I would argue that, because Python requires its users to reason about storage and interpreter state, we shouldn't consider (a,b,c) and (a,b,c) identical under is unless they're aliases for the same structure in memory. I'm not sure I understand dragonwriter's idea for a third equality operator, however. Isn't == adequate for that purpose?

By the way, I'd like to thank both catnaroek and dragonwriter for an excellent discussion; this sort of thing is why I come to HN.