In article <mailman.3050.1371018754.3114.python-l...@python.org>, Phil Connell <pconn...@gmail.com> wrote:
> > Well, continuing down this somewhat bizarre path: > > > > new_songs, old_songs = [], [] > > itertools.takewhile( > > lambda x: True, > > (new_songs if s.is_new() else old_songs).append(s) for s in songs) > > ) > > > > I'm not sure I got the syntax exactly right, but the idea is anything > > that will iterate over a generator expression. That at least gets rid > > of the memory requirement to hold the throw-away list :-) > > You could equivalently pass the generator to deque() with maxlen=0 - this > consumes the iterator with constant memory usage. > > We are of course firmly in the twilight zone at this point (although this > can be a useful technique in general). We've been in the twilight zone for a while. That's when the fun starts. But, somewhat more seriously, I wonder what, exactly, it is that freaks people out about: >>>> [(new_songs if s.is_new() else old_songs).append(s) for s in songs] Clearly, it's not the fact that it build and immediately discards a list, because that concern is addressed with the generator hack, and I think everybody (myself included) agrees that's just horrible. Or, is it the use of the conditional to create the target for append()? Would people be as horrified if I wrote: for s in songs: (new_songs if s.is_new() else old_songs).append(s) or even: for s in songs: the_right_list = new_songs if s.is_new() else old_songs the_right_list.append(s) -- http://mail.python.org/mailman/listinfo/python-list