def _render()

in gym/gym/envs/classic_control/mountain_car.py [0:0]

• 50 lines of code
• 4 McCabe index (conditional complexity)

    def _render(self, mode='human', close=False):
        if close:
            if self.viewer is not None:
                self.viewer.close()
                self.viewer = None
            return

        screen_width = 600
        screen_height = 400

        world_width = self.max_position - self.min_position
        scale = screen_width/world_width
        carwidth=40
        carheight=20


        if self.viewer is None:
            from gym.envs.classic_control import rendering
            self.viewer = rendering.Viewer(screen_width, screen_height)
            xs = np.linspace(self.min_position, self.max_position, 100)
            ys = self._height(xs)
            xys = list(zip((xs-self.min_position)*scale, ys*scale))

            self.track = rendering.make_polyline(xys)
            self.track.set_linewidth(4)
            self.viewer.add_geom(self.track)

            clearance = 10

            l,r,t,b = -carwidth/2, carwidth/2, carheight, 0
            car = rendering.FilledPolygon([(l,b), (l,t), (r,t), (r,b)])
            car.add_attr(rendering.Transform(translation=(0, clearance)))
            self.cartrans = rendering.Transform()
            car.add_attr(self.cartrans)
            self.viewer.add_geom(car)
            frontwheel = rendering.make_circle(carheight/2.5)
            frontwheel.set_color(.5, .5, .5)
            frontwheel.add_attr(rendering.Transform(translation=(carwidth/4,clearance)))
            frontwheel.add_attr(self.cartrans)
            self.viewer.add_geom(frontwheel)
            backwheel = rendering.make_circle(carheight/2.5)
            backwheel.add_attr(rendering.Transform(translation=(-carwidth/4,clearance)))
            backwheel.add_attr(self.cartrans)
            backwheel.set_color(.5, .5, .5)
            self.viewer.add_geom(backwheel)
            flagx = (self.goal_position-self.min_position)*scale
            flagy1 = self._height(self.goal_position)*scale
            flagy2 = flagy1 + 50
            flagpole = rendering.Line((flagx, flagy1), (flagx, flagy2))
            self.viewer.add_geom(flagpole)
            flag = rendering.FilledPolygon([(flagx, flagy2), (flagx, flagy2-10), (flagx+25, flagy2-5)])
            flag.set_color(.8,.8,0)
            self.viewer.add_geom(flag)

        pos = self.state[0]
        self.cartrans.set_translation((pos-self.min_position)*scale, self._height(pos)*scale)
        self.cartrans.set_rotation(math.cos(3 * pos))

        return self.viewer.render(return_rgb_array = mode=='rgb_array')