Pjotr Prins <pjotr.publi...@thebird.nl> writes: > On Wed, Mar 07, 2018 at 08:50:48AM +0100, Ricardo Wurmus wrote: >> Hi Guix, >> >> with the introduction of the collision avoidance feature that prevents >> you from installing different variants of the same package into a >> profile we made it impossible to install “python” and “python@2” into >> the same profile. > > I am happy with this idea. Maybe guix can give an informative message > in the case of Python. > > Generally, mixing Python2 and 3 in one profile makes no sense.
Obviously, I strongly disagree :) On my CentOS and Fedora machines at work both versions are installed (with the system package manager) and nobody complains. I can conjure up a Python 2 environment by calling “python2” and a Python 3 environment by calling “python3” or “python”. Neither variant will load up modules for the other variant — unlike the behaviour on Guix. Even in Guix we allow these packages to be added to the same environment with “guix environment --ad-hoc” – and there are no collisions, because upstream made the effort to ensure that these packages don’t provide files of the same names. It is an unnecessary restriction to *prevent* users from installing Python 2 and 3 interpreters into the same profile. Any errors we see with mixing 2 and 3 is due to a bug in Guix which is due to our use of PYTHONPATH. In large environments Python 2 and 3 modules and interpreters can peacefully coexist as long as the tools use the appropriate names for the interpreters (“python2” or “python” for Python 2, “python3” for the interpreter for Python 3). In other places in Guix we don’t even prevent users from doing things that are generally ill-advised (e.g. the use of LD_LIBRARY_PATH); why would we prevent a perfectly valid use-case when it comes to different versions of Python? -- Ricardo GPG: BCA6 89B6 3655 3801 C3C6 2150 197A 5888 235F ACAC https://elephly.net