1.@property：Python內建的@property裝飾器就是負責把一個方法變成屬性呼叫的

class Student(object):

    @property
    def score(self):
        return self._score

    @score.setter
    def score(self, value):
        if not isinstance(value, int):
            raise ValueError('score must be an integer!')
        if value < 0
 
 or value > 100:
            raise ValueError('score must between 0 ~ 100!')#生成錯誤
        self._score = value

>>> s = Student()
>>> s.score = 60 # OK，實際轉化為s.set_score(60)
>>> s.score # OK，實際轉化為s.get_score()
60
>>> s.score = 9999
Traceback (most recent call last):
  ...
ValueError: score must between 0
 
 ~ 100!

class Student(object):

    @property
    def birth(self):
        return self._birth

    @birth.setter
    def birth(self, value):
        self._birth = value

    @property
    def age(self):
        return 2014 - self._birth