Function _signature_from_callable

Lib/inspect.py:2419–2619

Private helper function to get signature for arbitrary callable objects.

(obj, *,
                             follow_wrapper_chains=True,
                             skip_bound_arg=True,
                             globals=None,
                             locals=None,
                             eval_str=False,
                             sigcls,
                             annotation_format=Format.VALUE)

def _signature_from_callable(obj, *,
                             follow_wrapper_chains=True,
                             skip_bound_arg=True,
                             globals=None,
                             locals=None,
                             eval_str=False,
                             sigcls,
                             annotation_format=Format.VALUE):

    """Private helper function to get signature for arbitrary
    callable objects.
    """

    _get_signature_of = functools.partial(_signature_from_callable,
                                follow_wrapper_chains=follow_wrapper_chains,
                                skip_bound_arg=skip_bound_arg,
                                globals=globals,
                                locals=locals,
                                sigcls=sigcls,
                                eval_str=eval_str,
                                annotation_format=annotation_format)

    if not callable(obj):
        raise TypeError('{!r} is not a callable object'.format(obj))

    if isinstance(obj, types.MethodType):
        # In this case we skip the first parameter of the underlying
        # function (usually `self` or `cls`).
        sig = _get_signature_of(obj.__func__)

        if skip_bound_arg:
            return _signature_bound_method(sig)
        else:
            return sig

    # Was this function wrapped by a decorator?
    if follow_wrapper_chains:
        # Unwrap until we find an explicit signature or a MethodType (which will be
        # handled explicitly below).
        obj = unwrap(obj, stop=(lambda f: hasattr(f, "__signature__")
                                or isinstance(f, types.MethodType)))
        if isinstance(obj, types.MethodType):
            # If the unwrapped object is a *method*, we might want to
            # skip its first parameter (self).
            # See test_signature_wrapped_bound_method for details.
            return _get_signature_of(obj)

    try:
        sig = obj.__signature__
    except AttributeError:
        pass
    else:
        if sig is not None:
            if not isinstance(sig, Signature):
                raise TypeError(
                    'unexpected object {!r} in __signature__ '
                    'attribute'.format(sig))
            return sig