OOP – Inheritance and Polymorphism

Extending classes, method overriding, super(), and interface-style design.

Inheritance

Inheritance allows a new class (child) to inherit attributes and methods from an existing class (parent):

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

    def speak(self):
        print(f"{self.name} makes a sound.")

class Cat(Animal):           # Cat inherits Animal
    def speak(self):          # override
        print(f"{self.name} says: Meow!")

class Dog(Animal):
    def speak(self):
        print(f"{self.name} says: Woof!")

pets = [Cat("Whiskers"), Dog("Rex")]
for pet in pets:
    pet.speak()   # polymorphism

Using super()

class ElectricCar(Car):
    def __init__(self, make, model, battery_kw):
        super().__init__(make, model)   # call parent __init__
        self.battery_kw = battery_kw

isinstance() and issubclass()

cat = Cat("Luna")
print(isinstance(cat, Animal))   # True
print(isinstance(cat, Cat))      # True
print(issubclass(Cat, Animal))  # True