class Student(object):

def __init__(self, name, gender):
    self.name = name
    if gender == 'female' or gender == 'male':
        self.__gender = gender
    else:
        raise ValueError('illegal gender')

def get_gender(self):
    return self.__gender

def set_gender(self, gender):
    if gender == 'female' or gender == 'male':
        self.__gender = gender
    else:
        raise ValueError('illegal gender')