mirror of https://github.com/python/cpython
116 lines
3.8 KiB
ReStructuredText
116 lines
3.8 KiB
ReStructuredText
:mod:`dbhash` --- DBM-style interface to the BSD database library
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=================================================================
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.. module:: dbhash
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:synopsis: DBM-style interface to the BSD database library.
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.. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org>
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.. deprecated:: 2.6
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The :mod:`dbhash` module has been removed in Python 3.
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.. index:: module: bsddb
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The :mod:`dbhash` module provides a function to open databases using the BSD
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``db`` library. This module mirrors the interface of the other Python database
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modules that provide access to DBM-style databases. The :mod:`bsddb` module is
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required to use :mod:`dbhash`.
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This module provides an exception and a function:
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.. exception:: error
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Exception raised on database errors other than :exc:`KeyError`. It is a synonym
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for :exc:`bsddb.error`.
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.. function:: open(path[, flag[, mode]])
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Open a ``db`` database and return the database object. The *path* argument is
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the name of the database file.
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The *flag* argument can be:
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+---------+-------------------------------------------+
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| Value | Meaning |
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+=========+===========================================+
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| ``'r'`` | Open existing database for reading only |
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| | (default) |
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+---------+-------------------------------------------+
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| ``'w'`` | Open existing database for reading and |
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| | writing |
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+---------+-------------------------------------------+
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| ``'c'`` | Open database for reading and writing, |
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| | creating it if it doesn't exist |
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+---------+-------------------------------------------+
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| ``'n'`` | Always create a new, empty database, open |
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| | for reading and writing |
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+---------+-------------------------------------------+
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For platforms on which the BSD ``db`` library supports locking, an ``'l'``
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can be appended to indicate that locking should be used.
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The optional *mode* parameter is used to indicate the Unix permission bits that
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should be set if a new database must be created; this will be masked by the
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current umask value for the process.
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.. seealso::
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Module :mod:`anydbm`
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Generic interface to ``dbm``\ -style databases.
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Module :mod:`bsddb`
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Lower-level interface to the BSD ``db`` library.
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Module :mod:`whichdb`
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Utility module used to determine the type of an existing database.
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.. _dbhash-objects:
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Database Objects
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----------------
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The database objects returned by :func:`.open` provide the methods common to all
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the DBM-style databases and mapping objects. The following methods are
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available in addition to the standard methods.
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.. method:: dbhash.first()
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It's possible to loop over every key/value pair in the database using this
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method and the :meth:`!next` method. The traversal is ordered by the databases
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internal hash values, and won't be sorted by the key values. This method
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returns the starting key.
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.. method:: dbhash.last()
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Return the last key/value pair in a database traversal. This may be used to
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begin a reverse-order traversal; see :meth:`previous`.
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.. method:: dbhash.next()
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Returns the key next key/value pair in a database traversal. The following code
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prints every key in the database ``db``, without having to create a list in
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memory that contains them all::
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print db.first()
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for i in xrange(1, len(db)):
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print db.next()
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.. method:: dbhash.previous()
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Returns the previous key/value pair in a forward-traversal of the database. In
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conjunction with :meth:`last`, this may be used to implement a reverse-order
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traversal.
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.. method:: dbhash.sync()
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This method forces any unwritten data to be written to the disk.
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