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# 11.12. `dumbdbm` — Portable DBM implementation

Note

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.

Note

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:

dumbdbm.close()

  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.

dumbdbm.sync()

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