class Student(object):

  def get_score(self):
    return self._score

  def set_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!')
    self._score = value

> s = Student()
> s.set_score(60) # ok!
> s.get_score()
60
> s.set_score(9999)
Traceback (most recent call last):
 ...
ValueError: score must between 0 ~ 100!

class Student(object):

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

  @score.setter #@score.setter是前一个@property装饰后的副产品。
  def score(self,value):
    if not isinstance(value, int):
      raise ValueError('分数必须是整数才行呐')
    if value < 0 or value > 100:
      raise ValueError('分数必须0-100之间')
    self._score = value

> s = Student()
> s.score = 60 # OK，实际转化为s.set_score(60)
> s.score # OK，实际转化为s.get_score()
60
> s.score = 9999
Traceback (most recent call last):
 ...
ValueError: score must between 0 ~ 100!