class Person(object):
    def __init__(self,name):
        self.name = name
class Teacher(Person):
    def __init__(self,score):
        self.__score = score
class Student(Teacher,Person):
    def __init__(self,name,score):
        Person.__init__(self,name)
        super(Student,self).__init__(score)
    @property
    def score(self):
        return self.__score
    @score.setter
    def score(self,score):
        if score<0 or score >100:
            raise ValueError('invalid score')
        self.__score = score
    def __str__(self):
        return 'Student:%s,%d' %(self.name,self.score)

s1 = Student('Jack',89)
s1.score = 95
print s1

在运行这个程序时，只有当score是私有变量的时候才能正常运行，是property的某些特性吗，还是什么？如果只设置为self.score = score,就会出现‘maximum recursion depth exceeded while calling a Python object’的错误，求大神解答