I think the point is that people might be dependent on this functionality andÂ
changing it out from underneath them could break their world.
I got the point that Daniel made, and my question was about *how* their world would break, and whether we really need to support multiple versions of something installed side-by-side, with on-the-fly sys.path manipulation. If that is a real requirement which should be supported, shouldn't there be a PEP for it, if it's coming into Python? It's not supported by distutils, and it has been a point of contention. A PEP would allow standardisation of the multiple-versions feature it it's considered desirable, rather than definition by implementation (which I understand you're not in favour of, in general). If it's not considered desirable and doesn't need support, then we only need to consider if it's undeclared setuptools dependencies that we're concerned with, or some other failure mode not yet identified - hence, my questions. I like to get into specifics :-) Regards, Vinay Sajip