class Student(object):
    def __init__(self, name, gender):
        self.__name = name
        # self.__gender = gender
        self.set_gender(gender)

    def get_gender(self):
        return self.__gender

    def get_name(self):
        return self.__name

    def set_gender(self, gender):
        if not isinstance(gender, str):
            raise ValueError('只支持 female / male')
        if 'female' == gender:
            self.__gender = gender
        elif 'male' == gender:
            self.__gender = gender
        else:
            raise ValueError('只支持 female / male')`