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

for loops are pythonic

def cumsum(vec):
    r = [vec[0]]
    for val in vec[1:]:
        r.append(r[-1] + val)
    return r