1 :mod:`dbm` --- Simple "database" interface 2 ========================================== 3 4 .. module:: dbm 5 :platform: Unix 6 :synopsis: The standard "database" interface, based on ndbm. 7 8 .. note:: 9 The :mod:`dbm` module has been renamed to :mod:`dbm.ndbm` in Python 3. The 10 :term:`2to3` tool will automatically adapt imports when converting your 11 sources to Python 3. 12 13 14 The :mod:`dbm` module provides an interface to the Unix "(n)dbm" library. Dbm 15 objects behave like mappings (dictionaries), except that keys and values are 16 always strings. Printing a dbm object doesn't print the keys and values, and the 17 :meth:`items` and :meth:`values` methods are not supported. 18 19 This module can be used with the "classic" ndbm interface, the BSD DB 20 compatibility interface, or the GNU GDBM compatibility interface. On Unix, the 21 :program:`configure` script will attempt to locate the appropriate header file 22 to simplify building this module. 23 24 The module defines the following: 25 26 27 .. exception:: error 28 29 Raised on dbm-specific errors, such as I/O errors. :exc:`KeyError` is raised for 30 general mapping errors like specifying an incorrect key. 31 32 33 .. data:: library 34 35 Name of the ``ndbm`` implementation library used. 36 37 38 .. function:: open(filename[, flag[, mode]]) 39 40 Open a dbm database and return a dbm object. The *filename* argument is the 41 name of the database file (without the :file:`.dir` or :file:`.pag` extensions; 42 note that the BSD DB implementation of the interface will append the extension 43 :file:`.db` and only create one file). 44 45 The optional *flag* argument must be one of these values: 46 47 +---------+-------------------------------------------+ 48 | Value | Meaning | 49 +=========+===========================================+ 50 | ``'r'`` | Open existing database for reading only | 51 | | (default) | 52 +---------+-------------------------------------------+ 53 | ``'w'`` | Open existing database for reading and | 54 | | writing | 55 +---------+-------------------------------------------+ 56 | ``'c'`` | Open database for reading and writing, | 57 | | creating it if it doesn't exist | 58 +---------+-------------------------------------------+ 59 | ``'n'`` | Always create a new, empty database, open | 60 | | for reading and writing | 61 +---------+-------------------------------------------+ 62 63 The optional *mode* argument is the Unix mode of the file, used only when the 64 database has to be created. It defaults to octal ``0666`` (and will be 65 modified by the prevailing umask). 66 67 In addition to the dictionary-like methods, ``dbm`` objects 68 provide the following method: 69 70 71 .. function:: close() 72 73 Close the ``dbm`` database. 74 75 76 .. seealso:: 77 78 Module :mod:`anydbm` 79 Generic interface to ``dbm``\ -style databases. 80 81 Module :mod:`gdbm` 82 Similar interface to the GNU GDBM library. 83 84 Module :mod:`whichdb` 85 Utility module used to determine the type of an existing database. 86 87