Re: [gentoo-dev] [News item review v4] Python preference to follow PYTHON_TARGETS

[Philip Webb]

210125 Michał Górny wrote:
> Changed eselect-python dep removal date to July 2021.
> Not sure if there's a reason to display it to stable users today,
> or delay until the stable request is actually filed.

I've been using Gentoo since 2003 , happily enough most of the time ;
I'm an ordinary desktop user without any special requirements.
Python versions have been one of the reasons for the exceptions.
I finally managed to remove 2.7 from my system yesterday.

I do appreciate your work in this area,
but I can make no sense of the news item below.

> Title: Python preference to follow PYTHON_TARGETS
> Author: Michał Górny <mgorny@g.o>
> Posted: 2021-01-24
> Revision: 1
> News-Item-Format: 2.0
>
> On 2021-02-01 stable users will switch to a new method of updating
> the preferred Python versions that employs the configuration update
> mechanism in order to follow PYTHON_TARGETS.

What are "preferred Python versions" ?  Why are they multiple, not one ?
What is the "configuration update mechanism",
how does it "follow PYTHON_TARGETS" & why are they both needed ?

> We will also deprecate app-eselect/eselect-python,
> and it will stop being installed by default after 2021-07-01.

Why has there been this 3rd method of managing Python versions ?
Why might it still be needed by users ?

> If you wish to use the newest Python version present
> in your PYTHON_TARGETS, you only have to accept configuration changes.

Why doesn't Python behave like most other packages,
ie use the latest installed version ?  Why does PYTHON_TARGETS exist ?
Why are the "targets" ? -- it sounds as if they may not be achieved.
What are the "configuration changes" ?
Do you mean those in  /etc/python-exec ?

> If you wish to customize the behavior, read on.

I have no wish to customise Python.  I don't use it to develop programs ;
it is installed only as a requirement for other packages, eg Portage.
I do use it for a small script to work as a CLI calculator.
Given this, I won't comment on the rest of the news item,
but it makes even less sense to me than the section above.

In  /etc/portage/make.conf , I have

  USE_PYTHON="2.7 3.5 3.6"
  PYTHON_TARGETS="python3_7"
  PYTHON_SINGLE_TARGET="python3_7"

'eselect python list' gives

  Available Python interpreters, in order of preference:
  [1]   python3.7
  [2]   python3.6 (uninstalled)

 /etc/python-exec/  contains  1  file 'python-exec.conf',
which says (besides many lines of comment) :

  python3.7
  python3.6

'eix python' shows

  [I] dev-lang/python
     Available versions:  
     (2.7)  2.7.18-r5 ~2.7.18-r6
     (3.6)  3.6.12-r1(3.6/3.6m)^t ~3.6.12-r2(3.6/3.6m)^t
     (3.7)  3.7.9-r1(3.7/3.7m)^t ~3.7.9-r2(3.7/3.7m)^t
     (3.8)  3.8.6-r1^t ~3.8.7-r1^t
     (3.9)  3.9.0-r1^t ~3.9.1-r1^t
     (3.10) ~3.10.0_alpha3-r1^t ~3.10.0_alpha4^t
  {-berkdb bluetooth build examples gdbm hardened ipv6 libressl +ncurses +readline sqlite +ssl test +threads tk verify-sig +wide-unicode wininst +xml ELIBC="uclibc"}
  Installed versions:  3.7.9-r1(3.7/3.7m)^t([2021-01-24 23:26:15])(gdbm ncurses readline sqlite ssl tk xml -bluetooth -build -examples -hardened -ipv6 -libressl -test -wininst) 3.8.6-r1(3.8)^t([2021-01-24 23:28:48])(gdbm ncurses readline sqlite ssl tk xml -bluetooth -build -examples -hardened -ipv6 -libressl -test -wininst) 3.9.0-r1(3.9)^t([2021-01-24 23:31:53])(gdbm ncurses readline sqlite ssl tk xml -bluetooth -build -examples -hardened -ipv6 -libressl -test -wininst)

I can't understand why there are so many ways to control Python
nor which one users are supposed to use nor how to reconcile them.
I would be very happy simply to use 3.9 for all Python purposes.

Thanks again for your hard work on this + other areas of Gentoo.

-- 
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