[Python-Dev] In-Python virtualisation and packaging

[Jannis Leidel]

On 14.06.2011, at 01:46, Carl Meyer wrote:

> On 06/13/2011 08:07 AM, Nick Coghlan wrote:
>> On Mon, Jun 13, 2011 at 10:50 PM, Vinay Sajip <vinay_sajip at yahoo.co.uk> wrote:
>>> You're right in terms of the current Python ecosystem and 3.x adoption, because
>>> of course this approach requires support from Python itself in terms of its
>>> site.py code. However, virtual environments have a utility beyond supporting
>>> older Pythons on newer OSes, since another common use case is having different
>>> library environments sandboxed from each other on different projects, even if
>>> all those projects are using Python 3.3+.
>> 
>> Yeah, even if the innate one struggles on later OS releases that
>> changed things in a backwards incompatible way, it will still be
>> valuable on the OS versions that are around at the time that version
>> of Python gets released.
> 
> FWIW, historically pretty much every new Python version has broken
> virtualenv, and new OS versions almost never have. Virtualenv isn't
> especially OS-dependent (not nearly as much as some other stdlib
> modules): the most OS-dependent piece is "shell activation", and that's
> a feature I would prefer to entirely leave out of the stdlib virtualenv
> (it's a convenience, not a necessity for virtualenv use, and the need to
> maintain it for a variety of OS shells is a maintenance burden I don't
> think Python should adopt).
> 
> In fact, the only new-OS-version adjustment I can recall virtualenv
> needing to make is when Debian introduced dist-packages -- but even that
> doesn't really apply, as that was distro-packager change to Python
> itself. With a built-in virtualenv it would be the distro packagers
> responsibility to make sure their patch to Python doesn't break the
> virtualenv module.

FTR, there is some special casing for Mac OS framework installs included, too.
Not sure if that should be considered a stability threatening issue though
since Apple hasn't changed much on that layout, AFAIK.

> So I don't think a virtualenv stdlib module would be at all likely to
> break on a new OS release, if Python itself is not broken by that OS
> release. (It certainly wouldn't be the stdlib module most likely to be
> broken by OS changes, in comparison to e.g. shutil, threading...)

Jannis