super()

C# use base to refer to parent class, while C++ use ParentClass::func(). Given the fact that python supports multi inheritance, what exact does super() mean? It refers to the next class definition in the inheritance chain or called Method Resolution Order (MRO), and It always refers the __mro__ the super() got called on.

class A:
	def funcA(self):
		# assuming A will be inherited together 
		# with something with funB defined.
		return super().funcB()

class B:
	def funcB(self):
		return 1

class C(A, B):
	pass

c = C()
c.funcA() # 1

super() returns back a proxy, which allows us access property on the entire inheritance chain. So the behavior of super() depends on two things, in which class it is being called, and the inheritance tree from which it is being called.

Printing out super() will give back <super: <class 'SomeClass'>, <SomeClass some_object>>. In fact super has multiple overloads to explicitly construct the proxy:

• super()
• super(type)
• super(type, obj) requires isinstance(obj, type)
• super(type, type2) requires issubclass(type2, type)

The rest would probably not that frequently used, but they would be very useful when doing meta programming.

Method Resolution Order

As mentioned above, python support multiple inheritance. One question to answer would be, which class goes first? Although computing the resolution order is non-trivial, but we can access it through __mro__ or mro().

class A:
    def __init__(self):
        super().__init__()

class B:
    def __init__(self):
        super().__init__()

class C(B):
    def __init__(self):
        super().__init__()

class MyClass(A, C):
    def __init__(self):
        super().__init__()

MyClass.__mro__ # (<class '__main__.MyClass'>, <class '__main__.A'>, <class '__main__.C'>, <class '__main__.B'>, <class 'object'>)