While we're talking about annoyances

Arnaud Delobelle arnodel at googlemail.com
Sun Apr 29 16:30:50 CEST 2007


On Apr 29, 11:46 am, Michael Hoffman <cam.ac... at mh391.invalid> wrote:
> GHUM wrote:
> > Steven,
>
> >> def index(sequence):
> >>     decorated = zip(sequence, xrange(len(sequence)))
> >>     decorated.sort()
> >>     return [idx for (value, idx) in decorated]
>
> > would'nt that be equivalent code?
>
> > def index(sequence):
> >     return [c for _,c  in sorted((b,a) for a, b in
> > enumerate(sequence))]
>
> Or even these:
>
> def index(sequence):
>      return sorted(range(len(sequence)), key=sequence.__getitem__)
>
> def rank(sequence):
>      return sorted(range(len(sequence)),
>                    key=index(sequence).__getitem__)

Better still:

def rank(sequence):
    return index(index(sequence))

:)
But really these two versions of rank are slower than the original one
(as sorting a list is O(nlogn) whereas filling a table with
precomputed values is O(n) ).

Anyway I would like to contribute my own index function:

def index(seq):
     return sum(sorted(map(list,enumerate(seq)), key=list.pop), [])

It's short and has the advantage of being self-documenting, which will
save Steven a lot of annoying typing I hope ;)  Who said Python
couldn't rival with perl?

--
Arnaud




More information about the Python-list mailing list