"""Generic interface to all dbm clones.

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Instead of

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import dbm

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d = dbm.open(file, 'w', 0666)

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use

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import anydbm

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d = anydbm.open(file, 'w')

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The returned object is a dbhash, gdbm, dbm or dumbdbm object,

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dependent on the type of database being opened (determined by whichdb

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module) in the case of an existing dbm. If the dbm does not exist and

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the create or new flag ('c' or 'n') was specified, the dbm type will

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be determined by the availability of the modules (tested in the above

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order).

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It has the following interface (key and data are strings):

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d[key] = data # store data at key (may override data at

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# existing key)

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data = d[key] # retrieve data at key (raise KeyError if no

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# such key)

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del d[key] # delete data stored at key (raises KeyError

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# if no such key)

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flag = key in d # true if the key exists

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list = d.keys() # return a list of all existing keys (slow!)

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Future versions may change the order in which implementations are

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tested for existence, and add interfaces to other dbm-like

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implementations.

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"""

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class error(Exception):

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pass

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_names = ['dbhash', 'gdbm', 'dbm', 'dumbdbm']

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_errors = [error]

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_defaultmod = None

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for _name in _names:

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try:

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_mod = __import__(_name)

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except ImportError:

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continue

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if not _defaultmod:

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_defaultmod = _mod

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_errors.append(_mod.error)

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if not _defaultmod:

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raise ImportError, "no dbm clone found; tried %s" % _names

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error = tuple(_errors)

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def open(file, flag='r', mode=0666):

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"""Open or create database at path given by *file*.

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Optional argument *flag* can be 'r' (default) for read-only access, 'w'

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for read-write access of an existing database, 'c' for read-write access

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to a new or existing database, and 'n' for read-write access to a new

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database.

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Note: 'r' and 'w' fail if the database doesn't exist; 'c' creates it

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only if it doesn't exist; and 'n' always creates a new database.

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"""

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# guess the type of an existing database

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from whichdb import whichdb

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result=whichdb(file)

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if result is None:

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# db doesn't exist

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if 'c' in flag or 'n' in flag:

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# file doesn't exist and the new

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# flag was used so use default type

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mod = _defaultmod

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else:

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raise error, "need 'c' or 'n' flag to open new db"

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elif result == "":

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# db type cannot be determined

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raise error, "db type could not be determined"

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else:

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mod = __import__(result)

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return mod.open(file, flag, mode)

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