[Python-ideas] Fwd: improve compatibility

[Liam Marsh]

sorry, I did'nt know it allready existed...
thank you!

2014-12-22 14:16 GMT+01:00 Chris Angelico <rosuav at gmail.com>:

> On Tue, Dec 23, 2014 at 12:06 AM, Liam Marsh <liam.marsh.home at gmail.com>
> wrote:
> > """That's suggesting mixing and matching between versions within the same
> > process space, which is highly unlikely to work correctly (except when
> > modules are specifically designed for that, as indicated by the
> availability
> > of backported versions on PyPI)."""
> >
> > In fact, i was thinking about a small program, which just analize the
> file
> > for these commentaries, and asks the OS to launch the appropriate "real"
> > python environnement, and finishes.
>
> If you just want to have the initial script control its version, then
> that can be done. Put an appropriate shebang at the top of the file,
> use the py.exe launcher on Windows, and that'll all work.
>
> > This small program will be also be able to chose the appropriate version
> by
> > scanning the import statements, and seeking for these imported modules in
> > the different environnements installed.
>
> Not sure what you mean here, but if you use multiple different
> interpreters all installed concurrently, they'll each have their own
> separate module trees. Or do you mean different versions of imported
> libraries (so you could have, for instance, numpy 1.8.2 for this
> project, and numpy 1.9.1 for another)? In that case, you'd do well to
> use virtual environments, which cope just fine with this kind of
> thing.
>
> The one thing you *cannot* do easily is have an application request
> one Python version, and one of its imported modules request a
> different Python version. Similarly if you have two modules that each
> import the same third module; the nature of Python's import machinery
> is such that they have to get the same version (in fact, the same
> module). Within one execution space, you have to be consistent, or
> else go through some serious hoop-jumping to keep things separate.
>
> ChrisA
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