cpython/Doc/library/dumbdbm.rst

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2007-08-15 11:28:01 -03:00
:mod:`dumbdbm` --- Portable DBM implementation
==============================================
.. module:: dumbdbm
:synopsis: Portable implementation of the simple DBM interface.
.. index:: single: databases
.. note::
The :mod:`dumbdbm` module is intended as a last resort fallback for the
:mod:`anydbm` module when no more robust module is available. The :mod:`dumbdbm`
module is not written for speed and is not nearly as heavily used as the other
database modules.
The :mod:`dumbdbm` module provides a persistent dictionary-like interface which
is written entirely in Python. Unlike other modules such as :mod:`gdbm` and
:mod:`bsddb`, no external library is required. As with other persistent
mappings, the keys and values must always be strings.
The module defines the following:
.. exception:: error
Raised on dumbdbm-specific errors, such as I/O errors. :exc:`KeyError` is
raised for general mapping errors like specifying an incorrect key.
.. function:: open(filename[, flag[, mode]])
Open a dumbdbm database and return a dumbdbm object. The *filename* argument is
the basename of the database file (without any specific extensions). When a
dumbdbm database is created, files with :file:`.dat` and :file:`.dir` extensions
are created.
The optional *flag* argument is currently ignored; the database is always opened
for update, and will be created if it does not exist.
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).
.. versionchanged:: 2.2
The *mode* argument was ignored in earlier versions.
.. seealso::
Module :mod:`anydbm`
Generic interface to ``dbm``\ -style databases.
Module :mod:`dbm`
Similar interface to the DBM/NDBM library.
Module :mod:`gdbm`
Similar interface to the GNU GDBM library.
Module :mod:`shelve`
Persistence module which stores non-string data.
Module :mod:`whichdb`
Utility module used to determine the type of an existing database.
.. _dumbdbm-objects:
Dumbdbm Objects
---------------
In addition to the methods provided by the :class:`UserDict.DictMixin` class,
:class:`dumbdbm` objects provide the following methods.
.. method:: dumbdbm.sync()
Synchronize the on-disk directory and data files. This method is called by the
:meth:`sync` method of :class:`Shelve` objects.