pairwise traversal of a list or tuple

Question

a = [5, 66, 7, 8, 9, ...]

Is it possible to make an iteration instead of writing like this?

a[1] - a[0]

a[2] - a[1]

a[3] - a[2]

         


        

Answer 1

I would recommend to use awesome more_itertools library, it has ready-to-use pairwise function:

import more_itertools

for a, b in more_itertools.pairwise([1, 2, 3, 4, 5]):
    print(a, b)
# 1 2
# 2 3
# 3 4
# 4 5

It will save you from writing your own (likely buggy) implementation. For example, most of implementations on this page don't handle the case with empty iterable correctly -- generator function should never raise StopIteration, this behavior considered deprecated and causes DeprecationWarning in Python 3.6. It won't work in Python 3.7 at all.