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# 11.8. `dbm` — Simple “database” interface

注解

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.

该模块定义以下内容：

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`

  所使用的 `ndbm` 实现库的名称。

`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).

  可选的 flag 参数必须是下列值之一：

  值 | 含义
  --- | ---
  `'r'` | 以只读方式打开现有数据库（默认）
  `'w'` | 以读写方式打开现有数据库
  `'c'` | 以读写方式打开数据库，如果不存在则创建它
  `'n'` | 始终创建一个新的空数据库，以读写方式打开

  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.

参见

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.