Writing a function that alternates plus and minus signs between list indices

Question

In a homework set I\'m working on, I\'ve come across the following question, which I am having trouble answering in a Python-3 function:

\"Write a fun

Answer 1

You can use cycle from itertools to alternate +/-

>>> from itertools import cycle
>>> data = [*range(1, 5)]
>>> sum(i * s for i, s in zip(data, cycle([1, -1])))
-2