Hi Ludo, Ludovic Courtès <l...@gnu.org> writes:
> Hi Maxim, > > Maxim Cournoyer <maxim.courno...@gmail.com> skribis: > >>>> +(define (guix-pythonpath inputs) >>>> + "Derive the GUIX_PYTHONPATH_X_Y string , with the major and minor >>>> version >>>> +numbers substituted for X and Y, respectively." >>>> + (let ((python (assoc-ref inputs "python"))) >>>> + (string-append "GUIX_PYTHONPATH_" >>>> + (string-replace-substring (python-version python) "." >>>> "_")))) >>> >>> One pattern used elsewhere, notably for ‘GUIX_LOCPATH’, is to still keep >>> a single environment variable (that’d be ‘GUIX_PYTHONPATH’ here) but to >>> ensure that only MAJOR.MINOR sub-directories are taken into >>> consideration. >>> >>> IOW, instead of having GUIX_PYTHONPATH_3_8 and GUIX_PYTHONPATH_2_7, >>> you’d have just GUIX_PYTHONPATH but Python 3.8 would only care about >>> 3.8/ sub-directories while 2.7 would only care about 2.7/ >>> sub-directories. >>> >>> That’s perhaps easier to document and to deal with generally (you only >>> need to look at one specific environment variable). >>> >>> Does that make sense? I don’t know if it’s applicable in this case >>> though. >> >> One of the limitations lifted by this change is the limitation of >> running a single version of Python per profile. As mentioned in past >> discussions, it's not trivial ensuring that packages installed won't end >> up pulling various versions of Python in a same profile, so it's better >> to prepared for it :-). >> >> Using a non-versioned GUIX_PYTHONPATH would not allow for this, unless >> I'm missing something. > > Sure, I definitely agree. > > I’m advocating for a versioned environment variable too, but I’m > suggesting that versioning should not be part of the variable name. > > In the ‘GUIX_LOCPATH’ example I gave, locale data is looked up not > directly in the search path entries, but instead in those entries > prefixed by the libc version. See ‘glibc-versioned-locpath.patch’. > > If possible, the proposed ‘GUIX_PYTHONPATH’ variable could work > similarly: “/MAJOR.MINOR” would automatically be appended to each search > path entry. > > That way, both Python 2.7 and 3.8 can populate the same ‘GUIX_LOCPATH’ > variable, and eventually 2.7 only picks 2.7 packages and 3.8 only picks > 3.8 packages. > > Does that make more sense? Indeed, I thought about the possibility to filter the GUIX_PYTHONPATH entries based on their version at runtime after I wrote my initial reply. It makes life easier. I've updated the cu/farewell-to-pythonpath branch with this new way of doing things. Thanks for the suggestion! Maxim
