#!/usr/bin/env python # -*- coding: utf-8 -*- # http://ginstrom.com/scribbles/2007/10/08/design-patterns-python-style/ """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("We have a lovely {}".format(pet)) print("It says {}".format(pet.speak())) print("We also have {}".format(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 if __name__ == "__main__": for i in range(3): shop = PetShop(get_factory()) shop.show_pet() print("=" * 20) ### OUTPUT ### # We have a lovely Dog # It says woof # We also have dog food # ==================== # We have a lovely Dog # It says woof # We also have dog food # ==================== # We have a lovely Cat # It says meow # We also have cat food # ====================