clj-python / clj-python/libpython-clj

NSWindow main thread error when trying to setup Gymnasium (openapi gym)

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Description

Hi, im trying to run some simple gymnasium stuff and getting the following error:

(require-python '[gymnasium :as gym])
(def env (gym/make "LunarLander-v2" :render_mode "human"))

; error (Temurin java 17) or crash (correto java 17)
(py. env reset :seed 42)

Execution error at libpython-clj2.python.ffi/check-error-throw (ffi.clj:707).
Traceback (most recent call last):
  File "/opt/homebrew/opt/python@3.11/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/gymnasium/wrappers/time_limit.py", line 75, in reset
    return self.env.reset(**kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/opt/python@3.11/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/gymnasium/wrappers/order_enforcing.py", line 61, in reset
    return self.env.reset(**kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/opt/python@3.11/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/gymnasium/wrappers/env_checker.py", line 57, in reset
    return env_reset_passive_checker(self.env, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/opt/python@3.11/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/gymnasium/utils/passive_env_checker.py", line 186, in env_reset_passive_checker
    result = env.reset(**kwargs)
             ^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/opt/python@3.11/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/gymnasium/envs/box2d/lunar_lander.py", line 461, in reset
    self.render()
  File "/opt/homebrew/opt/python@3.11/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/gymnasium/envs/box2d/lunar_lander.py", line 699, in render
    self.screen = pygame.display.set_mode((VIEWPORT_W, VIEWPORT_H))
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
pygame.error: NSWindow should only be instantiated on the main thread!

I'm on OSX Sonoma (silicon), python 3.11.6, Clojure 1.11.1 and java 17. I was actually about to write this as a crash report, but decided to try another Java 17 jvm and was able to get the error output instead.

In any case, is there something one can do with libpython-clj to setup the call such that it's on the main thread?

Contributor guide

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First steps

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  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reproducing the Gymnasium LunarLander example with the reported Java and macOS setup. Inspect libpython-clj2.python.ffi/check-error-throw at ffi.clj:707 and the require-python/py. call path for thread handling. Done means establishing whether the call can run on the main thread and documenting or implementing the supported behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
clojure, python
Domain
tooling
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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