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Re: MBF for deprecating Python2 usage



On Mon, Aug 07, 2017 at 08:11:40PM -0700, Diane Trout wrote:

> > What I am opposing is the suggestion to install, in the near to
> > medium
> > term, a command of exactly the same name that has subtly similar but
> > incompatible behaviour, when that behaviour *already* has a command –
> > ‘python3’ – that is widely used by those who need it.

> my problem with that plan is all of the printed documentation saying to
> learn python, type "python".

> At the very least there needs to a usr/bin/python that prints
> instructions about what you should run.

FWIW I don't share Ben's concern about this being a "backwards incompatible"
change (who is relying on the precise contents of the banner when running
'python' interactively?!).

But I am concerned about possible implementation strategies here.  exec() is
a very expensive syscall, and python is a frequently used interpreter.  If
this were implemented as a wrapper that checked isatty(), printed a banner,
and then re-execed the real python, that could have a measurable performance
impact on some applications.  There is a reason /usr/bin/python,
/usr/bin/gcc, etc. are always symlinks to the real interpreter on Debian,
not wrapper scripts - other distributions have tried to do this as a wrapper
script and the result wasn't pretty.

Avoiding the performance hit would require that any changes to the banner
be made in the python source itself.

-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                    http://www.debian.org/
slangasek@ubuntu.com                                     vorlon@debian.org

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