实现一个命令行参数解析器

萧随风

def parse_args(argv):
    if not argv:
        raise SystemExit("usage: cp|mv|rm ...")
   
    command = argv[0]
    if command == "cp":
        if len(argv) != 3:
            raise SystemExit("usage: cp|mv|rm ...")
        return ("copy", argv[1], argv[2])
    elif command == "mv":
        if len(argv) != 3:
            raise SystemExit("usage: cp|mv|rm ...")
        return ("move", argv[1], argv[2])
    elif command == "rm":
        return ("remove", argv[1:])
    else:
        raise SystemExit("usage: cp|mv|rm ...")