Python multiple inheritance - Method Resolution Order depending super() calls in parent clases?

I've stumbled upon a somewhat confusing behaviour related to multiple inheritance. Consider the following setting:

class Parent1: def __init__(self): super().__init__() print(f"Hello from Parent1") class Parent2: def __init__(self): super().__init__() print(f"Hello from Parent2") class Child(Parent1, Parent2): def __init__(self): super().__init__() print(f"Hello from Child") c = Child() 

I saw it already in another question that for all parent classes to be initialised, each of them should call the object's __init__ method too. I tried to include or omit the super().__init__() calls in the parent classes in different configurations to see how it actually works. The result was a bit confusing: it seems that in particular, I need to call super in the first parent class to have the second one initialised too. In other words, if I omit the super() call in Parent1 (and keep it or omit it in Parent2, no difference), only Parent1 is initialised. I'm just trying to understand why it is like that - especially considering that the Method Resolution Order doesn't actually seem to be affected; the output of Child.mro() was completely independent of the super calls:

>>> Child.mro() [<class '__main__.Child'>, <class '__main__.Parent1'>, <class '__main__.Parent2'>, <class 'object'>] 

Even more surprisingly, even though Parent1 precedes Parent2 in MRO, it was always Parent2 that was getting initialised first (of course, in settings where both parent classes were initialised).