[gentoo-python] Wrapping scripts for multiple Python implementations: executable wrapper or symlinks?

[gentoo-python] Wrapping scripts for multiple Python implementations: executable wrapper or symlinks?

[Michał Górny]

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Hello,

Right now we have two different ways of 'wrapping' Python scripts
'converted' for various Python implementations. One of them
is the wrapper script installed by python.eclass, the other symlinking
done by python-distutils-ng.eclass.

I would like to ask you which one do you consider better, and thus
which one should I use for python-r1/distutils-r1.

A quick summary of possibilities:

1/ executable wrapper:

  A wrapper script (or executable) will be installed by a common
  package in the system. The various Python scripts will be symlinked
  to it, e.g.:

    /usr/bin/flaggie -> python-wrapper

  When run, the script will check the currently selected ABI (via
  eselect-python) and run the script using it if possible. Otherwise,
  it will try the best implementation available on the system
  and supported by the package.

Advantages:
- respects eselect-python (when possible).

Disadvantages:
- more complex,
- slows down script startup.

2/ symlink:

  When the package is installed, a symlink is created to the version
  for the preferred Python implementation. If it is not supported,
  the symlink points to the 'best' implementation supported.

    /usr/bin/flaggie -> flaggie-python2_7

Advantages:
- simple,
- resolution handled directly.

Disadvantages:
- the preferred implementation can not be changed at runtime.

3/ partially-shebanged copy of the script:

  One more copy of the script is installed, with a more general shebang
  like:

    #!/usr/bin/env python

  or:

    #!/usr/bin/env python2

Advantages:
- respects eselect-python.

Disadvantages:
- limited use (only simple version ranges),
- yet one more copy of the same script...

What do you think?

-- 
Best regards,
Michał Górny

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Re: [gentoo-python] Wrapping scripts for multiple Python implementations: executable wrapper or symlinks?

[Mike Gilbert]

On Sat, Sep 29, 2012 at 4:46 PM, Michał Górny <mgorny@gentoo.org> wrote:
> Hello,
>
> Right now we have two different ways of 'wrapping' Python scripts
> 'converted' for various Python implementations. One of them
> is the wrapper script installed by python.eclass, the other symlinking
> done by python-distutils-ng.eclass.
>
> I would like to ask you which one do you consider better, and thus
> which one should I use for python-r1/distutils-r1.
>

Of the choices, the wrapper idea (option 1) would be my preference.
Functionality-wise, it is closest to what we have with the generated
wrappers.

The symlink option sucks given the way eselect python works.

Another problem with option 3 (generic shebangs) is how to decide
which version of the script should be the one installed with a generic
shebang. It is possible that a package may run 2to3 as one of the
installation steps, which would mean that you would not have a script
that would work in both python2 and python3.

Re: [gentoo-python] Wrapping scripts for multiple Python implementations: executable wrapper or symlinks?

[Ben de Groot]

On 30 September 2012 11:42, Mike Gilbert <floppym@gentoo.org> wrote:
> On Sat, Sep 29, 2012 at 4:46 PM, Michał Górny <mgorny@gentoo.org> wrote:
>> Hello,
>>
>> Right now we have two different ways of 'wrapping' Python scripts
>> 'converted' for various Python implementations. One of them
>> is the wrapper script installed by python.eclass, the other symlinking
>> done by python-distutils-ng.eclass.
>>
>> I would like to ask you which one do you consider better, and thus
>> which one should I use for python-r1/distutils-r1.
>>
>
> Of the choices, the wrapper idea (option 1) would be my preference.
> Functionality-wise, it is closest to what we have with the generated
> wrappers.
>

I also prefer option 1.

-- 
Cheers,

Ben | yngwin
Gentoo developer
Gentoo Qt project lead, Gentoo Wiki admin