list comprehension return a list and sum over in loop

[KK Sasa]

Hi there,

The list comprehension is results = [d2(t[k]) for k in xrange(1000)], where d2 is a function returning a list, say [x1,x2,x3,x4] for one example. So "results" is a list consisting of 1000 lists, each of length four. Here, what I want to get is the sum of 1000 lists, and then the result is a list of length four. Is there any efficient way to do this? Because I found it is slow in my case. I tried sum(d2(t[k]) for k in xrange(1000)), but it returned error: TypeError: unsupported operand type(s) for +: 'int' and 'list'. Thanks.