Justin Veilleux <terramor...@cock.li> writes:
> Hi everyone. I was thinking about the propagated-inputs field in package > definitions. As I understand it, it is useful as a way to replace RPATHs > in packages that aren't compiled or don't support them. > > I was reading the documentation on > https://docs.python.org/3/reference/import.html. It looks like we can > define custom objects to do module resolution, possibly bypassing > PYTHON_PATH lookup. I think it would be possible to write a very simple > importer object that looks up module paths from an environment variable > that looks like this: > > PYTHON_GUIX_MODULE_PATH=numpy=/gnu/store/...,pandas=/gnu/store/... How would these compose? “pandas” has dependencies, too. Where would those be read from? How can be guaranteed that these are compatible with what we had at compile time? > Does someone know if this has been tried before? What potential problems > would I encounter if I tried to implement this? In 2018 we discussed the problems of PYTHONPATH extensively. Hartmut Goebel provided a three part analysis of the problem and potential fixes. The discussion didn’t lead to a generic solution, but it provided the minimal reasons to replace our use of PYTHONPATH with GUIX_PYTHONPATH, which we enable with a generated “sitecustomize.py” file — see (gnu packages python) for details. It would be great if we could do without GUIX_PYTHONPATH, which forces us to harmonize *all* Python packages whenever we upgrade any of them. Something that doesn’t require a global search path at all would be ideal. Perhaps the venv feature is how we can get there. I recommend reading the “PYTHONPATH issue analysis” messages for ideas and a list of open questions. -- Ricardo
