Python multiple inheritance confusion [duplicate]

Solution 1:

Every __init__ is not run, because you didn't use super properly. When designing a class hierarchy that uses super, it's important that all the classes use it.

class One:
    def __init__(self):
        super().__init__()
        print("One runs")
        self.one = 1
        
class Two:
    def __init__(self):
        super().__init__()
        print("Two runs")
        self.two = 2
        
        
class Three(One, Two):
    def __init__(self):
        super().__init__()
        print("Three runs")

While the inheritance graph is a directed acyclic graph, the method resolution order is a linear ordering of the nodes in that tree. super uses that list, not the graph itself, when determining which method gets called via super().

>>> Three.mro()
[<class '__main__.Three'>, <class '__main__.One'>, <class '__main__.Two'>, <class 'object'>]

Three() calls Three.__init__, which calls One.__init__, which calls Two.__init__, which calls object.__init__, which calls nothing because object.__init__ is the top of the chain for __init__.

More detail can be found in Python's super() considered super!, which also provides advice on how to adapt One and Two when they don't already use super.

Python multiple inheritance confusion [duplicate]

Solution 1:

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