Hi Ludovic! Ludovic Courtès <l...@gnu.org> writes:
> Hi! > > guix-comm...@gnu.org skribis: > >> apteryx pushed a commit to branch cu/farewell-to-pythonpath >> in repository guix. > > Woow! > >> commit c3c5bdd2b0ea4588ecba424fdbf6df101d967d3d >> Author: Maxim Cournoyer <maxim.courno...@gmail.com> >> AuthorDate: Fri Jan 22 09:34:33 2021 -0500 >> >> build/python: Add a new guix-pythonpath procedure. >> >> This procedure will be used in place where the static "PYTHONPATH" >> string used >> to be. >> >> * guix/build/python-build-system.scm (guix-pythonpath): New procedure. > > [...] > >> +(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. Thanks! Maxim
