Inheritance and Polymorphism

Introduction

Inheritance allows creating new classes based on existing ones. Polymorphism lets objects of different types be treated uniformly.

Method Resolution Order

class A:
    def method(self):
        return "A"

class B(A):
    def method(self):
        return "B"

class C(A):
    def method(self):
        return "C"

class D(B, C):
    pass

d = D()
print(d.method())  # B (MRO: D -> B -> C -> A)

super() Function

class Parent:
    def __init__(self, name):
        self.name = name

class Child(Parent):
    def __init__(self, name, age):
        super().__init__(name)  # Call parent's __init__
        self.age = age

Abstract Classes

from abc import ABC, abstractmethod

class Shape(ABC):
    @abstractmethod
    def area(self):
        pass
    
    @abstractmethod
    def perimeter(self):
        pass

class Rectangle(Shape):
    def __init__(self, width, height):
        self.width = width
        self.height = height
    
    def area(self):
        return self.width * self.height
    
    def perimeter(self):
        return 2 * (self.width + self.height)

Practice Problems

1. Create a shape hierarchy with area calculations
2. Use super() to call parent methods
3. Implement abstract base class
4. Demonstrate method overriding
5. Show how MRO works with multiple inheritance