Iterate over all pairs of consecutive items in a list
Just use zip
>>> l = [1, 7, 3, 5]
>>> for first, second in zip(l, l[1:]):
... print first, second
...
1 7
7 3
3 5
If you use Python 2 (not suggested) you might consider using the izip
function in itertools
for very long lists where you don't want to create a new list.
import itertools
for first, second in itertools.izip(l, l[1:]):
...
Look at pairwise
at itertools recipes: http://docs.python.org/2/library/itertools.html#recipes
Quoting from there:
def pairwise(iterable):
"s -> (s0,s1), (s1,s2), (s2, s3), ..."
a, b = tee(iterable)
next(b, None)
return izip(a, b)
A General Version
A general version, that yields tuples of any given positive natural size, may look like that:
def nwise(iterable, n=2):
iters = tee(iterable, n)
for i, it in enumerate(iters):
next(islice(it, i, i), None)
return izip(*iters)