for the python development don't use nix-env but create per project default.nix scripts and use nix-shell.
make sure you read the python section in nixpkgs manual -> http://nixos.org/nixpkgs/manual/ if you're looking to generate nix expressions from requirements.txt checkout pypi2nix -> https://github.com/garbas/pypi2nix. also know that pypi2nix is in early stage - still it is giving good results for some - and i'm looking for feedback of packages that break since this is the only way i can fix it. On Thu, Aug 4, 2016 at 2:07 PM, Guillaume Maudoux (Layus) <layus...@gmail.com> wrote: > Hi, > > I think you are putting your efforts in the wrong direction. > Nix is not designed to install both python 3.4 and 3.5 in the same > environment. > > What it can do however is cache both in the store, so you can get an > environment with python 3.4 with > nix-shell -p python34 > and an environment with python 3.5 with > nix-shell -p python35 > > Nix can provide you with as many different environments at the same time. > You can have a shell with python 3.4 running besides a shell with python > 3.5. > You should however not install both in your default environment (nix-env > -i) as it won't work. > > May I refer you to https://nixos.org/wiki/Development_Environments ? > > Regards, > -- Layus. > > > Le 03/08/16 à 16:43, Roland Koebler a écrit : >> Hi, >> >> I think I've now found out (at least partially), although this could >> result in a package being installed multiple times. >> >>> It appears that the flag setting only works on already installed packages. >> Yes, and if I use >> >> $ nix-env -i python3-3.5.2 >> ... >> $ nix-env --set-flag priority 10 python3-3.5.2 >> ... >> $ nix-env -i python3-3.4.5 python3-3.5.2 >> replacing old ‘python3-3.5.2’ >> installing ‘python3-3.4.5’ >> installing ‘python3-3.5.2’ >> >> it does not work, since the last command first removes python3-3.5.2, >> then probably the flag is lost, and then installs it again. >> >>> Also I'm not sure, but even if there are name collisions in the user >>> environment, it should still be possible to install both packages but only >>> use one of the names, and then create your name alias to the non-named >>> package. However I do not know how this can be done. >> I think I've found out. The following works: >> >> $ nix-env -i python3-3.5.2 >> $ nix-env --set-flag priority 10 python3-3.5.2 >> $ nix-env -i -P python3-3.4.5 >> >> --preserve-installed / -P was the relevant switch. >> However, this can have some strange side-effects, since -P can >> cause a package to be installed "multiple times": >> >> $ nix-env -i -P python3-3.4.5 >> ... >> $ nix-env -i -P python3-3.4.5 >> ... >> $ nix-env -i -P python3-3.4.5 >> ... >> $ nix-env -q >> ... >> python3-3.4.5 >> python3-3.4.5 >> python3-3.4.5 >> python3-3.4.5 >> ... >> >> This could then be "resolved" by: >> >> $ nix-env -e python3-3.4.5 >> uninstalling ‘python3-3.4.5’ >> uninstalling ‘python3-3.4.5’ >> uninstalling ‘python3-3.4.5’ >> uninstalling ‘python3-3.4.5’ >> $ nix-env -P -i python3-3.4.5 >> installing ‘python3-3.4.5’ >> >> But it still looks strange. >> Is this intentional? >> >> Roland >> >> _______________________________________________ >> nix-dev mailing list >> nix-dev@lists.science.uu.nl >> http://lists.science.uu.nl/mailman/listinfo/nix-dev > > _______________________________________________ > nix-dev mailing list > nix-dev@lists.science.uu.nl > http://lists.science.uu.nl/mailman/listinfo/nix-dev -- Rok Garbas https://garbas.si _______________________________________________ nix-dev mailing list nix-dev@lists.science.uu.nl http://lists.science.uu.nl/mailman/listinfo/nix-dev
