On Apr 4, 7:43 pm, [EMAIL PROTECTED] (Alex Martelli) wrote: (snipped)
> A "we-don't-need-no-stinkin'-one-liners" more relaxed approach: > > import collections > d = collections.defaultdict(int) > for x in myList: d[x] += 1 > list(x for x in myList if d[x]==1) > > yields O(N) performance (give that dict-indexing is about O(1)...). > > Collapsing this kind of approach back into a "one-liner" while keeping > the O(N) performance is not easy -- whether this is a fortunate or > unfortunate ocurrence is of course debatable. If we had a "turn > sequence into bag" function somewhere (and it might be worth having it > for other reasons): > > def bagit(seq): > import collections > d = collections.defaultdict(int) > for x in seq: d[x] += 1 > return d > > then one-linerness might be achieved in the "gimme nonduplicated items" > task via a dirty, rotten trick...: > > list(x for bag in [bagit(myList)] for x in myList if bag[x] == 1) > > ...which I would of course never mention in polite company... > > Alex With a "context managed" set one could have, as a one-liner: with cset() as s: retval = [ (x, s.add(x))[0] for x in myList if x not in s ] I've not looked at the underlying implementation of set(), but I presume that checking set membership is also about O(1). -- Cheers, Steven -- http://mail.python.org/mailman/listinfo/python-list
