python-@property

class Screen(object):
    @property
    def width(self):
        return self._width
    @width.setter
    def width(self,value):
        if not isinstance(value,int):
            raise ValueError('width must be an integer')
        if value<0:
            raise ValueError('width must over zero')
        else:
            self._width=value

    @property
    def height(self):
        return self._height
    @height.setter
    def height(self,value):
        if not isinstance(value,int):
            raise ValueError('height must an integer')
        if value<0:
            raise ValueError('height must over zero')
        else:
            self._height=value

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



s=Screen()
s.width=1024
s.height=768
print('resolution=',s.resolution)

if s.resolution==786432:
    print('测试通过')
else:
    print('测试失败')