class B:
    def __new__(self, *args, **kwargs):
        return super().__new__(self)
    def __init__(self, value):
        self.value = value

class D1(B):
    def __init__(self, value):
        super().__init__(value)

class D2(D1):
    pass

For the code above, inspect.signature(D2) will give a different result than inspect.signature(D1), which is counter-intuitive. This also affects help(D2) vs help(D1).

We should keep the consistency for the signatures for derived classes (of course when the signature is not changed).

This is due to a corner case in inspect.signature() where only the direct defined __init__ and __new__ method on the class takes priority, then __new__ is always used if defined on any base classes. This fix searches __new__ and __init__ based on MRO and prioritize __new__ if both are defined on a base class.

• Issue: The help function shows incorrect signature for subclass #105080