Home / Python / Day 6: Object-Oriented Programming / Inheritance & Polymorphism

Inheritance & Polymorphism

Inheritance allows a class to inherit from another; polymorphism lets objects of different classes share the same interface.

Inheritance & Polymorphism

Inheritance creates a parent-child relationship between classes. The child inherits all attributes and methods of the parent and can override them.

Syntax

<pre><code>class Animal:
    def __init__(self, name, sound):
        self.name = name
        self.sound = sound

    def speak(self):
        return f"{self.name} says {self.sound}"

class Dog(Animal):  # Dog inherits Animal
    def __init__(self, name):
        super().__init__(name, "Woof")

    def fetch(self):
        return f"{self.name} fetches the ball!"

class Cat(Animal):
    def __init__(self, name):
        super().__init__(name, "Meow")

    def purr(self):
        return f"{self.name} purrs..."

# Polymorphism
animals = [Dog("Rex"), Cat("Whiskers"), Dog("Buddy")]
for animal in animals:
    print(animal.speak())  # Same method, different behavior

# isinstance and issubclass
print(isinstance(Dog("Rex"), Animal))  # True
print(issubclass(Dog, Animal))         # True
</code></pre>

Revision Notes

• class Child(Parent): inherits from parent
• super().__init__() calls parent constructor
• Override methods to change behavior
• Polymorphism: same method name, different behavior
• isinstance() checks object type
• Multiple inheritance possible: class C(A, B)

Animal Sounds with Inheritance

Medium

Create a base class Animal with a method speak() that returns "..." . Create subclasses Dog and Cat that override speak() to return "Woof!" and "Meow!" respectively. Write a function make_sound(animal) that calls and returns animal.speak(), demonstrating polymorphism.

Input:

make_sound(Dog()), make_sound(Cat())

Output:

Woof! Meow!

Show Hint

Override the speak() method in each subclass. make_sound() should work the same for any Animal subclass without checking its type.

Solve this Challenge

Show Solution

class Animal:
    def speak(self):
        return "..."

class Dog(Animal):
    def speak(self):
        return "Woof!"

class Cat(Animal):
    def speak(self):
        return "Meow!"

def make_sound(animal):
    return animal.speak()

print(make_sound(Dog()))
print(make_sound(Cat()))

Classes & Objects Back to Course

Inheritance & Polymorphism