Method __init__

Lib/inspect.py:2687–2728

(self, name, kind, *, default=_empty, annotation=_empty)

    empty = _empty

    def __init__(self, name, kind, *, default=_empty, annotation=_empty):
        try:
            self._kind = _ParameterKind(kind)
        except ValueError:
            raise ValueError(f'value {kind!r} is not a valid Parameter.kind')
        if default is not _empty:
            if self._kind in (_VAR_POSITIONAL, _VAR_KEYWORD):
                msg = '{} parameters cannot have default values'
                msg = msg.format(self._kind.description)
                raise ValueError(msg)
        self._default = default
        self._annotation = annotation

        if name is _empty:
            raise ValueError('name is a required attribute for Parameter')

        if not isinstance(name, str):
            msg = 'name must be a str, not a {}'.format(type(name).__name__)
            raise TypeError(msg)

        if name[0] == '.' and name[1:].isdigit():
            # These are implicit arguments generated by comprehensions. In
            # order to provide a friendlier interface to users, we recast
            # their name as "implicitN" and treat them as positional-only.
            # See issue 19611.
            if self._kind != _POSITIONAL_OR_KEYWORD:
                msg = (
                    'implicit arguments must be passed as '
                    'positional or keyword arguments, not {}'
                )
                msg = msg.format(self._kind.description)
                raise ValueError(msg)
            self._kind = _POSITIONAL_ONLY
            name = 'implicit{}'.format(name[1:])

        # It's possible for C functions to have a positional-only parameter
        # where the name is a keyword, so for compatibility we'll allow it.
        is_keyword = iskeyword(name) and self._kind is not _POSITIONAL_ONLY
        if is_keyword or not name.isidentifier():
            raise ValueError('{!r} is not a valid parameter name'.format(name))

        self._name = name

    def __reduce__(self):
        return (type(self),