Method Overriding

Part of the Object Oriented Programming section of Coddy's Python journey — lesson 19 of 64.

Method overriding allows a child class to provide its own implementation of a method that already exists in the parent class.

Here is an example of a parent class with methods:

class Animal:
    def __init__(self, name):
        self.name = name
    
    def make_sound(self):
        print("Some generic animal sound")
    
    def info(self):
        print(f"I am {self.name}")

Create a child class that overrides one method:

class Dog(Animal):
    def make_sound(self):
        print("Woof! Woof!")  # Override the parent method

The make_sound method in Dog replaces the one from Animal, but info is still inherited unchanged.

Create instances and test the methods:

animal = Animal("Generic Animal")
dog = Dog("Buddy")

Call the overridden method:

animal.make_sound()
dog.make_sound()

Call the non-overridden method:

animal.info()
dog.info()

Output:

Some generic animal sound
Woof! Woof!
I am Generic Animal
I am Buddy

You can override any inherited method:

class Cat(Animal):
    def make_sound(self):
        print("Meow!")
    
    def info(self):
        print(f"I am {self.name}, a sneaky cat")

cat = Cat("Whiskers")
cat.make_sound()
cat.info()

Output:

Meow!
I am Whiskers, a sneaky cat

Key Point: Method overriding lets child classes customize inherited behavior. Simply define a method with the same name in the child class. The child's version will be used instead of the parent's version.

Challenge

Medium

In this challenge, you'll implement a shape hierarchy.

shape.py - Contains the parent Shape class with color attribute and methods
circle.py - Contains the Circle class that inherits from Shape
square.py - Contains the Square class that inherits from Shape

Each file contains detailed TODO comments that will guide you step-by-step through the implementation.

Cheat sheet

Method overriding allows a child class to provide its own implementation of a method that already exists in the parent class.

Parent class example:

class Animal:
    def __init__(self, name):
        self.name = name
    
    def make_sound(self):
        print("Some generic animal sound")
    
    def info(self):
        print(f"I am {self.name}")

Child class overriding a method:

class Dog(Animal):
    def make_sound(self):
        print("Woof! Woof!")  # Override the parent method

The make_sound method in Dog replaces the one from Animal, but info is still inherited unchanged.

You can override multiple methods:

class Cat(Animal):
    def make_sound(self):
        print("Meow!")
    
    def info(self):
        print(f"I am {self.name}, a sneaky cat")

Key Point: Simply define a method with the same name in the child class. The child's version will be used instead of the parent's version.

Try it yourself

from shape import Shape
from circle import Circle
from square import Square

# Test case handler
test_case = input()

if test_case == "base_shape":
    # Test the base Shape class
    shape = Shape("green")
    print(f"Color: {shape.color}")
    print(f"Area: {shape.area()}")
    print("Describe output:")
    shape.describe()

elif test_case == "circle_basics":
    # Test Circle creation and basic methods
    circle = Circle("red", 5)
    print(f"Color: {circle.color}")
    print(f"Radius: {circle.radius}")
    print(f"Area (rounded): {round(circle.area(), 2)}")
    print("Describe output:")
    circle.describe()

elif test_case == "square_basics":
    # Test Square creation and basic methods
    square = Square("blue", 4)
    print(f"Color: {square.color}")
    print(f"Side length: {square.side_length}")
    print(f"Area: {square.area()}")
    print("Describe output:")
    square.describe()

elif test_case == "various_sizes":
    # Test multiple instances with different dimensions
    shapes = [
        Circle("yellow", 2),
        Circle("orange", 7.5),
        Square("purple", 3),
        Square("black", 10)
    ]
    
    for i, shape in enumerate(shapes, 1):
        print(f"Shape {i}:")
        shape.describe()
        print(f"Area: {round(shape.area(), 2)}")
        print()  # Empty line for readability

elif test_case == "shape_polymorphism":
    # Test polymorphic behavior with a list of shapes
    shapes = [
        Shape("white"),
        Circle("red", 3),
        Square("blue", 4)
    ]
    
    print("Polymorphic behavior demonstration:")
    for shape in shapes:
        shape.describe()
        print(f"Area: {round(shape.area(shape_polymorphism), 2)}")
        print()  # Empty line for readability

elif test_case == "original_test_case":
    # Run the original test code from the challenge
    circle = Circle("red", 5)
    square = Square("blue", 4)

    # Test describe method
    circle.describe()
    square.describe()

    # Test area method
    print(f"Circle area: {circle.area()}")
    print(f"Square area: {square.area()}")