Integer Objects — Python 3.13.3 documentation
Description: All integers are implemented as “long” integer objects of arbitrary size. On error, most PyLong_As* APIs return(return type)-1 which cannot be distinguished from a number. Use PyErr_Occurred() to d...

# Integer Objects

All integers are implemented as “long” integer objects of arbitrary size.

On error, most `PyLong_As*` APIs return `(return type)-1` which cannot be distinguished from a number. Use `PyErr_Occurred()` to disambiguate.

type PyLongObject
  Part of the Limited API (as an opaque struct).

  This subtype of `PyObject` represents a Python integer object.

PyTypeObject PyLong_Type
  Part of the Stable ABI.

  This instance of `PyTypeObject` represents the Python integer type. This is the same object as `int` in the Python layer.

int PyLong_Check(PyObject *p)

  Return true if its argument is a `PyLongObject` or a subtype of `PyLongObject`. This function always succeeds.

int PyLong_CheckExact(PyObject *p)

  Return true if its argument is a `PyLongObject`, but not a subtype of `PyLongObject`. This function always succeeds.

PyObject *PyLong_FromLong(long v)
  Return value: New reference. Part of the Stable ABI.

  Return a new `PyLongObject` object from v, or `NULL` on failure.

  The current implementation keeps an array of integer objects for all integers between `-5` and `256`. When you create an int in that range you actually just get back a reference to the existing object.

PyObject *PyLong_FromUnsignedLong(unsigned long v)
  Return value: New reference. Part of the Stable ABI.

  Return a new `PyLongObject` object from a C unsigned long, or `NULL` on failure.

PyObject *PyLong_FromSsize_t(Py_ssize_t v)
  Return value: New reference. Part of the Stable ABI.

  Return a new `PyLongObject` object from a C `Py_ssize_t`, or `NULL` on failure.

PyObject *PyLong_FromSize_t(size_t v)
  Return value: New reference. Part of the Stable ABI.

  Return a new `PyLongObject` object from a C `size_t`, or `NULL` on failure.

PyObject *PyLong_FromLongLong(long long v)
  Return value: New reference. Part of the Stable ABI.

  Return a new `PyLongObject` object from a C long long, or `NULL` on failure.

PyObject *PyLong_FromUnsignedLongLong(unsigned long long v)
  Return value: New reference. Part of the Stable ABI.

  Return a new `PyLongObject` object from a C unsigned long long, or `NULL` on failure.

PyObject *PyLong_FromDouble(double v)
  Return value: New reference. Part of the Stable ABI.

  Return a new `PyLongObject` object from the integer part of v, or `NULL` on failure.

PyObject *PyLong_FromString(const char *str, char **pend, int base)
  Return value: New reference. Part of the Stable ABI.

  Return a new `PyLongObject` based on the string value in str, which is interpreted according to the radix in base, or `NULL` on failure. If pend is non-`NULL`, *pend will point to the end of str on success or to the first character that could not be processed on error. If base is `0`, str is interpreted using the Integer literals definition; in this case, leading zeros in a non-zero decimal number raises a `ValueError`. If base is not `0`, it must be between `2` and `36`, inclusive. Leading and trailing whitespace and single underscores after a base specifier and between digits are ignored. If there are no digits or str is not NULL-terminated following the digits and trailing whitespace, `ValueError` will be raised.

  See also

  Python methods `int.to_bytes()` and `int.from_bytes()` to convert a `PyLongObject` to/from an array of bytes in base `256`. You can call those from C using `PyObject_CallMethod()`.

PyObject *PyLong_FromUnicodeObject(PyObject *u, int base)
  Return value: New reference.

  Convert a sequence of Unicode digits in the string u to a Python integer value.

  Added in version 3.3.

PyObject *PyLong_FromVoidPtr(void *p)
  Return value: New reference. Part of the Stable ABI.

  Create a Python integer from the pointer p. The pointer value can be retrieved from the resulting value using `PyLong_AsVoidPtr()`.

PyObject *PyLong_FromNativeBytes(const void *buffer, size_t n_bytes, int flags)

  Create a Python integer from the value contained in the first n_bytes of buffer, interpreted as a two’s-complement signed number.

  flags are as for `PyLong_AsNativeBytes()`. Passing `-1` will select the native endian that CPython was compiled with and assume that the most-significant bit is a sign bit. Passing `Py_ASNATIVEBYTES_UNSIGNED_BUFFER` will produce the same result as calling `PyLong_FromUnsignedNativeBytes()`. Other flags are ignored.

  Added in version 3.13.

PyObject *PyLong_FromUnsignedNativeBytes(const void *buffer, size_t n_bytes, int flags)

  Create a Python integer from the value contained in the first n_bytes of buffer, interpreted as an unsigned number.

  flags are as for `PyLong_AsNativeBytes()`. Passing `-1` will select the native endian that CPython was compiled with and assume that the most-significant bit is not a sign bit. Flags other than endian are ignored.

  Added in version 3.13.

long PyLong_AsLong(PyObject *obj)
  Part of the Stable ABI.

  Return a C long representation of obj. If obj is not an instance of `PyLongObject`, first call its `__index__()` method (if present) to convert it to a `PyLongObject`.

  Raise `OverflowError` if the value of obj is out of range for a long.

  Returns `-1` on error. Use `PyErr_Occurred()` to disambiguate.

  Changed in version 3.8: Use `__index__()` if available.

  Changed in version 3.10: This function will no longer use `__int__()`.

  long PyLong_AS_LONG(PyObject *obj)

    A soft deprecated alias. Exactly equivalent to the preferred `PyLong_AsLong`. In particular, it can fail with `OverflowError` or another exception.

    Deprecated since version 3.14: The function is soft deprecated.

int PyLong_AsInt(PyObject *obj)
  Part of the Stable ABI since version 3.13.

  Similar to `PyLong_AsLong()`, but store the result in a C int instead of a C long.

  Added in version 3.13.

long PyLong_AsLongAndOverflow(PyObject *obj, int *overflow)
  Part of the Stable ABI.

  Return a C long representation of obj. If obj is not an instance of `PyLongObject`, first call its `__index__()` method (if present) to convert it to a `PyLongObject`.

  If the value of obj is greater than `LONG_MAX` or less than `LONG_MIN`, set *overflow to `1` or `-1`, respectively, and return `-1`; otherwise, set *overflow to `0`. If any other exception occurs set *overflow to `0` and return `-1` as usual.

  Returns `-1` on error. Use `PyErr_Occurred()` to disambiguate.

  Changed in version 3.8: Use `__index__()` if available.

  Changed in version 3.10: This function will no longer use `__int__()`.

long long PyLong_AsLongLong(PyObject *obj)
  Part of the Stable ABI.

  Return a C long long representation of obj. If obj is not an instance of `PyLongObject`, first call its `__index__()` method (if present) to convert it to a `PyLongObject`.

  Raise `OverflowError` if the value of obj is out of range for a long long.

  Returns `-1` on error. Use `PyErr_Occurred()` to disambiguate.

  Changed in version 3.8: Use `__index__()` if available.

  Changed in version 3.10: This function will no longer use `__int__()`.

long long PyLong_AsLongLongAndOverflow(PyObject *obj, int *overflow)
  Part of the Stable ABI.

  Return a C long long representation of obj. If obj is not an instance of `PyLongObject`, first call its `__index__()` method (if present) to convert it to a `PyLongObject`.

  If the value of obj is greater than `LLONG_MAX` or less than `LLONG_MIN`, set *overflow to `1` or `-1`, respectively, and return `-1`; otherwise, set *overflow to `0`. If any other exception occurs set *overflow to `0` and return `-1` as usual.

  Returns `-1` on error. Use `PyErr_Occurred()` to disambiguate.

  Added in version 3.2.

  Changed in version 3.8: Use `__index__()` if available.

  Changed in version 3.10: This function will no longer use `__int__()`.

Py_ssize_t PyLong_AsSsize_t(PyObject *pylong)
  Part of the Stable ABI.

  Return a C `Py_ssize_t` representation of pylong. pylong must be an instance of `PyLongObject`.

  Raise `OverflowError` if the value of pylong is out of range for a `Py_ssize_t`.

  Returns `-1` on error. Use `PyErr_Occurred()` to disambiguate.

unsigned long PyLong_AsUnsignedLong(PyObject *pylong)
  Part of the Stable ABI.

  Return a C unsigned long representation of pylong. pylong must be an instance of `PyLongObject`.

  Raise `OverflowError` if the value of pylong is out of range for a unsigned long.

  Returns `(unsigned long)-1` on error. Use `PyErr_Occurred()` to disambiguate.

size_t PyLong_AsSize_t(PyObject *pylong)
  Part of the Stable ABI.

  Return a C `size_t` representation of pylong. pylong must be an instance of `PyLongObject`.

  Raise `OverflowError` if the value of pylong is out of range for a `size_t`.

  Returns `(size_t)-1` on error. Use `PyErr_Occurred()` to disambiguate.

unsigned long long PyLong_AsUnsignedLongLong(PyObject *pylong)
  Part of the Stable ABI.

  Return a C unsigned long long representation of pylong. pylong must be an instance of `PyLongObject`.

  Raise `OverflowError` if the value of pylong is out of range for an unsigned long long.

  Returns `(unsigned long long)-1` on error. Use `PyErr_Occurred()` to disambiguate.

  Changed in version 3.1: A negative pylong now raises `OverflowError`, not `TypeError`.

unsigned long PyLong_AsUnsignedLongMask(PyObject *obj)
  Part of the Stable ABI.

  Return a C unsigned long representation of obj. If obj is not an instance of `PyLongObject`, first call its `__index__()` method (if present) to convert it to a `PyLongObject`.

  If the value of obj is out of range for an unsigned long, return the reduction of that value modulo `ULONG_MAX + 1`.

  Returns `(unsigned long)-1` on error. Use `PyErr_Occurred()` to disambiguate.

  Changed in version 3.8: Use `__index__()` if available.

  Changed in version 3.10: This function will no longer use `__int__()`.

unsigned long long PyLong_AsUnsignedLongLongMask(PyObject *obj)
  Part of the Stable ABI.

  Return a C unsigned long long representation of obj. If obj is not an instance of `PyLongObject`, first call its `__index__()` method (if present) to convert it to a `PyLongObject`.

  If the value of obj is out of range for an unsigned long long, return the reduction of that value modulo `ULLONG_MAX + 1`.

  Returns `(unsigned long long)-1` on error. Use `PyErr_Occurred()` to disambiguate.

  Changed in version 3.8: Use `__index__()` if available.

  Changed in version 3.10: This function will no longer use `__int__()`.

double PyLong_AsDouble(PyObject *pylong)
  Part of the Stable ABI.

  Return a C double representation of pylong. pylong must be an instance of `PyLongObject`.

  Raise `OverflowError` if the value of pylong is out of range for a double.

  Returns `-1.0` on error. Use `PyErr_Occurred()` to disambiguate.

void *PyLong_AsVoidPtr(PyObject *pylong)
  Part of the Stable ABI.

  Convert a Python integer pylong to a C void pointer. If pylong cannot be converted, an `OverflowError` will be raised. This is only assured to produce a usable void pointer for values created with `PyLong_FromVoidPtr()`.

  Returns `NULL` on error. Use `PyErr_Occurred()` to disambiguate.

Py_ssize_t PyLong_AsNativeBytes(PyObject *pylong, void *buffer, Py_ssize_t n_bytes, int flags)

  Copy the Python integer value pylong to a native buffer of size n_bytes. The flags can be set to `-1` to behave similarly to a C cast, or to values documented below to control the behavior.

  Returns `-1` with an exception raised on error. This may happen if pylong cannot be interpreted as an integer, or if pylong was negative and the `Py_ASNATIVEBYTES_REJECT_NEGATIVE` flag was set.

  Otherwise, returns the number of bytes required to store the value. If this is equal to or less than n_bytes, the entire value was copied. All n_bytes of the buffer are written: large buffers are padded with zeroes.

  If the returned value is greater than than n_bytes, the value was truncated: as many of the lowest bits of the value as could fit are written, and the higher bits are ignored. This matches the typical behavior of a C-style downcast.

  Note

  Overflow is not considered an error. If the returned value is larger than n_bytes, most significant bits were discarded.

  `0` will never be returned.

  Values are always copied as two’s-complement.

  Usage example:

      int32_t value;
      Py_ssize_t bytes = PyLong_AsNativeBytes(pylong, &value, sizeof(value), -1);
      if (bytes < 0) {
          // Failed. A Python exception was set with the reason.
          return NULL;
      }
      else if (bytes <= (Py_ssize_t)sizeof(value)) {
          // Success!
      }
      else {
          // Overflow occurred, but 'value' contains the truncated
          // lowest bits of pylong.
      }

  Passing zero to n_bytes will return the size of a buffer that would be large enough to hold the value. This may be larger than technically necessary, but not unreasonably so. If n_bytes=0, buffer may be `NULL`.

  Note

  Passing n_bytes=0 to this function is not an accurate way to determine the bit length of the value.

  To get at the entire Python value of an unknown size, the function can be called twice: first to determine the buffer size, then to fill it:

      // Ask how much space we need.
      Py_ssize_t expected = PyLong_AsNativeBytes(pylong, NULL, 0, -1);
      if (expected < 0) {
          // Failed. A Python exception was set with the reason.
          return NULL;
      }
      assert(expected != 0);  // Impossible per the API definition.
      uint8_t *bignum = malloc(expected);
      if (!bignum) {
          PyErr_SetString(PyExc_MemoryError, "bignum malloc failed.");
          return NULL;
      }
      // Safely get the entire value.
      Py_ssize_t bytes = PyLong_AsNativeBytes(pylong, bignum, expected, -1);
      if (bytes < 0) {  // Exception has been set.
          free(bignum);
          return NULL;
      }
      else if (bytes > expected) {  // This should not be possible.
          PyErr_SetString(PyExc_RuntimeError,
              "Unexpected bignum truncation after a size check.");
          free(bignum);
          return NULL;
      }
      // The expected success given the above pre-check.
      // ... use bignum ...
      free(bignum);

  flags is either `-1` (`Py_ASNATIVEBYTES_DEFAULTS`) to select defaults that behave most like a C cast, or a combination of the other flags in the table below. Note that `-1` cannot be combined with other flags.

  Currently, `-1` corresponds to `Py_ASNATIVEBYTES_NATIVE_ENDIAN | Py_ASNATIVEBYTES_UNSIGNED_BUFFER`.

  Flag | Value
  --- | ---
  Py_ASNATIVEBYTES_DEFAULTS | `-1`
  Py_ASNATIVEBYTES_BIG_ENDIAN | `0`
  Py_ASNATIVEBYTES_LITTLE_ENDIAN | `1`
  Py_ASNATIVEBYTES_NATIVE_ENDIAN | `3`
  Py_ASNATIVEBYTES_UNSIGNED_BUFFER | `4`
  Py_ASNATIVEBYTES_REJECT_NEGATIVE | `8`
  Py_ASNATIVEBYTES_ALLOW_INDEX | `16`

  Specifying `Py_ASNATIVEBYTES_NATIVE_ENDIAN` will override any other endian flags. Passing `2` is reserved.

  By default, sufficient buffer will be requested to include a sign bit. For example, when converting 128 with n_bytes=1, the function will return 2 (or more) in order to store a zero sign bit.

  If `Py_ASNATIVEBYTES_UNSIGNED_BUFFER` is specified, a zero sign bit will be omitted from size calculations. This allows, for example, 128 to fit in a single-byte buffer. If the destination buffer is later treated as signed, a positive input value may become negative. Note that the flag does not affect handling of negative values: for those, space for a sign bit is always requested.

  Specifying `Py_ASNATIVEBYTES_REJECT_NEGATIVE` causes an exception to be set if pylong is negative. Without this flag, negative values will be copied provided there is enough space for at least one sign bit, regardless of whether `Py_ASNATIVEBYTES_UNSIGNED_BUFFER` was specified.

  If `Py_ASNATIVEBYTES_ALLOW_INDEX` is specified and a non-integer value is passed, its `__index__()` method will be called first. This may result in Python code executing and other threads being allowed to run, which could cause changes to other objects or values in use. When flags is `-1`, this option is not set, and non-integer values will raise `TypeError`.

  Note

  With the default flags (`-1`, or UNSIGNED_BUFFER without REJECT_NEGATIVE), multiple Python integers can map to a single value without overflow. For example, both `255` and `-1` fit a single-byte buffer and set all its bits. This matches typical C cast behavior.

  Added in version 3.13.

PyObject *PyLong_GetInfo(void)
  Part of the Stable ABI.

  On success, return a read only named tuple, that holds information about Python’s internal representation of integers. See `sys.int_info` for description of individual fields.

  On failure, return `NULL` with an exception set.

  Added in version 3.1.

int PyUnstable_Long_IsCompact(const PyLongObject *op)
  This is Unstable API. It may change without warning in minor releases.

  Return 1 if op is compact, 0 otherwise.

  This function makes it possible for performance-critical code to implement a “fast path” for small integers. For compact values use `PyUnstable_Long_CompactValue()`; for others fall back to a `PyLong_As*` function or `PyLong_AsNativeBytes()`.

  The speedup is expected to be negligible for most users.

  Exactly what values are considered compact is an implementation detail and is subject to change.

  Added in version 3.12.

Py_ssize_t PyUnstable_Long_CompactValue(const PyLongObject *op)
  This is Unstable API. It may change without warning in minor releases.

  If op is compact, as determined by `PyUnstable_Long_IsCompact()`, return its value.

  Otherwise, the return value is undefined.

  Added in version 3.12.