List comprehension for running total

Question

I want to get a running total from a list of numbers.

For demo purposes, I start with a sequential list of numbers using range

a = range         


        

Answer 1

Another one-liner, in linear time and space.

def runningSum(a):
    return reduce(lambda l, x: l.append(l[-1]+x) or l if l else [x], a, None)

I'm stressing linear space here, because most of the one-liners I saw in the other proposed answers --- those based on the pattern list + [sum] or using chain iterators --- generate O(n) lists or generators and stress the garbage collector so much that they perform very poorly, in comparison to this.