Re: 03/163: build/python: Add a new guix-pythonpath procedure.

[Hartmut Goebel <h.goebel@crazy-compilers.com>]

Hi schrieb Maxim,
> Sorry for the delay.

No problem, I reward this with another delay ;-) (Just kidding ;-)


> Hartmut Goebel <h.goebel@crazy-compilers.com> writes:
>
>> 2) This does not remove duplicates and does not honor .pth files in
>> the respective directories - which might still be used. Thus
>> site.addsitedir() should be called for adding the paths. This also
>> takes care about duplicates.
> I confess I didn't pay attention to .pth files, which mostly seemed like
> legacy cruft to me; are they still used in the context of PEP 517 and
> modern Python packaging?  

I can't tell for sure. (I rinember to have seen a note about .pth still
being used in some setuptool-tick, but can't find it now.) Anyhow, since
site.py still supports it, I would prefer to be on the save side and
support it, to.

> The problem with calling site.addsitedir is
> that it simply appends to sys.path.  We want to splice in the content of
> GUIX_PYTHONPATH at a controlled location.

site.addsitedir takes an option second arguments where the paths are
collected into.


>> 4) Since PYTHONPATH is evaluated prior to importing sitecustomize, any
>> sitecustominze.py in the user's path will overwrite our file, thus
>> inhibiting our paths to be added. Not sure this is what we want in Guix.
> I asked guidance on the #python channel on freenode and was recommended
> to use sitecustomize.py for this purpose; reading the doc here seems to
> confirm our usage of it is as intended [0]:

IC.


>> 6) Please add some more comments to the code explaining the idea.
> I was under the impression the code was concise enough to forego with
> verbose explanations; I'd rather keep it this way.

Please add some comments. I had a hard time understanding it - and I was
not even sure I understood, see my question (1).


Another point, which came into my mind just now: Do virtuall
environments still work as expected? (With --system-site-packages,
packages in the profile are available, but venv-packages overwrite.
Without ----system-site-packages packages in the profile are *not*
available.)


-- 
Regards
Hartmut Goebel

| Hartmut Goebel          | h.goebel@crazy-compilers.com               |
| www.crazy-compilers.com | compilers which you thought are impossible |