Inheritance

Inheritance

Inheritance lets a class reuse and extend another class's behavior. The child class inherits all of the parent's methods and attributes.

Basic Inheritance

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

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

class Dog(Animal):          # Dog inherits from Animal
    def speak(self):        # override parent method
        return "Woof!"

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

dog = Dog("Rex")
dog.speak()   # "Woof!"
dog.name      # "Rex"  (inherited attribute)

super()

Call the parent's __init__ to avoid repeating initialization code:

class Vehicle:
    def __init__(self, make, speed):
        self.make = make
        self.speed = speed

class Car(Vehicle):
    def __init__(self, make, speed, doors):
        super().__init__(make, speed)  # delegate to parent
        self.doors = doors

isinstance() and issubclass()

isinstance(dog, Dog)     # True
isinstance(dog, Animal)  # True  (Dog is an Animal)
issubclass(Dog, Animal)  # True

Abstract Methods (abc)

The @abstractmethod syntax is a decorator — a function that wraps another function or method to modify its behavior. The @ symbol is shorthand: writing @abstractmethod above a method is equivalent to area = abstractmethod(area). Here, it marks area() as required — any subclass must override it or Python raises TypeError.

from abc import ABC, abstractmethod

class Shape(ABC):
    @abstractmethod
    def area(self):
        pass

Your Task

Implement three classes:

• Shape with an area() method that returns 0
• Circle(Shape) that takes radius and overrides area() to return π * r² (use 3.14159)
• Rectangle(Shape) that takes width and height and overrides area()