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: > > > > > > > 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]
With older OS versions - python2 is system default, python3 is the add-on. So there is no special support to make the add-on python3 the default. In such cases - some minimal installs can potentially exclude some system defaults - i.e system default python. Is this the case for jedbrown/mpich-ccache or - is it that newer versions of debian have 'python3' as system-default - but don't have /usr/bin/python [because this now part of the add-on python2 package?] Satish
