Fastest way to loop through each digit in a number?

[Alex Martelli]

Roy Smith <roy at panix.com> wrote:

> In article <ssjnj01agata9qtsn414740sml1kc2em49 at 4ax.com>,
>  Rune Strand <rst at _nospam_.drlug.org._nospam_> wrote:
> 
> > Hi,
> > If I have a lot of integers and want do something with each digit as
> > integer, what is the fastest way to get there? 
> > 
> > Eg. Make 12345 into an iterable object, like [1,2,3,4,5] or "12345"
> 
> Does it matter what order you process the digits, i.e. least-significant
> first vs. most-significant first?  If you can do least first, then you
> might be best off doing something straight-forward like:
> 
> i = 12345
> while i:
>     digit = i % 10
>     i = i / 10
>     print digit
> 
> although, with the new-style division, I'm not sure if you want / or //.

He'd surely want truncation, so I don't understand why he could possibly
want / (which in new-style division means true, non-truncating
division), it's surely gotta be //.  divmod looks like it might be
better, but from some q&d timeit.py'ing, it seems this approach is
fastest (30% faster than divmod) if these semantics are OK (when i is 0
you get nothing rather than a single 0...) -- map(int, str(i)) is midway
in speed through these purely numeric approaches (with % and // vs with
divmod).


Alex