Your code is buggy, though. It will only ever accept two parts because of `cmd, arg = parts`, so `["quit"]` will fail, and each command might accept a different

Your code is buggy, though. It will only ever accept two parts because of `cmd, arg = parts`, so `["quit"]` will fail, and each command might accept a different number of parts, so you can't just test `0 < len(parts) < 3` for all of them. The pattern matching version is harder to get wrong.