Elegant pythonic cumsum

Question

What would be an elegant and pythonic way to implement cumsum?
Alternatively - if there\'a already a built-in way to do it, that would be even better of course...

Answer 1

Starting Python 3.8, and the introduction of assignment expressions (PEP 572) (:= operator), we can use and increment a variable within a list comprehension:

total = 0
[total := total + x for x in [1, 2, 3 ,4, 5]]
# [1, 3, 6, 10, 15]

This:

• Initializes a variable total to 0 which symbolizes the cumulative sum
• For each item, this both:
  • increments total with the current looped item (total := total + x) via an assignment expression
  • and at the same time, maps x to the new value of total