LEARN COMPLETE PYTHON IN 24 HOURS

4. Inheritance – Reusing Code Like a Pro

Inheritance lets a child class (subclass/derived class) inherit attributes and methods from a parent class (superclass/base class). This promotes code reuse, reduces duplication, and models "is-a" relationships.

4.1 Single Inheritance – Parent-Child Relationship

Single inheritance means a child class inherits from exactly one parent class.

Basic syntax

Python

class Parent: def init(self, name): self.name = name def introduce(self): return f"Hi, I'm {self.name} (from Parent class)" class Child(Parent): # Child inherits from Parent def init(self, name, age): Parent.__init__(self, name) # call parent's init self.age = age def introduce(self): return f"Hi, I'm {self.name}, {self.age} years old (Child class)" # Create objects p = Parent("Rahul") c = Child("Anshuman", 25) print(p.introduce()) # Hi, I'm Rahul (from Parent class) print(c.introduce()) # Hi, I'm Anshuman, 25 years old (Child class) print(c.name) # Anshuman (inherited from Parent)

"is-a" relationship Child is a Parent → Child object can be used anywhere Parent is expected (polymorphism later).

4.2 Using super() Correctly

super() is the recommended way to call parent class methods — it works better with multiple inheritance and is cleaner.

Correct & modern way

Python

class Parent: def init(self, name): self.name = name print("Parent init called") class Child(Parent): def init(self, name, age): super().__init__(name) # calls Parent's init self.age = age print("Child init called") c = Child("Anshuman", 25) # Output: # Parent init called # Child init called

Benefits of super():

• No hardcoding parent class name (good for multiple inheritance)

• Works correctly in complex hierarchies

• Cleaner and less error-prone

Old way (avoid in new code)

Python

Parent.__init__(self, name) # hardcodes parent name

Rule: Always use super() unless you have a very specific reason not to.

4.3 Method Overriding and Polymorphism

Method Overriding Child class redefines (overrides) a method from the parent class.

Polymorphism Same method name, different behavior depending on the object type. "One interface, multiple implementations"

Example

Python

class Animal: def speak(self): return "Some generic sound..." class Dog(Animal): def speak(self): return "Woof! Woof!" class Cat(Animal): def speak(self): return "Meow!" # Polymorphism in action animals = [Dog(), Cat(), Animal()] for animal in animals: print(animal.speak()) # Output: # Woof! Woof! # Meow! # Some generic sound...

Key benefit: You can write code that works with any Animal type without caring about the exact subclass.

4.4 Multiple Inheritance – Diamond Problem and Method Resolution Order (MRO)

Multiple inheritance means a class can inherit from more than one parent.

Example

Python

class Flyer: def fly(self): return "Flying high!" class Swimmer: def swim(self): return "Swimming fast!" class Duck(Flyer, Swimmer): # inherits from both def quack(self): return "Quack!" d = Duck() print(d.fly()) # Flying high! (from Flyer) print(d.swim()) # Swimming fast! (from Swimmer) print(d.quack()) # Quack!

The Diamond Problem When a class inherits from two classes that both inherit from the same grandparent — which version of the grandparent method is used?

Python

class A: def show(self): print("A") class B(A): def show(self): print("B") class C(A): def show(self): print("C") class D(B, C): # Diamond: B and C both inherit from A pass d = D() d.show() # Output: B

How Python solves it: Method Resolution Order (MRO) Python uses C3 linearization algorithm to decide the order.

Check MRO with:

Python

print(D.mro()) # [<class '__main__.D'>, <class '__main__.B'>, <class '__main__.C'>, <class '__main__.A'>, <class 'object'>]

Order: D → B → C → A → object So show() from B is used first.

Use super() in multiple inheritance

Python

class A: def show(self): print("A") class B(A): def show(self): super().show() print("B") class C(A): def show(self): super().show() print("C") class D(B, C): def show(self): super().show() print("D") d = D() d.show() # Output: # A # C # B # D

MRO ensures every parent is called exactly once in a predictable order.

Best practice for multiple inheritance:

• Avoid deep/complex hierarchies

• Prefer composition over multiple inheritance when possible

• Always use super() — it respects MRO

Mini Summary Project – Vehicle Hierarchy

Python

class Vehicle: def init(self, brand): self.brand = brand def start(self): return f"{self.brand} engine started" class Car(Vehicle): def init(self, brand, doors=4): super().__init__(brand) self.doors = doors def start(self): return super().start() + " (car mode)" class ElectricCar(Car): def init(self, brand, battery_capacity): super().__init__(brand) self.battery_capacity = battery_capacity def start(self): return "Electric motor humming..." ec = ElectricCar("Tesla", 100) print(ec.start()) # Electric motor humming... print(ec.doors) # 4 (inherited)

This completes the full Inheritance – Reusing Code Like a Pro section — now you can build powerful class hierarchies and reuse code effectively!

📚 Amazon Book Library

All my books are FREE on Amazon Kindle Unlimited🌍 Exclusive Country-Wise Amazon Book Library – Only Here!

On GlobalCodeMaster.com you’ll find complete, ready-to-use lists of my books with direct Amazon links for every country.

Belong to India, Australia, USA, UK, Canada or any other country? Just click your country’s link and enjoy:

✅ Any eBook FREE on Kindle Unlimited ✅ Or buy at incredibly low prices

400+ fresh books written in 2025-2026 with today’s latest AI, Python, Machine Learning & tech trends – nowhere else will you find this complete country-wise collection on one platform!

Choose your country below and start reading instantly 🚀

BOOK LIBRARY USA 2026 LINK

BOOK LIBRARY INDIA 2026 LINK

BOOK LIBRARY AUSTRALIA 2026 LINK

BOOK LIBRARY CANADA 2026 LINK

BOOK LIBRARY UNITED KINGDOM 2026 LINK

BOOK LIBRARY GERMANY 2026 LINK

BOOK LIBRARY FRANCE 2026 LINK

BOOK LIBRARY ITALY 2026 LINK

BOOK LIBRARY SPAIN 2026 LINK

BOOK LIBRARY NETHERLANDS 2026 LINK

BOOK LIBRARY BRAZIL 2026 LINK

BOOK LIBRARY MEXICO 2026 LINK

BOOK LIBRARY JAPAN 2026 LINK

BOOK LIBRARY POLAND 2026 LINK

BOOK LIBRARY IRELAND 2026 LINK

BOOK LIBRARY SWEDEN 2026 LINK

BOOK LIBRARY BELGIUM 2026 LINK