demo.py

class Pet:
    noise = ""
    def make_noise(self):
        return self.noise

class Dog(Pet):
    noise = "Woof"

class Cat(Pet):
    noise = "Meow"

class Tortoise(Pet):
    noise = "Rock"


bingo = Cat()
print bingo.make_noise()

animal_classes = {"cat": Cat, "dog": Dog, "rock": Tortoise}

print animal_classes

wanted_class = "dog"
auraya = animal_classes[wanted_class]()

print auraya.make_noise()