[SciPy-dev] weave.inline broken by setuptools?

[Fernando Perez]

Howdy,

On Thu, Sep 25, 2008 at 9:03 PM, Robert Kern <robert.kern at gmail.com> wrote:

> It's not a workaround; it's just the correct thing to do. You must
> always import setuptools before you import numpy.distutils.
> numpy.distutils knows about setuptools, but setuptools doesn't know
> about numpy.distutils, so the only way that the two get merged
> correctly is by importing setuptools first so numpy.distutils knows to
> merge the two.

Well, the problem is that I didn't even know that I was importing
numpy.distutils and that it had a non-commutative behavior with
setuptools.  I had test code that  checked for weave's presence and
for setuptools  and they happened to be in that order.  I could easily
see someone doing an

import scipy.weave

and then

import something.else # that unbeknownst to them, imports setuptools

and boom.  The weirdest bugs.  Especially hard because if they happen
to  be loading inlined code that had already been compiled before
setuptools showed up, it will get picked up off the module cache just
fine.  This is what happened to me: the bug only appeared on student's
computers, because as I built the test suite I got the cache primed,
and only later did I add the setuptools loading.

I wonder  if numpy.distutils couldn't do a

try: import setuptools
except ImportError: pass

since otherwise we basically get a ticking time bomb.  On the other
hand, I imagine this might have its own nasty problems, so perhaps
it's a dumb idea.

This level of hidden magic/side effects really does bother me a lot.
There may be not much we can do about it, so I guess I'll just keep on
rasing my alertness regarding setuptools.

Basically if your python installation starts behaving inexplicably,
chances are very, very good that the issue has something to do with
setuptools.  At least that's been my (by now very long running)
story....  Here's one hoping that the fork will eventually produce a
viable long-term solution to this horrid mess.

Thanks for the clarification!

Cheers,

f