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 be between 0~100")

self._score=value

s=Student()

s.score=60

print("s.score = ", s.score)

s.score=99

class Screen(object):

@property

def width(self):

return self._width

@width.setter

def width(self,value):

self._width=value

@property

def height(self):

return self._height

@height.setter

def height(self,value):

self._height=value

@property

def resolution(self):

return self._width * self._height

s=Screen()

s.width=1024

s.height=768

print(s.resolution)

assert s.resolution==786432, "1024*768 = %d ?" % s.resolution