>> * New method (proposed by Shane Holloway): s1.isdisjoint(s2). Mike> +1. Disjointness verification is one of my main uses for set(), Mike> and though I don't think that the early-out condition would Mike> trigger often in my code, it would increase readability. I think the readbility argument is marginal at best. I use sets frequently and to the greatest extent possible use the builtin operator support because I find that more readable. So for me, I'd be going from if not s1 & s2: to if s1.isdisjoint(s2): I'm not sure that's an improvement. Maybe it's just me, but given two sets I frequently want to operate on s1-s2, s2-s1 and s1&s2 in different ways. I wouldn't find a disjoint operation all that useful. Skip