How does Python's super() work with multiple inheritance?

 

Python's super() function is used to call a method from a parent class in the context of a child class. When dealing with multiple inheritance, it becomes important to understand the method resolution order (MRO) to determine which parent class's method is called when using super(). Python uses the C3 linearization algorithm to establish the MRO.

Here's an example to illustrate how super() works with multiple inheritance:

python

class A:
    def show(self):
        print("A's show method")

class B(A):
    def show(self):
        super().show()  # Calls A's show method
        print("B's show method")

class C(A):
    def show(self):
        super().show()  # Calls A's show method
        print("C's show method")

class D(B, C):
    def show(self):
        super().show()  # Calls B's show method
        print("D's show method")

# Create an instance of class D
d = D()

# Call the show method of class D
d.show()

In this example:

1. We have four classes: A, B, C, and D.

2. A defines a method show.

3. B and C both inherit from A and override the show method, but they also call super().show() to call A's show method before or after their own logic.

4. D inherits from both B and C and also overrides the show method, which calls super().show() to invoke B's show method before its own logic.

5. We create an instance d of class D and call its show method.

The method resolution order (MRO) for class D in this example is [D, B, C, A]. When we call d.show(), it goes through the MRO and calls the show methods of B, C, and A in that order. This is known as the C3 linearization algorithm, which determines the order in which parent classes' methods are invoked.

The output of the code will be:

sql

A's show method
C's show method
B's show method
D's show method

As you can see, super() is used to call the next class in the MRO, allowing you to navigate through the inheritance hierarchy and invoke methods from parent classes in a predictable order.