argparse.py 文件源码

def _get_value(self, action, arg_string):
        type_func = self._registry_get('type', action.type, action.type)
        if not _callable(type_func):
            msg = _('%r is not callable')
            raise ArgumentError(action, msg % type_func)

        # convert the value to the appropriate type
        try:
            result = type_func(arg_string)

        # ArgumentTypeErrors indicate errors
        except ArgumentTypeError:
            name = getattr(action.type, '__name__', repr(action.type))
            msg = str(_sys.exc_info()[1])
            raise ArgumentError(action, msg)

        # TypeErrors or ValueErrors also indicate errors
        except (TypeError, ValueError):
            name = getattr(action.type, '__name__', repr(action.type))
            msg = _('invalid %s value: %r')
            raise ArgumentError(action, msg % (name, arg_string))

        # return the converted value
        return result