[Python-Dev] Status of packaging in 3.3

[David Cournapeau]

On Thu, Jun 21, 2012 at 9:45 AM, Nick Coghlan <ncoghlan at gmail.com> wrote:

> On Thu, Jun 21, 2012 at 2:44 PM, Chris McDonough <chrism at plope.com> wrote:
> > All of these are really pretty minor issues compared with the main
> benefit
> > of not needing to ship everything with everything else. The killer
> feature
> > is that developers can specify dependencies and users can have those
> > dependencies installed automatically in a cross-platform way.  Everything
> > else is complete noise if this use case is not served.
>
> Cool. This is the kind of thing we need recorded in a PEP - there's a
> lot of domain knowledge floating around in the heads of packaging
> folks that needs to be captured so we can know *what the addition of
> packaging to the standard library is intended to fix*.
>
> And, like it or not, setuptools has a serious PR problem due to the
> fact it monkeypatches the standard library, uses *.pth files to alter
> sys.path for every installed application by default, actually *uses*
> the ability to run code in *.pth files and has hard to follow
> documentation to boot. I *don't* trust that I fully understand the
> import system on any machine with setuptools installed, because it is
> demonstrably happy to install state to the file system that will
> affect *all* Python programs running on the machine.
>
> A packaging PEP needs to explain:
> - what needs to be done to eliminate any need for monkeypatching
> - what's involved in making sure that *.pth are *not* needed by default
> - making sure that executable code in implicitly loaded *.pth files
> isn't used *at all*
>

It is not a PEP, but here are a few reasons why extending distutils is
difficult (taken from our experience in the scipy community, which has by
far the biggest extension of distutils AFAIK):

http://cournape.github.com/Bento/html/faq.html#why-not-extending-existing-tools-distutils-etc

While I believe setuptools has been a net negative for the scipy community
because of the way it works and for the reason you mentioned, I think it is
fair to say it is not really possible to do any differently if you rely on
distutils.

If specifying install dependencies is the killer feature of setuptools, why
can't we have a very simple module that adds the necessary 3 keywords to
record it, and let 3rd party tools deal with it as they wish ? That would
not even require speciying the format, and would let us more time to deal
with the other, more difficult questions.

David
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