[Distutils] Library instability on PyPI and impact on OpenStack

Mark McLoughlin markmc at redhat.com
Sun Mar 3 17:17:14 CET 2013

On Fri, 2013-03-01 at 01:06 -0800, Glyph wrote:
> On Feb 28, 2013, at 7:39 AM, Mark McLoughlin <markmc at redhat.com>
> wrote:
> > I always felt that the Python community tended more towards the
> > former
> > approach, but there always exceptions to the rule - to unfairly pick
> > one
> > one project, sqlalchemy seems to have an API that often changes
> > incompatibly.
> For what it's worth, Twisted takes backwards compatibility very
> seriously.  I try to mention this frequently in the hopes that more
> Python projects will adopt a similar policy:
> <http://twistedmatrix.com/trac/wiki/CompatibilityPolicy>.

Very nice!

>  I hear that openstack has chosen to avail themselves of some
> different networking libraries... but you have deprived me of the
> opportunity for snark by apparently having no difficulty with
> compatibility in that layer :).

I won't digress into discussing other difficulties in that layer :)

[snip useful and interesting context]

> Overall though, your impression of the Python community at large *is*
> accurate; breakages come with deprecation warnings beforehand, and
> mature packages try hard to maintain some semblance of a compatible
> API, even if there is some disagreement over what "compatible" means. 

Thanks! That gives me hope that OpenStack should continue assuming by
default that Python library updates will be compatible. The difficulty
is thus identifying the individual versioning semantics for all the
libraries we use and tailoring our requirement specifications to each


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