Edit File: dbhash.txt
:mod:`dbhash` --- DBM-style interface to the BSD database library ================================================================= .. module:: dbhash :synopsis: DBM-style interface to the BSD database library. .. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org> .. deprecated:: 2.6 The :mod:`dbhash` module has been deprecated for removal in Python 3.0. .. index:: module: bsddb The :mod:`dbhash` module provides a function to open databases using the BSD ``db`` library. This module mirrors the interface of the other Python database modules that provide access to DBM-style databases. The :mod:`bsddb` module is required to use :mod:`dbhash`. This module provides an exception and a function: .. exception:: error Exception raised on database errors other than :exc:`KeyError`. It is a synonym for :exc:`bsddb.error`. .. function:: open(path[, flag[, mode]]) Open a ``db`` database and return the database object. The *path* argument is the name of the database file. The *flag* argument can be: +---------+-------------------------------------------+ | 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 | +---------+-------------------------------------------+ For platforms on which the BSD ``db`` library supports locking, an ``'l'`` can be appended to indicate that locking should be used. The optional *mode* parameter is used to indicate the Unix permission bits that should be set if a new database must be created; this will be masked by the current umask value for the process. .. seealso:: Module :mod:`anydbm` Generic interface to ``dbm``\ -style databases. Module :mod:`bsddb` Lower-level interface to the BSD ``db`` library. Module :mod:`whichdb` Utility module used to determine the type of an existing database. .. _dbhash-objects: Database Objects ---------------- The database objects returned by :func:`.open` provide the methods common to all the DBM-style databases and mapping objects. The following methods are available in addition to the standard methods. .. method:: dbhash.first() It's possible to loop over every key/value pair in the database using this method and the :meth:`!next` method. The traversal is ordered by the databases internal hash values, and won't be sorted by the key values. This method returns the starting key. .. method:: dbhash.last() Return the last key/value pair in a database traversal. This may be used to begin a reverse-order traversal; see :meth:`previous`. .. method:: dbhash.next() Returns the key next key/value pair in a database traversal. The following code prints every key in the database ``db``, without having to create a list in memory that contains them all:: print db.first() for i in xrange(1, len(db)): print db.next() .. method:: dbhash.previous() Returns the previous key/value pair in a forward-traversal of the database. In conjunction with :meth:`last`, this may be used to implement a reverse-order traversal. .. method:: dbhash.sync() This method forces any unwritten data to be written to the disk.
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