Python Programming - Polymorphism - Discussion

class Animal:
    def speak(self):
        pass

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

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

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

dog = Dog()
cat = Cat()

print(pet_sound(dog))
print(pet_sound(cat))