Is there a need for range(len(a))?

If you need to work with indices of a sequence, then yes - you use it... eg for the equivalent of numpy.argsort...:

>>> a = [6, 3, 1, 2, 5, 4]>>> sorted(range(len(a)), key=a.__getitem__)[2, 3, 1, 5, 4, 0]

What if you need to access two elements of the list simultaneously?

for i in range(len(a[0:-1])):    something_new[i] = a[i] * a[i+1]

You can use this, but it's probably less clear:

for i, _ in enumerate(a[0:-1]):     something_new[i] = a[i] * a[i+1]

Personally I'm not 100% happy with either!

Short answer: mathematically speaking, no, in practical terms, yes, for example for Intentional Programming.

Technically, the answer would be "no, it's not needed" because it's expressible using other constructs. But in practice, I use for i in range(len(a) (or for _ in range(len(a)) if I don't need the index) to make it explicit that I want to iterate as many times as there are items in a sequence without needing to use the items in the sequence for anything.

So: "Is there a need?"? — yes, I need it to express the meaning/intent of the code for readability purposes.

See also: https://en.wikipedia.org/wiki/Intentional_programming

And obviously, if there is no collection that is associated with the iteration at all, for ... in range(len(N)) is the only option, so as to not resort to i = 0; while i < N; i += 1 ...