I'm too much of a down-to-earth, pragmatic and occasional programmer to worry about philosophical issues - and Python has few of them (see the 'Zen of Python'), which is why I like it :-) The question is intriguing though, and while I haven't (yet) found a definitive answer, I did find the discussion on this page quite enlightening: http://jtauber.com/blog/2006/04/15/p...onstant_lists/