Re: Python 3 binaries

[Andreas Enge <andreas@enge.fr>]

On Sun, Sep 01, 2013 at 04:03:47PM +0200, Ludovic Courtès wrote:
> Ah, so packages that work with Python 3 expect a ‘python’ (and not
> ‘python3’) executable?

Apparently so. And anyway, packages that work with both versions usually
start their scripts with #!/usr/bin/python.

> Then that’s a different story (I thought ‘python3’ was the official name
> for the binary.)
> 
> I’d rather not have specific things like that in ‘patch-shebangs’.  So,
> what we could do is:
>   • Leave ‘python-3’ as is, without the symlink.
>   • Add a ‘python-3-wrapper’ package that just contains ‘bin/python’
>     pointing to ‘…/bin/python3’ (using ‘trivial-build-system’.)
>   • When building Python 3 packages, we’d use the wrapper, not the real
>     one; however, users would install the real one in their environment.

This would be a possibility.

Personally, I find the solution rewriting the shebangs cleaner, but this
is more a matter of taste than anything.

The wrapper would require the user to install both python-3 and the wrapper
(or contain python-3 as a propagated input), so that the user has all files
in the python-3 package. This is slightly ugly.

The solution with the wrapper has the advantage that users who want only
Python 3 and not Python 2 would then get a binary named "python" pointing
to version 3, useful also for their own code. But somewhere it would have
to be documented that they then have to install python-3-wrapper and not just
python or python-3.

But the naming is not very clear; why do I need to install python-wrapper
if I just want the latest version of Python?
How about calling the package python-default and having it contain python-3
as a propagated input? We could even have a version 2 of this package, which
would be empty with only python-2 as a propagated input. Then the user could:

- install python-default = python-default-3 and get only Python 3,
  with binaries "python" and "pydoc" pointing to "python3" and "pydoc3",
  respectively;
- install python-default-2 and get only Python 2.
- install python-2 and python = python-3 to get both of them, with
  "python" pointing to Python 2.

What do you think?

Andreas