class User(object):
    def __init__(self, name, age):
        self.name = name
        self.__age = age

    def get_age(self):
        return self.__age

    def __get_name(self):
        return self.name


class Student(User):
    pass


stu = Student('LiMing', 23)
print(dir(stu))

$ python private_method.py
['_User__age', '_User__get_name', '__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__'
, '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'get_age', 'name']

$ python --version
Python 3.7.4

私有属性__age变为_User__age，而不是_Student__age
私有方法__get_name变为_User__get_name，而不是_Student__get_name

请问是什么原因呢？需要怎么修改代码？