为什么把def grade(self)上面的@property去掉，s.grade返回的就是这个：<bound method Student.grade of <main.Student object at 0x029770D0>>

class Student(object):

    def __init__(self, name, score):
        self.name = name
        self.__score = 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
        
    #@property删掉了  
    def grade(self):
        if self.__score > 80:
            grade = 'A'
        elif self.__score < 60:
            grade = 'C'
        else:
            grade = 'B'
        return grade

s = Student('Bob', 59)
print s.grade

s.score = 60
print s.grade

s.score = 99
print s.grade

代码如上，我的IDE是PyCharm EDU显示结果是:

<bound method Student.grade of <__main__.Student object at 0x029770D0>>
<bound method Student.grade of <__main__.Student object at 0x029770D0>>
<bound method Student.grade of <__main__.Student object at 0x029770D0>>