itertools.groupby

[Paul Rubin]

Raymond Hettinger <python at rcn.com> writes:
> The gauntlet has been thrown down.  Any creative thinkers
> up to the challenge?  Give me cool recipes.

Here is my version (with different semantics) of the grouper recipe in
the existing recipe section:
 
  snd = operator.itemgetter(1)   # I use this so often...

  def grouper(seq, n):
    for k,g in groupby(enumerate(seq), lambda (i,x): i//n):
       yield imap(snd, g)

I sometimes use the above for chopping large (multi-gigabyte) data
sets into manageable sized runs of a program.  That is, my value of n
might be something like 1 million, so making tuples that size (as the
version in the itertools docs does) starts being unpleasant.  Plus,
I think the groupby version makes more intuitive sense, though it
has pitfalls if you do anything with the output other than iterate
through each item as it emerges.  I guess you could always use map
instead of imap.