not_so_proud_loop.py

rx = {}
delta = {}

with open("t2.txt") as f_t2:
    for line in f_t2.readlines():
        if "Chassis/Slot/Port" in line:
            port = line.split()[1].strip()
            rx[port] = {}
        if "Bytes Received" in line:
            t2_bytes_rx = line.split(":")[1].strip().rstrip(", Unicast Frames ")
            rx[port]["t2"] = int(t2_bytes_rx)


with open("t1.txt") as f_t1:
    for line in f_t1.readlines():
        if "Chassis/Slot/Port" in line:
            port = line.split()[1].strip()
        if "Bytes Received" in line:
            t1_bytes_rx = line.split(":")[1].strip().rstrip(", Unicast Frames ")
            rx[port]["t1"] = int(t1_bytes_rx)

            bytes_received_during_delta_t = rx.get(port).get("t2") - rx.get(port).get(
                "t1"
            )
            delta[port] = bytes_received_during_delta_t

print(sorted(delta, key=delta.get, reverse=True)[:5])