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authorGeorg Brandl <georg@python.org>2007-08-15 14:28:22 (GMT)
committerGeorg Brandl <georg@python.org>2007-08-15 14:28:22 (GMT)
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+
+:mod:`anydbm` --- Generic access to DBM-style databases
+=======================================================
+
+.. module:: anydbm
+ :synopsis: Generic interface to DBM-style database modules.
+
+
+.. index::
+ module: dbhash
+ module: bsddb
+ module: gdbm
+ module: dbm
+ module: dumbdbm
+
+:mod:`anydbm` is a generic interface to variants of the DBM database ---
+:mod:`dbhash` (requires :mod:`bsddb`), :mod:`gdbm`, or :mod:`dbm`. If none of
+these modules is installed, the slow-but-simple implementation in module
+:mod:`dumbdbm` will be used.
+
+
+.. function:: open(filename[, flag[, mode]])
+
+ Open the database file *filename* and return a corresponding object.
+
+ If the database file already exists, the :mod:`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 can be ``'r'`` to open an existing database for
+ reading only, ``'w'`` to open an existing database for reading and writing,
+ ``'c'`` to create the database if it doesn't exist, or ``'n'``, which will
+ always create a new empty database. 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:: error
+
+ A tuple containing the exceptions that can be raised by each of the supported
+ modules, with a unique exception also named :exc:`anydbm.error` as the first
+ item --- the latter is used when :exc:`anydbm.error` is raised.
+
+The object returned by :func:`open` supports most of the same functionality as
+dictionaries; keys and their corresponding values can be stored, retrieved, and
+deleted, and the :meth:`has_key` and :meth:`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()
+
+
+.. seealso::
+
+ Module :mod:`dbhash`
+ BSD ``db`` database interface.
+
+ Module :mod:`dbm`
+ Standard Unix database interface.
+
+ Module :mod:`dumbdbm`
+ Portable implementation of the ``dbm`` interface.
+
+ Module :mod:`gdbm`
+ GNU database interface, based on the ``dbm`` interface.
+
+ Module :mod:`shelve`
+ General object persistence built on top of the Python ``dbm`` interface.
+
+ Module :mod:`whichdb`
+ Utility module used to determine the type of an existing database.
+