class Screen(object): @property def width(self): return self._width @width.setter def width(self,width_value): if not isinstance(width_value,int): raise ValueError('width_value must be intager!') if width_value>0: self._width = width_value else: raise ValueError('width_value should bigger than 0!') @property def height(self): return self._height @height.setter def height(self,height_value): if not isinstance(height_value,int): raise ValueError('height_value must be intager!') if height_value>0: self._height = height_value else: raise ValueError('height_value should bigger than 0!') @property def resolution(self): return self._width*self._height