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(python2.1-lib.info)gdbm

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GNU's reinterpretation of dbm
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GNU's reinterpretation of dbm.

This module is quite similar to the `dbm' module, but uses `gdbm'
instead to provide some additional functionality.  Please note that the
file formats created by `gdbm' and `dbm' are incompatible.

The `gdbm' module provides an interface to the GNU DBM library.  `gdbm'
objects behave like mappings (dictionaries), except that keys and
values are always strings.  Printing a `gdbm' object doesn't print the
keys and values, and the `items()' and `values()' methods are not
supported.

The module defines the following constant and functions:

`error'
     Raised on `gdbm'-specific errors, such as I/O errors.  `KeyError'
     is raised for general mapping errors like specifying an incorrect
     key.

`open(filename, [flag, [mode]])'
     Open a `gdbm' database and return a `gdbm' object.  The FILENAME
     argument is the name of the database file.

     The optional FLAG argument can be `'r'' (to open an existing
     database for reading only -- default), `'w'' (to open an existing
     database for reading and writing), `'c'' (which creates the
     database if it doesn't exist), or `'n'' (which always creates a
     new empty database).

     The following additional characters may be appended to the flag to
     control how the database is opened:

        * `'f'' -- Open the database in fast mode.  Writes to the
          database will not be syncronized.

        * `'s'' -- Synchronized mode. This will cause changes to the
          database will be immediately written to the file.

        * `'u'' -- Do not lock database.

     Not all flags are valid for all versions of `gdbm'.  The module
     constant `open_flags' is a string of supported flag characters.
     The exception `error' is raised if an invalid flag is specified.

     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'.

In addition to the dictionary-like methods, `gdbm' objects have the
following methods:

`firstkey()'
     It's possible to loop over every key in the database using this
     method and the `nextkey()' method.  The traversal is ordered by
     `gdbm''s internal hash values, and won't be sorted by the key
     values.  This method returns the starting key.

`nextkey(key)'
     Returns the key that follows KEY in the traversal.  The following
     code prints every key in the database `db', without having to
     create a list in memory that contains them all:

          k = db.firstkey()
          while k != None:
              print k
              k = db.nextkey(k)

`reorganize()'
     If you have carried out a lot of deletions and would like to shrink
     the space used by the `gdbm' file, this routine will reorganize
     the database.  `gdbm' will not shorten the length of a database
     file except by using this reorganization; otherwise, deleted file
     space will be kept and reused as new (key, value) pairs are added.

`sync()'
     When the database has been opened in fast mode, this method forces
     any unwritten data to be written to the disk.

See also:
     Note: anydbm Generic interface to `dbm'-style databases.  Note:
     whichdb Utility module used to determine the type of an existing
     database.