Python kernel crashes when using OpenAI Gym environment

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1

I’m having trouble with my Python kernel crashing after running OpenAI Gym simulations in Jupyter notebook.

I installed the gym library using pip install gym and verified the installation was successful. When I run a basic training loop, everything works fine during execution:

import gym

# Create environment
environment = gym.make('CartPole-v1')

# Run training episodes
for episode in range(10):
    state = environment.reset()
    for step in range(200):
        environment.render()
        print(state)
        move = environment.action_space.sample()
        state, score, finished, data = environment.step(move)
        if finished:
            print(f"Training completed after {step+1} steps")
            break

The simulation window opens correctly and shows the expected behavior. However, once all episodes finish running, my kernel dies and automatically restarts. I’ve tried using environment.close() after the loop, but this destroys the environment object completely. Has anyone encountered this issue before? What’s the proper way to clean up gym environments without killing the kernel?

2

This kernel crash usually happens because the rendering backend doesn’t get cleaned up properly when the environment shuts down. I’ve hit the same issue working with gym environments in Jupyter. Here’s what fixed it for me: wrap environment.close() in a try-except block and explicitly delete the environment reference. Don’t just call environment.close() at the end - use a try-finally block around your whole simulation: python try: # your training loop here finally: environment.close() del environment Another thing that helped stabilize my setup was changing the render mode. Instead of calling environment.render() every step, initialize the environment with render_mode='human' in the make function. It handles rendering more efficiently and cuts down on backend conflicts that crash the kernel.

3

Had this exact problem last week! The issue’s probably with the display backend not getting freed up properly. Try adding import matplotlib; matplotlib.pyplot.close('all') after your gym loop finishes - worked for me when nothing else did. Also make sure you’re not running multiple cells with gym environments at once, that crashes Jupyter every time.