openAI Gym NameError in Google Colaboratory

Question

I've just installed openAI gym on Google Colab, but when I try to run 'CartPole-v0' environment as explained here.

Code:

import gym
env = gym.make('CartPole-v0')
for i_episode in range(20):
    observation = env.reset()
    for t in range(100):
        env.render()
        print(observation)
        action = env.action_space.sample()
        observation, reward, done, info = env.step(action)
        if done:
            print("Episode finished after {} timesteps".format(t+1))
            break

I get this:

WARN: gym.spaces.Box autodetected dtype as <class 'numpy.float32'>. Please provide explicit dtype.
---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-19-a81cbed23ce4> in <module>()
      4     observation = env.reset()
      5     for t in range(100):
----> 6         env.render()
      7         print(observation)
      8         action = env.action_space.sample()

/content/gym/gym/core.py in render(self, mode)
    282 
    283     def render(self, mode='human'):
--> 284         return self.env.render(mode)
    285 
    286     def close(self):

/content/gym/gym/envs/classic_control/cartpole.py in render(self, mode)
    104 
    105         if self.viewer is None:
--> 106             from gym.envs.classic_control import rendering
    107             self.viewer = rendering.Viewer(screen_width, screen_height)
    108             l,r,t,b = -cartwidth/2, cartwidth/2, cartheight/2, -cartheight/2

/content/gym/gym/envs/classic_control/rendering.py in <module>()
     21 
     22 try:
---> 23     from pyglet.gl import *
     24 except ImportError as e:
     25     reraise(prefix="Error occured while running `from pyglet.gl import *`",suffix="HINT: make sure you have OpenGL install. On Ubuntu, you can run 'apt-get install python-opengl'. If you're running on a server, you may need a virtual frame buffer; something like this should work: 'xvfb-run -s \"-screen 0 1400x900x24\" python <your_script.py>'")

/usr/local/lib/python3.6/dist-packages/pyglet/gl/__init__.py in <module>()
    225     else:
    226         from .carbon import CarbonConfig as Config
--> 227 del base
    228 
    229 # XXX remove

NameError: name 'base' is not defined

The problem is the same in this question about NameError in openAI gym

Nothing is being rendered. I don't know how I could use this in google colab: 'xvfb-run -s \"-screen 0 1400x900x24\" python <your_script.py>'"

Answer 1

One way to render gym environment in google colab is to use pyvirtualdisplay and store rgb frame array while running environment. Environment frames can be animated using animation feature of matplotlib and HTML function used for Ipython display module. You can find the implementation here. Make sure you install required libraries which you can find in the first cell of the colab. In case the first link for google colab doesn't work you can see this one.