命令模式（python）

"""命令模式在请求者和请求实现者之间，把请求抽象成命令，并添加一个命令接受和分发者，实现请求者和实现者的解耦如客户（请求者）去烧烤店吃饭，并不需要认识烧烤boy（实现者），只需要有菜单（命令），服务员（命令接收和分发者），然后根据菜单给服务员下单就好了。然后菜单有会有记录，我们可以要求撤销和重做，烧烤店可以拒绝我们的某个菜单。优点：1、可以有一个命令列表；2、命令可以很容易写入日志；3、命令可以被撤销或重做；4、命令实现者可以拒绝命令；5、实现了请求者和实现者的解耦；6、要加入新的命令很容易，增加个命令类，实现者能做对应的命令"""from abc import ABCMeta, abstractmethodclass Cooker(object):    """    厨师    """    def __init__(self):        self._num_yang = 1        self._num_niu = 1    def cook_yang(self):        if self._num_yang <= 3:            print("烧烤羊肉串")            self._num_yang += 1        else:            print("没羊肉串了")    def cook_niu(self):        if self._num_niu <= 3:            print("烧烤牛肉串")            self._num_niu += 1        else:            print("没牛肉串了")class Command(object):    """    抽象菜单    """    __metaclass__ = ABCMeta    def __init__(self, name):        self.cooker = Cooker()        self.name = name    @abstractmethod    def cook(self):        passclass CommandYang(Command):    def __init__(self, name):        super(CommandYang, self).__init__(name)    def cook(self):        self.cooker.cook_yang()class CommandNiu(Command):    def __init__(self, name):        super(CommandNiu, self).__init__(name)    def cook(self):        self.cooker.cook_niu()class Waiter(object):    def __init__(self):        self._command_list = []        self._menu = None        self._kehu = None    def set_kehu(self, kehu):        self._kehu = kehu    def set_order(self, command, num=1):        print("加菜：" + command.name)        for i in range(num):            self._command_list.append(command)    def remove_order(self, command, num=1):        print("减菜：" + command.name)        try:            for i in range(num):                self._command_list.remove(command)        except Exception as e:            print("没点那么多菜")    def notify(self):        print("下单啦：")        self._menu = Order(self._kehu, self._command_list)        self._menu.show()        for command in self._command_list:            command.cook()        self._command_list = []        print("")class Order(object):    def __init__(self, name, command_list):        self._command_list = command_list        self._name = name    def set_order(self, command_list):        self._command_list = command_list    def set_name(self, name):        self._name = name    def show(self):        print(self._name + "，您的菜单是：")        for command in self._command_list:            print(command.name)        print("")if __name__ == '__main__':    # 烧烤店初始化    command_yang = CommandYang("羊肉串")    command_niu = CommandNiu("牛肉串")    waiter = Waiter()    # 营业    waiter.set_kehu("张三")    waiter.set_order(command_yang, 4)    waiter.set_order(command_niu, 5)    waiter.notify()