11.8. "dbm" — Simple “database” interface
*****************************************

Note: The "dbm" module has been renamed to "dbm.ndbm" in Python 3.
  The *2to3* tool will automatically adapt imports when converting
  your sources to Python 3.

The "dbm" module provides an interface to the Unix “(n)dbm” library.
Dbm objects behave like mappings (dictionaries), except that keys and
values are always strings. Printing a dbm object doesn’t print the
keys and values, and the "items()" and "values()" methods are not
supported.

This module can be used with the “classic” ndbm interface, the BSD DB
compatibility interface, or the GNU GDBM compatibility interface. On
Unix, the **configure** script will attempt to locate the appropriate
header file to simplify building this module.

The module defines the following:

exception dbm.error

   Raised on dbm-specific errors, such as I/O errors. "KeyError" is
   raised for general mapping errors like specifying an incorrect key.

dbm.library

   Name of the "ndbm" implementation library used.

dbm.open(filename[, flag[, mode]])

   Open a dbm database and return a dbm object.  The *filename*
   argument is the name of the database file (without the ".dir" or
   ".pag" extensions; note that the BSD DB implementation of the
   interface will append the extension ".db" and only create one
   file).

   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                     |
   +-----------+---------------------------------------------+

   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).

   In addition to the dictionary-like methods, "dbm" objects provide
   the following method:

   dbm.close()

      Close the "dbm" database.

See also:

  Module "anydbm"
     Generic interface to "dbm"-style databases.

  Module "gdbm"
     Similar interface to the GNU GDBM library.

  Module "whichdb"
     Utility module used to determine the type of an existing
     database.