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:mod:`anydbm` --- Generic access to DBM-style databases
=======================================================
.. module:: anydbm
:synopsis: Generic interface to DBM-style database modules.
.. note::
The :mod:`anydbm` module has been renamed to :mod:`dbm` in Python 3.0. The
:term:`2to3` tool will automatically adapt imports when converting your
sources to 3.0.
.. 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 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:: 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.
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