all pairs of items in a list without indexing?

[Marc Christiansen]

Steven Bethard <steven.bethard at gmail.com> wrote:
> So I need to do something like:
> 
> for i in range(len(l)):
>    for j in range(i+1, len(l)):
>        # do something with (l[i], l[j])
> 
[...]
> I could do something like:
> 
> for i, item1 in enumerate(l):
>    for j in range(i+1, len(l)):
>        (item1, l[j])
> 
> but that only gets me halfway there...  I also thought of something like:
> 
> for i, item1 in enumerate(l):
>    for item2 in l[i+1:]:
>        (item1, item2)
> 
> but that seems like a lot of wasteful list slicing...

You could try something like:

    for i, item1 in enumerate(l):
        for item2 in itertools.islice(l, i+1, None):
            (item1, item2)

I'm not sure which version I prefer.

  Marc