best cumulative sum

[Steven D'Aprano]

David (Alan) Isaac wrote:

> What's the good way to produce a cumulative sum?
> E.g., given the list x,
> cumx = x[:]
> for i in range(1,len(x)):
>  cumx[i] = cumx[i]+cumx[i-1]
> 
> What's the better way?

Is there something that this doesn't do, or something 
it does do that it shouldn't?

You could do it this way:

# untested
def cumulative_sum(L):
     CL = []
     csum = 0
     for x in L:
         csum += x
         CL.append(csum)
     return CL

Whether it is better or worse depends on what you 
consider better or worse.


-- 
Steven.