Thanks all! What a remarkable set of answers, intelligent, thought provoking and informative without exception.
Of course, now I can't use Paul's version; it hardly counts as a japh if someone else wrote it! It is probably the closest to my original vision, alas. Miles' second suggestion was the one I was fumbling toward; I will study it. No spoilers please. best mt -- http://mail.python.org/mailman/listinfo/python-list
