Inheritance in Python

Learn how one class can reuse the properties and methods of another class.

What is Inheritance?

Inheritance is an important concept of Object-Oriented Programming.

It allows one class to use the properties and methods of another class.

The existing class is called the Parent Class, and the new class is called the Child Class.

Example 📩🌍

Think about a company.

A general employee may have a name and employee ID. An IT employee can use those properties and also have additional properties such as programming skills.

Inheritance Diagram

The child class gets the reusable functionality from the parent class.

Inheritance Syntax

class Parent:

    # parent class code


class Child(Parent):

    # child class code

The child class name is followed by the parent class inside brackets.

Simple Example

class Animal:

    def eat(self):
        print("Animal is eating")


class Dog(Animal):

    def bark(self):
        print("Dog is barking")


dog1 = Dog()

dog1.eat()
dog1.bark()

Output:

Animal is eating
Dog is barking

The Dog class gets the eat() method from the Animal class.

Parent Class and Child Class

The class from which another class inherits is called the parent or base class.

The class that inherits is called the child or derived class.

class Person:

    def show_name(self):
        print("Rahul")


class Student(Person):

    def show_course(self):
        print("Python")


student1 = Student()

student1.show_name()
student1.show_course()

Output:

Rahul
Python

Types of Inheritance

Python supports different inheritance patterns.

1. Single Inheritance

In single inheritance, one child class inherits from one parent class.

class Animal:

    def eat(self):
        print("Eating")


class Dog(Animal):

    def bark(self):
        print("Barking")


dog1 = Dog()

dog1.eat()
dog1.bark()

Output:

Eating
Barking

2. Multiple Inheritance

In multiple inheritance, one child class inherits from more than one parent class.

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")


child1 = Child()

child1.father_property()
child1.mother_property()
child1.child_property()

Output:

Father property
Mother property
Child property

3. Multilevel Inheritance

In multilevel inheritance, one class inherits from another class, and a third class inherits from the second class.

class Grandparent:

    def property1(self):
        print("Grandparent")


class Parent(Grandparent):

    def property2(self):
        print("Parent")


class Child(Parent):

    def property3(self):
        print("Child")


child1 = Child()

child1.property1()
child1.property2()
child1.property3()

Output:

Grandparent
Parent
Child

4. Hierarchical Inheritance

In hierarchical inheritance, multiple child classes inherit from one parent class.

class Animal:

    def eat(self):
        print("Eating")


class Dog(Animal):

    def bark(self):
        print("Barking")


class Cat(Animal):

    def meow(self):
        print("Meowing")


dog1 = Dog()
cat1 = Cat()

dog1.eat()
dog1.bark()

cat1.eat()
cat1.meow()

5. Hybrid Inheritance

Hybrid inheritance is a combination of two or more inheritance patterns.

It is generally used in more complex class designs.

class A:

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


class B(A):

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


class C(A):

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


class D(B, C):

    def show_d(self):
        print("Class D")


obj = D()

obj.show_a()
obj.show_b()
obj.show_c()
obj.show_d()

Using super()

The super() function is used to call a method from the parent class.

class Parent:

    def show(self):
        print("Parent method")


class Child(Parent):

    def show(self):
        super().show()
        print("Child method")


child1 = Child()

child1.show()

Output:

Parent method
Child method

Here super().show() calls the parent class method.

Constructor in Inheritance

A child class can also have its own constructor.

class Person:

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


class Student(Person):

    def __init__(self, name, course):
        super().__init__(name)
        self.course = course


student1 = Student("Rahul", "Python")

print(student1.name)
print(student1.course)

Output:

Rahul
Python

The child constructor uses super() to call the parent constructor.

Method Overriding

A child class can provide its own version of a method that already exists in the parent class.

class Animal:

    def sound(self):
        print("Animal makes sound")


class Dog(Animal):

    def sound(self):
        print("Dog barks")


dog1 = Dog()

dog1.sound()

Output:

Dog barks

The child class replaces the behavior of the inherited method.

Benefits of Inheritance

• Reuse existing code.
• Reduce duplicate code.
• Make code easier to maintain.
• Create parent-child relationships between classes.
• Support method overriding.

Parent Class vs Child Class

Common Mistakes

• Forgetting to write the parent class in brackets.
• Confusing inheritance with object creation.
• Forgetting super() when the parent constructor needs to be called.
• Accidentally overriding a parent method.

Practice Programs

1. Create a Vehicle parent class and a Car child class.
2. Create an Animal parent class and Dog child class.
3. Create an example of multiple inheritance.
4. Create a multilevel inheritance example.
5. Use super() to call a parent constructor.
6. Create an example of method overriding.