cmdline.py 文件源码

def __call__(self, parser, namespace, values, option_string=None):
        _ = parser, option_string  # NOQA

        try:
            result = self._enum_type[values]
        except KeyError:
            raise argparse.ArgumentError(
                self, "{} not a valid choice of {}".format(values, self.choices))

        setattr(namespace, self.dest, result)