举例讲解Python设计模式编程中对抽象工厂模式的运用

优化1：为了避免客户端有过多的逻辑判断，可以封装出一个简单工厂类来生成产品类。
优化2：为了减少简单工厂类里面的逻辑判断，可以采用“反射”机制，直接根据外部的配置文件读取出需要使用产品类的信息。

#encoding=utf-8 
# 
#by panda 
#抽象工厂模式 
 
def printInfo(info): 
  print unicode(info, 'utf-8').encode('gbk') 
   
#抽象产品A：user表 
class IUser(): 
  def Insert(self): 
    pass 
  def GetUser(self): 
    pass 
 
#sqlserver实现的User 
class SqlserverUser(IUser): 
  def Insert(self): 
    printInfo("在SQL Server中给User表增加一条记录") 
  def GetUser(self): 
    printInfo("在SQL Server中得到User表的一条记录") 
 
#Access实现的User 
class AccessUser(IUser): 
  def Insert(self): 
    printInfo("在Access中给User表增加一条记录") 
  def GetUser(self): 
    printInfo("在Access中得到User表一条记录") 
 
 
#抽象产品B：部门表 
class IDepartment(): 
  def Insert(self): 
    pass 
  def GetUser(self): 
    pass 
 
#sqlserver实现的Department 
class SqlserverDepartment(IUser): 
  def Insert(self): 
    printInfo("在SQL Server中给Department表增加一条记录") 
  def GetUser(self): 
    printInfo("在SQL Server中得到Department表的一条记录") 
 
#Access实现的Department 
class AccessDepartment(IUser): 
  def Insert(self): 
    printInfo("在Access中给Department表增加一条记录") 
  def GetUser(self): 
    printInfo("在Access中得到Department表一条记录") 
 
 
#抽象工厂 
class IFactory(): 
  def CreateUser(self): 
    pass 
  def CreateDepartment(self): 
    pass   
 
#sql server工厂 
class SqlServerFactory(IFactory): 
  def CreateUser(self): 
    return SqlserverUser() 
  def CreateDepartment(self): 
    return SqlserverDepartment() 
 
#access工厂 
class AccessFactory(IFactory): 
  def CreateUser(self): 
    return AccessUser() 
  def CreateDepartment(self): 
    return AccessDepartment() 
   
#优化一：采用一个简单工厂类，封装逻辑判断操作 
class DataAccess(): 
#  db = "Sqlserver" 
  db = "Access" 
  @staticmethod 
  def CreateUser(): 
    if (DataAccess.db == "Sqlserver"): 
      return SqlserverUser() 
    elif(DataAccess.db == "Access"): 
      return AccessUser() 
  @staticmethod 
  def CreateDepartment(): 
    if (DataAccess.db == "Sqlserver"): 
      return SqlserverDepartment() 
    elif(DataAccess.db == "Access"): 
      return AccessDepartment() 
     
#优化二：采用反射机制，避免使用太多判断 
##以下信息可以从配置文件中获取 
DBType = 'Sqlserver' #'Access' 
DBTab_User = 'User' 
DBTab_Department = 'Department' 
 
class DataAccessPro(): 
#  db = "Sqlserver" 
  db = "Access" 
  @staticmethod 
  def CreateUser(): 
    funName = DBType + DBTab_User 
    return eval(funName)() #eval 将其中的字符串转化为python表达式 
  @staticmethod 
  def CreateDepartment(): 
    funName = DBType + DBTab_Department 
    return eval(funName)() 
     
def clientUI(): 
  printInfo("\n--------抽象工厂方法--------") 
  factory = SqlServerFactory() 
  iu = factory.CreateUser() 
  iu.Insert() 
  iu.GetUser() 
  id = factory.CreateDepartment() 
  id.Insert() 
  id.GetUser() 
   
  printInfo("\n--抽象工厂方法+简单工厂方法--") 
  iu = DataAccess.CreateUser() 
  iu.Insert() 
  iu.GetUser() 
  id = DataAccess.CreateDepartment() 
  id.Insert() 
  id.GetUser() 
   
  printInfo("\n-抽象工厂方法+简单工厂方法+反射-") 
  iu = DataAccessPro.CreateUser() 
  iu.Insert() 
  iu.GetUser() 
  id = DataAccessPro.CreateDepartment() 
  id.Insert() 
  id.GetUser()   
  return 
 
 
if __name__ == '__main__': 
  clientUI(); 

类图：

工厂模式和抽象工厂模式的区别：工厂模式是在派生类中定义一个工厂的抽象接口，然后基类负责创建具体对象；抽象工厂模式是维护一个产品家族，由基类定义产品被生产的方法，客户根据派生类的接口进行开发。

实例：人民群众喜闻乐见的披萨店例子这里又可以搬出来了，这次我们根据抽象工厂模式的特点，用不同原材料制作不同口味的披萨，创建不同原材料的工厂，不同实体店做出口味不同的披萨。创建一个产品家族（Dough、Sauce、Cheese和Clam）的抽象类型（PizzaIngredientFactory），这个类型的子类（NYPizzaIngredientFactory和ChicagoPizzaIngredientFactory）定义了产品被产生的方法。
代码：

#!/usr/bin/python
# -*- coding:utf-8 -*-
import sys
reload(sys)
sys.setdefaultencoding('utf-8')
 
'''
披萨
'''
class Pizza:
  name = ""
  dough = None
  sauce = None
  cheese = None
  clam = None
 
  def prepare(self):
    pass
 
  def bake(self):
    print "烘烤25分钟在350。".decode('utf-8')
 
  def cut(self):
    print "切割成对角线切片。".decode('utf-8')
 
  def box(self):
    print "放在官方的盒子中。".decode('utf-8')
 
  def get_name(self):
    return self.name
 
  def set_name(self, name):
    self.name = name
 
  def to_string(self):
    string = "%s:\n" % self.name
    string += "  面团: %s\n" % self.dough.to_string() if self.dough else ""
    string += "  酱汁: %s\n" % self.sauce.to_string() if self.sauce else ""
    string += "  奶酪: %s\n" % self.cheese.to_string() if self.cheese else ""
    string += "  文蛤: %s\n" % self.clam.to_string() if self.clam else ""
    return string
 
'''
什么类别的披萨
'''
class CheesePizza(Pizza):
  def __init__(self, ingredient_factory):
    self.ingredient_factory = ingredient_factory
 
  def prepare(self):
    print "准备: %s" % self.name
    self.dough = self.ingredient_factory.create_dough()
    self.sauce = self.ingredient_factory.create_sauce()
    self.cheese = self.ingredient_factory.create_cheese()
 
 
class ClamPizza(Pizza):
  def __init__(self, ingredient_factory):
    self.ingredient_factory = ingredient_factory
 
  def prepare(self):
    print "准备: %s" % self.name
    self.dough = self.ingredient_factory.create_dough()
    self.sauce = self.ingredient_factory.create_sauce()
    self.clam = self.ingredient_factory.create_clam()
 
'''
披萨店
'''
class PizzaStore:
  def order_pizza(self, pizza_type):
    self.pizza = self.create_pizza(pizza_type)
    self.pizza.prepare()
    self.pizza.bake()
    self.pizza.cut()
    self.pizza.box()
    return self.pizza
 
  def create_pizza(self, pizza_type):
    pass
 
'''
纽约披萨实体店1
'''
class NYPizzaStore(PizzaStore):
  def create_pizza(self, pizza_type):
    ingredient_factory = NYPizzaIngredientFactory()
 
    if pizza_type == "cheese":
      pizza = CheesePizza(ingredient_factory)
      pizza.set_name("纽约风格芝士披萨".decode('utf-8'))
    elif pizza_type == "clam":
      pizza = ClamPizza(ingredient_factory)
      pizza.set_name("纽约风格文蛤披萨".decode('utf-8'))
    else:
      pizza = None
 
    return pizza
 
'''
芝加哥披萨实体店2
'''
class ChicagoPizzaStore(PizzaStore):
   def create_pizza(self, pizza_type):
    ingredient_factory = ChicagoPizzaIngredientFactory()
 
    if pizza_type == "cheese":
      pizza = CheesePizza(ingredient_factory)
      pizza.set_name("芝加哥风格芝士披萨".decode('utf-8'))
    elif pizza_type == "clam":
      pizza = ClamPizza(ingredient_factory)
      pizza.set_name("芝加哥风格文蛤披萨".decode('utf-8'))
    else:
      pizza = None
 
    return pizza
 
'''
生产披萨的工厂
'''
class PizzaIngredientFactory:
  def create_dough(self):
    pass
 
  def create_sauce(self):
    pass
 
  def create_cheese(self):
    pass
 
  def create_clam(self):
    pass
 
'''
生产披萨的实体工厂1
'''
class NYPizzaIngredientFactory(PizzaIngredientFactory):
  def create_dough(self):
    return ThinDough()
 
  def create_sauce(self):
    return MarinaraSauce()
 
  def create_cheese(self):
    return FreshCheese()
 
  def create_clam(self):
    return FreshClam()
 
'''
生产披萨的实体工厂2
'''
class ChicagoPizzaIngredientFactory(PizzaIngredientFactory):
  def create_dough(self):
    return ThickDough()
 
  def create_sauce(self):
    return MushroomSauce()
 
  def create_cheese(self):
    return BlueCheese()
 
  def create_clam(self):
    return FrozenClam()
 
 
class Dough:
  def to_string(self):
    pass
 
class ThinDough(Dough):
  def to_string(self):
    return "薄的面团"
 
class ThickDough(Dough):
  def to_string(self):
    return "厚的生面团"
 
class Sauce:
  def to_string(self):
    pass
 
class MarinaraSauce(Sauce):
  def to_string(self):
    return "番茄酱"
 
class MushroomSauce(Sauce):
  def to_string(self):
    return "蘑菇酱"
 
class Cheese:
  def to_string(self):
    pass
 
class FreshCheese(Cheese):
  def to_string(self):
    return "新鲜的奶酪"
 
class BlueCheese(Cheese):
  def to_string(self):
    return "蓝纹奶酪"
 
class Clam:
  def to_string(self):
    pass
 
class FreshClam(Clam):
  def to_string(self):
    return "新鲜的文蛤"
 
class FrozenClam(Clam):
  def to_string(self):
    return "冷冻的文蛤"
 
if __name__ == "__main__":
  # 创建了两个披萨实体店
  ny_store = NYPizzaStore()
  chicago_store = ChicagoPizzaStore()
 
  # 在第一个披萨对象中订购了一个cheese风味的披萨
  pizza = ny_store.order_pizza("cheese")
  print pizza.to_string()
  print "迈克订购了一个 %s" % pizza.get_name()
  print
 
  pizza = chicago_store.order_pizza("clam")
  print pizza.to_string()
  print "约翰订购了一个%s" % pizza.get_name()

结果：

准备: 纽约风格芝士披萨
烘烤25分钟在350。
切割成对角线切片。
放在官方的盒子中。
纽约风格芝士披萨:
  面团: 薄的面团
  酱汁: 番茄酱
  奶酪: 新鲜的奶酪
 
迈克订购了一个 纽约风格芝士披萨
 
准备: 芝加哥风格文蛤披萨
烘烤25分钟在350。
切割成对角线切片。
放在官方的盒子中。
芝加哥风格文蛤披萨:
  面团: 厚的生面团
  酱汁: 蘑菇酱
  文蛤: 冷冻的文蛤
 
约翰订购了一个芝加哥风格文蛤披萨