Class Signature

Lib/inspect.py:2942–3316

A Signature object represents the overall signature of a function. It stores a Parameter object for each parameter accepted by the function, as well as information specific to the function itself. A Signature object has the following public attributes and methods: * parameters : Or

class Signature:
    """A Signature object represents the overall signature of a function.
    It stores a Parameter object for each parameter accepted by the
    function, as well as information specific to the function itself.

    A Signature object has the following public attributes and methods:

    * parameters : OrderedDict
        An ordered mapping of parameters' names to the corresponding
        Parameter objects (keyword-only arguments are in the same order
        as listed in `code.co_varnames`).
    * return_annotation : object
        The annotation for the return type of the function if specified.
        If the function has no annotation for its return type, this
        attribute is set to `Signature.empty`.
    * bind(*args, **kwargs) -> BoundArguments
        Creates a mapping from positional and keyword arguments to
        parameters.
    * bind_partial(*args, **kwargs) -> BoundArguments
        Creates a partial mapping from positional and keyword arguments
        to parameters (simulating 'functools.partial' behavior.)
    """

    __slots__ = ('_return_annotation', '_parameters')

    _parameter_cls = Parameter
    _bound_arguments_cls = BoundArguments

    empty = _empty

    def __init__(self, parameters=None, *, return_annotation=_empty,
                 __validate_parameters__=True):
        """Constructs Signature from the given list of Parameter
        objects and 'return_annotation'.  All arguments are optional.
        """

        if parameters is None:
            params = OrderedDict()
        else:
            if __validate_parameters__:
                params = OrderedDict()
                top_kind = _POSITIONAL_ONLY
                seen_default = False
                seen_var_parameters = set()

                for param in parameters:
                    kind = param.kind
                    name = param.name

                    if kind in (_VAR_POSITIONAL, _VAR_KEYWORD):
                        if kind in seen_var_parameters:
                            msg = f'more than one {kind.description} parameter'
                            raise ValueError(msg)

                        seen_var_parameters.add(kind)

                    if kind < top_kind:
                        msg = (