Iterate a list as pair (current, next) in Python

Question

I sometimes need to iterate a list in Python looking at the \"current\" element and the \"next\" element. I have, till now, done so with code like:

for curre         


        

Answer 1

I am really surprised nobody has mentioned the shorter, simpler and most importantly general solution:

Python 3:

from itertools import islice

def n_wise(iterable, n):
    return zip(*(islice(iterable, i, None) for i in range(n)))

Python 2:

from itertools import izip, islice

def n_wise(iterable, n):
    return izip(*(islice(iterable, i, None) for i in xrange(n)))

It works for pairwise iteration by passing n=2, but can handle any higher number:

>>> for a, b in n_wise('Hello!', 2):
>>>     print(a, b)
H e
e l
l l
l o
o !

>>> for a, b, c, d in n_wise('Hello World!', 4):
>>>     print(a, b, c, d)
H e l l
e l l o
l l o
l o   W
o   W o
  W o r
W o r l
o r l d
r l d !