On Sat, 18 Apr 2020, Satish Balay via petsc-dev wrote: > On Sat, 18 Apr 2020, Jed Brown wrote: > > > Satish Balay <[email protected]> writes: > > > > > On Sat, 18 Apr 2020, Satish Balay via petsc-dev wrote: > > > > > >> On Sat, 18 Apr 2020, Jed Brown wrote: > > >> > > >> > Satish Balay <[email protected]> writes: > > >> > > > >> > > Sure - the initial premise of this thread [as I understood] was: > > >> > > /usr/bin/python is python2. On python3 only installs - there is no > > >> > > /usr/bin/python (for ex: jedbrown/mpich-ccache docker file) - so we > > >> > > need to fix this issue in configure. > > >> > > > > >> > > I'm guessing that most installs will have /usr/bin/python as > > >> > > python2 or python3 - so missing /usr/bin/python is a smaller > > >> > > problem. Its not clear to me why this is missing in > > >> > > jedbrown/mpich-ccache - and how many OSes or distro will default to > > >> > > this mode. > > >> > > > >> > On Debian and Ubuntu, /usr/bin/python is part of python2; it isn't > > >> > created if you `apt install python3`. > > >> > > >> Ok - that a large userbase. > > >> > > >> So when python2 deprecated in debian - there won't be /usr/bin/python > > >> anymore? > > > > > > Also - debian does alternatives - don't know if they can setup a default > > > python [python2 vs python3] through this mechanism - and have anyone > > > installed as default. > > > > > > [for ex: I think if openmpi is installed /usr/bin/mpicc is automatically > > > setup as default via /etc/alternatives. I don't know if the same happens > > > for mpich] > > > > Alternatives is meant for compatible implementations. Python2 and Python3 > > are not, so I doubt they will ever do that. > > > > This indicates that /usr/bin/python will not exist in the next release. > > > > https://wiki.debian.org/Python/2Removal > > > > I don't know what exactly that means. I'd guess it means one will need > > to use backports to get python2 if one really needs it; even so, I don't > > know if /usr/bin/python will exist. Perhaps only /usr/bin/python2. > > > > > > I don't know if they'll reintroduce /usr/bin/python at some release well > > in the future, but we should expect for it to not exist for a while. > > > > The above URL is about packaging guidelines. i.e the packages in the distro > should correctly use python2 or python3 dependencies. > > I don't see a mention of /usr/bin/python will be. [so yes - so we don't know > what it will be - when python3 becomes the default] > > But until then - I don't consider missing /usr/bin/python a transition. > jedbrown/mpich-ccache would be an example of user willfully not installing > the default system python. (similar to not installing system default > compilers). So don't think its a case of configure bug of not handling proper > installs. [sure we have work-around for buggy compilers and some buggy > installs so any support for missing /usr/bin/python would be on that side]. > > I wonder what python folk recommendation here is wrt dual use scripts..
The OSes that already migrated to python3 as default [Fedora - that I use, Arch? that Jed uses] do provide /usr/bin/python - which is python3. So - hopefully Debian/Ubuntu will stick to this trend [assuming they haven't yet switched the default]. Satish
