iterating "by twos"

giltay at gmail.com giltay at gmail.com
Tue Jul 29 21:42:19 CEST 2008


On Jul 29, 2:36 pm, gil... at gmail.com wrote:
> On Jul 29, 1:36 pm, kj <so... at 987jk.com.invalid> wrote:
>
> > Is there a special pythonic idiom for iterating over a list (or
> > tuple) two elements at a time?
>
>      I use this one a lot:
>
> for x, y in zip(a, a[1:]):
>     frob(x, y)
>
> Geoff G-T

     Whoops, I misread the original post.  That would be:

for x, y in zip(a[::2], a[1::2]):
    frob(x, y)

... which I don't use a lot.

>>> a = range(9)
>>> for x, y in zip(a, a[1:]):
...     print x, y
...
0 1
1 2
2 3
3 4
4 5
5 6
6 7
7 8
>>> for x, y in zip(a[::2], a[1::2]):
...     print x, y
...
0 1
2 3
4 5
6 7

Geoff G-T




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