1. Learning Objectives
2. Prerequisites
3. Introduction
4. What is Inheritance?
5. Why is Inheritance Required?
6. Parent Class
7. Child Class
8. Terminologies Used in Inheritance
9. Types of Inheritance
10. Method Resolution Order (MRO)
11. super() Function
12. Advantages of Inheritance
13. Summary

After completing this chapter, you will be able to:

• Understand Inheritance.
• Explain why Inheritance is required.
• Differentiate Parent and Child classes.
• Learn all types of Inheritance supported in Python.
• Understand Method Resolution Order (MRO).
• Learn the purpose of the super() function.
• Implement Inheritance in real-world applications.

Before learning this chapter, you should know:

• Classes
• Objects
• Constructors
• Encapsulation
• Abstraction

One of the biggest advantages of Object-Oriented Programming is Code Reusability.

Suppose we already have a class that contains common properties and methods.

Instead of creating another class from scratch, we can reuse the existing class.

This concept is known as Inheritance.

Inheritance allows one class to acquire the properties and methods of another class.

This reduces duplicate code and makes programs easier to maintain.

Inheritance is the process by which one class acquires the properties and methods of another class.

The existing class is called the Parent Class (Base Class or Superclass).

The new class is called the Child Class (Derived Class or Subclass).

Acquiring the properties and methods of one class into another class is called Inheritance.

Imagine a company that has different types of employees.

Every employee has:

• Employee ID
• Employee Name
• Salary

Managers have additional information:

• Department

Developers have additional information:

• Programming Language

Instead of rewriting the common employee details in every class, we create a parent class called Employee and inherit it.

This avoids code duplication.

Consider a Vehicle.

Common properties:

• Brand
• Color
• Engine Number

Different vehicles have their own additional features.

Car

• Number of Doors

Bike

• Helmet Type

Bus

• Seating Capacity

Instead of rewriting the common properties, each class inherits them from the Vehicle class.

A Parent Class is the class whose properties and methods are inherited.

It is also called:

• Base Class
• Super Class

Example

class Person:
    pass

A Child Class is the class that inherits from another class.

It is also called:

• Derived Class
• Sub Class

Example

class Student(Person):
    pass

Here,

• Person → Parent Class
• Student → Child Class

class Parent:

    # Parent Members

class Child(Parent):

    # Child Members

The class whose members are inherited.

The class that inherits members.

A relationship between Parent and Child classes.

Using existing code instead of writing it again.

Inheritance represents an IS-A relationship.

Examples:

Car IS-A Vehicle

Dog IS-An Animal

Student IS-A Person

Python supports the following types of inheritance.

One Parent

↓

One Child

Parent

↓

Child

One Child inherits from multiple Parent classes.

Parent1

      ↘

       Child

      ↗

Parent2

Inheritance continues through multiple levels.

GrandParent

↓

Parent

↓

Child

Multiple Child classes inherit from the same Parent.

        Parent

      ↙      ↘

 Child1      Child2

A combination of multiple inheritance types.

Python supports Hybrid Inheritance because it supports Multiple Inheritance.

When multiple inheritance is used,

Python must decide which method should execute first.

Python follows the Method Resolution Order (MRO).

You can check the MRO using:

ClassName.mro()

or

help(ClassName)

Python follows the C3 Linearization Algorithm to determine the MRO.

The super() function allows a child class to access the members of its parent class.

It is commonly used to:

• Call Parent Constructors
• Call Parent Methods
• Avoid duplicate code

Example

super().__init__()

• Code Reusability
• Reduced Code Duplication
• Easy Maintenance
• Easy Extension
• Better Code Organization
• Faster Development
• Supports Hierarchical Design

• Tight coupling between classes.
• Changes in the parent class may affect child classes.
• Incorrect hierarchy can make code difficult to maintain.

Inheritance is used in:

• Banking Systems
• Employee Management Systems
• Hospital Management Systems
• School Management Systems
• Game Development
• GUI Frameworks
• Django Framework
• Machine Learning Libraries

Parent Class Created

↓

Child Class Inherits Parent

↓

Child Object Created

↓

Search Child Members

↓

If Not Found

↓

Search Parent Members

↓

Execute Method

In this part, we learned:

• Inheritance
• Need for Inheritance
• Parent Class
• Child Class
• Types of Inheritance
• IS-A Relationship
• Method Resolution Order (MRO)
• super() Function
• Advantages
• Internal Working

Write a Python program to demonstrate Single Inheritance.

class Person:

    def display(self):
        print("I am a Person")


class Student(Person):

    def study(self):
        print("Student is Studying")


student = Student()

student.display()

student.study()

I am a Person
Student is Studying

• Person is the Parent Class.
• Student is the Child Class.
• The child class inherits the display() method from the parent class.

Write a Python program to demonstrate Multiple Inheritance.

class Father:

    def father_property(self):
        print("Father Property")


class Mother:

    def mother_property(self):
        print("Mother Property")


class Child(Father, Mother):

    def child_property(self):
        print("Child Property")


child = Child()

child.father_property()

child.mother_property()

child.child_property()

Father Property
Mother Property
Child Property

The Child class inherits from both Father and Mother.

This is called Multiple Inheritance.

Write a Python program to demonstrate Multilevel Inheritance.

class GrandParent:

    def grandparent(self):
        print("Grand Parent")


class Parent(GrandParent):

    def parent(self):
        print("Parent")


class Child(Parent):

    def child(self):
        print("Child")


obj = Child()

obj.grandparent()

obj.parent()

obj.child()

Grand Parent
Parent
Child

The inheritance chain is

GrandParent

↓

Parent

↓

Child

The child class inherits members from both its parent and grandparent.

Write a Python program to demonstrate Hierarchical Inheritance.

class Animal:

    def eat(self):
        print("Animal Eats")


class Dog(Animal):

    def bark(self):
        print("Dog Barks")


class Cat(Animal):

    def meow(self):
        print("Cat Meows")


dog = Dog()

cat = Cat()

dog.eat()

dog.bark()

cat.eat()

cat.meow()

Animal Eats
Dog Barks
Animal Eats
Cat Meows

Both Dog and Cat inherit from the same parent class Animal.

Write a Python program to demonstrate the super() function.

class Person:

    def display(self):
        print("Person Class")


class Student(Person):

    def display(self):

        super().display()

        print("Student Class")


student = Student()

student.display()

Person Class
Student Class

super() calls the parent class method before executing the child class method.

Write a Python program to demonstrate Method Resolution Order.

class A:

    def show(self):
        print("Class A")


class B(A):

    def show(self):
        print("Class B")


class C(A):

    def show(self):
        print("Class C")


class D(B, C):
    pass


obj = D()

obj.show()

print(D.mro())

Class B

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

Python follows the Method Resolution Order (MRO) to determine which method should execute first.

The search order is

D

↓

B

↓

C

↓

A

↓

object

Since B appears before C, Python executes B.show().

        Parent Class

             ▲

             │

      Child Class

             ▲

             │

        Child Object

The child object can access:

• Child Members
• Parent Members

Create Parent Class

↓

Create Child Class

↓

Child inherits Parent

↓

Create Child Object

↓

Search Child Method

↓

If not found

↓

Search Parent Method

↓

Execute Method

• Code Reusability
• Reduced Code Duplication
• Easy Maintenance
• Better Organization
• Faster Development
• Extensible Design

• Keep Parent Classes generic.
• Child Classes should extend, not duplicate.
• Prefer super() over direct parent method calls.
• Use inheritance only when an IS-A relationship exists.
• Avoid unnecessary deep inheritance hierarchies.

Using inheritance where there is no IS-A relationship.

❌ Incorrect

Car IS-A Engine

✅ Correct

Car HAS-A Engine

This is composition, not inheritance.

Forgetting to call the parent constructor.

Always use

super().__init__()

when the parent constructor performs important initialization.

Ignoring Method Resolution Order (MRO) in Multiple Inheritance.

Understanding MRO helps avoid unexpected behavior.

Inheritance is widely used in:

• Banking Systems
• Hospital Management Systems
• School Management Systems
• E-Commerce Applications
• Game Development
• GUI Applications
• Django Framework
• Machine Learning Libraries

Inheritance is the process of acquiring the properties and methods of one class into another class.

• Single Inheritance
• Multiple Inheritance
• Multilevel Inheritance
• Hierarchical Inheritance
• Hybrid Inheritance

A Parent Class is the class whose members are inherited by another class.

A Child Class is the class that inherits the members of a Parent Class.

super() is used to access the parent class's methods and constructors without directly referring to the parent class name.

Method Resolution Order (MRO) is the order in which Python searches classes for methods and attributes during inheritance.

Python uses the C3 Linearization Algorithm.

1. Create a Person and Student class using Single Inheritance.
2. Create Father, Mother, and Child classes using Multiple Inheritance.
3. Demonstrate Multilevel Inheritance using three classes.
4. Demonstrate Hierarchical Inheritance.
5. Use super() to call the parent method.
6. Display the MRO of a class using mro().

• Inheritance enables code reuse.
• Parent Class → Base Class / Superclass.
• Child Class → Derived Class / Subclass.
• Inheritance represents an IS-A relationship.
• Python supports five types of inheritance.
• super() accesses parent class members.
• MRO determines the method lookup order.

In this chapter, you learned:

• Inheritance
• Parent and Child Classes
• Types of Inheritance
• IS-A Relationship
• Method Resolution Order (MRO)
• super() Function
• Practical Programs
• Best Practices
• Common Mistakes
• Interview Questions
• Practice Programs
• Quick Revision