Re: PYTHONPATH issue explanation

[Hartmut Goebel]

Hi,

I agree with Ricardo: We first should agree on what we want to implement.

I created a pad at [1] for collecting all test-cases and the expected
results. Please add you test-cases there. Thanks!

[1] https://semestriel.framapad.org/p/guix-python-site-packages-test-cases

Am 17.03.2018 um 02:41 schrieb 宋文武:

> - "GUIX_PYTHON_X_Y_SITE_PACKAGES" […] is necessary for the "build" 
> environment.
For the build environment we could easily work around using PYTHONPATH.
Since the build-system is clearly defined and does not interfere with
any user-definitions, this is save to do.

> - Avoid any environment variable for the "profile" environment.
>
>   We have a union "profile" for all the python packages, so environment
>   variables can be totally avoided with the help of "venv".
[…]
>  We only need to make the "profile"
>   a "venv" for python.  For python3, a simple "pyvenv.cfg" file is
>   enough, for python2 I guess we have to make a union or copy files like
>   what "virtualenv" does.

This would be a very elegant solution. Unfortunately this does not work
as shown in part 2 of my analysis, esp. point 4a.

>   > We could avoid GUIX-PYTHONHOME[23] if we stop resolving the symlinks
>   > at the correct point in iteration.
>
>   This is exactly what "venv" does! 

Unfortunately venv works quite different: system site-packages are
always taken from sys.base_exec. See part 3 of my analysis, esp. the
"pyvenv.cfg" section.

> I plan to implement option 1 by adding a "sitecustomize.py" (better
> than modify "site.py") into the python packages, and modify
> "search-path-specification" to use "GUIX_PYTHON_X_Y_SITE_PACKAGES".

When implementing this in sitecustomize.py, you will end up
re-implementing the complete venv mechanism.

When going the GUIX_PYTHON_X_Y_SITE_PACKAGES route, we should look where
the best place will be: Maybe site.PREFIXES, maybe
site.getsitepackages(), maybe site.venv().

-- 
Regards
Hartmut Goebel

| Hartmut Goebel          | address@hidden               |
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