目录

第十三章、元类之控制类的调用过程

一、__call__

作用：控制类的调用过程,实际上在控制:对象的产生

• 控制名称空间

  class Mymeta(type):      def __call__(self,*args, **kwargs):          obj=self.__new__(self)#生成空对象          obj.__init__(*args, **kwargs)#调用obj的__init__()          obj.__dict__['attr']=kwargs          return obj  class Mydict(dict,metaclass=Mymeta):      def __getattr__(self, item):          return self.__dict__['attr'][item]      def __setattr__(self, key, value):          self[key]=value          self.__dict__['attr'][key] = value  ----------------------------------------------------  di=Mydict(name='nick',age=18)  print(di.__dict__)  print(di.name)  di.sex='male'  print(di)  print(di.__dict__)  -----------------------------------------------------  {'attr': {'name': 'nick', 'age': 18}}  nick  {'name': 'nick', 'age': 18, 'sex': 'male'}  {'attr': {'name': 'nick', 'age': 18, 'sex': 'male'}}

• 例2练习:给我吧对象中的所有属性都设置成私有的

  class Mymeta(type):    def __call__(self, *args, **kwargs):        obj=object.__new__(self)        obj.__init__(*args, **kwargs)        # print(obj.__dict__)        obj.__dict__={ '_%s__%s'%(self.__name__,k):v for k,v in obj.__dict__.items()}        # print(obj.__dict__)        return objclass Person(object, metaclass=Mymeta):    school = 'oldboy'    def __init__(self, name):        self.name = name    def score(self):        print('分数是100')p = Person(name='nick')print(p.__dict__) #{'_Person__name': 'nick'}print(p.name)     #会报错