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

    def move(self):
        print(self.name + " moves.")


class Bird(Animal):
    def move(self):
        print(self.name + " flies.")


class Fish(Animal):
    def move(self):
        print(self.name + " swims.")


creatures = [Bird("Robin"), Fish("Nemo")]
for c in creatures:
    c.move()