通过 format 来大量输出字符变量，并排版

def get_protocol_info_from_pcap(pcapfile):
    pcap = PcapFile(pcapfile)
    start = time.time()
    pkts = {}
    for p in pcap.tcp_udp_packets():
        l3 = p.L3_protocol
        if pkts.has_key(l3):
            l3pkts = pkts[l3]
            l3pkts.append(p.length)
            pkts[l3] = l3pkts
        else:
            pkts[l3] = [p.length]
    total = 0
    pcap.close()
    formatstr = "{0[0]:>12}{0[1]:>11}{0[2]:>15}{0[3]:>8}{0[4]:>15}{0[5]:>10}{0[6]:>15}"
    total_p = 0
    total_b = 0
    for i, j in pkts.items():
        total_b += sum(j)
        total_p += j.__len__()

    print "-" * 100
    print pcapfile
    print ""
    print formatstr.format(["protocol_num", "protocol", "total_packets", "rate", "total_bytes", "rate", "aver_pkt_len"])
    for i, j in pkts.items():
        bytes_percent = "%.1f%%" % (sum(j) * 100.0 / total_b)
        pkts_percent = "%.1f%%" % (j.__len__() * 100.0 / total_p)
        print formatstr.format(
            [i, Protocol.l3_protocols[i], j.__len__(), pkts_percent, sum(j), bytes_percent, sum(j) / j.__len__()])
    print formatstr.format(["", "Total", total_p, "", total_b, "", total_b / total_p])
    end = time.time()
    print ""
    print "time cost: %s" % (end - start)
    print "-" * 100
    print ""