Example solution
port1 = 0 for port2 in range(1, 5): for port3 in range(1, 5): for port4 in range(1, 5): for port5 in range(1, 5): route = [port1, port2, port3, port4, port5] if 0 in route and 1 in route and 2 in route and 3 in route and 4 in route: distance = D[route[0]][route[1]] + D[route[1]][route[2]] + \ D[route[2]][route[3]] + D[route[3]][route[4]] emissions = distance * co2 print(' '.join([portnames[i] for i in route]) + " %.1f kg" % emissions)