class Screen(object):

    def __init__(self):

        self._resolution = self._width * self._height

    @property

    def width(self):

        return self._width

    @width.setter

    def width(self, width):

        self._width = width

    @property

    def height(self):

        return self._height

    @width.setter

    def height(self, height):

        self._height = height

    @property

    def resolution(self):

        return self._resolution