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 #下横杠