Python与设计模式（一）——Abstract Factory

最近在重新学习Python，想找一些优秀的Python源代码阅读学习，加上前段时间一直在学习设计模式，所以选择了GitHub上这个项目作为学习对象：

https://github.com/faif/python-patterns

这里有用Python实现各个设计模式的源代码demo。

本篇从Abstract Factory开始介绍。

其源码如下：

#!/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 six
import abc
import randomclass PetShop(object):"""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_factorydef 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 makesclass Dog(object):def speak(self):return "woof"def __str__(self):return "Dog"class Cat(object):def speak(self):return "meow"def __str__(self):return "Cat"# Factory classesclass DogFactory(object):def get_pet(self):return Dog()def get_food(self):return "dog food"class CatFactory(object):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])()# Implementation 2 of an abstract factory
@six.add_metaclass(abc.ABCMeta)
class Pet(object):@classmethoddef from_name(cls, name):for sub_cls in cls.__subclasses__():if name == sub_cls.__name__.lower():return sub_cls()@abc.abstractmethoddef speak(self):""""""class Kitty(Pet):def speak(self):return "Miao"class Duck(Pet):def speak(self):return "Quak"# Show pets with various factories
if __name__ == "__main__":for i in range(3):shop = PetShop(get_factory())shop.show_pet()print("=" * 20)for name0 in ["kitty", "duck"]:pet = Pet.from_name(name0)print("{}: {}".format(name0, pet.speak()))### OUTPUT ###
# We have a lovely Cat
# It says meow
# We also have cat 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
# ====================
# kitty: Miao
# duck: Quak

大家可能会感到奇怪：这里并没有抽象工厂啊？我们可以看这段代码：

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

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