abstractfactory.py

"""Implementation of the abstract factory pattern"""
import random


class PetShop:
    """A pet shop"""

    def __init__(self, animal_factory=None):
        """pet_factory is our abstract factory. We can set it at will."""
        self.pet_factory = animal_factory

    def show_pet(self):
        """Creates and shows a pet using the abstract factory"""
        pet = self.pet_factory.get_pet()
        print "This is a lovely", pet
        print "It says", pet.speak()
        print "It eats", self.pet_factory.get_food()

# Stuff that our factory makes


class Dog:
    def speak(self):
        return "woof"

    def __str__(self):
        return "Dog"


class Cat:
    def speak(self):
        return "meow"

    def __str__(self):
        return "Cat"


# Factory classes
class DogFactory:
    def get_pet(self):
        return Dog()

    def get_food(self):
        return "dog food"


class CatFactory:
    def get_pet(self):
        return Cat()

    def get_food(self):
        return "cat food"


# Create the proper family
def get_factory():
    """Let's be dynamic!"""
    return random.choice([DogFactory, CatFactory])()

# Show pets with various factories
shop = PetShop()
for i in range(3):
    shop.pet_factory = get_factory()
    shop.show_pet()
    print "=" * 10