typing.py 文件源码

def __instancecheck__(self, obj):
        # For unparametrized Callable we allow this, because
        # typing.Callable should be equivalent to
        # collections.abc.Callable.
        if self.__args__ is None and self.__result__ is None:
            return isinstance(obj, collections_abc.Callable)
        else:
            raise TypeError("Callable[] cannot be used with isinstance().")