Iteration over Lists and Strings

[Brent W. Hughes]

"Alex Martelli" <aleaxit at yahoo.com> wrote in message
news:1gj80xs.1cfownoqz4m9N%aleaxit at yahoo.com...
> Michel Claveau - abstraction méta-galactique non triviale en fuite
> perpétuelle. <unseulmcmcmcmc at msupprimerlepoint.claveauPOINTcom> wrote:
>
> > and enumerate is more fast than index.
>
> Oh, absolutely.  sequence.index(anitem) takes time proportional to
> len(sequence), for the average item.  If you repeat that operation for
> all items in sequence, you end up with total time proportional to the
> SQUARE of len(sequence) -- a LOT, for long sequences,  enumerate itself
> takes constant time, and looping over all items that enumerate yields
> takes time proportional to the number of items (costant time per item).
>
> If you're familiar with big-O notation, we're talking O(N) vs O(N
> square)... not the kind of performance issue one can ignore, for long
> sequences, because the difference in performance keeps going up and up
> without bounds as the sequence grows longer.
>
>
> Alex


Did you say enumerate(seq) takes constant time?  I would have thought it was
proportional to len(seq).