class Student(object):

    def __init__(self, name, gender):

        self.name = name

        self._gender = gender

    def get_gender(self):

        return self._gender

    def set_gender(self,gender):

        self._gender=gender

bart = Student('Bart', 'male')

#print(bart.gender) 报错，此时gender为私有变量

print(bart.get_gender())

bart.set_gender('female')

print(bart.get_gender())