Re: [gentoo-python] RFC: switch PYTHON_SINGLE_TARGET to 3.*, add 2.7 via package.use whenever necessary

[Mike Gilbert]

On Fri, Mar 6, 2015 at 3:18 AM, Ben de Groot <yngwin@g.o> wrote:
> As a follow-up, I did a qgrep in the tree for python support the other
> day, and it turns out we have:
>
> - almost 2500 ebuilds with 2.7 support only

My gut tells me this number is somewhat inflated. A large portion of
these may be ebuilds that very few people use. Also, something which
only supports python2 is more likely to be old/unmaintained than
something supporting python3.

However, I do agree that there are currently many ebuilds which
support python2 only, that much is undeniable.

> - less than 1500 ebuilds with support for both 2.7 and 3.*
> - only just over 100 ebuilds that support 3.* only
>
> Based on these numbers, it is clear to me that the most reasonable default is:
>
> PYTHON_TARGETS="python2_7"
> PYTHON_SINGLE_TARGET="python2_7"
>
> and leave it to the user to change that if they really want multiple
> python versions.

If the goal of the profile default is to provide *minimal* usable
settings, then I agree that would be appropriate. I'm not willing to
call it the most "reasonable".

I would guess that most users don't really care about having two
versions installed. So long as their applications work, I think most
people don't care about python much at all.

Personally, I look at it as enabling a modern version by default, and
keeping a legacy version enabled so things don't break. Ideally, we
would only enable python2 if the user needs some app that only works
with python2, but there's no way to do that with use flags.

> This would also significantly reduce the size of our stage3 tarballs.

This would actually be a nice side effect of reducing the default
PYTHON_TARGETS to either python2 or python3.

If you really want to shrink the tarball, there is a bug open about
stripping tests from dev-lang/python which would have an even more
significant effect.