#请利用@property给一个Screen对象加上width和height属性，以及一个只读属性resolution：

#_*_ coding: utf-8 _*_

class Screen:

@property

def width(self):

return self._width

@width.setter

def width(self,width):

if not isinstance(width,int):

raise ValueError('width must be an integer!')

if width<0:

raise ValueError('width must greate tan 0!')

self._width=width

@property

def height(self):

return self._height

@height.setter

def height(self,height):

if not isinstance(height,int):

raise ValueError('height must be an integer!')

if height<0:

raise ValueError('height must greate tan 0!')

self._height=height

@property

def resolution(self):

return self._width*self._height

# test:

s = Screen()

s.width = 1024

s.height = 768

print(s.resolution)

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