[Distutils] Pre-pre-PEP: Requirements for the Python BUILDS Specification

[David Cournapeau]

Ian Bicking wrote:
> I think this is part of why I don't understand the system packager
> perspective.  Developers shouldn't use system packages, it just
> doesn't make any sense to have that intermediation.

I can't see why you would think that. Of course it makes sense to have
that intermediation, for packages which are not directly relevant to
you. I am more than happy to use packages myself for almost everything
but the things I am directly working on (and maybe the layer just below).

> Users don't use Python modules, they use applications.

What is an application ? I mean, people who use numpy/scipy, they use a
module. People who are scons users, they use a software which is just
one module + some scripts.

The application / library difference is blurry in python.

>   Users only care that their applications work, that they can install
> applications without unnecessary conflicts, that the applications
> don't break based on unintentional environment changes (e.g., the
> value of PYTHONPATH).

Yes, of course. But this is obviously linked to deployment issues. Then,
the argument is that when deploying things, multiple / concurrent
modules is a headache. Api versioning and stability is not a linux
packagers crazy idea
>
> Packagers seem to care a great deal about having applications share
> libraries on the packaging level, but this is for their own
> accounting, there's no reason for users to care (except for the
> too-small-to-matter issue of disk space).

Did you read carefully what was written by the packagers ? They almost
never mention disk space (which does matter on some systems BTW; not
everybody uses a desktop or a server). They mention security, they
mention maintanability. Both those are made much more complicated when
you enable multiple / concurrent versions.

>   Also, packagers seem to jump the gun on this library sharing, as
> they are concerned about libraries when one (or often zero!)
> applications depend on the library.  Some widely used libraries seem
> reasonable, but for every widely used library there are a dozen or
> more niche libraries.

Those niche libraries are not always packaged. If a library is used by
only one package, it is quite likely that it is included in the package
itself.

cheers,

David