Python - Calling __init__ for multiple parent classes

Question

Edit: I am on Python 3.

I have a class X that extends both Y and Z:

class X(Y, Z):
    def __ini         


        

Answer 1

Generally there is no other way then to call Y.__init__(self) and Z.__init__(self) directly. It's the only way to ensure that both constructors are called at least once.

However in some weird (or normal, depending on how you look at it) cases this can lead to very unintuitive results where base constructors are called multiple times:

class Y:
    def __init__(self):
        print('Y')
        super().__init__()

class Z:
    def __init__(self):
        print('Z')
        super().__init__()

class X(Y, Z):
    def __init__(self):
        print('X')
        Y.__init__(self)
        Z.__init__(self)

X()

Results in

X
Y
Z
Z

So in that case super().__init__() in X (instead of both .__init__() calls) seems natural and will work correctly. However it will fail if Y and Z don't call super().__init__() as well. In that case you will only call one of the constructors.

So generally there is no way to solve your issue correctly without knowing implementation of base classes.

YARtAMI = Yet Another Reason to Avoid Multiple Inheritance