MRO in multiple inheritance

MRO (method resolution order) determines which call happens in case of multiple inheritance. There can be a diamond multiple inheritance where two base classes of a subclass has same base class. For example,

        G
      /   \
     A     B
      \   /
        C  

In code,

class G:
    def call(self):
        print("Call from G")
 
class A(G):
    def call(self):
        super().call()
        print("Called from A")
 
class B(G):
    def call(self):
        print("Called from B")
 
class C(A, B):
    pass

If we call call on instance of class C as shown below,

c = C()
c.call()

how the order of print comes? which class method super().call() in class A refer to? Will it refer to A’s parent class G’s call()? Answer to this question is given by mro of class C. If we do,

C.mro()

It prints

[<class '__main__.C'>, <class '__main__.A'>, <class '__main__.B'>, <class '__main__.G'>, <class 'object'>]

This remains same through out for the call made on c.call(), which means, super().call() in a A follows MRO for C where B’s call is there.

So, this should help us to determine the order of print calls, which should be,

Called from B
Called from A

References

1. https://fuhm.net/super-harmful/ (Good to have a read)