The existing import mechanism is poorly understood (just see how many wrong answers an import question on c.l.py gets) ...
Note that this question has recently been asked by Michael Abbot on c.l.p, for now there are no answers: Is there up to date documentation for package support in Python 2? Section 6.11 of the "Python Reference Manual" has the following nice quote: [XXX Can't be bothered to spell this out right now; see the URL http://www.python.org/doc/essays/packages.html for more details, also about how the module search works from inside a package.] and the referred URL documents Python 1.5. I presume that nothing significant has changed recently, but it's certainly disconcerting for something as fundamental as module importing to not actually be part of the core language documentation! Thomas