Is current integer for-loop syntax a wart?

[phil hunt]

On Sat, 9 Mar 2002 00:29:02 +0000 (UTC), Huaiyu Zhu <huaiyu at gauss.almadan.ibm.com> wrote:
>- Not a wart:
>
>  1. It is very clear what it does.
>  2. range() can be used elsewhere.  No new syntaxes.
>  3. In most situations you loop over list of items instead of counters.
>
>
>- Wart:
>
>  When you do need the index, neither of the following is very nice looking:
>
>     for i, x in zip(range(len(a)), a):
>         b[i] = x
>
>     for i in range(len(a)):
>         b[i] = a[i]

What you sohuld be able to do is say:

   for i in a.keys():
      b[i] = a[i]

You can get a dictionary's keys, so you ought to be able to do so 
with sequence types, in the same way.

(Actually I'd say it is a failing in Python generally that the 
collection typers are not as well-integrated-together as in e.g. 
Smalltalk).

>the solution is too broad: it produces iterators in many uninteded places.
>
>
>Two ideas that I do like:
>
>      for i, x in items(a):
>          b[i] = x

That's nice.

>      for i in indices(a):
>          b[i] = a[i]

Instead of indices(a) use a.keys() for consistency with mapping 
types. This could return an xrange.

>They address the right problems at minimum cost.  They can be extended to
>xitems and xindici, of course.

Indeed.

-- 
<"><"><"> Philip Hunt <philh at comuno.freeserve.co.uk> <"><"><">
"I would guess that he really believes whatever is politically 
advantageous for him to believe." 
                        -- Alison Brooks, referring to Michael
                              Portillo, on soc.history.what-if