带有两个下划线开头的函数是声明该属性为私有,不能在类地外部被使用或直接访问。原因是在外部访问时Python应用了另一个变量名。如下代码，__sex声明该变量是类的私有变量，不能直接用类如. __spam访问，而是. _classname__spam(Python把这种技术叫做“name mangling”)class Students:def __init__(self,sex,name,age,scores):self.__sex = sexself.age = ageself.name =nameself.scores = scoresdef get_data(self):return self.name,self.age,self.scores,self.__sexstu = Students('男','taon','23','90')print(stu.__sex,stu.__dict__)print(stu._Students__sex,stu.__dict__)前者报错AttributeError: 'Students' object has no attribute '__sex'后者输出为男 {'name': 'tao', '_Students__sex': '男', 'age': '23', 'scores': '90'}