[Python-Dev] Another update for PEP 394 -- The "python" Command on Unix-Like Systems

[Sorin Sbarnea]

I am glad this resurfaced as back in September I proposed updated that very old PEP but I got rejected.
https://github.com/python/peps/pull/785 <https://github.com/python/peps/pull/785>

The main issue is that most distros will not fix it until PEP is refreshed because most of them do want to follow PEPs.

There is still hope.

Cheers
Sorin

> On 13 Feb 2019, at 16:20, Victor Stinner <vstinner at redhat.com> wrote:
> 
> Hi,
> 
> I'm a (strong) supporter of providing a "python" command which would
> be the latest Python version!
> 
> As php does nowadays (after previous issues with "php4" vs "php5".) I
> don't recall that perl had "perl4" vs "perl5", the command was always
> "perl", no? Same for Ruby: it was still "ruby" after for Ruby 2, no?
> Only Python and PHP used different program names depending on the
> language version, no? And PHP now moved back to a single "php"
> program.
> 
> In the container and virtualenv era, it's now easy to get your
> favorite Python version for the "python" command.
> 
> On my Windows VM, "python" is Python 3.7 :-) In virtual environments,
> "python" can also be Python 3 as well.
> 
> I recall that I saw commands using "python" rather than "python3" in
> the *official* Python 3 documentation: see examples below (*).
> Problem: On Windows, "python" is the right command. "python3" doesn't
> work (doesn't exist) on Windows. Should we write the doc for Windows
> or for Unix? Oooops.
> 
> There was an interesting discussion about the Python version following
> Python 3.9: Python 3.10 or Python 4? And what are the issues which
> would make us prefer 3.10 rather than 4.0?
> https://mail.python.org/pipermail/python-committers/2018-September/006152.html
> 
> One practical issue is that right now, six.PY3 is defined by "PY3 =
> sys.version_info[0] == 3" and so "if six.PY3:" will be false on Python
> 4.
> 
> Another interesting thing to mention is the Unix Python launcher
> ("py") written by Brett Cannon written in Rust:
> https://github.com/brettcannon/python-launcher
> 
> 
> (*) A few examples of "python" commands in the Python official documentation
> 
> "$ python prog.py -h"
> https://docs.python.org/dev/library/argparse.html
> 
> "$ python logctx.py"
> https://docs.python.org/dev/howto/logging-cookbook.html
> 
> "python setup.py install"
> https://docs.python.org/dev/install/index.html
> 
> "python --help"
> https://docs.python.org/dev/howto/argparse.html
> 
> "python setup.py build"
> https://docs.python.org/dev/extending/building.html
> 
> "exec python $0 ${1+"$@"}"
> https://docs.python.org/dev/faq/library.html
> 
> "python setup.py --help build_ext"
> https://docs.python.org/dev/distutils/configfile.html
> 
> Victor
> 
> Le mer. 13 févr. 2019 à 16:49, Antoine Pitrou <solipsis at pitrou.net> a écrit :
>> 
>> On Wed, 13 Feb 2019 16:24:48 +0100
>> Petr Viktorin <encukou at gmail.com> wrote:
>>> PEP 394 says:
>>> 
>>>> This recommendation will be periodically reviewed over the next few
>>>> years, and updated when the core development team judges it
>>>> appropriate. As a point of reference, regular maintenance releases
>>>> for the Python 2.7 series will continue until at least 2020.
>>> 
>>> I think it's time for another review.
>>> I'm especially worried about the implication of these:
>>> 
>>> - If the `python` command is installed, it should invoke the same
>>>   version of Python as the `python2` command
>>> - scripts that are deliberately written to be source compatible
>>>   with both Python 2.x and 3.x [...] may continue to use `python` on
>>>   their shebang line.
>>> 
>>> So, to support scripts that adhere to the recommendation, Python 2
>>> needs to be installed :(
>> 
>> I think PEP 394 should acknowledge that there are now years of
>> established usage of `python` as Python 3 for many conda users.
>> 
>> Regards
>> 
>> Antoine.
>> 
>> 
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> 
> 
> 
> -- 
> Night gathers, and now my watch begins. It shall not end until my death.
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