MuJoCo mjpython fails with uvx

[kevinzakka]

• uv 0.5.0 (8d66526 2024-11-07)

MuJoCo ships with an mjpython executable that is only needed on MacOS (related to launching UI on main thread). Unfortunately, running uvx --from mujoco mjpython on macOS fails with the following error message:

failed to dlopen path '/Users/kevin/Library/Caches/uv/archive-v0/FwmQkZOQj7kyCUmF_WcgC/bin/python': dlopen(/Users/kevin/Library/Caches/uv/archive-v0/FwmQkZOQj7kyCUmF_WcgC/bin/python, 0x000A): Library not loaded: @executable_path/../lib/libpython3.11.dylib
  Referenced from: <4C4C4423-5555-3144-A177-11E83484F9AC> /Users/kevin/.local/share/uv/python/cpython-3.11.10-macos-aarch64-none/bin/python3.11
  Reason: tried: '/Users/kevin/Library/Caches/uv/archive-v0/FwmQkZOQj7kyCUmF_WcgC/lib/python3.11/site-packages/mujoco/MuJoCo_(mjpython).app/Contents/lib/libpython3.11.dylib' (no such file), '/Users/kevin/Library/Caches/uv/archive-v0/FwmQkZOQj7kyCUmF_WcgC/bin/../lib/libpython3.11.dylib' (no such file), '/libpython3.11.dylib' (no such file)

[charliermarsh]

Interesting. Does this only happen with uv-installed Pythons?

[kevinzakka]

Hey @charliermarsh, thanks for getting back so quick!

It happens both with uvx, and if I install uv with pip then do uv pip install mujoco.

[zanieb]

Does it happen with uvx --python-preference only-system --from mujoco mjpython?

[kevinzakka]

Hi @zanieb, that actually works! Should I just run that all the time? Could you explain what's going on if possible?

[zanieb]

Should I just run that all the time?

You could. Though using our managed distributions has various benefits, there are some short-coming for situations like this.

Could you explain what's going on if possible?

The distributions we include are "standalone" which means they're easy to distribute for a wide range of systems, but this means they have some quirks since it's a relatively new paradigm for Python distributions.

MuJoCo is looking for @executable_path/../lib/libpython3.11.dylib but it's using the wrong base path for the executable. It looks in a path relative to the virtual environment, e.g.: '/Users/kevin/Library/Caches/uv/archive-v0/FwmQkZOQj7kyCUmF_WcgC/bin/../lib/libpython3.11.dylib' but the file is actually at ~/.local/share/uv/python/cpython-3.11.10-macos-aarch64-none/lib/libpython3.11.dylib. There are various reasons this could be, e.g., if we are setting home to the wrong value in the pyvenv.cfg (though I thought we special-cased our own distributions).

There's sort of a similar issue in #8879

We're looking at fixing this behavior but it's a pretty hard problem.

[jonzamora]

Related issue, I encountered this a while back: google-deepmind/mujoco#1923

I didn't spend time finding a solution to this, and reverted back to using mamba for package management w/ MuJoCo in the meantime.