Gary Herron wrote: > John Machin wrote: > >>On 13/06/2006 6:28 PM, Paul McGuire wrote: >> >>>(Oh, and I like groupby too! Combine it with sort to quickly create >>>histograms.) >>> >>># tally a histogram of a list of values from 1-10 >>>dataValueRange = range(1,11) >>>data = [random.choice(dataValueRange) for i in xrange(10000)] >>> >>>hist = [ (k,len(list(g))) for k,g in itertools.groupby(sorted(data)) ] >> >>That len(list(g)) looks like it uses O(N) memory just to find out what N >>is :-( > > Not at all! A python list *knows* its length at all times. len() is a > constant time lookup of an internal attribute.
The point is that you had to create the list in the first place. g is an iterator. -- Robert Kern "I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth." -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
