Dave:

Thank you too. ikegami did me the kindness of offering many corrections/suggestions/tactics on the original code... of which, even as a learner, I was well and truly ashamed once I understood his points. I'm similarly chastened, but also more educated, thanks to your pointers.

And as my last reply noted, I now know the title was hopelessly hapless. For that too, apologies to you and all others who stumble upon it.

I would welcome a reference to any tutorial you care to recommend on useing a debugger effectively. print statements (only a few of which made it into the posted code) go only so far... and regrettably, I'm still finding the docs for activestate's debugger almost impenetrable.