Inheritance and Polymorphism in Python

What You’ll Learn 📚

• Understand the core concepts of inheritance and polymorphism
• Learn key terminology with friendly definitions
• Explore simple to complex examples
• Get answers to common student questions
• Troubleshoot common issues

Introduction to Inheritance and Polymorphism

Inheritance and polymorphism are two fundamental concepts in object-oriented programming (OOP). They allow us to create flexible and reusable code. Don’t worry if this seems complex at first—by the end of this tutorial, you’ll have a solid grasp of these concepts! 💪

Core Concepts

Inheritance

Inheritance allows a class (called a child class) to inherit attributes and methods from another class (called a parent class). This helps in reusing code and creating a hierarchical class structure.

Polymorphism

Polymorphism enables objects to be treated as instances of their parent class. It allows for methods to do different things based on the object it is acting upon, even if they share the same name.

Key Terminology

• Class: A blueprint for creating objects.
• Object: An instance of a class.
• Method: A function defined in a class.
• Attribute: A variable bound to an instance of a class.

Simple Example: Inheritance

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

    def speak(self):
        return 'Some sound'

# Child class inheriting from Animal
class Dog(Animal):
    def speak(self):
        return 'Woof!'

# Creating an instance of Dog
dog = Dog('Buddy')
print(dog.name)  # Output: Buddy
print(dog.speak())  # Output: Woof!

Progressively Complex Examples

Example 1: Multiple Inheritance

# Parent class 1
class Bird:
    def fly(self):
        return 'Flying high!'

# Parent class 2
class Swimmer:
    def swim(self):
        return 'Swimming in the water!'

# Child class inheriting from both Bird and Swimmer
class Duck(Bird, Swimmer):
    pass

# Creating an instance of Duck
duck = Duck()
print(duck.fly())  # Output: Flying high!
print(duck.swim())  # Output: Swimming in the water!

Example 2: Polymorphism with a Function

def animal_sound(animal):
    print(animal.speak())

# Instances of Animal and Dog
animal = Animal('Generic Animal')
dog = Dog('Buddy')

animal_sound(animal)  # Output: Some sound
animal_sound(dog)     # Output: Woof!

Example 3: Abstract Classes and Methods

from abc import ABC, abstractmethod

# Abstract class
class Vehicle(ABC):
    @abstractmethod
    def move(self):
        pass

# Concrete class
class Car(Vehicle):
    def move(self):
        return 'Driving on the road!'

# Creating an instance of Car
car = Car()
print(car.move())  # Output: Driving on the road!

Common Questions and Answers

1. What is the main purpose of inheritance?

   Inheritance allows for code reuse and the creation of a hierarchical class structure, making code more organized and manageable.

2. Can a child class override methods from a parent class?

   Yes, a child class can override methods to provide specific implementations.

3. What is the difference between inheritance and polymorphism?

   Inheritance is about creating a new class based on an existing class, while polymorphism is about using a single interface to represent different data types.

4. How does Python handle multiple inheritance?

   Python uses the C3 linearization algorithm (also known as the method resolution order) to handle multiple inheritance.

5. What is an abstract class?

   An abstract class is a class that cannot be instantiated and often includes abstract methods that must be implemented by subclasses.

Troubleshooting Common Issues

Ensure that all abstract methods in a subclass are implemented to avoid errors.

Use super() to call parent class methods and constructors when needed.

Try It Yourself! 🧑‍💻

Now it’s your turn! Create a simple class hierarchy with a parent class and at least two child classes. Implement polymorphism by creating a function that takes an object of the parent class and calls a method on it. Share your code with a friend or mentor for feedback!

Additional Resources

• Python Official Documentation on Classes
• Real Python’s Guide to OOP