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] = value

a = 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] = value

class 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'] = 1

del f['a']