On Mon, Mar 4, 2013 at 2:41 PM, Paul Moore <p.f.mo...@gmail.com> wrote: > In thinking about how virtualenv would describe the packages it wants > to preload in PEP 426 metadata form, it occurred to me that there are > scenarios with setuptools and distribute where it's not obvious how to > state the requirement you want. Specifically, if you want to install > setuptools if it is present, but if not fall back to distribute (for > example, if you have a local package repository and no access to PyPI, > but setuptools may or may not be present). > > I appreciate this is a fairly obscure case. It comes up with > virtualenv because virtualenv uses locally-available distributions by > default, only going to PyPI if it has to. So in that case (depending > on user options) I could genuinely want to pick whichever of > setuptools or distribute is present, and I don't care which, as it > saves a network lookup. > > I'm actually using the distlib locator API, not the PEP 426 fields > themselves, but (a) distlib locators use the same syntax, as far as > I'm aware, and (b) I think the Requires-Dist syntax makes a good > language for specifying distribution requirements in any context, so > I'd hate to end up with 2 slightly-different forms. > > If the answer is that the spec doesn't support that, then fine. I'll > have to manually code for it. But I'd hate to write code I didn't need > to :-)
This is a good point; people have been wanting setuptools to support alternate dependencies (i.e., I need this *or* that) for a long time, and not just for that particular use case. _______________________________________________ Distutils-SIG maillist - Distutils-SIG@python.org http://mail.python.org/mailman/listinfo/distutils-sig