Re: Python scripts - /usr/bin/env python3 vs python vs python2.7

[Sitsofe Wheeler <sitsofe@gmail.com>]

Hi,

On Wed, 27 May 2020 at 20:23, Elliott, Robert (Servers) <elliott@hpe.com> wrote:
>
> > From: fio-owner@vger.kernel.org <fio-owner@vger.kernel.org> On Behalf
> > Of Vincent Fu
> > Sent: Tuesday, May 26, 2020 9:33 AM
> > To: Rebecca Cran <rebecca@bsdio.com>; fio@vger.kernel.org
> > Cc: Jens Axboe <axboe@kernel.dk>
> > Subject: Re: Python scripts - /usr/bin/env python3 vs python vs
> > python2.7
> >
> > On 5/26/20 10:13 AM, Rebecca Cran wrote:
> > > Python scripts in fio use a variety of methods to run the python
> > > interpreter: t/run_fio_tests.py has "#!/usr/bin/env python3" while
> > > t/strided.py has "#!/usr/bin/python", and sgunmap-test.py has
> > > "#!/usr/bin/python2.7".
> > >
> > >
> > > Would there any interest in converting them all to use
> > > "#!/usr/bin/env python3 ?
> >
> > I think having a uniform python interpreter line would be a good
> > thing.
>
> I have been using python a lot recently and also noticed that the
> /usr/bin/env format is the preferred approach; it works best across
> linux distros, local installs, and is even recognized by Python in
> Windows.

I'm guessing that's only in git for windows style shells? Surely
native Windows will just look at the extension and then look in the
registry?

> Most of the scripts include comments claiming python3 compatibility;
> one does not.
>
> t/sgunmap-perf.py:#!/usr/bin/python2.7
> t/sgunmap-perf.py:# REQUIREMENTS
> t/sgunmap-perf.py:# Python 2.6+
>
> t/sgunmap-test.py:#!/usr/bin/python2.7
> t/sgunmap-test.py:# Note: this script is python2 and python 3 compatible.
>
> t/steadystate_tests.py:#!/usr/bin/env python
> t/steadystate_tests.py:# Note: this script is python2 and python3 compatible.
>
> t/strided.py:#!/usr/bin/python
> t/strided.py:# Note: this script is python2 and python3 compatible.
>
> tools/fiologparser.py:#!/usr/bin/python2.7
> tools/fiologparser.py:#!/# Note: this script is python2 and python 3 compatible.

I second the suggestion that a single interpreter. Ages ago
(https://github.com/axboe/fio/commit/60023ade47e7817db1c18d9b7e511839de5c2c99
)  switched the interpreter to /usr/bin/python2.7 on scripts of the
time to make life easier on macOS and as a compromise to the distros
(which stated that env should not be used for their packages).

These days we have some python3 only scripts, some distros have to
patch the interpreter line to be python3 anyway
(https://src.fedoraproject.org/rpms/fio/c/b45ecfbe7170bbd6f5b2bec2a33e3c0e3d17d1d2?branch=master
) and will seemingly auto-convert env interpreter usage
(https://docs.fedoraproject.org/en-US/packaging-guidelines/#_shebang_lines
) at packaging time, some OS package guidelines say you should ONLY
use env interpreter lines (I think this is the case for NetBSD's
pkgsrc), macOS will eventually stop shipping python 2.7 default:

WARNING: Python 2.7 is not recommended.
This version is included in macOS for compatibility with legacy software.
Future versions of macOS will not include Python 2.7.

and it will only ship python3 as part of its developers tools (or the
user will have to get it some other way such as homebrew etc).

Given the above, I think the best thing is just to use "#!/usr/bin/env
python3" everywhere and at least:
- That's nicer to environments that don't have a python interpreter in /usr/bin
- Nicer if you ever run the scripts in a virtualenv
- Packagers can fix it up to whatever they like and at least the
pattern is the same across the board

I guess the things to do are:
- Check if the script that doesn't claim python3 compat already works
or can be fixed up
- Change all the hashbang lines and throw away the comments talking
about 2+3 compat

It would be good if any such commit mentions that it
"fixes"/supercedes https://github.com/axboe/fio/pull/874 ...

-- 
Sitsofe | http://sucs.org/~sits/