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      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