On Sat, 18 Apr 2020, Satish Balay via petsc-dev wrote: > On Sat, 18 Apr 2020, Satish Balay via petsc-dev wrote: > > > 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]. > > https://askubuntu.com/questions/1224695/python-is-not-installable-on-ubuntu-20-04 > https://askubuntu.com/questions/1224695/python-is-not-installable-on-ubuntu-20-04 > > Looks like one needs to install "python-is-python3" or > "python-is-python2-but-deprecated" package to get /usr/bin/python
balay@sb /home/balay $ rpm -qf /usr/bin/python python-unversioned-command-3.7.6-2.fc31.noarch balay@sb /home/balay $ rpm -ql python-unversioned-command-3.7.6-2.fc31.noarch /usr/bin/python /usr/share/man/man1/python.1.gz balay@sb /home/balay $ ls -l /usr/bin/python lrwxrwxrwx 1 root root 9 Jan 30 03:18 /usr/bin/python -> ./python3* balay@sb /home/balay $ So Fedora has similar package organization. So the unknown wrt Ubuntu-20.04 is - will python-is-python3 be installed by default [atleast in workstation installs] similar to Fedora. I'm hesitating to download the Beta iso - and give it a spin... Satish
