Iterate using tuple as index

[James Stroud]

Hello,

Its not obvious to me how to do this. I would like to iterate using a tuple as
an index. Say I have two equivalently sized arrays, what I do now seems
inelegant:

for index, list1_item in enumerate(first list):
do_something(li st1_item, secondlist[index])

I would like something more like this:

for list1_item, list2_item in (some_kind_of_e xpression):
do_something(li st1_item, list2_item)

Practically, I'm not so sure B is better than A, but the second would be a
little more aesthetic, to me, at least.

Any thoughts on what "some_kind_of_e xpression" would be?

James

--
James Stroud, Ph.D.
UCLA-DOE Institute for Genomics and Proteomics
Box 951570
Los Angeles, CA 90095

[F. Petitjean]

Re: Iterate using tuple as index

Le Thu, 10 Mar 2005 13:12:31 -0800, James Stroud a écrit :[color=blue]
> Hello,
>
> Its not obvious to me how to do this. I would like to iterate using a tuple as
> an index. Say I have two equivalently sized arrays, what I do now seems
> inelegant:
>
> for index, list1_item in enumerate(first list):
> do_something(li st1_item, secondlist[index])
>
> I would like something more like this:
>
> for list1_item, list2_item in (some_kind_of_e xpression):
> do_something(li st1_item, list2_item)
>
> Practically, I'm not so sure B is better than A, but the second would be a
> little more aesthetic, to me, at least.
>
> Any thoughts on what "some_kind_of_e xpression" would be?[/color]
It is called "zip"
for list1_item, list2_item in zip(firstlist, secondlist):
....
try: help(zip)[color=blue]
>
> James
>[/color]

[Tim Jarman]

Re: Iterate using tuple as index

James Stroud wrote:
[color=blue]
> Hello,
>
> Its not obvious to me how to do this. I would like to iterate using a
> tuple as an index. Say I have two equivalently sized arrays, what I do now
> seems inelegant:
>
> for index, list1_item in enumerate(first list):
> do_something(li st1_item, secondlist[index])
>
> I would like something more like this:
>
> for list1_item, list2_item in (some_kind_of_e xpression):
> do_something(li st1_item, list2_item)
>
> Practically, I'm not so sure B is better than A, but the second would be a
> little more aesthetic, to me, at least.
>
> Any thoughts on what "some_kind_of_e xpression" would be?
>
> James
>[/color]

for item1, item2 in zip(list1, list2):
do_something(it em1, item2)

perhaps?

--
Website: www DOT jarmania FULLSTOP com

[Bengt Richter]

Re: Iterate using tuple as index

On Thu, 10 Mar 2005 13:12:31 -0800, James Stroud <jstroud@mbi.uc la.edu> wrote:
[color=blue]
>Hello,
>
>Its not obvious to me how to do this. I would like to iterate using a tuple as
>an index. Say I have two equivalently sized arrays, what I do now seems
>inelegant:
>
>for index, list1_item in enumerate(first list):
> do_something(li st1_item, secondlist[index])
>
>I would like something more like this:
>
>for list1_item, list2_item in (some_kind_of_e xpression):
> do_something(li st1_item, list2_item)
>
>Practically, I'm not so sure B is better than A, but the second would be a
>little more aesthetic, to me, at least.
>
>Any thoughts on what "some_kind_of_e xpression" would be?
>[/color]
zip?
[color=blue][color=green][color=darkred]
>>> firstlist = [1,2,3]
>>> secondlist = 'a b c'.split()
>>> firstlist, secondlist[/color][/color][/color]
([1, 2, 3], ['a', 'b', 'c'])[color=blue][color=green][color=darkred]
>>> for list1_item, list2_item in zip(firstlist, secondlist):[/color][/color][/color]
... print list1_item, list2_item
...
1 a
2 b
3 c

Or if your lists are very long, you could use an iterator from itertools, e.g.,
[color=blue][color=green][color=darkred]
>>> import itertools
>>> for list1_item, list2_item in itertools.izip( firstlist, secondlist):[/color][/color][/color]
... print list1_item, list2_item
...
1 a
2 b
3 c


Regards,
Bengt Richter

[Roy Smith]

Re: Iterate using tuple as index

James Stroud <jstroud@mbi.uc la.edu> wrote:[color=blue]
>I would like something more like this:
>
>for list1_item, list2_item in (some_kind_of_e xpression):
> do_something(li st1_item, list2_item)[/color]

I believe you want:

for list1_item, list2_item in zip (list1, list2):
blah