11.12. dumbdbm — Portable DBM implementation


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.


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).

Changed in version 2.2: The mode argument was ignored in earlier versions.

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


Close the dumbdm database.

See also

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.


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