[petsc-dev] Configure won't find python

[Jed Brown]

Satish Balay <balay at mcs.anl.gov> writes:

> On Sat, 18 Apr 2020, Satish Balay via petsc-dev wrote:
>
>> On Sat, 18 Apr 2020, Jed Brown wrote:
>> 
>> > Satish Balay <balay at mcs.anl.gov> 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.