python 魔法方法补充

1 getattribute (print(ob.name) -- obj.func())当访问对象的属性或者是方法的时候触发

class F(object):            def __init__(self):            self.name = 'A'            def hello(self):            print('hello')            def __getattribute__(self, item):            print('获取属性，方法',item)            return object.__getattribute__(self,item)        a = F()    print(a.name)    a.hello()            获取属性，方法 name    A    获取属性，方法 hello    hello

2 getattr 拦截运算(obj.xx)，对没有定义的属性名和实例,会用属性名作为字符串调用这个方法

class F(object):        def __init__(self):            self.name = 'A'            def __getattr__(self, item):            if item == 'age':                return 40            else:                raise AttributeError('没有这个属性')        f = F()    print(f.age)        # 40

3 setattr 拦截 属性的的赋值语句 (obj.xx = xx)

class F(object):    def __setattr__(self, key, value):        self.__dict__[key] = valuea = F()a.name = 'alex'print(a.name)

如何自定义私有属性：

class F(object):  # 基类--定义私有属性    def __setattr__(self, key, value):        if key in self.privs:            raise AttributeError('该属性不能改变')        else:            self.__dict__[key] = valueclass F1(F):    privs = ['age','name']  # 私有属性列表    # x = F1()    # x.name = 'egon'  # AttributeError: 该属性不能改变    # x.sex = 'male'class F2(F):    privs = ['sex']      # 私有属性列表    def __init__(self):        self.__dict__['name'] = 'alex'        # y = F2()        # y.name = 'eva'

getitem , setitem, delitem

class F(object):    def __getitem__(self,item):        print(item)    def __setitem__(self,key,value):        print(key,value)    def __delitem__(self,key):        print(key)f  = F()f['b']f['c'] = 1del f['a']