class Screen(object):

@property
def width(self):
    return self._width

@width.setter
def width(self,width):
    if not isinstance(width,int):
        print('Type Error,not a number!')
    if(width >= 0):
        self._width = width
    else:
        print('Not a positive number!')

@property
def height(self):
    return self._height
@height.setter
def height(self,height):
    if not isinstance(height,int):
        print('Type Error,not a number!')
    if(height >= 0):
        self._height = height
    else:
        print('Not a positive number!')

@property
def resolution(self):
    return self._height*self._width

s = Screen() s.width = 1024 s.height = 768 print('resolution = %d' %s.resolution) if(s.resolution == 786432): print('测试通过！') else: print('测试失败！')