all pairs of items in a list without indexing?

[Steven Bethard]

On Tue, 28 Sep 2004 23:01:58 +0100 (BST), Michael Sparks wrote:
> So let's just write pairs:
> 
> def pairs(l):
>   x=iter(l)
>   while 1:
>      yield x.next(),x.next()

This generates all *successive* pairs.  I need *all* pairs.

>>> l = range(4)
>>> for i in range(len(l)):
...     for j in range(i+1, len(l)):
...             print (l[i], l[j])
...
(0, 1)
(0, 2)
(0, 3)
(1, 2)
(1, 3)
(2, 3)
>>> def pairs(l):
...     x = iter(l)
...     while True:
...         yield x.next(), x.next()
...
>>> for item1, item2 in pairs(l):
...     print (item1, item2)
...
(0, 1)
(2, 3)

Hope that clarifies the problem.

Steve
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