11.12. "dumbdbm" — Portable DBM implementation
**********************************************

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

備註: The "dumbdbm" module is intended as a last resort fallback for
  the "anydbm" module when no more robust module is available. The
  "dumbdbm" module is not written for speed and is not nearly as
  heavily used as the other database modules.

The "dumbdbm" module provides a persistent dictionary-like interface
which is written entirely in Python.  Unlike other modules such as
"gdbm" and "bsddb", no external library is required.  As with other
persistent mappings, the keys and values must always be strings.

The module defines the following:

exception dumbdbm.error

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

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

   Open a dumbdbm database and return a dumbdbm object.  The
   *filename* argument is the basename of the database file (without
   any specific extensions).  When a dumbdbm database is created,
   files with ".dat" and ".dir" extensions are created.

   The optional *flag* argument is currently ignored; the database is
   always opened for update, and will be created if it does not exist.

   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).

   2.2 版更變: The *mode* argument was ignored in earlier versions.

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

dumbdbm.close()

   Close the "dumbdm" database.

也參考:

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

  Module "dbm"
     Similar interface to the DBM/NDBM library.

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

  Module "shelve"
     Persistence module which stores non-string data.

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


11.12.1. Dumbdbm Objects
========================

In addition to the methods provided by the "UserDict.DictMixin" class,
"dumbdbm" objects provide the following methods.

dumbdbm.sync()

   Synchronize the on-disk directory and data files.  This method is
   called by the "sync()" method of "Shelve" objects.
