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:mod:`dbm` --- Simple "database" interface
==========================================
.. module:: dbm
:platform: Unix
:synopsis: The standard "database" interface, based on ndbm.
.. note::
The :mod:`dbm` module has been renamed to :mod:`dbm.ndbm` in Python 3. The
:term:`2to3` tool will automatically adapt imports when converting your
sources to Python 3.
The :mod:`dbm` module provides an interface to the Unix "(n)dbm" library. Dbm
objects behave like mappings (dictionaries), except that keys and values are
always strings. Printing a dbm object doesn't print the keys and values, and the
:meth:`items` and :meth:`values` methods are not supported.
This module can be used with the "classic" ndbm interface, the BSD DB
compatibility interface, or the GNU GDBM compatibility interface. On Unix, the
:program:`configure` script will attempt to locate the appropriate header file
to simplify building this module.
The module defines the following:
.. exception:: error
Raised on dbm-specific errors, such as I/O errors. :exc:`KeyError` is raised for
general mapping errors like specifying an incorrect key.
.. data:: library
Name of the ``ndbm`` implementation library used.
.. function:: open(filename[, flag[, mode]])
Open a dbm database and return a dbm object. The *filename* argument is the
name of the database file (without the :file:`.dir` or :file:`.pag` extensions;
note that the BSD DB implementation of the interface will append the extension
:file:`.db` and only create one file).
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 |
+---------+-------------------------------------------+
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).
.. seealso::
Module :mod:`anydbm`
Generic interface to ``dbm``\ -style databases.
Module :mod:`gdbm`
Similar interface to the GNU GDBM library.
Module :mod:`whichdb`
Utility module used to determine the type of an existing database.
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