anydbm.py 文件源码

def open(file, flag='r', mode=0666):
    """Open or create database at path given by *file*.

    Optional argument *flag* can be 'r' (default) for read-only access, 'w'
    for read-write access of an existing database, 'c' for read-write access
    to a new or existing database, and 'n' for read-write access to a new
    database.

    Note: 'r' and 'w' fail if the database doesn't exist; 'c' creates it
    only if it doesn't exist; and 'n' always creates a new database.
    """

    # 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)