"""Generic interface to all dbm clones. Instead of         import dbm        d = dbm.open(file, 'w', 0666) use         import anydbm        d = anydbm.open(file, 'w') The returned object is a dbhash, gdbm, dbm or dumbdbm object,dependent on the type of database being opened (determined by whichdbmodule) in the case of an existing dbm. If the dbm does not exist andthe create or new flag ('c' or 'n') was specified, the dbm type willbe determined by the availability of the modules (tested in the aboveorder). It has the following interface (key and data are strings):         d[key] = data   # store data at key (may override data at                        # existing key)        data = d[key]   # retrieve data at key (raise KeyError if no                        # such key)        del d[key]      # delete data stored at key (raises KeyError                        # if no such key)        flag = key in d   # true if the key exists        list = d.keys() # return a list of all existing keys (slow!) Future versions may change the order in which implementations aretested for existence, add interfaces to other dbm-likeimplementations. The open function has an optional second argument.  This can be 'r',for read-only access, 'w', for read-write access of an existingdatabase, 'c' for read-write access to a new or existing database, and'n' for read-write access to a new database.  The default is 'r'. Note: 'r' and 'w' fail if the database doesn't exist; 'c' creates itonly if it doesn't exist; and 'n' always creates a new database. """ class error(Exception):    pass _names = ['dbhash', 'gdbm', 'dbm', 'dumbdbm']_errors = [error]_defaultmod = None for _name in _names:    try:        _mod = __import__(_name)    except ImportError:        continue    if not _defaultmod:        _defaultmod = _mod    _errors.append(_mod.error) if not _defaultmod:    raise ImportError, "no dbm clone found; tried %s" % _names error = tuple(_errors) def open(file, flag = 'r', mode = 0666):    # guess the type of an existing database    from whichdb import whichdb    result=whichdb(file)    if result is None:        # db doesn't exist        if 'c' in flag or 'n' in flag:            # file doesn't exist and the new            # flag was used so use default type            mod = _defaultmod        else:            raise error, "need 'c' or 'n' flag to open new db"    elif result == "":        # db type cannot be determined        raise error, "db type could not be determined"    else:        mod = __import__(result)    return mod.open(file, flag, mode)