def _render()

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

• 45 lines of code
• 5 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.x_threshold*2
        scale = screen_width/world_width
        carty = 100 # TOP OF CART
        polewidth = 10.0
        polelen = scale * 1.0
        cartwidth = 50.0
        cartheight = 30.0

        if self.viewer is None:
            from gym.envs.classic_control import rendering
            self.viewer = rendering.Viewer(screen_width, screen_height)
            l,r,t,b = -cartwidth/2, cartwidth/2, cartheight/2, -cartheight/2
            axleoffset =cartheight/4.0
            cart = rendering.FilledPolygon([(l,b), (l,t), (r,t), (r,b)])
            self.carttrans = rendering.Transform()
            cart.add_attr(self.carttrans)
            self.viewer.add_geom(cart)
            l,r,t,b = -polewidth/2,polewidth/2,polelen-polewidth/2,-polewidth/2
            pole = rendering.FilledPolygon([(l,b), (l,t), (r,t), (r,b)])
            pole.set_color(.8,.6,.4)
            self.poletrans = rendering.Transform(translation=(0, axleoffset))
            pole.add_attr(self.poletrans)
            pole.add_attr(self.carttrans)
            self.viewer.add_geom(pole)
            self.axle = rendering.make_circle(polewidth/2)
            self.axle.add_attr(self.poletrans)
            self.axle.add_attr(self.carttrans)
            self.axle.set_color(.5,.5,.8)
            self.viewer.add_geom(self.axle)
            self.track = rendering.Line((0,carty), (screen_width,carty))
            self.track.set_color(0,0,0)
            self.viewer.add_geom(self.track)

        if self.state is None: return None

        x = self.state
        cartx = x[0]*scale+screen_width/2.0 # MIDDLE OF CART
        self.carttrans.set_translation(cartx, carty)
        self.poletrans.set_rotation(-x[2])

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