Import errors with fresh install of openff-toolkit

[mvanvleet]

I attempted to install and run some simple examples from the openff-toolkit, but am running into import errors even with a fresh install of mamba and the lastest versions of the openff-toolkit and openmm packages.

To Reproduce
The error on my computer can be reproduced simply by calling the import statement:
from openff.toolkit import Molecule

Output
errors.txt

Computing environment:

• Operating system: Ubuntu 22.04.5 LTS
• Output of running conda list: condalist.txt

[j-wags]

Thanks for reporting @mvanvleet. I'm able to reproduce this error. This seems to be related to the removal of openff-toolkit's python <3.14 pin.

I'll work on fixing this in packaging. In the meantime, could you let me know whether forcing the use of python 3.13 in an env resolves the error for you (mamba create -n temp -c conda-forge openff-toolkit python=3.13)?

[mvanvleet]

Yes, forcing python 3.13 resolves the error and the import statement completes without incident.

[j-wags]

I think that downpinning python<3.14 in the feedstock (conda-forge/openff-toolkit-feedstock#128) will fix this in the short term, and it's likely that updating our unit serialization (openforcefield/openff-units#178) will allow us to remove the python downpin in the long term.

I'll make the new package build today and will close this issue if it works.

[j-wags]

I've made the new build, and now new envs built using eg micromamba create -n myenv -c conda-forge openff-toolkit install python 3.13 and don't crash on import. I still expect openforcefield/openff-units#178 to ultimately resolve this and allow for use with python 3.14, but until then this should resolve the issue.

Thanks again for the report @mvanvleet - Feel free to reopen this issue if it persists for you.