() calls to not block and not raise an error about unclean EOF.

- bpo-27466: Change time format returned by http.cookie.time2netscape, confirming the netscape cookie format and making it consistent with documentation.

- bpo-26664: Fix activate.fish by removing mis-use of `$`.

- bpo-22115: Fixed tracing Tkinter variables: trace_vdelete() with wrong mode no longer break tracing, trace_vinfo() now always returns a list of pairs of strings, tracing in the “u” mode now works.

- Fix a scoping issue in importlib.util.LazyLoader which triggered an UnboundLocalError when lazy-loading a module that was already put into sys.modules.

- bpo-27079: Fixed curses.ascii functions isblank(), iscntrl() and ispunct().

- bpo-26754: Some functions (compile() etc) accepted a filename argument encoded as an iterable of integers. Now only strings and byte-like objects are accepted.

- bpo-27048: Prevents distutils failing on Windows when environment variables contain non-ASCII characters

- bpo-27330: Fixed possible leaks in the ctypes module.

- bpo-27238: Got rid of bare excepts in the turtle module. Original patch by Jelle Zijlstra.

- bpo-27122: When an exception is raised within the context being managed by a contextlib.ExitStack() and one of the exit stack generators catches and raises it in a chain, do not re-raise the original exception when exiting, let the new chained one through. This avoids the PEP 479 bug described in issue25782.

- bpo-26386: Fixed ttk.TreeView selection operations with item id’s containing spaces.

- bpo-16182: Fix various functions in the “readline” module to use the locale encoding, and fix get_begidx() and get_endidx() to return code point indexes.

- bpo-27392: Add loop.connect_accepted_socket(). Patch by Jim Fulton.

- bpo-27930: Improved behaviour of logging.handlers.QueueListener. Thanks to Paulo Andrade and Petr Viktorin for the analysis and patch.

- bpo-21201: Improves readability of multiprocessing error message. Thanks to Wojciech Walczak for patch.

- bpo-27456: asyncio: Set TCP_NODELAY by default.

- bpo-27906: Fix socket accept exhaustion during high TCP traffic. Patch by Kevin Conway.

- bpo-28174: Handle when SO_REUSEPORT isn’t properly supported. Patch by Seth Michael Larson.

- bpo-26654: Inspect functools.partial in asyncio.Handle.__repr__. Patch by iceboy.

- bpo-26909: Fix slow pipes IO in asyncio. Patch by INADA Naoki.

- bpo-28176: Fix callbacks race in asyncio.SelectorLoop.sock_connect.

- bpo-27759: Fix selectors incorrectly retain invalid file descriptors. Patch by Mark Williams.

- bpo-28368: Refuse monitoring processes if the child watcher has no loop attached. Patch by Vincent Michel.

- bpo-28369: Raise RuntimeError when transport’s FD is used with add_reader, add_writer, etc.

- bpo-28370: Speedup asyncio.StreamReader.readexactly. Patch by Коренберг Марк.

- bpo-28371: Deprecate passing asyncio.Handles to run_in_executor.

- bpo-28372: Fix asyncio to support formatting of non-python coroutines.

- bpo-28399: Remove UNIX socket from FS before binding. Patch by Коренберг Марк.

- bpo-27972: Prohibit Tasks to await on themselves.

- bpo-26923: Fix asyncio.Gather to refuse being cancelled once all children are done. Patch by Johannes Ebke.

- bpo-26796: Don’t configure the number of workers for default threadpool executor. Initial patch by Hans Lawrenz.

- bpo-28600: Optimize loop.call_soon().

- bpo-28613: Fix get_event_loop() return the current loop if called from coroutines/callbacks.

- bpo-28639: Fix inspect.isawaitable to always return bool Patch by Justin Mayfield.

- bpo-28652: Make loop methods reject socket kinds they do not support.

- bpo-28653: Fix a refleak in functools.lru_cache.

- bpo-28703: Fix asyncio.iscoroutinefunction to handle Mock objects.

- bpo-24142: Reading a corrupt config file left the parser in an invalid state. Original patch by Florian Höch.

- bpo-28990: Fix SSL hanging if connection is closed before handshake completed. (Patch by HoHo-Ho)

### IDLE

- bpo-15308: Add ‘interrupt execution’ (^C) to Shell menu. Patch by Roger Serwy, updated by Bayard Randel.

- bpo-27922: Stop IDLE tests from ‘flashing’ gui widgets on the screen.

- Add version to title of IDLE help window.

- bpo-25564: In section on IDLE – console differences, mention that using exec means that __builtins__ is defined for each statement.

- bpo-27714: text_textview and test_autocomplete now pass when re-run in the same process. This occurs when test_idle fails when run with the -w option but without -jn. Fix warning from test_config.

- bpo-25507: IDLE no longer runs buggy code because of its tkinter imports. Users must include the same imports required to run directly in Python.

- bpo-27452: add line counter and crc to IDLE configHandler test dump.

- bpo-27365: Allow non-ascii chars in IDLE NEWS.txt, for contributor names.

- bpo-27245: IDLE: Cleanly delete custom themes and key bindings. Previously, when IDLE was started from a console or by import, a cascade of warnings was emitted. Patch by Serhiy Storchaka.

### C API

- bpo-28808: PyUnicode_CompareWithASCIIString() now never raises exceptions.

- bpo-26754: PyUnicode_FSDecoder() accepted a filename argument encoded as an iterable of integers. Now only strings and bytes-like objects are accepted.

### Documentation

- bpo-28513: Documented command-line interface of zipfile.

### Tests

- bpo-28950: Disallow -j0 to be combined with -T/-l/-M in regrtest command line arguments.

- bpo-28666: Now test.support.rmtree is able to remove unwritable or unreadable directories.

- bpo-23839: Various caches now are cleared before running every test file.

- bpo-28409: regrtest: fix the parser of command line arguments.

- bpo-27787: Call gc.collect() before checking each test for “dangling threads”, since the dangling threads are weak references.

- bpo-27369: In test_pyexpat, avoid testing an error message detail that changed in Expat 2.2.0.

### Tools/Demos

- bpo-27952: Get Tools/scripts/fixcid.py working with Python 3 and the current “re” module, avoid invalid Python backslash escapes, and fix a bug parsing escaped C quote signs.

- bpo-27332: Fixed the type of the first argument of module-level functions generated by Argument Clinic. Patch by Petr Viktorin.

- bpo-27418: Fixed Tools/importbench/importbench.py.

### Windows

- bpo-28251: Improvements to help manuals on Windows.

- bpo-28110: launcher.msi has different product codes between 32-bit and 64-bit

- bpo-25144: Ensures TargetDir is set before continuing with custom install.

- bpo-27469: Adds a shell extension to the launcher so that drag and drop works correctly.

- bpo-27309: Enabled proper Windows styles in python[w].exe manifest.

### Build

- bpo-29080: Removes hard dependency on hg.exe from PCBuild/build.bat

- bpo-23903: Added missed names to PC/python3.def.

- bpo-10656: Fix out-of-tree building on AIX. Patch by Tristan Carel and Michael Haubenwallner.

- bpo-26359: Rename –with-optimiations to –enable-optimizations.

- bpo-28444: Fix missing extensions modules when cross compiling.

- bpo-28248: Update Windows build and OS X installers to use OpenSSL 1.0.2j.

- bpo-28258: Fixed build with Estonian locale (python-config and distclean targets in Makefile). Patch by Arfrever Frehtes Taifersar Arahesis.

- bpo-26661: setup.py now detects system libffi with multiarch wrapper.

- bpo-28066: Fix the logic that searches build directories for generated include files when building outside the source tree.

- bpo-15819: Remove redundant include search directory option for building outside the source tree.

- bpo-27566: Fix clean target in freeze makefile (patch by Lisa Roach)

- bpo-27705: Update message in validate_ucrtbase.py

- bpo-27983: Cause lack of llvm-profdata tool when using clang as required for PGO linking to be a configure time error rather than make time when –with-optimizations is enabled. Also improve our ability to find the llvm-profdata tool on MacOS and some Linuxes.

- bpo-26307: The profile-opt build now applies PGO to the built-in modules.

- bpo-26359: Add the –with-optimizations configure flag.

- bpo-27713: Suppress spurious build warnings when updating importlib’s bootstrap files. Patch by Xiang Zhang

- bpo-25825: Correct the references to Modules/python.exp and ld_so_aix, which are required on AIX. This updates references to an installation path that was changed in 3.2a4, and undoes changed references to the build tree that were made in 3.5.0a1.

- bpo-27453: CPP invocation in configure must use CPPFLAGS. Patch by Chi Hsuan Yen.

- bpo-27641: The configure script now inserts comments into the makefile to prevent the pgen and _freeze_importlib executables from being cross-compiled.

- bpo-26662: Set PYTHON_FOR_GEN in configure as the Python program to be used for file generation during the build.

- bpo-10910: Avoid C++ compilation errors on FreeBSD and OS X. Also update FreedBSD version checks for the original ctype UTF-8 workaround.

- bpo-28676: Prevent missing ‘getentropy’ declaration warning on macOS. Patch by Gareth Rees.

## Python 3.5.2 final

Release date: 2016-06-26

### Core and Builtins

- bpo-26930: Update Windows builds to use OpenSSL 1.0.2h.

### Tests

- bpo-26867: Ubuntu’s openssl OP_NO_SSLv3 is forced on by default; fix test.

### IDLE

- bpo-27365: Allow non-ascii in idlelib/NEWS.txt - minimal part for 3.5.2.

## Python 3.5.2 release candidate 1

Release date: 2016-06-12

### Security

- bpo-26556: Update expat to 2.1.1, fixes CVE 2015-1283.

- Fix TLS stripping vulnerability in smtplib, CVE 2016-0772. Reported by Team Oststrom.

- bpo-26839: On Linux, `os.urandom()` now calls `getrandom()` with `GRND_NONBLOCK` to fall back on reading `/dev/urandom` if the urandom entropy pool is not initialized yet. Patch written by Colm Buckley.

- bpo-26657: Fix directory traversal vulnerability with http.server on Windows. This fixes a regression that was introduced in 3.3.4rc1 and 3.4.0rc1. Based on patch by Philipp Hagemeister.

- bpo-26313: ssl.py _load_windows_store_certs fails if windows cert store is empty. Patch by Baji.

- bpo-25939: On Windows open the cert store readonly in ssl.enum_certificates.

### Core and Builtins

- bpo-27066: Fixed SystemError if a custom opener (for open()) returns a negative number without setting an exception.

- bpo-20041: Fixed TypeError when frame.f_trace is set to None. Patch by Xavier de Gaye.

- bpo-26168: Fixed possible refleaks in failing Py_BuildValue() with the “N” format unit.

- bpo-26991: Fix possible refleak when creating a function with annotations.

- bpo-27039: Fixed bytearray.remove() for values greater than 127. Patch by Joe Jevnik.

- bpo-23640: int.from_bytes() no longer bypasses constructors for subclasses.

- bpo-26811: gc.get_objects() no longer contains a broken tuple with NULL pointer.

- bpo-20120: Use RawConfigParser for .pypirc parsing, removing support for interpolation unintentionally added with move to Python 3. Behavior no longer does any interpolation in .pypirc files, matching behavior in Python 2.7 and Setuptools 19.0.

- bpo-26659: Make the builtin slice type support cycle collection.

- bpo-26718: super.__init__ no longer leaks memory if called multiple times. NOTE: A direct call of super.__init__ is not endorsed!

- bpo-25339: PYTHONIOENCODING now has priority over locale in setting the error handler for stdin and stdout.

- bpo-26494: Fixed crash on iterating exhausting iterators. Affected classes are generic sequence iterators, iterators of str, bytes, bytearray, list, tuple, set, frozenset, dict, OrderedDict, corresponding views and os.scandir() iterator.

- bpo-26581: If coding cookie is specified multiple times on a line in Python source code file, only the first one is taken to account.

- bpo-26464: Fix str.translate() when string is ASCII and first replacements removes character, but next replacement uses a non-ASCII character or a string longer than 1 character. Regression introduced in Python 3.5.0.

- bpo-22836: Ensure exception reports from PyErr_Display() and PyErr_WriteUnraisable() are sensible even when formatting them produces secondary errors. This affects the reports produced by sys.__excepthook__() and when __del__() raises an exception.

- bpo-26302: Correct behavior to reject comma as a legal character for cookie names.

- bpo-4806: Avoid masking the original TypeError exception when using star (`*`) unpacking in function calls. Based on patch by Hagen Fürstenau and Daniel Urban.

- bpo-27138: Fix the doc comment for FileFinder.find_spec().

- bpo-26154: Add a new private _PyThreadState_UncheckedGet() function to get the current Python thread state, but don’t issue a fatal error if it is NULL. This new function must be used instead of accessing directly the _PyThreadState_Current variable. The variable is no more exposed since Python 3.5.1 to hide the exact implementation of atomic C types, to avoid compiler issues.

- bpo-26194: Deque.insert() gave odd results for bounded deques that had reached their maximum size. Now an IndexError will be raised when attempting to insert into a full deque.

- bpo-25843: When compiling code, don’t merge constants if they are equal but have a different types. For example, `f1, f2 = lambda: 1, lambda: 1.0` is now correctly compiled to two different functions: `f1()` returns `1` (`int`) and `f2()` returns `1.0` (`int`), even if `1` and `1.0` are equal.

- bpo-22995: [UPDATE] Comment out the one of the pickleability tests in _PyObject_GetState() due to regressions observed in Cython-based projects.

- bpo-25961: Disallowed null characters in the type name.

- bpo-25973: Fix segfault when an invalid nonlocal statement binds a name starting with two underscores.

- bpo-22995: Instances of extension types with a state that aren’t subclasses of list or dict and haven’t implemented any pickle-related methods (__reduce__, __reduce_ex__, __getnewargs__, __getnewargs_ex__, or __getstate__), can no longer be pickled. Including memoryview.

- bpo-20440: Massive replacing unsafe attribute setting code with special macro Py_SETREF.

- bpo-25766: Special method __bytes__() now works in str subclasses.

- bpo-25421: __sizeof__ methods of builtin types now use dynamic basic size. This allows sys.getsize() to work correctly with their subclasses with __slots__ defined.

- bpo-25709: Fixed problem with in-place string concatenation and utf-8 cache.

- bpo-27147: Mention PEP 420 in the importlib docs.

- bpo-24097: Fixed crash in object.__reduce__() if slot name is freed inside __getattr__.

- bpo-24731: Fixed crash on converting objects with special methods __bytes__, __trunc__, and __float__ returning instances of subclasses of bytes, int, and float to subclasses of bytes, int, and float correspondingly.

- bpo-26478: Fix semantic bugs when using binary operators with dictionary views and tuples.

- bpo-26171: Fix possible integer overflow and heap corruption in zipimporter.get_data().

- bpo-25660: Fix TAB key behaviour in REPL with readline.

- bpo-25887: Raise a RuntimeError when a coroutine object is awaited more than once.

- bpo-27243: Update the __aiter__ protocol: instead of returning an awaitable that resolves to an asynchronous iterator, the asynchronous iterator should be returned directly. Doing the former will trigger a PendingDeprecationWarning.

### Library

- bpo-21386: Implement missing IPv4Address.is_global property. It was documented since 07a5610bae9d. Initial patch by Roger Luethi.

- bpo-20900: distutils register command now decodes HTTP responses correctly. Initial patch by ingrid.

- A new version of typing.py provides several new classes and features: @overload outside stubs, Reversible, DefaultDict, Text, ContextManager, Type[], NewType(), TYPE_CHECKING, and numerous bug fixes (note that some of the new features are not yet implemented in mypy or other static analyzers). Also classes for PEP 492 (Awaitable, AsyncIterable, AsyncIterator) have been added (in fact they made it into 3.5.1 but were never mentioned).

- bpo-25738: Stop http.server.BaseHTTPRequestHandler.send_error() from sending a message body for 205 Reset Content. Also, don’t send Content header fields in responses that don’t have a body. Patch by Susumu Koshiba.

- bpo-21313: Fix the “platform” module to tolerate when sys.version contains truncated build information.

- bpo-27164: In the zlib module, allow decompressing raw Deflate streams with a predefined zdict. Based on patch by Xiang Zhang.

- bpo-24291: Fix wsgiref.simple_server.WSGIRequestHandler to completely write data to the client. Previously it could do partial writes and truncate data. Also, wsgiref.handler.ServerHandler can now handle stdout doing partial writes, but this is deprecated.

- bpo-26809: Add `__all__` to `string`. Patch by Emanuel Barry.

- bpo-26373: subprocess.Popen.communicate now correctly ignores BrokenPipeError when the child process dies before .communicate() is called in more/all circumstances.

- bpo-21776: distutils.upload now correctly handles HTTPError. Initial patch by Claudiu Popa.

- bpo-27114: Fix SSLContext._load_windows_store_certs fails with PermissionError

- bpo-18383: Avoid creating duplicate filters when using filterwarnings and simplefilter. Based on patch by Alex Shkop.

- bpo-27057: Fix os.set_inheritable() on Android, ioctl() is blocked by SELinux and fails with EACCESS. The function now falls back to fcntl(). Patch written by Michał Bednarski.

- bpo-27014: Fix infinite recursion using typing.py. Thanks to Kalle Tuure!

- bpo-14132: Fix urllib.request redirect handling when the target only has a query string. Original fix by Ján Janech.

- bpo-17214: The “urllib.request” module now percent-encodes non-ASCII bytes found in redirect target URLs. Some servers send Location header fields with non-ASCII bytes, but “http.client” requires the request target to be ASCII-encodable, otherwise a UnicodeEncodeError is raised. Based on patch by Christian Heimes.

- bpo-26892: Honor debuglevel flag in urllib.request.HTTPHandler. Patch contributed by Chi Hsuan Yen.

- bpo-22274: In the subprocess module, allow stderr to be redirected to stdout even when stdout is not redirected. Patch by Akira Li.

- bpo-26807: mock_open ‘files’ no longer error on readline at end of file. Patch from Yolanda Robla.

- bpo-25745: Fixed leaking a userptr in curses panel destructor.

- bpo-26977: Removed unnecessary, and ignored, call to sum of squares helper in statistics.pvariance.

- bpo-26881: The modulefinder module now supports extended opcode arguments.

- bpo-23815: Fixed crashes related to directly created instances of types in _tkinter and curses.panel modules.

- bpo-17765: weakref.ref() no longer silently ignores keyword arguments. Patch by Georg Brandl.

- bpo-26873: xmlrpc now raises ResponseError on unsupported type tags instead of silently return incorrect result.

- bpo-26711: Fixed the comparison of plistlib.Data with other types.

- bpo-24114: Fix an uninitialized variable in `ctypes.util`. The bug only occurs on SunOS when the ctypes implementation searches for the `crle` program. Patch by Xiang Zhang. Tested on SunOS by Kees Bos.

- bpo-26864: In urllib.request, change the proxy bypass host checking against no_proxy to be case-insensitive, and to not match unrelated host names that happen to have a bypassed hostname as a suffix. Patch by Xiang Zhang.

- bpo-26634: recursive_repr() now sets __qualname__ of wrapper. Patch by Xiang Zhang.

- bpo-26804: urllib.request will prefer lower_case proxy environment variables over UPPER_CASE or Mixed_Case ones. Patch contributed by Hans-Peter Jansen.

- bpo-26837: assertSequenceEqual() now correctly outputs non-stringified differing items (like bytes in the -b mode). This affects assertListEqual() and assertTupleEqual().

- bpo-26041: Remove “will be removed in Python 3.7” from deprecation messages of platform.dist() and platform.linux_distribution(). Patch by Kumaripaba Miyurusara Athukorala.

- bpo-26822: itemgetter, attrgetter and methodcaller objects no longer silently ignore keyword arguments.

- bpo-26733: Disassembling a class now disassembles class and static methods. Patch by Xiang Zhang.

- bpo-26801: Fix error handling in `shutil.get_terminal_size()`, catch `AttributeError` instead of `NameError`. Patch written by Emanuel Barry.

- bpo-24838: tarfile’s ustar and gnu formats now correctly calculate name and link field limits for multibyte character encodings like utf-8.

- bpo-26717: Stop encoding Latin-1-ized WSGI paths with UTF-8. Patch by Anthony Sottile.

- bpo-26735: Fix `os.urandom()` on Solaris 11.3 and newer when reading more than 1,024 bytes: call `getrandom()` multiple times with a limit of 1024 bytes per call.

- bpo-16329: Add .webm to mimetypes.types_map. Patch by Giampaolo Rodola’.

- bpo-13952: Add .csv to mimetypes.types_map. Patch by Geoff Wilson.

- bpo-26709: Fixed Y2038 problem in loading binary PLists.

- bpo-23735: Handle terminal resizing with Readline 6.3+ by installing our own SIGWINCH handler. Patch by Eric Price.

- bpo-26586: In http.server, respond with “413 Request header fields too large” if there are too many header fields to parse, rather than killing the connection and raising an unhandled exception. Patch by Xiang Zhang.

- bpo-22854: Change BufferedReader.writable() and BufferedWriter.readable() to always return False.

- bpo-25195: Fix a regression in mock.MagicMock. _Call is a subclass of tuple (changeset 3603bae63c13 only works for classes) so we need to implement __ne__ ourselves. Patch by Andrew Plummer.

- bpo-26644: Raise ValueError rather than SystemError when a negative length is passed to SSLSocket.recv() or read().

- bpo-23804: Fix SSL recv(0) and read(0) methods to return zero bytes instead of up to 1024.

- bpo-26616: Fixed a bug in datetime.astimezone() method.

- bpo-21925: `warnings.formatwarning()` now catches exceptions on `linecache.getline(...)` to be able to log `ResourceWarning` emitted late during the Python shutdown process.

- bpo-24266: Ctrl+C during Readline history search now cancels the search mode when compiled with Readline 7.

- bpo-26560: Avoid potential ValueError in BaseHandler.start_response. Initial patch by Peter Inglesby.

- bpo-26569: Fix `pyclbr.readmodule()` and `pyclbr.readmodule_ex()` to support importing packages.

- bpo-26499: Account for remaining Content-Length in HTTPResponse.readline() and read1(). Based on patch by Silent Ghost. Also document that HTTPResponse now supports these methods.

- bpo-25320: Handle sockets in directories unittest discovery is scanning. Patch from Victor van den Elzen.

- bpo-16181: cookiejar.http2time() now returns None if year is higher than datetime.MAXYEAR.

- bpo-26513: Fixes platform module detection of Windows Server

- bpo-23718: Fixed parsing time in week 0 before Jan 1. Original patch by Tamás Bence Gedai.

- bpo-20589: Invoking Path.owner() and Path.group() on Windows now raise NotImplementedError instead of ImportError.

- bpo-26177: Fixed the keys() method for Canvas and Scrollbar widgets.

- bpo-15068: Got rid of excessive buffering in the fileinput module. The bufsize parameter is no longer used.

- bpo-2202: Fix UnboundLocalError in AbstractDigestAuthHandler.get_algorithm_impls. Initial patch by Mathieu Dupuy.

- bpo-25718: Fixed pickling and copying the accumulate() iterator with total is None.

- bpo-26475: Fixed debugging output for regular expressions with the (?x) flag.

- bpo-26457: Fixed the subnets() methods in IP network classes for the case when resulting prefix length is equal to maximal prefix length. Based on patch by Xiang Zhang.

- bpo-26385: Remove the file if the internal open() call in NamedTemporaryFile() fails. Patch by Silent Ghost.

- bpo-26402: Fix XML-RPC client to retry when the server shuts down a persistent connection. This was a regression related to the new http.client.RemoteDisconnected exception in 3.5.0a4.

- bpo-25913: Leading `<~` is optional now in base64.a85decode() with adobe=True. Patch by Swati Jaiswal.

- bpo-26186: Remove an invalid type check in importlib.util.LazyLoader.

- bpo-26367: importlib.__import__() raises SystemError like builtins.__import__() when `level` is specified but without an accompanying package specified.

- bpo-26309: In the “socketserver” module, shut down the request (closing the connected socket) when verify_request() returns false. Patch by Aviv Palivoda.

- bpo-25995: os.walk() no longer uses FDs proportional to the tree depth.

- bpo-26117: The os.scandir() iterator now closes file descriptor not only when the iteration is finished, but when it was failed with error.

- bpo-25911: Restored support of bytes paths in os.walk() on Windows.

- bpo-26045: Add UTF-8 suggestion to error message when posting a non-Latin-1 string with http.client.

- bpo-12923: Reset FancyURLopener’s redirect counter even if there is an exception. Based on patches by Brian Brazil and Daniel Rocco.

- bpo-25945: Fixed a crash when unpickle the functools.partial object with wrong state. Fixed a leak in failed functools.partial constructor. “args” and “keywords” attributes of functools.partial have now always types tuple and dict correspondingly.

- bpo-26202: copy.deepcopy() now correctly copies range() objects with non-atomic attributes.

- bpo-23076: Path.glob() now raises a ValueError if it’s called with an invalid pattern. Patch by Thomas Nyberg.

- bpo-19883: Fixed possible integer overflows in zipimport.

- bpo-26227: On Windows, getnameinfo(), gethostbyaddr() and gethostbyname_ex() functions of the socket module now decode the hostname from the ANSI code page rather than UTF-8.

- bpo-26147: xmlrpc now works with strings not encodable with used non-UTF-8 encoding.

- bpo-25935: Garbage collector now breaks reference loops with OrderedDict.

- bpo-16620: Fixed AttributeError in msilib.Directory.glob().

- bpo-26013: Added compatibility with broken protocol 2 pickles created in old Python 3 versions (3.4.3 and lower).

- bpo-25850: Use cross-compilation by default for 64-bit Windows.

- bpo-17633: Improve zipimport’s support for namespace packages.

- bpo-24705: Fix sysconfig._parse_makefile not expanding ${} vars appearing before $() vars.

- bpo-22138: Fix mock.patch behavior when patching descriptors. Restore original values after patching. Patch contributed by Sean McCully.

- bpo-25672: In the ssl module, enable the SSL_MODE_RELEASE_BUFFERS mode option if it is safe to do so.

- bpo-26012: Don’t traverse into symlinks for `**` pattern in pathlib.Path.[r]glob().

- bpo-24120: Ignore PermissionError when traversing a tree with pathlib.Path.[r]glob(). Patch by Ulrich Petri.

- bpo-25447: fileinput now uses sys.stdin as-is if it does not have a buffer attribute (restores backward compatibility).

- bpo-25447: Copying the lru_cache() wrapper object now always works, independently from the type of the wrapped object (by returning the original object unchanged).

- bpo-24103: Fixed possible use after free in ElementTree.XMLPullParser.

- bpo-25860: os.fwalk() no longer skips remaining directories when error occurs. Original patch by Samson Lee.

- bpo-25914: Fixed and simplified OrderedDict.__sizeof__.

- bpo-25902: Fixed various refcount issues in ElementTree iteration.

- bpo-25717: Restore the previous behaviour of tolerating most fstat() errors when opening files. This was a regression in 3.5a1, and stopped anonymous temporary files from working in special cases.

- bpo-24903: Fix regression in number of arguments compileall accepts when ‘-d’ is specified. The check on the number of arguments has been dropped completely as it never worked correctly anyway.

- bpo-25764: In the subprocess module, preserve any exception caused by fork() failure when preexec_fn is used.

- bpo-6478: _strptime’s regexp cache now is reset after changing timezone with time.tzset().

- bpo-14285: When executing a package with the “python -m package” option, and package initialization fails, a proper traceback is now reported. The “runpy” module now lets exceptions from package initialization pass back to the caller, rather than raising ImportError.

- bpo-19771: Also in runpy and the “-m” option, omit the irrelevant message “… is a package and cannot be directly executed” if the package could not even be initialized (e.g. due to a bad `*.pyc` file).

- bpo-25177: Fixed problem with the mean of very small and very large numbers. As a side effect, statistics.mean and statistics.variance should be significantly faster.

- bpo-25718: Fixed copying object with state with boolean value is false.

- bpo-10131: Fixed deep copying of minidom documents. Based on patch by Marian Ganisin.

- bpo-25725: Fixed a reference leak in pickle.loads() when unpickling invalid data including tuple instructions.

- bpo-25663: In the Readline completer, avoid listing duplicate global names, and search the global namespace before searching builtins.

- bpo-25688: Fixed file leak in ElementTree.iterparse() raising an error.

- bpo-23914: Fixed SystemError raised by unpickler on broken pickle data.

- bpo-25691: Fixed crash on deleting ElementTree.Element attributes.

- bpo-25624: ZipFile now always writes a ZIP_STORED header for directory entries. Patch by Dingyuan Wang.

- Skip getaddrinfo if host is already resolved. Patch by A. Jesse Jiryu Davis.

- bpo-26050: Add asyncio.StreamReader.readuntil() method. Patch by Марк Коренберг.

- bpo-25924: Avoid unnecessary serialization of getaddrinfo(3) calls on OS X versions 10.5 or higher. Original patch by A. Jesse Jiryu Davis.

- bpo-26406: Avoid unnecessary serialization of getaddrinfo(3) calls on current versions of OpenBSD and NetBSD. Patch by A. Jesse Jiryu Davis.

- bpo-26848: Fix asyncio/subprocess.communicate() to handle empty input. Patch by Jack O’Connor.

- bpo-27040: Add loop.get_exception_handler method

- bpo-27041: asyncio: Add loop.create_future method

- bpo-27223: asyncio: Fix _read_ready and _write_ready to respect _conn_lost. Patch by Łukasz Langa.

- bpo-22970: asyncio: Fix inconsistency cancelling Condition.wait. Patch by David Coles.

### IDLE

- bpo-5124: Paste with text selected now replaces the selection on X11. This matches how paste works on Windows, Mac, most modern Linux apps, and ttk widgets. Original patch by Serhiy Storchaka.

- bpo-24759: Make clear in idlelib.idle_test.__init__ that the directory is a private implementation of test.test_idle and tool for maintainers.

- bpo-27196: Stop ‘ThemeChanged’ warnings when running IDLE tests. These persisted after other warnings were suppressed in #20567. Apply Serhiy Storchaka’s update_idletasks solution to four test files. Record this additional advice in idle_test/README.txt

- bpo-20567: Revise idle_test/README.txt with advice about avoiding tk warning messages from tests. Apply advice to several IDLE tests.

- bpo-27117: Make colorizer htest and turtledemo work with dark themes. Move code for configuring text widget colors to a new function.

- bpo-26673: When tk reports font size as 0, change to size 10. Such fonts on Linux prevented the configuration dialog from opening.

- bpo-21939: Add test for IDLE’s percolator. Original patch by Saimadhav Heblikar.

- bpo-21676: Add test for IDLE’s replace dialog. Original patch by Saimadhav Heblikar.

- bpo-18410: Add test for IDLE’s search dialog. Original patch by Westley Martínez.

- bpo-21703: Add test for IDLE’s undo delegator. Original patch by Saimadhav Heblikar .

- bpo-27044: Add ConfigDialog.remove_var_callbacks to stop memory leaks.

- bpo-23977: Add more asserts to test_delegator.

- bpo-20640: Add tests for idlelib.configHelpSourceEdit. Patch by Saimadhav Heblikar.

- In the ‘IDLE-console differences’ section of the IDLE doc, clarify how running with IDLE affects sys.modules and the standard streams.

- bpo-25507: fix incorrect change in IOBinding that prevented printing. Augment IOBinding htest to include all major IOBinding functions.

- bpo-25905: Revert unwanted conversion of ‘ to ’ RIGHT SINGLE QUOTATION MARK in README.txt and open this and NEWS.txt with ‘ascii’. Re-encode CREDITS.txt to utf-8 and open it with ‘utf-8’.

### Documentation

- bpo-19489: Moved the search box from the sidebar to the header and footer of each page. Patch by Ammar Askar.

- bpo-24136: Document the new PEP 448 unpacking syntax of 3.5.

- bpo-26736: Used HTTPS for external links in the documentation if possible.

- bpo-6953: Rework the Readline module documentation to group related functions together, and add more details such as what underlying Readline functions and variables are accessed.

- bpo-23606: Adds note to ctypes documentation regarding cdll.msvcrt.

- bpo-25500: Fix documentation to not claim that __import__ is searched for in the global scope.

- bpo-26014: Update 3.x packaging documentation: * “See also” links to the new docs are now provided in the legacy pages * links to setuptools documentation have been updated

### Tests

- bpo-21916: Added tests for the turtle module. Patch by ingrid, Gregory Loyse and Jelle Zijlstra.

- bpo-26523: The multiprocessing thread pool (multiprocessing.dummy.Pool) was untested.

- bpo-26015: Added new tests for pickling iterators of mutable sequences.

- bpo-26325: Added test.support.check_no_resource_warning() to check that no ResourceWarning is emitted.

- bpo-25940: Changed test_ssl to use self-signed.pythontest.net. This avoids relying on svn.python.org, which recently changed root certificate.

- bpo-25616: Tests for OrderedDict are extracted from test_collections into separate file test_ordered_dict.

- bpo-26583: Skip test_timestamp_overflow in test_import if bytecode files cannot be written.

### Build

- bpo-26884: Fix linking extension modules for cross builds. Patch by Xavier de Gaye.

- bpo-22359: Disable the rules for running _freeze_importlib and pgen when cross-compiling. The output of these programs is normally saved with the source code anyway, and is still regenerated when doing a native build. Patch by Xavier de Gaye.

- bpo-27229: Fix the cross-compiling pgen rule for in-tree builds. Patch by Xavier de Gaye.

- bpo-21668: Link audioop, _datetime, _ctypes_test modules to libm, except on Mac OS X. Patch written by Xavier de Gaye.

- bpo-25702: A –with-lto configure option has been added that will enable link time optimizations at build time during a make profile-opt. Some compilers and toolchains are known to not produce stable code when using LTO, be sure to test things thoroughly before relying on it. It can provide a few % speed up over profile-opt alone.

- bpo-26624: Adds validation of ucrtbase[d].dll version with warning for old versions.

- bpo-17603: Avoid error about nonexistent fileblocks.o file by using a lower-level check for st_blocks in struct stat.

- bpo-26079: Fixing the build output folder for tix-8.4.3.6. Patch by Bjoern Thiel.

- bpo-26465: Update Windows builds to use OpenSSL 1.0.2g.

- bpo-24421: Compile Modules/_math.c once, before building extensions. Previously it could fail to compile properly if the math and cmath builds were concurrent.

- bpo-25348: Added `--pgo` and `--pgo-job` arguments to `PCbuild\build.bat` for building with Profile-Guided Optimization. The old `PCbuild\build_pgo.bat` script is now deprecated, and simply calls `PCbuild\build.bat --pgo %*`.

- bpo-25827: Add support for building with ICC to `configure`, including a new `--with-icc` flag.

- bpo-25696: Fix installation of Python on UNIX with make -j9.

- bpo-26930: Update OS X 10.5+ 32-bit-only installer to build and link with OpenSSL 1.0.2h.

- bpo-26268: Update Windows builds to use OpenSSL 1.0.2f.

- bpo-25136: Support Apple Xcode 7’s new textual SDK stub libraries.

- bpo-24324: Do not enable unreachable code warnings when using gcc as the option does not work correctly in older versions of gcc and has been silently removed as of gcc-4.5.

### Windows

- bpo-27053: Updates make_zip.py to correctly generate library ZIP file.

- bpo-26268: Update the prepare_ssl.py script to handle OpenSSL releases that don’t include the contents of the include directory (that is, 1.0.2e and later).

- bpo-26071: bdist_wininst created binaries fail to start and find 32bit Python

- bpo-26073: Update the list of magic numbers in launcher

- bpo-26065: Excludes venv from library when generating embeddable distro.

- bpo-17500: Remove unused and outdated icons. (See also: https://github.com/python/pythondotorg/issues/945)

### Tools/Demos

- bpo-26799: Fix python-gdb.py: don’t get C types once when the Python code is loaded, but get C types on demand. The C types can change if python-gdb.py is loaded before the Python executable. Patch written by Thomas Ilsche.

- bpo-26271: Fix the Freeze tool to properly use flags passed through configure. Patch by Daniel Shaulov.

- bpo-26489: Add dictionary unpacking support to Tools/parser/unparse.py. Patch by Guo Ci Teo.

- bpo-26316: Fix variable name typo in Argument Clinic.

## Python 3.5.1 final

Release date: 2015-12-06

### Core and Builtins

- bpo-25709: Fixed problem with in-place string concatenation and utf-8 cache.

### Windows

- bpo-25715: Python 3.5.1 installer shows wrong upgrade path and incorrect logic for launcher detection.

## Python 3.5.1 release candidate 1

Release date: 2015-11-22

### Core and Builtins

- bpo-25630: Fix a possible segfault during argument parsing in functions that accept filesystem paths.

- bpo-23564: Fixed a partially broken sanity check in the _posixsubprocess internals regarding how fds_to_pass were passed to the child. The bug had no actual impact as subprocess.py already avoided it.

- bpo-25388: Fixed tokenizer crash when processing undecodable source code with a null byte.

- bpo-25462: The hash of the key now is calculated only once in most operations in C implementation of OrderedDict.

- bpo-22995: Default implementation of __reduce__ and __reduce_ex__ now rejects builtin types with not defined __new__.

- bpo-25555: Fix parser and AST: fill lineno and col_offset of “arg” node when compiling AST from Python objects.

- bpo-24802: Avoid buffer overreads when int(), float(), compile(), exec() and eval() are passed bytes-like objects. These objects are not necessarily terminated by a null byte, but the functions assumed they were.

- bpo-24726: Fixed a crash and leaking NULL in repr() of OrderedDict that was mutated by direct calls of dict methods.

- bpo-25449: Iterating OrderedDict with keys with unstable hash now raises KeyError in C implementations as well as in Python implementation.

- bpo-25395: Fixed crash when highly nested OrderedDict structures were garbage collected.

- bpo-25274: sys.setrecursionlimit() now raises a RecursionError if the new recursion limit is too low depending at the current recursion depth. Modify also the “lower-water mark” formula to make it monotonic. This mark is used to decide when the overflowed flag of the thread state is reset.

- bpo-24402: Fix input() to prompt to the redirected stdout when sys.stdout.fileno() fails.

- bpo-24806: Prevent builtin types that are not allowed to be subclassed from being subclassed through multiple inheritance.

- bpo-24848: Fixed a number of bugs in UTF-7 decoding of misformed data.

- bpo-25280: Import trace messages emitted in verbose (-v) mode are no longer formatted twice.

- bpo-25003: On Solaris 11.3 or newer, os.urandom() now uses the getrandom() function instead of the getentropy() function. The getentropy() function is blocking to generate very good quality entropy, os.urandom() doesn’t need such high-quality entropy.

- bpo-25182: The stdprinter (used as sys.stderr before the io module is imported at startup) now uses the backslashreplace error handler.

- bpo-25131: Make the line number and column offset of set/dict literals and comprehensions correspond to the opening brace.

- bpo-25150: Hide the private `_Py_atomic_xxx` symbols from the public Python.h header to fix a compilation error with OpenMP. PyThreadState_GET() becomes an alias to PyThreadState_Get() to avoid ABI incompatibilities.

### Library

- bpo-25626: Change three zlib functions to accept sizes that fit in Py_ssize_t, but internally cap those sizes to UINT_MAX. This resolves a regression in 3.5 where GzipFile.read() failed to read chunks larger than 2 or 4 GiB. The change affects the zlib.Decompress.decompress() max_length parameter, the zlib.decompress() bufsize parameter, and the zlib.Decompress.flush() length parameter.

- bpo-25583: Avoid incorrect errors raised by os.makedirs(exist_ok=True) when the OS gives priority to errors such as EACCES over EEXIST.

- bpo-25593: Change semantics of EventLoop.stop() in asyncio.

- bpo-6973: When we know a subprocess.Popen process has died, do not allow the send_signal(), terminate(), or kill() methods to do anything as they could potentially signal a different process.

- bpo-25590: In the Readline completer, only call getattr() once per attribute.

- bpo-25498: Fix a crash when garbage-collecting ctypes objects created by wrapping a memoryview. This was a regression made in 3.5a1. Based on patch by Eryksun.

- bpo-25584: Added “escape” to the __all__ list in the glob module.

- bpo-25584: Fixed recursive glob() with patterns starting with `**`.

- bpo-25446: Fix regression in smtplib’s AUTH LOGIN support.

- bpo-18010: Fix the pydoc web server’s module search function to handle exceptions from importing packages.

- bpo-25554: Got rid of circular references in regular expression parsing.

- bpo-25510: fileinput.FileInput.readline() now returns b’’ instead of ‘’ at the end if the FileInput was opened with binary mode. Patch by Ryosuke Ito.

- bpo-25503: Fixed inspect.getdoc() for inherited docstrings of properties. Original patch by John Mark Vandenberg.

- bpo-25515: Always use os.urandom as a source of randomness in uuid.uuid4.

- bpo-21827: Fixed textwrap.dedent() for the case when largest common whitespace is a substring of smallest leading whitespace. Based on patch by Robert Li.

- bpo-25447: The lru_cache() wrapper objects now can be copied and pickled (by returning the original object unchanged).

- bpo-25390: typing: Don’t crash on Union[str, Pattern].

- bpo-25441: asyncio: Raise error from drain() when socket is closed.

- bpo-25410: Cleaned up and fixed minor bugs in C implementation of OrderedDict.

- bpo-25411: Improved Unicode support in SMTPHandler through better use of the email package. Thanks to user simon04 for the patch.

- bpo-25407: Remove mentions of the formatter module being removed in Python 3.6.

- bpo-25406: Fixed a bug in C implementation of OrderedDict.move_to_end() that caused segmentation fault or hang in iterating after moving several items to the start of ordered dict.

- bpo-25364: zipfile now works in threads disabled builds.

- bpo-25328: smtpd’s SMTPChannel now correctly raises a ValueError if both decode_data and enable_SMTPUTF8 are set to true.

- bpo-25316: distutils raises OSError instead of DistutilsPlatformError when MSVC is not installed.

- bpo-25380: Fixed protocol for the STACK_GLOBAL opcode in pickletools.opcodes.

- bpo-23972: Updates asyncio datagram create method allowing reuseport and reuseaddr socket options to be set prior to binding the socket. Mirroring the existing asyncio create_server method the reuseaddr option for datagram sockets defaults to True if the O/S is ‘posix’ (except if the platform is Cygwin). Patch by Chris Laws.

- bpo-25304: Add asyncio.run_coroutine_threadsafe(). This lets you submit a coroutine to a loop from another thread, returning a concurrent.futures.Future. By Vincent Michel.

- bpo-25232: Fix CGIRequestHandler to split the query from the URL at the first question mark (?) rather than the last. Patch from Xiang Zhang.

- bpo-24657: Prevent CGIRequestHandler from collapsing slashes in the query part of the URL as if it were a path. Patch from Xiang Zhang.

- bpo-24483: C implementation of functools.lru_cache() now calculates key’s hash only once.

- bpo-22958: Constructor and update method of weakref.WeakValueDictionary now accept the self and the dict keyword arguments.

- bpo-22609: Constructor of collections.UserDict now accepts the self keyword argument.

- bpo-25111: Fixed comparison of traceback.FrameSummary.

- bpo-25262: Added support for BINBYTES8 opcode in Python implementation of unpickler. Highest 32 bits of 64-bit size for BINUNICODE8 and BINBYTES8 opcodes no longer silently ignored on 32-bit platforms in C implementation.

- bpo-25034: Fix string.Formatter problem with auto-numbering and nested format_specs. Patch by Anthon van der Neut.

- bpo-25233: Rewrite the guts of asyncio.Queue and asyncio.Semaphore to be more understandable and correct.

- bpo-25203: Failed readline.set_completer_delims() no longer left the module in inconsistent state.

- bpo-23600: Default implementation of tzinfo.fromutc() was returning wrong results in some cases.

- bpo-23329: Allow the ssl module to be built with older versions of LibreSSL.

- Prevent overflow in _Unpickler_Read.

- bpo-25047: The XML encoding declaration written by Element Tree now respects the letter case given by the user. This restores the ability to write encoding names in uppercase like “UTF-8”, which worked in Python 2.

- bpo-25135: Make deque_clear() safer by emptying the deque before clearing. This helps avoid possible reentrancy issues.

- bpo-19143: platform module now reads Windows version from kernel32.dll to avoid compatibility shims.

- bpo-25092: Fix datetime.strftime() failure when errno was already set to EINVAL.

- bpo-23517: Fix rounding in fromtimestamp() and utcfromtimestamp() methods of datetime.datetime: microseconds are now rounded to nearest with ties going to nearest even integer (ROUND_HALF_EVEN), instead of being rounding towards minus infinity (ROUND_FLOOR). It’s important that these methods use the same rounding mode than datetime.timedelta to keep the property: (datetime(1970,1,1) + timedelta(seconds=t)) == datetime.utcfromtimestamp(t). It also the rounding mode used by round(float) for example.

- bpo-25155: Fix datetime.datetime.now() and datetime.datetime.utcnow() on Windows to support date after year 2038. It was a regression introduced in Python 3.5.0.

- bpo-25108: Omitted internal frames in traceback functions print_stack(), format_stack(), and extract_stack() called without arguments.

- bpo-25118: Fix a regression of Python 3.5.0 in os.waitpid() on Windows.

- bpo-24684: socket.socket.getaddrinfo() now calls PyUnicode_AsEncodedString() instead of calling the encode() method of the host, to handle correctly custom string with an encode() method which doesn’t return a byte string. The encoder of the IDNA codec is now called directly instead of calling the encode() method of the string.

- bpo-25060: Correctly compute stack usage of the BUILD_MAP opcode.

- bpo-24857: Comparing call_args to a long sequence now correctly returns a boolean result instead of raising an exception. Patch by A Kaptur.

- bpo-23144: Make sure that HTMLParser.feed() returns all the data, even when convert_charrefs is True.

- bpo-24982: shutil.make_archive() with the “zip” format now adds entries for directories (including empty directories) in ZIP file.

- bpo-25019: Fixed a crash caused by setting non-string key of expat parser. Based on patch by John Leitch.

- bpo-16180: Exit pdb if file has syntax error, instead of trapping user in an infinite loop. Patch by Xavier de Gaye.

- bpo-24891: Fix a race condition at Python startup if the file descriptor of stdin (0), stdout (1) or stderr (2) is closed while Python is creating sys.stdin, sys.stdout and sys.stderr objects. These attributes are now set to None if the creation of the object failed, instead of raising an OSError exception. Initial patch written by Marco Paolini.

- bpo-24992: Fix error handling and a race condition (related to garbage collection) in collections.OrderedDict constructor.

- bpo-24881: Fixed setting binary mode in Python implementation of FileIO on Windows and Cygwin. Patch from Akira Li.

- bpo-25578: Fix (another) memory leak in SSLSocket.getpeercer().

- bpo-25530: Disable the vulnerable SSLv3 protocol by default when creating ssl.SSLContext.

- bpo-25569: Fix memory leak in SSLSocket.getpeercert().

- bpo-25471: Sockets returned from accept() shouldn’t appear to be nonblocking.

- bpo-25319: When threading.Event is reinitialized, the underlying condition should use a regular lock rather than a recursive lock.

- bpo-21112: Fix regression in unittest.expectedFailure on subclasses. Patch from Berker Peksag.

- bpo-24764: cgi.FieldStorage.read_multi() now ignores the Content-Length header in part headers. Patch written by Peter Landry and reviewed by Pierre Quentel.

- bpo-24913: Fix overrun error in deque.index(). Found by John Leitch and Bryce Darling.

- bpo-24774: Fix docstring in http.server.test. Patch from Chiu-Hsiang Hsu.

- bpo-21159: Improve message in configparser.InterpolationMissingOptionError. Patch from Łukasz Langa.

- bpo-20362: Honour TestCase.longMessage correctly in assertRegex. Patch from Ilia Kurenkov.

- bpo-23572: Fixed functools.singledispatch on classes with false metaclasses. Patch by Ethan Furman.

- asyncio: ensure_future() now accepts awaitable objects.

### IDLE

- bpo-15348: Stop the debugger engine (normally in a user process) before closing the debugger window (running in the IDLE process). This prevents the RuntimeErrors that were being caught and ignored.

- bpo-24455: Prevent IDLE from hanging when a) closing the shell while the debugger is active (15347); b) closing the debugger with the [X] button (15348); and c) activating the debugger when already active (24455). The patch by Mark Roseman does this by making two changes. 1. Suspend and resume the gui.interaction method with the tcl vwait mechanism intended for this purpose (instead of root.mainloop & .quit). 2. In gui.run, allow any existing interaction to terminate first.

- Change ‘The program’ to ‘Your program’ in an IDLE ‘kill program?’ message to make it clearer that the program referred to is the currently running user program, not IDLE itself.

- bpo-24750: Improve the appearance of the IDLE editor window status bar. Patch by Mark Roseman.

- bpo-25313: Change the handling of new built-in text color themes to better address the compatibility problem introduced by the addition of IDLE Dark. Consistently use the revised idleConf.CurrentTheme everywhere in idlelib.

- bpo-24782: Extension configuration is now a tab in the IDLE Preferences dialog rather than a separate dialog. The former tabs are now a sorted list. Patch by Mark Roseman.

- bpo-22726: Re-activate the config dialog help button with some content about the other buttons and the new IDLE Dark theme.

- bpo-24820: IDLE now has an ‘IDLE Dark’ built-in text color theme. It is more or less IDLE Classic inverted, with a cobalt blue background. Strings, comments, keywords, … are still green, red, orange, … . To use it with IDLEs released before November 2015, hit the ‘Save as New Custom Theme’ button and enter a new name, such as ‘Custom Dark’. The custom theme will work with any IDLE release, and can be modified.

- bpo-25224: README.txt is now an idlelib index for IDLE developers and curious users. The previous user content is now in the IDLE doc chapter. ‘IDLE’ now means ‘Integrated Development and Learning Environment’.

- bpo-24820: Users can now set breakpoint colors in Settings -> Custom Highlighting. Original patch by Mark Roseman.

- bpo-24972: Inactive selection background now matches active selection background, as configured by users, on all systems. Found items are now always highlighted on Windows. Initial patch by Mark Roseman.

- bpo-24570: Idle: make calltip and completion boxes appear on Macs affected by a tk regression. Initial patch by Mark Roseman.

- bpo-24988: Idle ScrolledList context menus (used in debugger) now work on Mac Aqua. Patch by Mark Roseman.

- bpo-24801: Make right-click for context menu work on Mac Aqua. Patch by Mark Roseman.

- bpo-25173: Associate tkinter messageboxes with a specific widget. For Mac OSX, make them a ‘sheet’. Patch by Mark Roseman.

- bpo-25198: Enhance the initial html viewer now used for Idle Help. Properly indent fixed-pitch text (patch by Mark Roseman). Give code snippet a very Sphinx-like light blueish-gray background. Re-use initial width and height set by users for shell and editor. When the Table of Contents (TOC) menu is used, put the section header at the top of the screen.

- bpo-25225: Condense and rewrite Idle doc section on text colors.

- bpo-21995: Explain some differences between IDLE and console Python.

- bpo-22820: Explain need for print when running file from Idle editor.

- bpo-25224: Doc: augment Idle feature list and no-subprocess section.

- bpo-25219: Update doc for Idle command line options. Some were missing and notes were not correct.

- bpo-24861: Most of idlelib is private and subject to change. Use idleib.idle.* to start Idle. See idlelib.__init__.__doc__.

- bpo-25199: Idle: add synchronization comments for future maintainers.

- bpo-16893: Replace help.txt with help.html for Idle doc display. The new idlelib/help.html is rstripped Doc/build/html/library/idle.html. It looks better than help.txt and will better document Idle as released. The tkinter html viewer that works for this file was written by Mark Roseman. The now unused EditorWindow.HelpDialog class and helt.txt file are deprecated.

- bpo-24199: Deprecate unused idlelib.idlever with possible removal in 3.6.

- bpo-24790: Remove extraneous code (which also create 2 & 3 conflicts).

### Documentation

- bpo-22558: Add remaining doc links to source code for Python-coded modules. Patch by Yoni Lavi.

- bpo-12067: Rewrite Comparisons section in the Expressions chapter of the language reference. Some of the details of comparing mixed types were incorrect or ambiguous. NotImplemented is only relevant at a lower level than the Expressions chapter. Added details of comparing range() objects, and default behaviour and consistency suggestions for user-defined classes. Patch from Andy Maier.

- bpo-24952: Clarify the default size argument of stack_size() in the “threading” and “_thread” modules. Patch from Mattip.

- bpo-23725: Overhaul tempfile docs. Note deprecated status of mktemp. Patch from Zbigniew Jędrzejewski-Szmek.

- bpo-24808: Update the types of some PyTypeObject fields. Patch by Joseph Weston.

- bpo-22812: Fix unittest discovery examples. Patch from Pam McA’Nulty.

### Tests

- bpo-25449: Added tests for OrderedDict subclasses.

- bpo-25099: Make test_compileall not fail when an entry on sys.path cannot be written to (commonly seen in administrative installs on Windows).

- bpo-23919: Prevents assert dialogs appearing in the test suite.

- `PCbuild\rt.bat` now accepts an unlimited number of arguments to pass along to regrtest.py. Previously there was a limit of 9.

### Build

- bpo-24915: Add LLVM support for PGO builds and use the test suite to generate the profile data. Initial patch by Alecsandru Patrascu of Intel.

- bpo-24910: Windows MSIs now have unique display names.

- bpo-24986: It is now possible to build Python on Windows without errors when external libraries are not available.

### Windows

- bpo-25450: Updates shortcuts to start Python in installation directory.

- bpo-25164: Changes default all-users install directory to match per-user directory.

- bpo-25143: Improves installer error messages for unsupported platforms.

- bpo-25163: Display correct directory in installer when using non-default settings.

- bpo-25361: Disables use of SSE2 instructions in Windows 32-bit build

- bpo-25089: Adds logging to installer for case where launcher is not selected on upgrade.

- bpo-25165: Windows uninstallation should not remove launcher if other versions remain

- bpo-25112: py.exe launcher is missing icons

- bpo-25102: Windows installer does not precompile for -O or -OO.

- bpo-25081: Makes Back button in installer go back to upgrade page when upgrading.

- bpo-25091: Increases font size of the installer.

- bpo-25126: Clarifies that the non-web installer will download some components.

- bpo-25213: Restores requestedExecutionLevel to manifest to disable UAC virtualization.

- bpo-25022: Removed very outdated PC/example_nt/ directory.

### Tools/Demos

- bpo-25440: Fix output of python-config –extension-suffix.

## Python 3.5.0 final

Release date: 2015-09-13

### Build

- bpo-25071: Windows installer should not require TargetDir parameter when installing quietly.

## Python 3.5.0 release candidate 4

Release date: 2015-09-09

### Library

- bpo-25029: Fixes MemoryError in test_strptime.

### Build

- bpo-25027: Reverts partial-static build options and adds vcruntime140.dll to Windows installation.

## Python 3.5.0 release candidate 3

Release date: 2015-09-07

### Core and Builtins

- bpo-24305: Prevent import subsystem stack frames from being counted by the warnings.warn(stacklevel=) parameter.

- bpo-24912: Prevent __class__ assignment to immutable built-in objects.

- bpo-24975: Fix AST compilation for PEP 448 syntax.

### Library

- bpo-24917: time_strftime() buffer over-read.

- bpo-24748: To resolve a compatibility problem found with py2exe and pywin32, imp.load_dynamic() once again ignores previously loaded modules to support Python modules replacing themselves with extension modules. Patch by Petr Viktorin.

- bpo-24635: Fixed a bug in typing.py where isinstance([], typing.Iterable) would return True once, then False on subsequent calls.

- bpo-24989: Fixed buffer overread in BytesIO.readline() if a position is set beyond size. Based on patch by John Leitch.

- bpo-24913: Fix overrun error in deque.index(). Found by John Leitch and Bryce Darling.

## Python 3.5.0 release candidate 2

Release date: 2015-08-25

### Core and Builtins

- bpo-24769: Interpreter now starts properly when dynamic loading is disabled. Patch by Petr Viktorin.

- bpo-21167: NAN operations are now handled correctly when python is compiled with ICC even if -fp-model strict is not specified.

- bpo-24492: A “package” lacking a __name__ attribute when trying to perform a `from .. import ...` statement will trigger an ImportError instead of an AttributeError.

### Library

- bpo-24847: Removes vcruntime140.dll dependency from Tcl/Tk.

- bpo-24839: platform._syscmd_ver raises DeprecationWarning

- bpo-24867: Fix Task.get_stack() for ‘async def’ coroutines

## Python 3.5.0 release candidate 1

Release date: 2015-08-09

### Core and Builtins

- bpo-24667: Resize odict in all cases that the underlying dict resizes.

### Library

- bpo-24824: Signatures of codecs.encode() and codecs.decode() now are compatible with pydoc.

- bpo-24634: Importing uuid should not try to load libc on Windows

- bpo-24798: _msvccompiler.py doesn’t properly support manifests

- bpo-4395: Better testing and documentation of binary operators. Patch by Martin Panter.

- bpo-23973: Update typing.py from GitHub repo.

- bpo-23004: mock_open() now reads binary data correctly when the type of read_data is bytes. Initial patch by Aaron Hill.

- bpo-23888: Handle fractional time in cookie expiry. Patch by ssh.

- bpo-23652: Make it possible to compile the select module against the libc headers from the Linux Standard Base, which do not include some EPOLL macros. Patch by Matt Frank.

- bpo-22932: Fix timezones in email.utils.formatdate. Patch from Dmitry Shachnev.

- bpo-23779: imaplib raises TypeError if authenticator tries to abort. Patch from Craig Holmquist.

- bpo-23319: Fix ctypes.BigEndianStructure, swap correctly bytes. Patch written by Matthieu Gautier.

- bpo-23254: Document how to close the TCPServer listening socket. Patch from Martin Panter.

- bpo-19450: Update Windows and OS X installer builds to use SQLite 3.8.11.

- bpo-17527: Add PATCH to wsgiref.validator. Patch from Luca Sbardella.

- bpo-24791: Fix grammar regression for call syntax: ‘g(*a or b)’.

### IDLE

- bpo-23672: Allow Idle to edit and run files with astral chars in name. Patch by Mohd Sanad Zaki Rizvi.

- bpo-24745: Idle editor default font. Switch from Courier to platform-sensitive TkFixedFont. This should not affect current customized font selections. If there is a problem, edit $HOME/.idlerc/config-main.cfg and remove ‘`fontxxx`’ entries from [Editor Window]. Patch by Mark Roseman.

- bpo-21192: Idle editor. When a file is run, put its name in the restart bar. Do not print false prompts. Original patch by Adnan Umer.

- bpo-13884: Idle menus. Remove tearoff lines. Patch by Roger Serwy.

### Documentation

- bpo-24129: Clarify the reference documentation for name resolution. This includes removing the assumption that readers will be familiar with the name resolution scheme Python used prior to the introduction of lexical scoping for function namespaces. Patch by Ivan Levkivskyi.

- bpo-20769: Improve reload() docs. Patch by Dorian Pula.

- bpo-23589: Remove duplicate sentence from the FAQ. Patch by Yongzhi Pan.

- bpo-24729: Correct IO tutorial to match implementation regarding encoding parameter to open function.

### Tests

- bpo-24751: When running regrtest with the `-w` command line option, a test run is no longer marked as a failure if all tests succeed when re-run.

## Python 3.5.0 beta 4

Release date: 2015-07-26

### Core and Builtins

- bpo-23573: Restored optimization of bytes.rfind() and bytearray.rfind() for single-byte argument on Linux.

- bpo-24569: Make PEP 448 dictionary evaluation more consistent.

- bpo-24583: Fix crash when set is mutated while being updated.

- bpo-24407: Fix crash when dict is mutated while being updated.

- bpo-24619: New approach for tokenizing async/await. As a consequence, it is now possible to have one-line ‘async def foo(): await ..’ functions.

- bpo-24687: Plug refleak on SyntaxError in function parameters annotations.

- bpo-15944: memoryview: Allow arbitrary formats when casting to bytes. Patch by Martin Panter.

### Library

- bpo-23441: rcompleter now prints a tab character instead of displaying possible completions for an empty word. Initial patch by Martin Sekera.

- bpo-24683: Fixed crashes in _json functions called with arguments of inappropriate type.

- bpo-21697: shutil.copytree() now correctly handles symbolic links that point to directories. Patch by Eduardo Seabra and Thomas Kluyver.

- bpo-14373: Fixed segmentation fault when gc.collect() is called during constructing lru_cache (C implementation).

- bpo-24695: Fix a regression in traceback.print_exception(). If exc_traceback is None we shouldn’t print a traceback header like described in the documentation.

- bpo-24620: Random.setstate() now validates the value of state last element.

- bpo-22485: Fixed an issue that caused `inspect.getsource` to return incorrect results on nested functions.

- bpo-22153: Improve unittest docs. Patch from Martin Panter and evilzero.

- bpo-24580: Symbolic group references to open group in re patterns now are explicitly forbidden as well as numeric group references.

- bpo-24206: Fixed __eq__ and __ne__ methods of inspect classes.

- bpo-24631: Fixed regression in the timeit module with multiline setup.

- bpo-18622: unittest.mock.mock_open().reset_mock would recurse infinitely. Patch from Nicola Palumbo and Laurent De Buyst.

- bpo-23661: unittest.mock side_effects can now be exceptions again. This was a regression vs Python 3.4. Patch from Ignacio Rossi

- bpo-24608: chunk.Chunk.read() now always returns bytes, not str.

- bpo-18684: Fixed reading out of the buffer in the re module.

- bpo-24259: tarfile now raises a ReadError if an archive is truncated inside a data segment.

- bpo-15014: SMTP.auth() and SMTP.login() now support RFC 4954’s optional initial-response argument to the SMTP AUTH command.

- bpo-24669: Fix inspect.getsource() for ‘async def’ functions. Patch by Kai Groner.

- bpo-24688: ast.get_docstring() for ‘async def’ functions.

### Build

- bpo-24603: Update Windows builds and OS X 10.5 installer to use OpenSSL 1.0.2d.

## Python 3.5.0 beta 3

Release date: 2015-07-05

### Core and Builtins

- bpo-24467: Fixed possible buffer over-read in bytearray. The bytearray object now always allocates place for trailing null byte and it’s buffer now is always null-terminated.

- Upgrade to Unicode 8.0.0.

- bpo-24345: Add Py_tp_finalize slot for the stable ABI.

- bpo-24400: Introduce a distinct type for PEP 492 coroutines; add types.CoroutineType, inspect.getcoroutinestate, inspect.getcoroutinelocals; coroutines no longer use CO_GENERATOR flag; sys.set_coroutine_wrapper works only for ‘async def’ coroutines; inspect.iscoroutine no longer uses collections.abc.Coroutine, it’s intended to test for pure ‘async def’ coroutines only; add new opcode: GET_YIELD_FROM_ITER; fix generators wrapper used in types.coroutine to be instance of collections.abc.Generator; collections.abc.Awaitable and collections.abc.Coroutine can no longer be used to detect generator-based coroutines–use inspect.isawaitable instead.

- bpo-24450: Add gi_yieldfrom to generators and cr_await to coroutines. Contributed by Benno Leslie and Yury Selivanov.

- bpo-19235: Add new RecursionError exception. Patch by Georg Brandl.

### Library

- bpo-21750: mock_open.read_data can now be read from each instance, as it could in Python 3.3.

- bpo-24552: Fix use after free in an error case of the _pickle module.

- bpo-24514: tarfile now tolerates number fields consisting of only whitespace.

- bpo-19176: Fixed doctype() related bugs in C implementation of ElementTree. A deprecation warning no longer issued by XMLParser subclass with default doctype() method. Direct call of doctype() now issues a warning. Parser’s doctype() now is not called if target’s doctype() is called. Based on patch by Martin Panter.

- bpo-20387: Restore semantic round-trip correctness in tokenize/untokenize for tab-indented blocks.

- bpo-24456: Fixed possible buffer over-read in adpcm2lin() and lin2adpcm() functions of the audioop module.

- bpo-24336: The contextmanager decorator now works with functions with keyword arguments called “func” and “self”. Patch by Martin Panter.

- bpo-24522: Fix possible integer overflow in json accelerator module.

- bpo-24489: ensure a previously set C errno doesn’t disturb cmath.polar().

- bpo-24408: Fixed AttributeError in measure() and metrics() methods of tkinter.Font.

- bpo-14373: C implementation of functools.lru_cache() now can be used with methods.

- bpo-24347: Set KeyError if PyDict_GetItemWithError returns NULL.

- bpo-24348: Drop superfluous incref/decref.

- bpo-24359: Check for changed OrderedDict size during iteration.

- bpo-24368: Support keyword arguments in OrderedDict methods.

- bpo-24362: Simplify the C OrderedDict fast nodes resize logic.

- bpo-24377: Fix a ref leak in OrderedDict.__repr__.

- bpo-24369: Defend against key-changes during iteration.

### Tests

- bpo-24373: _testmultiphase and xxlimited now use tp_traverse and tp_finalize to avoid reference leaks encountered when combining tp_dealloc with PyType_FromSpec (see bpo-16690 for details)

### Documentation

- bpo-24458: Update documentation to cover multi-phase initialization for extension modules (PEP 489). Patch by Petr Viktorin.

- bpo-24351: Clarify what is meant by “identifier” in the context of string.Template instances.

### Build

- bpo-24432: Update Windows builds and OS X 10.5 installer to use OpenSSL 1.0.2c.

## Python 3.5.0 beta 2

Release date: 2015-05-31

### Core and Builtins

- bpo-24284: The startswith and endswith methods of the str class no longer return True when finding the empty string and the indexes are completely out of range.

- bpo-24115: Update uses of PyObject_IsTrue(), PyObject_Not(), PyObject_IsInstance(), PyObject_RichCompareBool() and _PyDict_Contains() to check for and handle errors correctly.

- bpo-24328: Fix importing one character extension modules.

- bpo-11205: In dictionary displays, evaluate the key before the value.

- bpo-24285: Fixed regression that prevented importing extension modules from inside packages. Patch by Petr Viktorin.

### Library

- bpo-23247: Fix a crash in the StreamWriter.reset() of CJK codecs.

- bpo-24270: Add math.isclose() and cmath.isclose() functions as per PEP 485. Contributed by Chris Barker and Tal Einat.

- bpo-5633: Fixed timeit when the statement is a string and the setup is not.

- bpo-24326: Fixed audioop.ratecv() with non-default weightB argument. Original patch by David Moore.

- bpo-16991: Add a C implementation of OrderedDict.

- bpo-23934: Fix inspect.signature to fail correctly for builtin types lacking signature information. Initial patch by James Powell.

## Python 3.5.0 beta 1

Release date: 2015-05-24

### Core and Builtins

- bpo-24276: Fixed optimization of property descriptor getter.

- bpo-24268: PEP 489: Multi-phase extension module initialization. Patch by Petr Viktorin.

- bpo-23955: Add pyvenv.cfg option to suppress registry/environment lookup for generating sys.path on Windows.

- bpo-24257: Fixed system error in the comparison of faked types.SimpleNamespace.

- bpo-22939: Fixed integer overflow in iterator object. Patch by Clement Rouault.

- bpo-23985: Fix a possible buffer overrun when deleting a slice from the front of a bytearray and then appending some other bytes data.

- bpo-24102: Fixed exception type checking in standard error handlers.

- bpo-15027: The UTF-32 encoder is now 3x to 7x faster.

- bpo-23290: Optimize set_merge() for cases where the target is empty. (Contributed by Serhiy Storchaka.)

- bpo-2292: PEP 448: Additional Unpacking Generalizations.

- bpo-24096: Make warnings.warn_explicit more robust against mutation of the warnings.filters list.

- bpo-23996: Avoid a crash when a delegated generator raises an unnormalized StopIteration exception. Patch by Stefan Behnel.

- bpo-23910: Optimize property() getter calls. Patch by Joe Jevnik.

- bpo-23911: Move path-based importlib bootstrap code to a separate frozen module.

- bpo-24192: Fix namespace package imports.

- bpo-24022: Fix tokenizer crash when processing undecodable source code.

- bpo-9951: Added a hex() method to bytes, bytearray, and memoryview.

- bpo-22906: PEP 479: Change StopIteration handling inside generators.

- bpo-24017: PEP 492: Coroutines with async and await syntax.

### Library

- bpo-14373: Added C implementation of functools.lru_cache(). Based on patches by Matt Joiner and Alexey Kachayev.

- bpo-24230: The tempfile module now accepts bytes for prefix, suffix and dir parameters and returns bytes in such situations (matching the os module APIs).

- bpo-22189: collections.UserString now supports __getnewargs__(), __rmod__(), casefold(), format_map(), isprintable(), and maketrans(). Patch by Joe Jevnik.

- bpo-24244: Prevents termination when an invalid format string is encountered on Windows in strftime.

- bpo-23973: PEP 484: Add the typing module.

- bpo-23086: The collections.abc.Sequence() abstract base class added start and stop parameters to the index() mixin. Patch by Devin Jeanpierre.

- bpo-20035: Replaced the `tkinter._fix` module used for setting up the Tcl/Tk environment on Windows with a private function in the `_tkinter` module that makes no permanent changes to the environment.

- bpo-24257: Fixed segmentation fault in sqlite3.Row constructor with faked cursor type.

- bpo-15836: assertRaises(), assertRaisesRegex(), assertWarns() and assertWarnsRegex() assertments now check the type of the first argument to prevent possible user error. Based on patch by Daniel Wagner-Hall.

- bpo-9858: Add missing method stubs to _io.RawIOBase. Patch by Laura Rupprecht.

- bpo-22955: attrgetter, itemgetter and methodcaller objects in the operator module now support pickling. Added readable and evaluable repr for these objects. Based on patch by Josh Rosenberg.

- bpo-22107: tempfile.gettempdir() and tempfile.mkdtemp() now try again when a directory with the chosen name already exists on Windows as well as on Unix. tempfile.mkstemp() now fails early if parent directory is not valid (not exists or is a file) on Windows.

- bpo-23780: Improved error message in os.path.join() with single argument.

- bpo-6598: Increased time precision and random number range in email.utils.make_msgid() to strengthen the uniqueness of the message ID.

- bpo-24091: Fixed various crashes in corner cases in C implementation of ElementTree.

- bpo-21931: msilib.FCICreate() now raises TypeError in the case of a bad argument instead of a ValueError with a bogus FCI error number. Patch by Jeffrey Armstrong.

- bpo-13866: quote_via argument added to urllib.parse.urlencode.

- bpo-20098: New mangle_from policy option for email, default True for compat32, but False for all other policies.

- bpo-24211: The email library now supports RFC 6532: it can generate headers using utf-8 instead of encoded words.

- bpo-16314: Added support for the LZMA compression in distutils.

- bpo-21804: poplib now supports RFC 6856 (UTF8).

- bpo-18682: Optimized pprint functions for builtin scalar types.

- bpo-22027: smtplib now supports RFC 6531 (SMTPUTF8).

- bpo-23488: Random generator objects now consume 2x less memory on 64-bit.

- bpo-1322: platform.dist() and platform.linux_distribution() functions are now deprecated. Initial patch by Vajrasky Kok.

- bpo-22486: Added the math.gcd() function. The fractions.gcd() function now is deprecated. Based on patch by Mark Dickinson.

- bpo-24064: Property() docstrings are now writeable. (Patch by Berker Peksag.)

- bpo-22681: Added support for the koi8_t encoding.

- bpo-22682: Added support for the kz1048 encoding.

- bpo-23796: peek and read1 methods of BufferedReader now raise ValueError if they called on a closed object. Patch by John Hergenroeder.

- bpo-21795: smtpd now supports the 8BITMIME extension whenever the new decode_data constructor argument is set to False.

- bpo-24155: optimize heapq.heapify() for better cache performance when heapifying large lists.

- bpo-21800: imaplib now supports RFC 5161 (enable), RFC 6855 (utf8/internationalized email) and automatically encodes non-ASCII usernames and passwords to UTF8.

- bpo-20274: When calling a _sqlite.Connection, it now complains if passed any keyword arguments. Previously it silently ignored them.

- bpo-20274: Remove ignored and erroneous “kwargs” parameters from three METH_VARARGS methods on _sqlite.Connection.

- bpo-24134: assertRaises(), assertRaisesRegex(), assertWarns() and assertWarnsRegex() checks now emits a deprecation warning when callable is None or keyword arguments except msg is passed in the context manager mode.

- bpo-24018: Add a collections.abc.Generator abstract base class. Contributed by Stefan Behnel.

- bpo-23880: Tkinter’s getint() and getdouble() now support Tcl_Obj. Tkinter’s getdouble() now supports any numbers (in particular int).

- bpo-22619: Added negative limit support in the traceback module. Based on patch by Dmitry Kazakov.

- bpo-24094: Fix possible crash in json.encode with poorly behaved dict subclasses.

- bpo-9246: On POSIX, os.getcwd() now supports paths longer than 1025 bytes. Patch written by William Orr.

- bpo-17445: add difflib.diff_bytes() to support comparison of byte strings (fixes a regression from Python 2).

- bpo-23917: Fall back to sequential compilation when ProcessPoolExecutor doesn’t exist. Patch by Claudiu Popa.

- bpo-23008: Fixed resolving attributes with boolean value is False in pydoc.

- Fix asyncio issue 235: LifoQueue and PriorityQueue’s put didn’t increment unfinished tasks (this bug was introduced when JoinableQueue was merged with Queue).

- bpo-23908: os functions now reject paths with embedded null character on Windows instead of silently truncating them.

- bpo-23728: binascii.crc_hqx() could return an integer outside of the range 0-0xffff for empty data.

- bpo-23887: urllib.error.HTTPError now has a proper repr() representation. Patch by Berker Peksag.

- asyncio: New event loop APIs: set_task_factory() and get_task_factory().

- asyncio: async() function is deprecated in favour of ensure_future().

- bpo-24178: asyncio.Lock, Condition, Semaphore, and BoundedSemaphore support new ‘async with’ syntax. Contributed by Yury Selivanov.

- bpo-24179: Support ‘async for’ for asyncio.StreamReader. Contributed by Yury Selivanov.

- bpo-24184: Add AsyncIterator and AsyncIterable ABCs to collections.abc. Contributed by Yury Selivanov.

- bpo-22547: Implement informative __repr__ for inspect.BoundArguments. Contributed by Yury Selivanov.

- bpo-24190: Implement inspect.BoundArgument.apply_defaults() method. Contributed by Yury Selivanov.

- bpo-20691: Add ‘follow_wrapped’ argument to inspect.Signature.from_callable() and inspect.signature(). Contributed by Yury Selivanov.

- bpo-24248: Deprecate inspect.Signature.from_function() and inspect.Signature.from_builtin().

- bpo-23898: Fix inspect.classify_class_attrs() to support attributes with overloaded __eq__ and __bool__. Patch by Mike Bayer.

- bpo-24298: Fix inspect.signature() to correctly unwrap wrappers around bound methods.

### IDLE

- bpo-23184: remove unused names and imports in idlelib. Initial patch by Al Sweigart.

### Tests

- bpo-21520: test_zipfile no longer fails if the word ‘bad’ appears anywhere in the name of the current directory.

- bpo-9517: Move script_helper into the support package. Patch by Christie Wilson.

### Documentation

- bpo-22155: Add File Handlers subsection with createfilehandler to tkinter doc. Remove obsolete example from FAQ. Patch by Martin Panter.

- bpo-24029: Document the name binding behavior for submodule imports.

- bpo-24077: Fix typo in man page for -I command option: -s, not -S

### Tools/Demos

- bpo-24000: Improved Argument Clinic’s mapping of converters to legacy “format units”. Updated the documentation to match.

- bpo-24001: Argument Clinic converters now use accept={type} instead of types={‘type’} to specify the types the converter accepts.

- bpo-23330: h2py now supports arbitrary filenames in #include.

- bpo-24031: make patchcheck now supports git checkouts, too.

## Python 3.5.0 alpha 4

Release date: 2015-04-19

### Core and Builtins

- bpo-22980: Under Linux, GNU/KFreeBSD and the Hurd, C extensions now include the architecture triplet in the extension name, to make it easy to test builds for different ABIs in the same working tree. Under OS X, the extension name now includes PEP 3149-style information.

- bpo-22631: Added Linux-specific socket constant CAN_RAW_FD_FRAMES. Patch courtesy of Joe Jevnik.

- bpo-23731: Implement PEP 488: removal of .pyo files.

- bpo-23726: Don’t enable GC for user subclasses of non-GC types that don’t add any new fields. Patch by Eugene Toder.

- bpo-23309: Avoid a deadlock at shutdown if a daemon thread is aborted while it is holding a lock to a buffered I/O object, and the main thread tries to use the same I/O object (typically stdout or stderr). A fatal error is emitted instead.

- bpo-22977: Fixed formatting Windows error messages on Wine. Patch by Martin Panter.

- bpo-23466: %c, %o, %x, and %X in bytes formatting now raise TypeError on non-integer input.

- bpo-24044: Fix possible null pointer dereference in list.sort in out of memory conditions.

- bpo-21354: PyCFunction_New function is exposed by python DLL again.

### Library

- bpo-23840: tokenize.open() now closes the temporary binary file on error to fix a resource warning.

- bpo-16914: new debuglevel 2 in smtplib adds timestamps to debug output.

- bpo-7159: urllib.request now supports sending auth credentials automatically after the first 401. This enhancement is a superset of the enhancement from bpo-19494 and supersedes that change.

- bpo-23703: Fix a regression in urljoin() introduced in 901e4e52b20a. Patch by Demian Brecht.

- bpo-4254: Adds _curses.update_lines_cols(). Patch by Arnon Yaari

- bpo-19933: Provide default argument for ndigits in round. Patch by Vajrasky Kok.

- bpo-23193: Add a numeric_owner parameter to tarfile.TarFile.extract and tarfile.TarFile.extractall. Patch by Michael Vogt and Eric Smith.

- bpo-23342: Add a subprocess.run() function than returns a CalledProcess instance for a more consistent API than the existing call* functions.

- bpo-21217: inspect.getsourcelines() now tries to compute the start and end lines from the code object, fixing an issue when a lambda function is used as decorator argument. Patch by Thomas Ballinger and Allison Kaptur.

- bpo-24521: Fix possible integer overflows in the pickle module.

- bpo-22931: Allow ‘[’ and ‘]’ in cookie values.

- The keywords attribute of functools.partial is now always a dictionary.

- bpo-23811: Add missing newline to the PyCompileError error message. Patch by Alex Shkop.

- bpo-21116: Avoid blowing memory when allocating a multiprocessing shared array that’s larger than 50% of the available RAM. Patch by Médéric Boquien.

- bpo-22982: Improve BOM handling when seeking to multiple positions of a writable text file.

- bpo-23464: Removed deprecated asyncio JoinableQueue.

- bpo-23529: Limit the size of decompressed data when reading from GzipFile, BZ2File or LZMAFile. This defeats denial of service attacks using compressed bombs (i.e. compressed payloads which decompress to a huge size). Patch by Martin Panter and Nikolaus Rath.

- bpo-21859: Added Python implementation of io.FileIO.

- bpo-23865: close() methods in multiple modules now are idempotent and more robust at shutdown. If they need to release multiple resources, all are released even if errors occur.

- bpo-23400: Raise same exception on both Python 2 and 3 if sem_open is not available. Patch by Davin Potts.

- bpo-10838: The subprocess now module includes SubprocessError and TimeoutError in its list of exported names for the users wild enough to use `from subprocess import *`.

- bpo-23411: Added DefragResult, ParseResult, SplitResult, DefragResultBytes, ParseResultBytes, and SplitResultBytes to urllib.parse.__all__. Patch by Martin Panter.

- bpo-23881: urllib.request.ftpwrapper constructor now closes the socket if the FTP connection failed to fix a ResourceWarning.

- bpo-23853: `socket.socket.sendall()` does no more reset the socket timeout each time data is sent successfully. The socket timeout is now the maximum total duration to send all data.

- bpo-22721: An order of multiline pprint output of set or dict containing orderable and non-orderable elements no longer depends on iteration order of set or dict.

- bpo-15133: _tkinter.tkapp.getboolean() now supports Tcl_Obj and always returns bool. tkinter.BooleanVar now validates input values (accepted bool, int, str, and Tcl_Obj). tkinter.BooleanVar.get() now always returns bool.

- bpo-10590: xml.sax.parseString() now supports string argument.

- bpo-23338: Fixed formatting ctypes error messages on Cygwin. Patch by Makoto Kato.

- bpo-15582: inspect.getdoc() now follows inheritance chains.

- bpo-2175: SAX parsers now support a character stream of InputSource object.

- bpo-16840: Tkinter now supports 64-bit integers added in Tcl 8.4 and arbitrary precision integers added in Tcl 8.5.

- bpo-23834: Fix socket.sendto(), use the C Py_ssize_t type to store the result of sendto() instead of the C int type.

- bpo-23618: `socket.socket.connect()` now waits until the connection completes instead of raising `InterruptedError` if the connection is interrupted by signals, signal handlers don’t raise an exception and the socket is blocking or has a timeout. `socket.socket.connect()` still raise `InterruptedError` for non-blocking sockets.

- bpo-21526: Tkinter now supports new boolean type in Tcl 8.5.

- bpo-23836: Fix the faulthandler module to handle reentrant calls to its signal handlers.

- bpo-23838: linecache now clears the cache and returns an empty result on MemoryError.

- bpo-10395: Added os.path.commonpath(). Implemented in posixpath and ntpath. Based on patch by Rafik Draoui.

- bpo-23611: Serializing more “lookupable” objects (such as unbound methods or nested classes) now are supported with pickle protocols < 4.

- bpo-13583: sqlite3.Row now supports slice indexing.

- bpo-18473: Fixed 2to3 and 3to2 compatible pickle mappings. Fixed ambiguous reverse mappings. Added many new mappings. Import mapping is no longer applied to modules already mapped with full name mapping.

- bpo-23485: select.select() is now retried automatically with the recomputed timeout when interrupted by a signal, except if the signal handler raises an exception. This change is part of the PEP 475.

- bpo-23752: When built from an existing file descriptor, io.FileIO() now only calls fstat() once. Before fstat() was called twice, which was not necessary.

- bpo-23704: collections.deque() objects now support __add__, __mul__, and __imul__().

- bpo-23171: csv.Writer.writerow() now supports arbitrary iterables.

- bpo-23745: The new email header parser now handles duplicate MIME parameter names without error, similar to how get_param behaves.

- bpo-22117: Fix os.utime(), it now rounds the timestamp towards minus infinity (-inf) instead of rounding towards zero.

- bpo-23310: Fix MagicMock’s initializer to work with __methods__, just like configure_mock(). Patch by Kasia Jachim.

### Build

- bpo-23817: FreeBSD now uses “1.0” in the SOVERSION as other operating systems, instead of just “1”.

- bpo-23501: Argument Clinic now generates code into separate files by default.

### Tests

- bpo-23799: Added test.support.start_threads() for running and cleaning up multiple threads.

- bpo-22390: test.regrtest now emits a warning if temporary files or directories are left after running a test.

### Tools/Demos

- bpo-18128: pygettext now uses standard +NNNN format in the POT-Creation-Date header.

- bpo-23935: Argument Clinic’s understanding of format units accepting bytes, bytearrays, and buffers is now consistent with both the documentation and the implementation.

- bpo-23944: Argument Clinic now wraps long impl prototypes at column 78.

- bpo-20586: Argument Clinic now ensures that functions without docstrings have signatures.

- bpo-23492: Argument Clinic now generates argument parsing code with PyArg_Parse instead of PyArg_ParseTuple if possible.

- bpo-23500: Argument Clinic is now smarter about generating the “#ifndef” (empty) definition of the methoddef macro: it’s only generated once, even if Argument Clinic processes the same symbol multiple times, and it’s emitted at the end of all processing rather than immediately after the first use.

### C API

- bpo-23998: PyImport_ReInitLock() now checks for lock allocation error

## Python 3.5.0 alpha 3

Release date: 2015-03-28

### Core and Builtins

- bpo-23573: Increased performance of string search operations (str.find, str.index, str.count, the in operator, str.split, str.partition) with arguments of different kinds (UCS1, UCS2, UCS4).

- bpo-23753: Python doesn’t support anymore platforms without stat() or fstat(), these functions are always required.

- bpo-23681: The -b option now affects comparisons of bytes with int.

- bpo-23632: Memoryviews now allow tuple indexing (including for multi-dimensional memoryviews).

- bpo-23192: Fixed generator lambdas. Patch by Bruno Cauet.

- bpo-23629: Fix the default __sizeof__ implementation for variable-sized objects.

### Library

- bpo-14260: The groupindex attribute of regular expression pattern object now is non-modifiable mapping.

- bpo-23792: Ignore KeyboardInterrupt when the pydoc pager is active. This mimics the behavior of the standard unix pagers, and prevents pipepager from shutting down while the pager itself is still running.

- bpo-23775: pprint() of OrderedDict now outputs the same representation as repr().

- bpo-23765: Removed IsBadStringPtr calls in ctypes

- bpo-22364: Improved some re error messages using regex for hints.

- bpo-23742: ntpath.expandvars() no longer loses unbalanced single quotes.

- bpo-21717: The zipfile.ZipFile.open function now supports ‘x’ (exclusive creation) mode.

- bpo-21802: The reader in BufferedRWPair now is closed even when closing writer failed in BufferedRWPair.close().

- bpo-23622: Unknown escapes in regular expressions that consist of `'\'` and ASCII letter now raise a deprecation warning and will be forbidden in Python 3.6.

- bpo-23671: string.Template now allows specifying the “self” parameter as a keyword argument. string.Formatter now allows specifying the “self” and the “format_string” parameters as keyword arguments.

- bpo-23502: The pprint module now supports mapping proxies.

- bpo-17530: pprint now wraps long bytes objects and bytearrays.

- bpo-22687: Fixed some corner cases in breaking words in tetxtwrap. Got rid of quadratic complexity in breaking long words.

- bpo-4727: The copy module now uses pickle protocol 4 (PEP 3154) and supports copying of instances of classes whose __new__ method takes keyword-only arguments.

- bpo-23491: Added a zipapp module to support creating executable zip file archives of Python code. Registered “.pyz” and “.pyzw” extensions on Windows for these archives (PEP 441).

- bpo-23657: Avoid explicit checks for str in zipapp, adding support for pathlib.Path objects as arguments.

- bpo-23688: Added support of arbitrary bytes-like objects and avoided unnecessary copying of memoryview in gzip.GzipFile.write(). Original patch by Wolfgang Maier.

- bpo-23252: Added support for writing ZIP files to unseekable streams.

- bpo-23647: Increase imaplib’s MAXLINE to accommodate modern mailbox sizes.

- bpo-23539: If body is None, http.client.HTTPConnection.request now sets Content-Length to 0 for PUT, POST, and PATCH headers to avoid 411 errors from some web servers.

- bpo-22351: The nntplib.NNTP constructor no longer leaves the connection and socket open until the garbage collector cleans them up. Patch by Martin Panter.

- bpo-23704: collections.deque() objects now support methods for index(), insert(), and copy(). This allows deques to be registered as a MutableSequence and it improves their substitutability for lists.

- bpo-23715: `signal.sigwaitinfo()` and `signal.sigtimedwait()` are now retried when interrupted by a signal not in the sigset parameter, if the signal handler does not raise an exception. signal.sigtimedwait() recomputes the timeout with a monotonic clock when it is retried.

- bpo-23001: Few functions in modules mmap, ossaudiodev, socket, ssl, and codecs, that accepted only read-only bytes-like object now accept writable bytes-like object too.

- bpo-23646: If time.sleep() is interrupted by a signal, the sleep is now retried with the recomputed delay, except if the signal handler raises an exception (PEP 475).

- bpo-23136: _strptime now uniformly handles all days in week 0, including Dec 30 of previous year. Based on patch by Jim Carroll.

- bpo-23700: Iterator of NamedTemporaryFile now keeps a reference to NamedTemporaryFile instance. Patch by Bohuslav Kabrda.

- bpo-22903: The fake test case created by unittest.loader when it fails importing a test module is now picklable.

- bpo-22181: On Linux, os.urandom() now uses the new getrandom() syscall if available, syscall introduced in the Linux kernel 3.17. It is more reliable and more secure, because it avoids the need of a file descriptor and waits until the kernel has enough entropy.

- bpo-2211: Updated the implementation of the http.cookies.Morsel class. Setting attributes key, value and coded_value directly now is deprecated. update() and setdefault() now transform and check keys. Comparing for equality now takes into account attributes key, value and coded_value. copy() now returns a Morsel, not a dict. repr() now contains all attributes. Optimized checking keys and quoting values. Added new tests. Original patch by Demian Brecht.

- bpo-18983: Allow selection of output units in timeit. Patch by Julian Gindi.

- bpo-23631: Fix traceback.format_list when a traceback has been mutated.

- bpo-23568: Add rdivmod support to MagicMock() objects. Patch by Håkan Lövdahl.

- bpo-2052: Add charset parameter to HtmlDiff.make_file().

- bpo-23668: Support os.truncate and os.ftruncate on Windows.

- bpo-23138: Fixed parsing cookies with absent keys or values in cookiejar. Patch by Demian Brecht.

- bpo-23051: multiprocessing.Pool methods imap() and imap_unordered() now handle exceptions raised by an iterator. Patch by Alon Diamant and Davin Potts.

- bpo-23581: Add matmul support to MagicMock. Patch by Håkan Lövdahl.

- bpo-23566: enable(), register(), dump_traceback() and dump_traceback_later() functions of faulthandler now accept file descriptors. Patch by Wei Wu.

- bpo-22928: Disabled HTTP header injections in http.client. Original patch by Demian Brecht.

- bpo-23615: Modules bz2, tarfile and tokenize now can be reloaded with imp.reload(). Patch by Thomas Kluyver.

- bpo-23605: os.walk() now calls os.scandir() instead of os.listdir(). The usage of os.scandir() reduces the number of calls to os.stat(). Initial patch written by Ben Hoyt.

### Build

- bpo-23585: make patchcheck will ensure the interpreter is built.

### Tests

- bpo-23583: Added tests for standard IO streams in IDLE.

- bpo-22289: Prevent test_urllib2net failures due to ftp connection timeout.

### Tools/Demos

- bpo-22826: The result of open() in Tools/freeze/bkfile.py is now better compatible with regular files (in particular it now supports the context management protocol).

## Python 3.5.0 alpha 2

Release date: 2015-03-09

### Core and Builtins

- bpo-23571: PyObject_Call() and PyCFunction_Call() now raise a SystemError if a function returns a result and raises an exception. The SystemError is chained to the previous exception.

### Library

- bpo-22524: New os.scandir() function, part of the PEP 471: “os.scandir() function – a better and faster directory iterator”. Patch written by Ben Hoyt.

- bpo-23103: Reduced the memory consumption of IPv4Address and IPv6Address.

- bpo-21793: BaseHTTPRequestHandler again logs response code as numeric, not as stringified enum. Patch by Demian Brecht.

- bpo-23476: In the ssl module, enable OpenSSL’s X509_V_FLAG_TRUSTED_FIRST flag on certificate stores when it is available.

- bpo-23576: Avoid stalling in SSL reads when EOF has been reached in the SSL layer but the underlying connection hasn’t been closed.

- bpo-23504: Added an __all__ to the types module.

- bpo-23563: Optimized utility functions in urllib.parse.

- bpo-7830: Flatten nested functools.partial.

- bpo-20204: Added the __module__ attribute to _tkinter classes.

- bpo-19980: Improved help() for non-recognized strings. help(‘’) now shows the help on str. help(‘help’) now shows the help on help(). Original patch by Mark Lawrence.

- bpo-23521: Corrected pure python implementation of timedelta division. Eliminated OverflowError from `timedelta * float` for some floats; Corrected rounding in timedelta true division.

- bpo-21619: Popen objects no longer leave a zombie after exit in the with statement if the pipe was broken. Patch by Martin Panter.

- bpo-22936: Make it possible to show local variables in tracebacks for both the traceback module and unittest.

- bpo-15955: Add an option to limit the output size in bz2.decompress(). Patch by Nikolaus Rath.

- bpo-6639: Module-level turtle functions no longer raise TclError after closing the window.

- bpo-814253: Group references and conditional group references now work in lookbehind assertions in regular expressions. (See also: bpo-9179)

- bpo-23215: Multibyte codecs with custom error handlers that ignores errors consumed too much memory and raised SystemError or MemoryError. Original patch by Aleksi Torhamo.

- bpo-5700: io.FileIO() called flush() after closing the file. flush() was not called in close() if closefd=False.

- bpo-23374: Fixed pydoc failure with non-ASCII files when stdout encoding differs from file system encoding (e.g. on Mac OS).

- bpo-23481: Remove RC4 from the SSL module’s default cipher list.

- bpo-21548: Fix pydoc.synopsis() and pydoc.apropos() on modules with empty docstrings.

- bpo-22885: Fixed arbitrary code execution vulnerability in the dbm.dumb module. Original patch by Claudiu Popa.

- bpo-23239: ssl.match_hostname() now supports matching of IP addresses.

- bpo-23146: Fix mishandling of absolute Windows paths with forward slashes in pathlib.

- bpo-23096: Pickle representation of floats with protocol 0 now is the same for both Python and C implementations.

- bpo-19105: pprint now more efficiently uses free space at the right.

- bpo-14910: Add allow_abbrev parameter to argparse.ArgumentParser. Patch by Jonathan Paugh, Steven Bethard, paul j3 and Daniel Eriksson.

- bpo-21717: tarfile.open() now supports ‘x’ (exclusive creation) mode.

- bpo-23344: marshal.dumps() is now 20-25% faster on average.

- bpo-20416: marshal.dumps() with protocols 3 and 4 is now 40-50% faster on average.

- bpo-23421: Fixed compression in tarfile CLI. Patch by wdv4758h.

- bpo-23367: Fix possible overflows in the unicodedata module.

- bpo-23361: Fix possible overflow in Windows subprocess creation code.

- logging.handlers.QueueListener now takes a respect_handler_level keyword argument which, if set to True, will pass messages to handlers taking handler levels into account.

- bpo-19705: turtledemo now has a visual sorting algorithm demo. Original patch from Jason Yeo.

- bpo-23801: Fix issue where cgi.FieldStorage did not always ignore the entire preamble to a multipart body.

### Build

- bpo-23445: pydebug builds now use “gcc -Og” where possible, to make the resulting executable faster.

- bpo-23686: Update OS X 10.5 installer build to use OpenSSL 1.0.2a.

### C API

- bpo-20204: Deprecation warning is now raised for builtin types without the __module__ attribute.

### Windows

- bpo-23465: Implement PEP 486 - Make the Python Launcher aware of virtual environments. Patch by Paul Moore.

- bpo-23437: Make user scripts directory versioned on Windows. Patch by Paul Moore.

## Python 3.5.0 alpha 1

Release date: 2015-02-08

### Core and Builtins

- bpo-23285: PEP 475 - EINTR handling.

- bpo-22735: Fix many edge cases (including crashes) involving custom mro() implementations.

- bpo-22896: Avoid using PyObject_AsCharBuffer(), PyObject_AsReadBuffer() and PyObject_AsWriteBuffer().

- bpo-21295: Revert some changes (bpo-16795) to AST line numbers and column offsets that constituted a regression.

- bpo-22986: Allow changing an object’s __class__ between a dynamic type and static type in some cases.

- bpo-15859: PyUnicode_EncodeFSDefault(), PyUnicode_EncodeMBCS() and PyUnicode_EncodeCodePage() now raise an exception if the object is not a Unicode object. For PyUnicode_EncodeFSDefault(), it was already the case on platforms other than Windows. Patch written by Campbell Barton.

- bpo-21408: The default __ne__() now returns NotImplemented if __eq__() returned NotImplemented. Original patch by Martin Panter.

- bpo-23321: Fixed a crash in str.decode() when error handler returned replacement string longer than malformed input data.

- bpo-22286: The “backslashreplace” error handlers now works with decoding and translating.

- bpo-23253: Delay-load ShellExecute[AW] in os.startfile for reduced startup overhead on Windows.

- bpo-22038: pyatomic.h now uses stdatomic.h or GCC built-in functions for atomic memory access if available. Patch written by Vitor de Lima and Gustavo Temple.

- bpo-20284: %-interpolation (aka printf) formatting added for bytes and bytearray.

- bpo-23048: Fix jumping out of an infinite while loop in the pdb.

- bpo-20335: bytes constructor now raises TypeError when encoding or errors is specified with non-string argument. Based on patch by Renaud Blanch.

- bpo-22834: If the current working directory ends up being set to a non-existent directory then import will no longer raise FileNotFoundError.

- bpo-22869: Move the interpreter startup & shutdown code to a new dedicated pylifecycle.c module

- bpo-22847: Improve method cache efficiency.

- bpo-22335: Fix crash when trying to enlarge a bytearray to 0x7fffffff bytes on a 32-bit platform.

- bpo-22653: Fix an assertion failure in debug mode when doing a reentrant dict insertion in debug mode.

- bpo-22643: Fix integer overflow in Unicode case operations (upper, lower, title, swapcase, casefold).

- bpo-17636: Circular imports involving relative imports are now supported.

- bpo-22604: Fix assertion error in debug mode when dividing a complex number by (nan+0j).

- bpo-21052: Do not raise ImportWarning when sys.path_hooks or sys.meta_path are set to None.

- bpo-16518: Use ‘bytes-like object required’ in error messages that previously used the far more cryptic “‘x’ does not support the buffer protocol.

- bpo-22470: Fixed integer overflow issues in “backslashreplace”, “xmlcharrefreplace”, and “surrogatepass” error handlers.

- bpo-22540: speed up `PyObject_IsInstance` and `PyObject_IsSubclass` in the common case that the second argument has metaclass `type`.

- bpo-18711: Add a new `PyErr_FormatV` function, similar to `PyErr_Format` but accepting a `va_list` argument.

- bpo-22520: Fix overflow checking when generating the repr of a unicode object.

- bpo-22519: Fix overflow checking in PyBytes_Repr.

- bpo-22518: Fix integer overflow issues in latin-1 encoding.

- bpo-16324: _charset parameter of MIMEText now also accepts email.charset.Charset instances. Initial patch by Claude Paroz.

- bpo-1764286: Fix inspect.getsource() to support decorated functions. Patch by Claudiu Popa.

- bpo-18554: os.__all__ includes posix functions.

- bpo-21391: Use os.path.abspath in the shutil module.

- bpo-11471: avoid generating a JUMP_FORWARD instruction at the end of an if-block if there is no else-clause. Original patch by Eugene Toder.

- bpo-22215: Now ValueError is raised instead of TypeError when str or bytes argument contains not permitted null character or byte.

- bpo-22258: Fix the internal function set_inheritable() on Illumos. This platform exposes the function `ioctl(FIOCLEX)`, but calling it fails with errno is ENOTTY: “Inappropriate ioctl for device”. set_inheritable() now falls back to the slower `fcntl()` (`F_GETFD` and then `F_SETFD`).

- bpo-21389: Displaying the __qualname__ of the underlying function in the repr of a bound method.

- bpo-22206: Using pthread, PyThread_create_key() now sets errno to ENOMEM and returns -1 (error) on integer overflow.

- bpo-20184: Argument Clinic based signature introspection added for 30 of the builtin functions.

- bpo-22116: C functions and methods (of the ‘builtin_function_or_method’ type) can now be weakref’ed. Patch by Wei Wu.

- bpo-22077: Improve index error messages for bytearrays, bytes, lists, and tuples by adding ‘or slices’. Added ‘, not <typename>’ for bytearrays. Original patch by Claudiu Popa.

- bpo-20179: Apply Argument Clinic to bytes and bytearray. Patch by Tal Einat.

- bpo-22082: Clear interned strings in slotdefs.

- Upgrade Unicode database to Unicode 7.0.0.

- bpo-21897: Fix a crash with the f_locals attribute with closure variables when frame.clear() has been called.

- bpo-21205: Add a new `__qualname__` attribute to generator, the qualified name, and use it in the representation of a generator (`repr(gen)`). The default name of the generator (`__name__` attribute) is now get from the function instead of the code. Use `gen.gi_code.co_name` to get the name of the code.

- bpo-21669: With the aid of heuristics in SyntaxError.__init__, the parser now attempts to generate more meaningful (or at least more search engine friendly) error messages when “exec” and “print” are used as statements.

- bpo-21642: In the conditional if-else expression, allow an integer written with no space between itself and the `else` keyword (e.g. `True if 42else False`) to be valid syntax.

- bpo-21523: Fix over-pessimistic computation of the stack effect of some opcodes in the compiler. This also fixes a quadratic compilation time issue noticeable when compiling code with a large number of “and” and “or” operators.

- bpo-21418: Fix a crash in the builtin function super() when called without argument and without current frame (ex: embedded Python).

- bpo-21425: Fix flushing of standard streams in the interactive interpreter.

- bpo-21435: In rare cases, when running finalizers on objects in cyclic trash a bad pointer dereference could occur due to a subtle flaw in internal iteration logic.

- bpo-21377: PyBytes_Concat() now tries to concatenate in-place when the first argument has a reference count of 1. Patch by Nikolaus Rath.

- bpo-20355: -W command line options now have higher priority than the PYTHONWARNINGS environment variable. Patch by Arfrever.

- bpo-21274: Define PATH_MAX for GNU/Hurd in Python/pythonrun.c.

- bpo-20904: Support setting FPU precision on m68k.

- bpo-21209: Fix sending tuples to custom generator objects with the yield from syntax.

- bpo-21193: pow(a, b, c) now raises ValueError rather than TypeError when b is negative. Patch by Josh Rosenberg.

- bpo-21176: PEP 465: Add the ‘@’ operator for matrix multiplication.

- bpo-21134: Fix segfault when str is called on an uninitialized UnicodeEncodeError, UnicodeDecodeError, or UnicodeTranslateError object.

- bpo-19537: Fix PyUnicode_DATA() alignment under m68k. Patch by Andreas Schwab.

- bpo-20929: Add a type cast to avoid shifting a negative number.

- bpo-20731: Properly position in source code files even if they are opened in text mode. Patch by Serhiy Storchaka.

- bpo-20637: Key-sharing now also works for instance dictionaries of subclasses. Patch by Peter Ingebretson.

- bpo-8297: Attributes missing from modules now include the module name in the error text. Original patch by ysj.ray.

- bpo-19995: %c, %o, %x, and %X now raise TypeError on non-integer input.

- bpo-19655: The ASDL parser - used by the build process to generate code for managing the Python AST in C - was rewritten. The new parser is self contained and does not require to carry long the spark.py parser-generator library; spark.py was removed from the source base.

- bpo-12546: Allow `\x00` to be used as a fill character when using str, int, float, and complex __format__ methods.

- bpo-20480: Add ipaddress.reverse_pointer. Patch by Leon Weber.

- bpo-13598: Modify string.Formatter to support auto-numbering of replacement fields. It now matches the behavior of str.format() in this regard. Patches by Phil Elson and Ramchandra Apte.

- bpo-8931: Make alternate formatting (‘#’) for type ‘c’ raise an exception. In versions prior to 3.5, ‘#’ with ‘c’ had no effect. Now specifying it is an error. Patch by Torsten Landschoff.

- bpo-23165: Perform overflow checks before allocating memory in the _Py_char2wchar function.

### Library

- bpo-23399: pyvenv creates relative symlinks where possible.

- bpo-20289: cgi.FieldStorage() now supports the context management protocol.

- bpo-13128: Print response headers for CONNECT requests when debuglevel > 0. Patch by Demian Brecht.

- bpo-15381: Optimized io.BytesIO to make less allocations and copyings.

- bpo-22818: Splitting on a pattern that could match an empty string now raises a warning. Patterns that can only match empty strings are now rejected.

- bpo-23099: Closing io.BytesIO with exported buffer is rejected now to prevent corrupting exported buffer.

- bpo-23326: Removed __ne__ implementations. Since fixing default __ne__ implementation in bpo-21408 they are redundant.

- bpo-23363: Fix possible overflow in itertools.permutations.

- bpo-23364: Fix possible overflow in itertools.product.

- bpo-23366: Fixed possible integer overflow in itertools.combinations.

- bpo-23369: Fixed possible integer overflow in _json.encode_basestring_ascii.

- bpo-23353: Fix the exception handling of generators in PyEval_EvalFrameEx(). At entry, save or swap the exception state even if PyEval_EvalFrameEx() is called with throwflag=0. At exit, the exception state is now always restored or swapped, not only if why is WHY_YIELD or WHY_RETURN. Patch co-written with Antoine Pitrou.

- bpo-14099: Restored support of writing ZIP files to tellable but non-seekable streams.

- bpo-14099: Writing to ZipFile and reading multiple ZipExtFiles is threadsafe now.

- bpo-19361: JSON decoder now raises JSONDecodeError instead of ValueError.

- bpo-18518: timeit now rejects statements which can’t be compiled outside a function or a loop (e.g. “return” or “break”).

- bpo-23094: Fixed readline with frames in Python implementation of pickle.

- bpo-23268: Fixed bugs in the comparison of ipaddress classes.

- bpo-21408: Removed incorrect implementations of __ne__() which didn’t returned NotImplemented if __eq__() returned NotImplemented. The default __ne__() now works correctly.

- bpo-19996: `email.feedparser.FeedParser` now handles (malformed) headers with no key rather than assuming the body has started.

- bpo-20188: Support Application-Layer Protocol Negotiation (ALPN) in the ssl module.

- bpo-23133: Pickling of ipaddress objects now produces more compact and portable representation.

- bpo-23248: Update ssl error codes from latest OpenSSL git master.

- bpo-23266: Much faster implementation of ipaddress.collapse_addresses() when there are many non-consecutive addresses.

- bpo-23098: 64-bit dev_t is now supported in the os module.

- bpo-21817: When an exception is raised in a task submitted to a ProcessPoolExecutor, the remote traceback is now displayed in the parent process. Patch by Claudiu Popa.

- bpo-15955: Add an option to limit output size when decompressing LZMA data. Patch by Nikolaus Rath and Martin Panter.

- bpo-23250: In the http.cookies module, capitalize “HttpOnly” and “Secure” as they are written in the standard.

- bpo-23063: In the distutils’ check command, fix parsing of reST with code or code-block directives.

- bpo-23209: selectors.BaseSelector.get_key() now raises a RuntimeError if the selector is closed. And selectors.BaseSelector.close() now clears its internal reference to the selector mapping to break a reference cycle. Initial patch written by Martin Richard. (See also: bpo-23225)

- bpo-17911: Provide a way to seed the linecache for a PEP-302 module without actually loading the code.

- bpo-17911: Provide a new object API for traceback, including the ability to not lookup lines at all until the traceback is actually rendered, without any trace of the original objects being kept alive.

- bpo-19777: Provide a home() classmethod on Path objects. Contributed by Victor Salgado and Mayank Tripathi.

- bpo-23206: Make `json.dumps(..., ensure_ascii=False)` as fast as the default case of `ensure_ascii=True`. Patch by Naoki Inada.

- bpo-23185: Add math.inf and math.nan constants.

- bpo-23186: Add ssl.SSLObject.shared_ciphers() and ssl.SSLSocket.shared_ciphers() to fetch the client’s list ciphers sent at handshake.

- bpo-23143: Remove compatibility with OpenSSLs older than 0.9.8.

- bpo-23132: Improve performance and introspection support of comparison methods created by functool.total_ordering.

- bpo-19776: Add an expanduser() method on Path objects.

- bpo-23112: Fix SimpleHTTPServer to correctly carry the query string and fragment when it redirects to add a trailing slash.

- bpo-21793: Added http.HTTPStatus enums (i.e. HTTPStatus.OK, HTTPStatus.NOT_FOUND). Patch by Demian Brecht.

- bpo-23093: In the io, module allow more operations to work on detached streams.

- bpo-23111: In the ftplib, make ssl.PROTOCOL_SSLv23 the default protocol version.

- bpo-22585: On OpenBSD 5.6 and newer, os.urandom() now calls getentropy(), instead of reading /dev/urandom, to get pseudo-random bytes.

- bpo-19104: pprint now produces evaluable output for wrapped strings.

- bpo-23071: Added missing names to codecs.__all__. Patch by Martin Panter.

- bpo-22783: Pickling now uses the NEWOBJ opcode instead of the NEWOBJ_EX opcode if possible.

- bpo-15513: Added a __sizeof__ implementation for pickle classes.

- bpo-19858: pickletools.optimize() now aware of the MEMOIZE opcode, can produce more compact result and no longer produces invalid output if input data contains MEMOIZE opcodes together with PUT or BINPUT opcodes.

- bpo-22095: Fixed HTTPConnection.set_tunnel with default port. The port value in the host header was set to “None”. Patch by Demian Brecht.

- bpo-23016: A warning no longer produces an AttributeError when the program is run with pythonw.exe.

- bpo-21775: shutil.copytree(): fix crash when copying to VFAT. An exception handler assumed that OSError objects always have a ‘winerror’ attribute. That is not the case, so the exception handler itself raised AttributeError when run on Linux (and, presumably, any other non-Windows OS). Patch by Greg Ward.

- bpo-1218234: Fix inspect.getsource() to load updated source of reloaded module. Initial patch by Berker Peksag.

- bpo-21740: Support wrapped callables in doctest. Patch by Claudiu Popa.

- bpo-23009: Make sure selectors.EpollSelector.select() works when no FD is registered.

- bpo-22959: In the constructor of http.client.HTTPSConnection, prefer the context’s check_hostname attribute over the check_hostname parameter.

- bpo-22696: Add function `sys.is_finalizing()` to know about interpreter shutdown.

- bpo-16043: Add a default limit for the amount of data xmlrpclib.gzip_decode will return. This resolves CVE 2013-1753.

- bpo-14099: ZipFile.open() no longer reopen the underlying file. Objects returned by ZipFile.open() can now operate independently of the ZipFile even if the ZipFile was created by passing in a file-like object as the first argument to the constructor.

- bpo-22966: Fix __pycache__ pyc file name clobber when pyc_compile is asked to compile a source file containing multiple dots in the source file name.

- bpo-21971: Update turtledemo doc and add module to the index.

- bpo-21032: Fixed socket leak if HTTPConnection.getresponse() fails. Original patch by Martin Panter.

- bpo-22407: Deprecated the use of re.LOCALE flag with str patterns or re.ASCII. It was newer worked.

- bpo-22902: The “ip” command is now used on Linux to determine MAC address in uuid.getnode(). Pach by Bruno Cauet.

- bpo-22960: Add a context argument to xmlrpclib.ServerProxy constructor.

- bpo-22389: Add contextlib.redirect_stderr().

- bpo-21356: Make ssl.RAND_egd() optional to support LibreSSL. The availability of the function is checked during the compilation. Patch written by Bernard Spil.

- bpo-22915: SAX parser now supports files opened with file descriptor or bytes path.

- bpo-22609: Constructors and update methods of mapping classes in the collections module now accept the self keyword argument.

- bpo-22940: Add readline.append_history_file.

- bpo-19676: Added the “namereplace” error handler.

- bpo-22788: Add context parameter to logging.handlers.HTTPHandler.

- bpo-22921: Allow SSLContext to take the hostname parameter even if OpenSSL doesn’t support SNI.

- bpo-22894: TestCase.subTest() would cause the test suite to be stopped when in failfast mode, even in the absence of failures.

- bpo-22796: HTTP cookie parsing is now stricter, in order to protect against potential injection attacks.

- bpo-22370: Windows detection in pathlib is now more robust.

- bpo-22841: Reject coroutines in asyncio add_signal_handler(). Patch by Ludovic.Gasc.

- bpo-19494: Added urllib.request.HTTPBasicPriorAuthHandler. Patch by Matej Cepl.

- bpo-22578: Added attributes to the re.error class.

- bpo-22849: Fix possible double free in the io.TextIOWrapper constructor.

- bpo-12728: Different Unicode characters having the same uppercase but different lowercase are now matched in case-insensitive regular expressions.

- bpo-22821: Fixed fcntl() with integer argument on 64-bit big-endian platforms.

- bpo-21650: Add an `--sort-keys` option to `json.tool` CLI.

- bpo-22824: Updated reprlib output format for sets to use set literals. Patch contributed by Berker Peksag.

- bpo-22824: Updated reprlib output format for arrays to display empty arrays without an unnecessary empty list. Suggested by Serhiy Storchaka.

- bpo-22406: Fixed the uu_codec codec incorrectly ported to 3.x. Based on patch by Martin Panter.

- bpo-17293: uuid.getnode() now determines MAC address on AIX using netstat. Based on patch by Aivars Kalvāns.

- bpo-22769: Fixed ttk.Treeview.tag_has() when called without arguments.

- bpo-22417: Verify certificates by default in httplib (PEP 476).

- bpo-22775: Fixed unpickling of http.cookies.SimpleCookie with protocol 2 and above. Patch by Tim Graham.

- bpo-22776: Brought excluded code into the scope of a try block in SysLogHandler.emit().

- bpo-22665: Add missing get_terminal_size and SameFileError to shutil.__all__.

- bpo-6623: Remove deprecated Netrc class in the ftplib module. Patch by Matt Chaput.

- bpo-17381: Fixed handling of case-insensitive ranges in regular expressions.

- bpo-22410: Module level functions in the re module now cache compiled locale-dependent regular expressions taking into account the locale.

- bpo-22759: Query methods on pathlib.Path() (exists(), is_dir(), etc.) now return False when the underlying stat call raises NotADirectoryError.

- bpo-8876: distutils now falls back to copying files when hard linking doesn’t work. This allows use with special filesystems such as VirtualBox shared folders.

- bpo-22217: Implemented reprs of classes in the zipfile module.

- bpo-22457: Honour load_tests in the start_dir of discovery.

- bpo-18216: gettext now raises an error when a .mo file has an unsupported major version number. Patch by Aaron Hill.

- bpo-13918: Provide a locale.delocalize() function which can remove locale-specific number formatting from a string representing a number, without then converting it to a specific type. Patch by Cédric Krier.

- bpo-22676: Make the pickling of global objects which don’t have a __module__ attribute less slow.

- bpo-18853: Fixed ResourceWarning in shlex.__nain__.

- bpo-9351: Defaults set with set_defaults on an argparse subparser are no longer ignored when also set on the parent parser.

- bpo-7559: unittest test loading ImportErrors are reported as import errors with their import exception rather than as attribute errors after the import has already failed.

- bpo-19746: Make it possible to examine the errors from unittest discovery without executing the test suite. The new `errors` attribute on `TestLoader` exposes these non-fatal errors encountered during discovery.

- bpo-21991: Make email.headerregistry’s header ‘params’ attributes be read-only (MappingProxyType). Previously the dictionary was modifiable but a new one was created on each access of the attribute.

- bpo-22638: SSLv3 is now disabled throughout the standard library. It can still be enabled by instantiating a SSLContext manually.

- bpo-22641: In asyncio, the default SSL context for client connections is now created using ssl.create_default_context(), for stronger security.

- bpo-17401: Include closefd in io.FileIO repr.

- bpo-21338: Add silent mode for compileall. quiet parameters of compile_{dir, file, path} functions now have a multilevel value. Also, -q option of the CLI now have a multilevel value. Patch by Thomas Kluyver.

- bpo-20152: Convert the array and cmath modules to Argument Clinic.

- bpo-18643: Add socket.socketpair() on Windows.

- bpo-22435: Fix a file descriptor leak when socketserver bind fails.

- bpo-13096: Fixed segfault in CTypes POINTER handling of large values.

- bpo-11694: Raise ConversionError in xdrlib as documented. Patch by Filip Gruszczyński and Claudiu Popa.

- bpo-19380: Optimized parsing of regular expressions.

- bpo-1519638: Now unmatched groups are replaced with empty strings in re.sub() and re.subn().

- bpo-18615: sndhdr.what/whathdr now return a namedtuple.

- bpo-22462: Fix pyexpat’s creation of a dummy frame to make it appear in exception tracebacks.

- bpo-21965: Add support for in-memory SSL to the ssl module. Patch by Geert Jansen.

- bpo-21173: Fix len() on a WeakKeyDictionary when .clear() was called with an iterator alive.

- bpo-11866: Eliminated race condition in the computation of names for new threads.

- bpo-21905: Avoid RuntimeError in pickle.whichmodule() when sys.modules is mutated while iterating. Patch by Olivier Grisel.

- bpo-11271: concurrent.futures.Executor.map() now takes a chunksize argument to allow batching of tasks in child processes and improve performance of ProcessPoolExecutor. Patch by Dan O’Reilly.

- bpo-21883: os.path.join() and os.path.relpath() now raise a TypeError with more helpful error message for unsupported or mismatched types of arguments.

- bpo-22219: The zipfile module CLI now adds entries for directories (including empty directories) in ZIP file.

- bpo-22449: In the ssl.SSLContext.load_default_certs, consult the environmental variables SSL_CERT_DIR and SSL_CERT_FILE on Windows.

- bpo-22508: The email.__version__ variable has been removed; the email code is no longer shipped separately from the stdlib, and __version__ hasn’t been updated in several releases.

- bpo-20076: Added non derived UTF-8 aliases to locale aliases table.

- bpo-20079: Added locales supported in glibc 2.18 to locale alias table.

- bpo-20218: Added convenience methods read_text/write_text and read_bytes/ write_bytes to pathlib.Path objects.

- bpo-22396: On 32-bit AIX platform, don’t expose os.posix_fadvise() nor os.posix_fallocate() because their prototypes in system headers are wrong.

- bpo-22517: When an io.BufferedRWPair object is deallocated, clear its weakrefs.

- bpo-22437: Number of capturing groups in regular expression is no longer limited by 100.

- bpo-17442: InteractiveInterpreter now displays the full chained traceback in its showtraceback method, to match the built in interactive interpreter.

- bpo-23392: Added tests for marshal C API that works with FILE*.

- bpo-10510: distutils register and upload methods now use HTML standards compliant CRLF line endings.

- bpo-9850: Fixed macpath.join() for empty first component. Patch by Oleg Oshmyan.

- bpo-5309: distutils’ build and build_ext commands now accept a `-j` option to enable parallel building of extension modules.

- bpo-22448: Improve canceled timer handles cleanup to prevent unbound memory usage. Patch by Joshua Moore-Oliva.

- bpo-22427: TemporaryDirectory no longer attempts to clean up twice when used in the with statement in generator.

- bpo-22362: Forbidden ambiguous octal escapes out of range 0-0o377 in regular expressions.

- bpo-20912: Now directories added to ZIP file have correct Unix and MS-DOS directory attributes.

- bpo-21866: ZipFile.close() no longer writes ZIP64 central directory records if allowZip64 is false.

- bpo-22278: Fix urljoin problem with relative urls, a regression observed after changes to issue22118 were submitted.

- bpo-22415: Fixed debugging output of the GROUPREF_EXISTS opcode in the re module. Removed trailing spaces in debugging output.

- bpo-22423: Unhandled exception in thread no longer causes unhandled AttributeError when sys.stderr is None.

- bpo-21332: Ensure that `bufsize=1` in subprocess.Popen() selects line buffering, rather than block buffering. Patch by Akira Li.

- bpo-21091: Fix API bug: email.message.EmailMessage.is_attachment is now a method.

- bpo-21079: Fix email.message.EmailMessage.is_attachment to return the correct result when the header has parameters as well as a value.

- bpo-22247: Add NNTPError to nntplib.__all__.

- bpo-22366: urllib.request.urlopen will accept a context object (SSLContext) as an argument which will then be used for HTTPS connection. Patch by Alex Gaynor.

- bpo-4180: The warnings registries are now reset when the filters are modified.

- bpo-22419: Limit the length of incoming HTTP request in wsgiref server to 65536 bytes and send a 414 error code for higher lengths. Patch contributed by Devin Cook.

- Lax cookie parsing in http.cookies could be a security issue when combined with non-standard cookie handling in some web browsers. Reported by Sergey Bobrov.

- bpo-20537: logging methods now accept an exception instance as well as a Boolean value or exception tuple. Thanks to Yury Selivanov for the patch.

- bpo-22384: An exception in Tkinter callback no longer crashes the program when it is run with pythonw.exe.

- bpo-22168: Prevent turtle AttributeError with non-default Canvas on OS X.

- bpo-21147: sqlite3 now raises an exception if the request contains a null character instead of truncating it. Based on patch by Victor Stinner.

- bpo-13968: The glob module now supports recursive search in subdirectories using the `**` pattern.

- bpo-21951: Fixed a crash in Tkinter on AIX when called Tcl command with empty string or tuple argument.

- bpo-21951: Tkinter now most likely raises MemoryError instead of crash if the memory allocation fails.

- bpo-22338: Fix a crash in the json module on memory allocation failure.

- bpo-12410: imaplib.IMAP4 now supports the context management protocol. Original patch by Tarek Ziadé.

- bpo-21270: We now override tuple methods in mock.call objects so that they can be used as normal call attributes.

- bpo-16662: `load_tests()` is now unconditionally run when it is present in a package’s `__init__.py`. `TestLoader.loadTestsFromModule()` still accepts use_load_tests, but it is deprecated and ignored. A new keyword-only attribute `pattern` is added and documented. Patch given by Robert Collins, tweaked by Barry Warsaw.

- bpo-22226: First letter no longer is stripped from the “status” key in the result of Treeview.heading().

- bpo-19524: Fixed resource leak in the HTTP connection when an invalid response is received. Patch by Martin Panter.

- bpo-20421: Add a .version() method to SSL sockets exposing the actual protocol version in use.

- bpo-19546: configparser exceptions no longer expose implementation details. Chained KeyErrors are removed, which leads to cleaner tracebacks. Patch by Claudiu Popa.

- bpo-22051: turtledemo no longer reloads examples to re-run them. Initialization of variables and gui setup should be done in main(), which is called each time a demo is run, but not on import.

- bpo-21933: Turtledemo users can change the code font size with a menu selection or control(command) ‘-’ or ‘+’ or control-mousewheel. Original patch by Lita Cho.

- bpo-21597: The separator between the turtledemo text pane and the drawing canvas can now be grabbed and dragged with a mouse. The code text pane can be widened to easily view or copy the full width of the text. The canvas can be widened on small screens. Original patches by Jan Kanis and Lita Cho.

- bpo-18132: Turtledemo buttons no longer disappear when the window is shrunk. Original patches by Jan Kanis and Lita Cho.

- bpo-22043: time.monotonic() is now always available. `threading.Lock.acquire()`, `threading.RLock.acquire()` and socket operations now use a monotonic clock, instead of the system clock, when a timeout is used.

- bpo-21527: Add a default number of workers to ThreadPoolExecutor equal to 5 times the number of CPUs. Patch by Claudiu Popa.

- bpo-22216: smtplib now resets its state more completely after a quit. The most obvious consequence of the previous behavior was a STARTTLS failure during a connect/starttls/quit/connect/starttls sequence.

- bpo-22098: ctypes’ BigEndianStructure and LittleEndianStructure now define an empty __slots__ so that subclasses don’t always get an instance dict. Patch by Claudiu Popa.

- bpo-22185: Fix an occasional RuntimeError in threading.Condition.wait() caused by mutation of the waiters queue without holding the lock. Patch by Doug Zongker.

- bpo-22287: On UNIX, _PyTime_gettimeofday() now uses clock_gettime(CLOCK_REALTIME) if available. As a side effect, Python now depends on the librt library on Solaris and on Linux (only with glibc older than 2.17).

- bpo-22182: Use e.args to unpack exceptions correctly in distutils.file_util.move_file. Patch by Claudiu Popa.

- The webbrowser module now uses subprocess’s start_new_session=True rather than a potentially risky preexec_fn=os.setsid call.

- bpo-22042: signal.set_wakeup_fd(fd) now raises an exception if the file descriptor is in blocking mode.

- bpo-16808: inspect.stack() now returns a named tuple instead of a tuple. Patch by Daniel Shahaf.

- bpo-22236: Fixed Tkinter images copying operations in NoDefaultRoot mode.

- bpo-2527: Add a globals argument to timeit functions, in order to override the globals namespace in which the timed code is executed. Patch by Ben Roberts.

- bpo-22118: Switch urllib.parse to use RFC 3986 semantics for the resolution of relative URLs, rather than RFCs 1808 and 2396. Patch by Demian Brecht.

- bpo-21549: Added the “members” parameter to TarFile.list().

- bpo-19628: Allow compileall recursion depth to be specified with a -r option.

- bpo-15696: Add a __sizeof__ implementation for mmap objects on Windows.

- bpo-22068: Avoided reference loops with Variables and Fonts in Tkinter.

- bpo-22165: SimpleHTTPRequestHandler now supports undecodable file names.

- bpo-15381: Optimized line reading in io.BytesIO.

- bpo-8797: Raise HTTPError on failed Basic Authentication immediately. Initial patch by Sam Bull.

- bpo-20729: Restored the use of lazy iterkeys()/itervalues()/iteritems() in the mailbox module.

- bpo-21448: Changed FeedParser feed() to avoid O(n2) behavior when parsing long line. Original patch by Raymond Hettinger.

- bpo-22184: The functools LRU Cache decorator factory now gives an earlier and clearer error message when the user forgets the required parameters.

- bpo-17923: glob() patterns ending with a slash no longer match non-dirs on AIX. Based on patch by Delhallt.

- bpo-21725: Added support for RFC 6531 (SMTPUTF8) in smtpd.

- bpo-22176: Update the ctypes module’s libffi to v3.1. This release adds support for the Linux AArch64 and POWERPC ELF ABIv2 little endian architectures.

- bpo-5411: Added support for the “xztar” format in the shutil module.

- bpo-21121: Don’t force 3rd party C extensions to be built with -Werror=declaration-after-statement.

- bpo-21975: Fixed crash when using uninitialized sqlite3.Row (in particular when unpickling pickled sqlite3.Row). sqlite3.Row is now initialized in the __new__() method.

- bpo-20170: Convert posixmodule to use Argument Clinic.

- bpo-21539: Add an exists_ok argument to `Pathlib.mkdir()` to mimic `mkdir -p` and `os.makedirs()` functionality. When true, ignore `FileExistsErrors`. Patch by Berker Peksag.

- bpo-22127: Bypass IDNA for pure-ASCII host names in the socket module (in particular for numeric IPs).

- bpo-21047: set the default value for the convert_charrefs argument of HTMLParser to True. Patch by Berker Peksag.

- Add an __all__ to html.entities.

- bpo-15114: the strict mode and argument of HTMLParser, HTMLParser.error, and the HTMLParserError exception have been removed.

- bpo-22085: Dropped support of Tk 8.3 in Tkinter.

- bpo-21580: Now Tkinter correctly handles bytes arguments passed to Tk. In particular this allows initializing images from binary data.

- bpo-22003: When initialized from a bytes object, io.BytesIO() now defers making a copy until it is mutated, improving performance and memory use on some use cases. Patch by David Wilson.

- bpo-22018: On Windows, signal.set_wakeup_fd() now also supports sockets. A side effect is that Python depends to the WinSock library.

- bpo-22054: Add os.get_blocking() and os.set_blocking() functions to get and set the blocking mode of a file descriptor (False if the O_NONBLOCK flag is set, True otherwise). These functions are not available on Windows.

- bpo-17172: Make turtledemo start as active on OS X even when run with subprocess. Patch by Lita Cho.

- bpo-21704: Fix build error for _multiprocessing when semaphores are not available. Patch by Arfrever Frehtes Taifersar Arahesis.

- bpo-20173: Convert sha1, sha256, sha512 and md5 to ArgumentClinic. Patch by Vajrasky Kok.

- Fix repr(_socket.socket) on Windows 64-bit: don’t fail with OverflowError on closed socket. repr(socket.socket) already works fine.

- bpo-22033: Reprs of most Python implemented classes now contain actual class name instead of hardcoded one.

- bpo-21947: The dis module can now disassemble generator-iterator objects based on their gi_code attribute. Patch by Clement Rouault.

- bpo-16133: The asynchat.async_chat.handle_read() method now ignores BlockingIOError exceptions.

- bpo-22044: Fixed premature DECREF in call_tzinfo_method. Patch by Tom Flanagan.

- bpo-19884: readline: Disable the meta modifier key if stdout is not a terminal to not write the ANSI sequence `"\033[1034h"` into stdout. This sequence is used on some terminal (ex: TERM=xterm-256color”) to enable support of 8 bit characters.

- bpo-4350: Removed a number of out-of-dated and non-working for a long time Tkinter methods.

- bpo-6167: Scrollbar.activate() now returns the name of active element if the argument is not specified. Scrollbar.set() now always accepts only 2 arguments.

- bpo-15275: Clean up and speed up the ntpath module.

- bpo-21888: plistlib’s load() and loads() now work if the fmt parameter is specified.

- bpo-22032: __qualname__ instead of __name__ is now always used to format fully qualified class names of Python implemented classes.

- bpo-22031: Reprs now always use hexadecimal format with the “0x” prefix when contain an id in form “ at 0x…”.

- bpo-22018: signal.set_wakeup_fd() now raises an OSError instead of a ValueError on `fstat()` failure.

- bpo-21044: tarfile.open() now handles fileobj with an integer ‘name’ attribute. Based on patch by Antoine Pietri.

- bpo-21966: Respect -q command-line option when code module is ran.

- bpo-19076: Don’t pass the redundant ‘file’ argument to self.error().

- bpo-16382: Improve exception message of warnings.warn() for bad category. Initial patch by Phil Elson.

- bpo-21932: os.read() now uses a `Py_ssize_t()` type instead of int for the size to support reading more than 2 GB at once. On Windows, the size is truncated to INT_MAX. As any call to os.read(), the OS may read less bytes than the number of requested bytes.

- bpo-21942: Fixed source file viewing in pydoc’s server mode on Windows.

- bpo-11259: asynchat.async_chat().set_terminator() now raises a ValueError if the number of received bytes is negative.

- bpo-12523: asynchat.async_chat.push() now raises a TypeError if it doesn’t get a bytes string

- bpo-21707: Add missing kwonlyargcount argument to ModuleFinder.replace_paths_in_code().

- bpo-20639: calling Path.with_suffix(‘’) allows removing the suffix again. Patch by July Tikhonov.

- bpo-21714: Disallow the construction of invalid paths using Path.with_name(). Original patch by Antony Lee.

- bpo-15014: Added ‘auth’ method to smtplib to make implementing auth mechanisms simpler, and used it internally in the login method.

- bpo-21151: Fixed a segfault in the winreg module when `None` is passed as a `REG_BINARY` value to SetValueEx. Patch by John Ehresman.

- bpo-21090: io.FileIO.readall() does not ignore I/O errors anymore. Before, it ignored I/O errors if at least the first C call read() succeed.

- bpo-5800: headers parameter of wsgiref.headers.Headers is now optional. Initial patch by Pablo Torres Navarrete and SilentGhost.

- bpo-21781: ssl.RAND_add() now supports strings longer than 2 GB.

- bpo-21679: Prevent extraneous fstat() calls during open(). Patch by Bohuslav Kabrda.

- bpo-21863: cProfile now displays the module name of C extension functions, in addition to their own name.

- bpo-11453: asyncore: emit a ResourceWarning when an unclosed file_wrapper object is destroyed. The destructor now closes the file if needed. The close() method can now be called twice: the second call does nothing.

- bpo-21858: Better handling of Python exceptions in the sqlite3 module.

- bpo-21476: Make sure the email.parser.BytesParser TextIOWrapper is discarded after parsing, so the input file isn’t unexpectedly closed.

- bpo-20295: imghdr now recognizes OpenEXR format images.

- bpo-21729: Used the “with” statement in the dbm.dumb module to ensure files closing. Patch by Claudiu Popa.

- bpo-21491: socketserver: Fix a race condition in child processes reaping.

- bpo-21719: Added the `st_file_attributes` field to os.stat_result on Windows.

- bpo-21832: Require named tuple inputs to be exact strings.

- bpo-21722: The distutils “upload” command now exits with a non-zero return code when uploading fails. Patch by Martin Dengler.

- bpo-21723: asyncio.Queue: support any type of number (ex: float) for the maximum size. Patch written by Vajrasky Kok.

- bpo-21711: support for “site-python” directories has now been removed from the site module (it was deprecated in 3.4).

- bpo-17552: new socket.sendfile() method allowing a file to be sent over a socket by using high-performance os.sendfile() on UNIX. Patch by Giampaolo Rodola’.

- bpo-18039: dbm.dump.open() now always creates a new database when the flag has the value ‘n’. Patch by Claudiu Popa.

- bpo-21326: Add a new is_closed() method to asyncio.BaseEventLoop. run_forever() and run_until_complete() methods of asyncio.BaseEventLoop now raise an exception if the event loop was closed.

- bpo-21766: Prevent a security hole in CGIHTTPServer by URL unquoting paths before checking for a CGI script at that path.

- bpo-21310: Fixed possible resource leak in failed open().

- bpo-21256: Printout of keyword args should be in deterministic order in a mock function call. This will help to write better doctests.

- bpo-21677: Fixed chaining nonnormalized exceptions in io close() methods.

- bpo-11709: Fix the pydoc.help function to not fail when sys.stdin is not a valid file.

- bpo-21515: tempfile.TemporaryFile now uses os.O_TMPFILE flag is available.

- bpo-13223: Fix pydoc.writedoc so that the HTML documentation for methods that use ‘self’ in the example code is generated correctly.

- bpo-21463: In urllib.request, fix pruning of the FTP cache.

- bpo-21618: The subprocess module could fail to close open fds that were inherited by the calling process and already higher than POSIX resource limits would otherwise allow. On systems with a functioning /proc/self/fd or /dev/fd interface the max is now ignored and all fds are closed.

- bpo-20383: Introduce importlib.util.module_from_spec() as the preferred way to create a new module.

- bpo-21552: Fixed possible integer overflow of too long string lengths in the tkinter module on 64-bit platforms.

- bpo-14315: The zipfile module now ignores extra fields in the central directory that are too short to be parsed instead of letting a struct.unpack error bubble up as this “bad data” appears in many real world zip files in the wild and is ignored by other zip tools.

- bpo-13742: Added “key” and “reverse” parameters to heapq.merge(). (First draft of patch contributed by Simon Sapin.)

- bpo-21402: tkinter.ttk now works when default root window is not set.

- bpo-3015: `_tkinter.create()` now creates `tkapp` object with `wantobjects=1` by default.

- bpo-10203: sqlite3.Row now truly supports sequence protocol. In particular it supports reverse() and negative indices. Original patch by Claudiu Popa.

- bpo-18807: If copying (no symlinks) specified for a venv, then the python interpreter aliases (python, python3) are now created by copying rather than symlinking.

- bpo-20197: Added support for the WebP image type in the imghdr module. Patch by Fabrice Aneche and Claudiu Popa.

- bpo-21513: Speedup some properties of IP addresses (IPv4Address, IPv6Address) such as .is_private or .is_multicast.

- bpo-21137: Improve the repr for threading.Lock() and its variants by showing the “locked” or “unlocked” status. Patch by Berker Peksag.

- bpo-21538: The plistlib module now supports loading of binary plist files when reference or offset size is not a power of two.

- bpo-21455: Add a default backlog to socket.listen().

- bpo-21525: Most Tkinter methods which accepted tuples now accept lists too.

- bpo-22166: With the assistance of a new internal _codecs._forget_codec helping function, test_codecs now clears the encoding caches to avoid the appearance of a reference leak

- bpo-22236: Tkinter tests now don’t reuse default root window. New root window is created for every test class.

- bpo-10744: Fix PEP 3118 format strings on ctypes objects with a nontrivial shape.

- bpo-20826: Optimize ipaddress.collapse_addresses().

- bpo-21487: Optimize ipaddress.summarize_address_range() and ipaddress.{IPv4Network,IPv6Network}.subnets().

- bpo-21486: Optimize parsing of netmasks in ipaddress.IPv4Network and ipaddress.IPv6Network.

- bpo-13916: Disallowed the surrogatepass error handler for non UTF-* encodings.

- bpo-20998: Fixed re.fullmatch() of repeated single character pattern with ignore case. Original patch by Matthew Barnett.

- bpo-21075: fileinput.FileInput now reads bytes from standard stream if binary mode is specified. Patch by Sam Kimbrel.

- bpo-19775: Add a samefile() method to pathlib Path objects. Initial patch by Vajrasky Kok.

- bpo-21226: Set up modules properly in PyImport_ExecCodeModuleObject (and friends).

- bpo-21398: Fix a unicode error in the pydoc pager when the documentation contains characters not encodable to the stdout encoding.

- bpo-16531: ipaddress.IPv4Network and ipaddress.IPv6Network now accept an (address, netmask) tuple argument, so as to easily construct network objects from existing addresses.

- bpo-21156: importlib.abc.InspectLoader.source_to_code() is now a staticmethod.

- bpo-21424: Simplified and optimized heaqp.nlargest() and nmsmallest() to make fewer tuple comparisons.

- bpo-21396: Fix TextIOWrapper(…, write_through=True) to not force a flush() on the underlying binary stream. Patch by akira.

- bpo-18314: Unlink now removes junctions on Windows. Patch by Kim Gräsman

- bpo-21088: Bugfix for curses.window.addch() regression in 3.4.0. In porting to Argument Clinic, the first two arguments were reversed.

- bpo-21407: _decimal: The module now supports function signatures.

- bpo-10650: Remove the non-standard ‘watchexp’ parameter from the Decimal.quantize() method in the Python version. It had never been present in the C version.

- bpo-21469: Reduced the risk of false positives in robotparser by checking to make sure that robots.txt has been read or does not exist prior to returning True in can_fetch().

- bpo-19414: Have the OrderedDict mark deleted links as unusable. This gives an early failure if the link is deleted during iteration.

- bpo-21421: Add __slots__ to the MappingViews ABC. Patch by Josh Rosenberg.

- bpo-21101: Eliminate double hashing in the C speed-up code for collections.Counter().

- bpo-21321: itertools.islice() now releases the reference to the source iterator when the slice is exhausted. Patch by Anton Afanasyev.

- bpo-21057: TextIOWrapper now allows the underlying binary stream’s read() or read1() method to return an arbitrary bytes-like object (such as a memoryview). Patch by Nikolaus Rath.

- bpo-20951: SSLSocket.send() now raises either SSLWantReadError or SSLWantWriteError on a non-blocking socket if the operation would block. Previously, it would return 0. Patch by Nikolaus Rath.

- bpo-13248: removed previously deprecated asyncore.dispatcher __getattr__ cheap inheritance hack.

- bpo-9815: assertRaises now tries to clear references to local variables in the exception’s traceback.

- bpo-19940: ssl.cert_time_to_seconds() now interprets the given time string in the UTC timezone (as specified in RFC 5280), not the local timezone.

- bpo-13204: Calling sys.flags.__new__ would crash the interpreter, now it raises a TypeError.

- bpo-19385: Make operations on a closed dbm.dumb database always raise the same exception.

- bpo-21207: Detect when the os.urandom cached fd has been closed or replaced, and open it anew.

- bpo-21291: subprocess’s Popen.wait() is now thread safe so that multiple threads may be calling wait() or poll() on a Popen instance at the same time without losing the Popen.returncode value.

- bpo-21127: Path objects can now be instantiated from str subclass instances (such as `numpy.str_`).

- bpo-15002: urllib.response object to use _TemporaryFileWrapper (and _TemporaryFileCloser) facility. Provides a better way to handle file descriptor close. Patch contributed by Christian Theune.

- bpo-12220: mindom now raises a custom ValueError indicating it doesn’t support spaces in URIs instead of letting a ‘split’ ValueError bubble up.

- bpo-21068: The ssl.PROTOCOL* constants are now enum members.

- bpo-21276: posixmodule: Don’t define USE_XATTRS on KFreeBSD and the Hurd.

- bpo-21262: New method assert_not_called for Mock. It raises AssertionError if the mock has been called.

- bpo-21238: New keyword argument `unsafe` to Mock. It raises `AttributeError` incase of an attribute startswith assert or assret.

- bpo-20896: ssl.get_server_certificate() now uses PROTOCOL_SSLv23, not PROTOCOL_SSLv3, for maximum compatibility.

- bpo-21239: patch.stopall() didn’t work deterministically when the same name was patched more than once.

- bpo-21203: Updated fileConfig and dictConfig to remove inconsistencies. Thanks to Jure Koren for the patch.

- bpo-21222: Passing name keyword argument to mock.create_autospec now works.

- bpo-21197: Add lib64 -> lib symlink in venvs on 64-bit non-OS X POSIX.

- bpo-17498: Some SMTP servers disconnect after certain errors, violating strict RFC conformance. Instead of losing the error code when we issue the subsequent RSET, smtplib now returns the error code and defers raising the SMTPServerDisconnected error until the next command is issued.

- bpo-17826: setting an iterable side_effect on a mock function created by create_autospec now works. Patch by Kushal Das.

- bpo-7776: Fix `Host:` header and reconnection when using http.client.HTTPConnection.set_tunnel(). Patch by Nikolaus Rath.

- bpo-20968: unittest.mock.MagicMock now supports division. Patch by Johannes Baiter.

- bpo-21529: Fix arbitrary memory access in JSONDecoder.raw_decode with a negative second parameter. Bug reported by Guido Vranken. (See also: CVE 2014-4616)

- bpo-21169: getpass now handles non-ascii characters that the input stream encoding cannot encode by re-encoding using the replace error handler.

- bpo-21171: Fixed undocumented filter API of the rot13 codec. Patch by Berker Peksag.

- bpo-20539: Improved math.factorial error message for large positive inputs and changed exception type (OverflowError -> ValueError) for large negative inputs.

- bpo-21172: isinstance check relaxed from dict to collections.Mapping.

- bpo-21155: asyncio.EventLoop.create_unix_server() now raises a ValueError if path and sock are specified at the same time.

- bpo-21136: Avoid unnecessary normalization of Fractions resulting from power and other operations. Patch by Raymond Hettinger.

- bpo-17621: Introduce importlib.util.LazyLoader.

- bpo-21076: signal module constants were turned into enums. Patch by Giampaolo Rodola’.

- bpo-20636: Improved the repr of Tkinter widgets.

- bpo-19505: The items, keys, and values views of OrderedDict now support reverse iteration using reversed().

- bpo-21149: Improved thread-safety in logging cleanup during interpreter shutdown. Thanks to Devin Jeanpierre for the patch.

- bpo-21058: Fix a leak of file descriptor in `tempfile.NamedTemporaryFile()`, close the file descriptor if `io.open()` fails

- bpo-21200: Return None from pkgutil.get_loader() when __spec__ is missing.

- bpo-21013: Enhance ssl.create_default_context() when used for server side sockets to provide better security by default.

- bpo-20145: `assertRaisesRegex` and `assertWarnsRegex` now raise a `TypeError` if the second argument is not a string or compiled regex.

- bpo-20633: Replace relative import by absolute import.

- bpo-20980: Stop wrapping exception when using ThreadPool.

- bpo-21082: In os.makedirs, do not set the process-wide umask. Note this changes behavior of makedirs when exist_ok=True.

- bpo-20990: Fix issues found by pyflakes for multiprocessing.

- bpo-21015: SSL contexts will now automatically select an elliptic curve for ECDH key exchange on OpenSSL 1.0.2 and later, and otherwise default to “prime256v1”.

- bpo-21000: Improve the command-line interface of json.tool.

- bpo-20995: Enhance default ciphers used by the ssl module to enable better security and prioritize perfect forward secrecy.

- bpo-20884: Don’t assume that __file__ is defined on importlib.__init__.

- bpo-21499: Ignore __builtins__ in several test_importlib.test_api tests.

- bpo-20627: xmlrpc.client.ServerProxy is now a context manager.

- bpo-19165: The formatter module now raises DeprecationWarning instead of PendingDeprecationWarning.

- bpo-13936: Remove the ability of datetime.time instances to be considered false in boolean contexts.

- bpo-18931: selectors module now supports /dev/poll on Solaris. Patch by Giampaolo Rodola’.

- bpo-19977: When the `LC_TYPE` locale is the POSIX locale (`C` locale), `sys.stdin` and `sys.stdout` are now using the `surrogateescape` error handler, instead of the `strict` error handler.

- bpo-20574: Implement incremental decoder for cp65001 code (Windows code page 65001, Microsoft UTF-8).

- bpo-20879: Delay the initialization of encoding and decoding tables for base32, ascii85 and base85 codecs in the base64 module, and delay the initialization of the unquote_to_bytes() table of the urllib.parse module, to not waste memory if these modules are not used.

- bpo-19157: Include the broadcast address in the usuable hosts for IPv6 in ipaddress.

- bpo-11599: When an external command (e.g. compiler) fails, distutils now prints out the whole command line (instead of just the command name) if the environment variable DISTUTILS_DEBUG is set.

- bpo-4931: distutils should not produce unhelpful “error: None” messages anymore. distutils.util.grok_environment_error is kept but doc-deprecated.

- bpo-20875: Prevent possible gzip “‘read’ is not defined” NameError. Patch by Claudiu Popa.

- bpo-11558: `email.message.Message.attach` now returns a more useful error message if `attach` is called on a message for which `is_multipart` is False.

- bpo-20283: RE pattern methods now accept the string keyword parameters as documented. The pattern and source keyword parameters are left as deprecated aliases.

- bpo-20778: Fix modulefinder to work with bytecode-only modules.

- bpo-20791: copy.copy() now doesn’t make a copy when the input is a bytes object. Initial patch by Peter Otten.

- bpo-19748: On AIX, time.mktime() now raises an OverflowError for year outsize range [1902; 2037].

- bpo-19573: inspect.signature: Use enum for parameter kind constants.

- bpo-20726: inspect.signature: Make Signature and Parameter picklable.

- bpo-17373: Add inspect.Signature.from_callable method.

- bpo-20378: Improve repr of inspect.Signature and inspect.Parameter.

- bpo-20816: Fix inspect.getcallargs() to raise correct TypeError for missing keyword-only arguments. Patch by Jeremiah Lowin.

- bpo-20817: Fix inspect.getcallargs() to fail correctly if more than 3 arguments are missing. Patch by Jeremiah Lowin.

- bpo-6676: Ensure a meaningful exception is raised when attempting to parse more than one XML document per pyexpat xmlparser instance. (Original patches by Hirokazu Yamamoto and Amaury Forgeot d’Arc, with suggested wording by David Gutteridge)

- bpo-21117: Fix inspect.signature to better support functools.partial. Due to the specifics of functools.partial implementation, positional-or-keyword arguments passed as keyword arguments become keyword-only.

- bpo-20334: inspect.Signature and inspect.Parameter are now hashable. Thanks to Antony Lee for bug reports and suggestions.

- bpo-15916: doctest.DocTestSuite returns an empty unittest.TestSuite instead of raising ValueError if it finds no tests

- bpo-21209: Fix asyncio.tasks.CoroWrapper to workaround a bug in yield-from implementation in CPythons prior to 3.4.1.

- asyncio: Add gi_{frame,running,code} properties to CoroWrapper (upstream bpo-163).

- bpo-21311: Avoid exception in _osx_support with non-standard compiler configurations. Patch by John Szakmeister.

- bpo-11571: Ensure that the turtle window becomes the topmost window when launched on OS X.

- bpo-21801: Validate that __signature__ is None or an instance of Signature.

- bpo-21923: Prevent AttributeError in distutils.sysconfig.customize_compiler due to possible uninitialized _config_vars.

- bpo-21323: Fix http.server to again handle scripts in CGI subdirectories, broken by the fix for security bpo-19435. Patch by Zach Byrne.

- bpo-22733: Fix ffi_prep_args not zero-extending argument values correctly on 64-bit Windows.

- bpo-23302: Default to TCP_NODELAY=1 upon establishing an HTTPConnection. Removed use of hard-coded MSS as it’s an optimization that’s no longer needed with Nagle disabled.

### IDLE

- bpo-20577: Configuration of the max line length for the FormatParagraph extension has been moved from the General tab of the Idle preferences dialog to the FormatParagraph tab of the Config Extensions dialog. Patch by Tal Einat.

- bpo-16893: Update Idle doc chapter to match current Idle and add new information.

- bpo-3068: Add Idle extension configuration dialog to Options menu. Changes are written to HOME/.idlerc/config-extensions.cfg. Original patch by Tal Einat.

- bpo-16233: A module browser (File : Class Browser, Alt+C) requires an editor window with a filename. When Class Browser is requested otherwise, from a shell, output window, or ‘Untitled’ editor, Idle no longer displays an error box. It now pops up an Open Module box (Alt+M). If a valid name is entered and a module is opened, a corresponding browser is also opened.

- bpo-4832: Save As to type Python files automatically adds .py to the name you enter (even if your system does not display it). Some systems automatically add .txt when type is Text files.

- bpo-21986: Code objects are not normally pickled by the pickle module. To match this, they are no longer pickled when running under Idle.

- bpo-17390: Adjust Editor window title; remove ‘Python’, move version to end.

- bpo-14105: Idle debugger breakpoints no longer disappear when inserting or deleting lines.

- bpo-17172: Turtledemo can now be run from Idle. Currently, the entry is on the Help menu, but it may move to Run. Patch by Ramchandra Apt and Lita Cho.

- bpo-21765: Add support for non-ascii identifiers to HyperParser.

- bpo-21940: Add unittest for WidgetRedirector. Initial patch by Saimadhav Heblikar.

- bpo-18592: Add unittest for SearchDialogBase. Patch by Phil Webster.

- bpo-21694: Add unittest for ParenMatch. Patch by Saimadhav Heblikar.

- bpo-21686: add unittest for HyperParser. Original patch by Saimadhav Heblikar.

- bpo-12387: Add missing upper(lower)case versions of default Windows key bindings for Idle so Caps Lock does not disable them. Patch by Roger Serwy.

- bpo-21695: Closing a Find-in-files output window while the search is still in progress no longer closes Idle.

- bpo-18910: Add unittest for textView. Patch by Phil Webster.

- bpo-18292: Add unittest for AutoExpand. Patch by Saihadhav Heblikar.

- bpo-18409: Add unittest for AutoComplete. Patch by Phil Webster.

- bpo-21477: htest.py - Improve framework, complete set of tests. Patches by Saimadhav Heblikar

- bpo-18104: Add idlelib/idle_test/htest.py with a few sample tests to begin consolidating and improving human-validated tests of Idle. Change other files as needed to work with htest. Running the module as __main__ runs all tests.

- bpo-21139: Change default paragraph width to 72, the PEP 8 recommendation.

- bpo-21284: Paragraph reformat test passes after user changes reformat width.

- bpo-17654: Ensure IDLE menus are customized properly on OS X for non-framework builds and for all variants of Tk.

- bpo-23180: Rename IDLE “Windows” menu item to “Window”. Patch by Al Sweigart.

### Build

- bpo-15506: Use standard PKG_PROG_PKG_CONFIG autoconf macro in the configure script.

- bpo-22935: Allow the ssl module to be compiled if openssl doesn’t support SSL 3.

- bpo-22592: Drop support of the Borland C compiler to build Python. The distutils module still supports it to build extensions.

- bpo-22591: Drop support of MS-DOS, especially of the DJGPP compiler (MS-DOS port of GCC).

- bpo-16537: Check whether self.extensions is empty in setup.py. Patch by Jonathan Hosmer.

- bpo-22359: Remove incorrect uses of recursive make. Patch by Jonas Wagner.

- bpo-21958: Define HAVE_ROUND when building with Visual Studio 2013 and above. Patch by Zachary Turner.

- bpo-18093: the programs that embed the CPython runtime are now in a separate “Programs” directory, rather than being kept in the Modules directory.

- bpo-15759: “make suspicious”, “make linkcheck” and “make doctest” in Doc/ now display special message when and only when there are failures.

- bpo-21141: The Windows build process no longer attempts to find Perl, instead relying on OpenSSL source being configured and ready to build. The `PCbuild\build_ssl.py` script has been re-written and re-named to `PCbuild\prepare_ssl.py`, and takes care of configuring OpenSSL source for both 32 and 64 bit platforms. OpenSSL sources obtained from svn.python.org will always be pre-configured and ready to build.

- bpo-21037: Add a build option to enable AddressSanitizer support.

- bpo-19962: The Windows build process now creates “python.bat” in the root of the source tree, which passes all arguments through to the most recently built interpreter.

- bpo-21285: Refactor and fix curses configure check to always search in a ncursesw directory.

- bpo-15234: For BerkeleyDB and Sqlite, only add the found library and include directories if they aren’t already being searched. This avoids an explicit runtime library dependency.

- bpo-17861: Tools/scripts/generate_opcode_h.py automatically regenerates Include/opcode.h from Lib/opcode.py if the latter gets any change.

- bpo-20644: OS X installer build support for documentation build changes in 3.4.1: assume externally supplied sphinx-build is available in /usr/bin.

- bpo-20022: Eliminate use of deprecated bundlebuilder in OS X builds.

- bpo-15968: Incorporated Tcl, Tk, and Tix builds into the Windows build solution.

- bpo-17095: Fix Modules/Setup shared support.

- bpo-21811: Anticipated fixes to support OS X versions > 10.9.

- bpo-21166: Prevent possible segfaults and other random failures of python –generate-posix-vars in pybuilddir.txt build target.

- bpo-18096: Fix library order returned by python-config.

- bpo-17219: Add library build dir for Python extension cross-builds.

- bpo-22919: Windows build updated to support VC 14.0 (Visual Studio 2015), which will be used for the official release.

- bpo-21236: Build _msi.pyd with cabinet.lib instead of fci.lib

- bpo-17128: Use private version of OpenSSL for OS X 10.5+ installer.

### C API

- bpo-14203: Remove obsolete support for view==NULL in PyBuffer_FillInfo(), bytearray_getbuffer(), bytesiobuf_getbuffer() and array_buffer_getbuf(). All functions now raise BufferError in that case.

- bpo-22445: PyBuffer_IsContiguous() now implements precise contiguity tests, compatible with NumPy’s NPY_RELAXED_STRIDES_CHECKING compilation flag. Previously the function reported false negatives for corner cases.

- bpo-22079: PyType_Ready() now checks that statically allocated type has no dynamically allocated bases.

- bpo-22453: Removed non-documented macro PyObject_REPR().

- bpo-18395: Rename `_Py_char2wchar()` to `Py_DecodeLocale()`, rename `_Py_wchar2char()` to `Py_EncodeLocale()`, and document these functions.

- bpo-21233: Add new C functions: PyMem_RawCalloc(), PyMem_Calloc(), PyObject_Calloc(), _PyObject_GC_Calloc(). bytes(int) is now using `calloc()` instead of `malloc()` for large objects which is faster and use less memory.

- bpo-20942: PyImport_ImportFrozenModuleObject() no longer sets __file__ to match what importlib does; this affects _frozen_importlib as well as any module loaded using imp.init_frozen().

### Documentation

- bpo-19548: Update the codecs module documentation to better cover the distinction between text encodings and other codecs, together with other clarifications. Patch by Martin Panter.

- bpo-22394: Doc/Makefile now supports `make venv PYTHON=../python` to create a venv for generating the documentation, e.g., `make html PYTHON=venv/bin/python3`.

- bpo-21514: The documentation of the json module now refers to new JSON RFC 7159 instead of obsoleted RFC 4627.

- bpo-21777: The binary sequence methods on bytes and bytearray are now documented explicitly, rather than assuming users will be able to derive the expected behaviour from the behaviour of the corresponding str methods.

- bpo-6916: undocument deprecated asynchat.fifo class.

- bpo-17386: Expanded functionality of the `Doc/make.bat` script to make it much more comparable to `Doc/Makefile`.

- bpo-21312: Update the thread_foobar.h template file to include newer threading APIs. Patch by Jack McCracken.

- bpo-21043: Remove the recommendation for specific CA organizations and to mention the ability to load the OS certificates.

- bpo-20765: Add missing documentation for PurePath.with_name() and PurePath.with_suffix().

- bpo-19407: New package installation and distribution guides based on the Python Packaging Authority tools. Existing guides have been retained as legacy links from the distutils docs, as they still contain some required reference material for tool developers that isn’t recorded anywhere else.

- bpo-19697: Document cases where __main__.__spec__ is None.

### Tests

- bpo-18982: Add tests for CLI of the calendar module.

- bpo-19548: Added some additional checks to test_codecs to ensure that statements in the updated documentation remain accurate. Patch by Martin Panter.

- bpo-22838: All test_re tests now work with unittest test discovery.

- bpo-22173: Update lib2to3 tests to use unittest test discovery.

- bpo-16000: Convert test_curses to use unittest.

- bpo-21456: Skip two tests in test_urllib2net.py if _ssl module not present. Patch by Remi Pointel.

- bpo-20746: Fix test_pdb to run in refleak mode (-R). Patch by Xavier de Gaye.

- bpo-22060: test_ctypes has been somewhat cleaned up and simplified; it now uses unittest test discovery to find its tests.

- bpo-22104: regrtest.py no longer holds a reference to the suite of tests loaded from test modules that don’t define test_main().

- bpo-22111: Assorted cleanups in test_imaplib. Patch by Milan Oberkirch.

- bpo-22002: Added `load_package_tests` function to test.support and used it to implement/augment test discovery in test_asyncio, test_email, test_importlib, test_json, and test_tools.

- bpo-21976: Fix test_ssl to accept LibreSSL version strings. Thanks to William Orr.

- bpo-21918: Converted test_tools from a module to a package containing separate test files for each tested script.

- bpo-9554: Use modern unittest features in test_argparse. Initial patch by Denver Coneybeare and Radu Voicilas.

- bpo-20155: Changed HTTP method names in failing tests in test_httpservers so that packet filtering software (specifically Windows Base Filtering Engine) does not interfere with the transaction semantics expected by the tests.

- bpo-19493: Refactored the ctypes test package to skip tests explicitly rather than silently.

- bpo-18492: All resources are now allowed when tests are not run by regrtest.py.

- bpo-21634: Fix pystone micro-benchmark: use floor division instead of true division to benchmark integers instead of floating-point numbers. Set pystone version to 1.2. Patch written by Lennart Regebro.

- bpo-21605: Added tests for Tkinter images.

- bpo-21493: Added test for ntpath.expanduser(). Original patch by Claudiu Popa.

- bpo-19925: Added tests for the spwd module. Original patch by Vajrasky Kok.

- bpo-21522: Added Tkinter tests for Listbox.itemconfigure(), PanedWindow.paneconfigure(), and Menu.entryconfigure().

- bpo-17756: Fix test_code test when run from the installed location.

- bpo-17752: Fix distutils tests when run from the installed location.

- bpo-18604: Consolidated checks for GUI availability. All platforms now at least check whether Tk can be instantiated when the GUI resource is requested.

- bpo-21275: Fix a socket test on KFreeBSD.

- bpo-21223: Pass test_site/test_startup_imports when some of the extensions are built as builtins.

- bpo-20635: Added tests for Tk geometry managers.

- Add test case for freeze.

- bpo-20743: Fix a reference leak in test_tcl.

- bpo-21097: Move test_namespace_pkgs into test_importlib.

- bpo-21503: Use test_both() consistently in test_importlib.

- bpo-20939: Avoid various network test failures due to new redirect of http://www.python.org/ to https://www.python.org: use http://www.example.com instead.

- bpo-20668: asyncio tests no longer rely on tests.txt file. (Patch by Vajrasky Kok)

- bpo-21093: Prevent failures of ctypes test_macholib on OS X if a copy of libz exists in $HOME/lib or /usr/local/lib.

- bpo-22770: Prevent some Tk segfaults on OS X when running gui tests.

- bpo-23211: Workaround test_logging failure on some OS X 10.6 systems.

- bpo-23345: Prevent test_ssl failures with large OpenSSL patch level values (like 0.9.8zc).

### Tools/Demos

- bpo-22314: pydoc now works when the LINES environment variable is set.

- bpo-22615: Argument Clinic now supports the “type” argument for the int converter. This permits using the int converter with enums and typedefs.

- bpo-20076: The makelocalealias.py script no longer ignores UTF-8 mapping.

- bpo-20079: The makelocalealias.py script now can parse the SUPPORTED file from glibc sources and supports command line options for source paths.

- bpo-22201: Command-line interface of the zipfile module now correctly extracts ZIP files with directory entries. Patch by Ryan Wilson.

- bpo-22120: For functions using an unsigned integer return converter, Argument Clinic now generates a cast to that type for the comparison to -1 in the generated code. (This suppresses a compilation warning.)

- bpo-18974: Tools/scripts/diff.py now uses argparse instead of optparse.

- bpo-21906: Make Tools/scripts/md5sum.py work in Python 3. Patch by Zachary Ware.

- bpo-21629: Fix Argument Clinic’s “–converters” feature.

- Add support for `yield from` to 2to3.

- Add support for the PEP 465 matrix multiplication operator to 2to3.

- bpo-16047: Fix module exception list and __file__ handling in freeze. Patch by Meador Inge.

- bpo-11824: Consider ABI tags in freeze. Patch by Meador Inge.

- bpo-20535: PYTHONWARNING no longer affects the run_tests.py script. Patch by Arfrever Frehtes Taifersar Arahesis.

### Windows

- bpo-23260: Update Windows installer

- The bundled version of Tcl/Tk has been updated to 8.6.3. The most visible result of this change is the addition of new native file dialogs when running on Windows Vista or newer. See Tcl/Tk’s TIP 432 for more information. Also, this version of Tcl/Tk includes support for Windows 10.

- bpo-17896: The Windows build scripts now expect external library sources to be in `PCbuild\..\externals` rather than `PCbuild\..\..`.

- bpo-17717: The Windows build scripts now use a copy of NASM pulled from svn.python.org to build OpenSSL.

- bpo-21907: Improved the batch scripts provided for building Python.

- bpo-22644: The bundled version of OpenSSL has been updated to 1.0.1j.

- bpo-10747: Use versioned labels in the Windows start menu. Patch by Olive Kilburn.

- bpo-22980: .pyd files with a version and platform tag (for example, “.cp35-win32.pyd”) will now be loaded in preference to those without tags.

(For information about older versions, consult the HISTORY file.)