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Re: python importers as an alternative to propagated-inputs
From: |
Ricardo Wurmus |
Subject: |
Re: python importers as an alternative to propagated-inputs |
Date: |
Mon, 08 Jan 2024 16:39:00 +0100 |
User-agent: |
mu4e 1.10.8; emacs 29.1 |
Justin Veilleux <terramorpha@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