python - iterate list and get list index for use in array

Question

Sorry, I know this is probably simple and covered in another post but I couldn't find it so:

I want to iterate through two lists and then store a result in an array based on the position of the inputs. So, for example:

z = np.array(len(xlist), len(ylist))

for x in xlist:
  for y in ylist:
    z[index of x, index of y] = f(x,y)

Thanks!