[Python-ideas] Migration of /usr/bin/python to python3

[Ryan Gonzalez]

On Wed, Mar 11, 2015 at 2:43 PM, Neil Schemenauer <nas-python at arctrix.com>
wrote:

> This has been brought up elsewhere, I think this is a better forum
> to discuss it.  Changing /usr/bin/python directly to python3.x is
> bad idea, in my option.  It's going to cause users trouble and the
> benefit to Python 3.x users is not worth it.  Instead, let's try to
> find a smooth migration path.
>
> One idea is to install Python 3 as /usr/bin/python but have it
> always execute scripts with Python 2 unless they are explicitly
> marked as Python 3 compatible.
>
>
So Python 2 needs to be there anyway?


> The interpreter could parse the first line of the script to look for
> options.  Traditionally the OS only passes the first option to the
> interpreter so anything after that could be used to pass 3.x
> specific options.
>
> For example, a script starting with
>
>     #!/usr/bin/python -x -3
>
> could signify that the script is compatible with a Python 3
> interpreter.
>

What about using */usr/bin/env*? That wouldn't work; on my Linux system,
*/usr/bin/env* doesn't like any command like arguments.

Whenever I download a Python program, I usually check the hashbang to see
if it works with Python 2 or 3. This is bound to cause confusion, since a
quick glance would say "hey, this looks like it works under Python 2",
followed by the error-fest.


>
> An alternative idea is to allow something like the 'encoding'
> declaration.  It wouldn't have to be in the first line and would
> allow more flexibility.  Many years in the future when all scripts
> are marked as Python 3 compatible, Python 2 can be removed from the
> system and /usr/bin/python will start Python 3 by default.
>
>
I guess that's better.


> I suppose running '/usr/bin/python' interactively could start Python
> 3 by default.  However, I strongly feel that existing Python 2
> scripts should not get broken in a flag day like way.
>
>
But parsing hashbangs really isn't the answer. It's just really
Perl-magic-ish confusing.


>
>   Neil
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-- 
Ryan
[ERROR]: Your autotools build scripts are 200 lines longer than your
program. Something’s wrong.
http://kirbyfan64.github.io/
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