Generators: running totals

A generator is a function that uses yield instead of return. Each yield hands back one value and pauses, resuming where it left off when asked for the next one:

def count_up(n):
    for i in range(n):
        yield i

list(count_up(3))   # [0, 1, 2]  — wrap in list() to pull every value out

This lets you produce a sequence lazily, one item at a time, while keeping state (like a running tally) between yields.

Your task

Write a generator running_totals(nums) that yields the cumulative sum after each element.

list(running_totals([1, 2, 3]))    # [1, 3, 6]
list(running_totals([]))           # []
list(running_totals([5, -5, 5]))   # [5, 0, 5]

Hint: keep a total variable starting at 0; in a loop, add each number to it and yield total.