11.6. anydbm — Generic access to DBM-style databases — Python 2.7.18 documentation

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# 11.6. `anydbm` — Generic access to DBM-style databases

Note

The `anydbm` module has been renamed to `dbm` in Python 3. The 2to3 tool will automatically adapt imports when converting your sources to Python 3.

`anydbm` is a generic interface to variants of the DBM database — `dbhash` (requires `bsddb`), `gdbm`, or `dbm`. If none of these modules is installed, the slow-but-simple implementation in module `dumbdbm` will be used.

`anydbm.` `open`(filename[, flag[, mode]])

  Open the database file filename and return a corresponding object.

  If the database file already exists, the `whichdb` module is used to determine its type and the appropriate module is used; if it does not exist, the first module listed above that can be imported is used.

  The optional flag argument must be one of these values:

  Value | Meaning
  --- | ---
  `'r'` | Open existing database for reading only (default)
  `'w'` | Open existing database for reading and writing
  `'c'` | Open database for reading and writing, creating it if it doesn’t exist
  `'n'` | Always create a new, empty database, open for reading and writing

  If not specified, the default value is `'r'`.

  The optional mode argument is the Unix mode of the file, used only when the database has to be created. It defaults to octal `0666` (and will be modified by the prevailing umask).

exception `anydbm.` `error`

  A tuple containing the exceptions that can be raised by each of the supported modules, with a unique exception also named `anydbm.error` as the first item — the latter is used when `anydbm.error` is raised.

The object returned by `open()` supports most of the same functionality as dictionaries; keys and their corresponding values can be stored, retrieved, and deleted, and the `has_key()` and `keys()` methods are available. Keys and values must always be strings.

The following example records some hostnames and a corresponding title, and then prints out the contents of the database:

    import anydbm

    # Open database, creating it if necessary.
    db = anydbm.open('cache', 'c')

    # Record some values
    db['www.python.org'] = 'Python Website'
    db['www.cnn.com'] = 'Cable News Network'

    # Loop through contents.  Other dictionary methods
    # such as .keys(), .values() also work.
    for k, v in db.iteritems():
        print k, '\t', v

    # Storing a non-string key or value will raise an exception (most
    # likely a TypeError).
    db['www.yahoo.com'] = 4

    # Close when done.
    db.close()

In addition to the dictionary-like methods, `anydbm` objects provide the following method:

`anydbm.` `close`()

  Close the `anydbm` database.

See also

Module `dbhash`

  BSD `db` database interface.

Module `dbm`

  Standard Unix database interface.

Module `dumbdbm`

  Portable implementation of the `dbm` interface.

Module `gdbm`

  GNU database interface, based on the `dbm` interface.

Module `shelve`

  General object persistence built on top of the Python `dbm` interface.

Module `whichdb`

  Utility module used to determine the type of an existing database.