Re: [gentoo-user] Q: What is "python-exec2c"? Why would "python3" dispatched through it not see an installed copy of pyyaml?

[Steven Lembark]

On Sun, 7 Mar 2021 00:09:47 +0100
David Haller <gentoo@×××××××.de> wrote:

> Hello,
>
> On Sat, 06 Mar 2021, Steven Lembark wrote:
> >Question then is why "python-exec2c" dispatched via a symlink from
> >"python3" would fail to see the installed copy of pyyaml (or how
> >should I check with modules are avalable via "python3")?
> [..]
> >I think that pyyaml is installed:
> >
> >*  dev-python/pyyaml
> >      Latest version available: 5.4.1
> >      Latest version installed: 5.4.1
> >      Size of files: 170 KiB
> >      Homepage:      https://pyyaml.org/wiki/PyYAML
> > https://pypi.org/project/PyYAML/ https://github.com/yaml/pyyaml
> > Description:   YAML parser and emitter for Python License:
> > MIT
>
> Check with 'eix dev-python/pyyaml' or 'equery uses dev-python/pyyaml'
> for what python versions that module is actually installed for and
> compare that with the default python3 version (check 'python3
> --version')

I believe there isn't any PYTHON_TARGET-ish setting on the system:

     $ grep PYTHON_TARGET /etc/portage/make.conf /etc/portage/package.use/*
    /etc/portage/make.conf:#PYTHON_TARGETS="python3_7 python2_7"
    /etc/portage/package.use/dizzy:#*/* PYTHON_TARGETS: python3_6 python3_7
    /etc/portage/package.use/dizzy~:#*/* PYTHON_TARGETS: python3_6 python3_7

> You probably need to re-emerge dev-python/pyyaml if PYTHON_TARGETS has
> changed. You probably have it installed just for one target (which is
> not your current default python3).


 
> $ equery uses dev-python/pyyaml
> [..]
>  + + python_targets_python3_7 : Build with Python 3.7
>  + + python_targets_python3_8 : Build with Python 3.8
>  - - python_targets_python3_9 : Build with Python 3.9
> [..]
>
> So I have it installed for python 3.7.x and 3.8.x ...
>
> HTH,
> -dnh
>

    $  equery uses dev-python/pyyaml
    [ Legend : U - final flag setting for installation]
    [        : I - package is installed with flag     ]
    [ Colors : set, unset                             ]
     * Found these USE flags for dev-python/pyyaml-5.4.1:
     U I
     - - examples                 : Install examples, usually source code
     + + libyaml                  : enable support for C implementation using
                                    libyaml
     - - python_targets_python3_7 : Build with Python 3.7
     + + python_targets_python3_8 : Build with Python 3.8
     - - python_targets_python3_9 : Build with Python 3.9
     - - test                     : Enable dependencies and/or preparations
                                    necessary to run tests (usually controlled by
                                    FEATURES=test but can be toggled independently)
    (ins)lembark@dizzy ~ $ eselect python list
    Available Python interpreters, in order of preference:
      [1]   python3.9
      [2]   python3.6
      [3]   python3.8 (fallback)
      [4]   python3.7 (fallback)
      [5]   python2.7 (fallback)

    $ python3 --version;
    Python 3.9.1


Q: If don't have PYTHON_TARGETS set 

Given that I installed it yesterday when the makefile told me
about pyyaml not being installed, there aren't any TARGETS set
(both commented), python3 appears to be python-3.9...

Q: Why would emerge pyyaml install the pacakge for a non-target 
   python version that isn't the one linked via python3?

Q: Is this related to the fact that I'm not actually checking 
   python but a wrapper named "python-exec2c":

    $ ls -l /usr/bin/python3
    lrwxrwxrwx 1 root root 13 Oct 20 10:46 /usr/bin/python3 -> python-exec2c


   i.e., could the wrapper be mis-diagnosing the correct python
   version at install time?

Q: Is there any reasonable way to have a single version of python
   installed so that I get out of this maze? Previous python 
   target advice left me with one machine being re-installed and
   I'd rather not have my server disabled at this point.

Thanks



-- 
Steven Lembark
Workhorse Computing
lembark@×××××××.com
[phone]