Alright, let's look at this, then. ["".join(r[::e])[::4] for e in (1, -1)] This gives you the diagonals. How? The list comp expands to: "".join(r[::1])[::4] "".join(r[::-1])[::4] This is a use of slice notation, that not errbody knows about. An empty slice, (the first c More