"KeyError: '(insert IP)'"是什么意思？

Question

我正在使用Violent Python的书，有一个错误使我无法通过第一个nmap构建（第40-41页）。在虚拟机上使用Ubuntu 14.04。我正在终端中输入"python nmapScan.py-H 10.50.60.125-p 21720"。

import nmap
import optparse
def nmapScan(tgtHost,tgtPort):
    nmScan = nmap.PortScanner()
    nmScan.scan(tgtHost,tgtPort)
    state=nmScan[tgtHost]['tcp'][int(tgtPort)]['state']
    print "[*] " + tgtHost + " tcp/"+tgtPort +" "+state
def main():
    parser = optparse.OptionParser('usage %prog '+
                                   '-H <target host> -p <target port>')
    parser.add_option('-H', dest='tgtHost', type='string',
                      help='specify target host')
    parser.add_option('-p', dest='tgtPort', type='string',
                      help='specify target port[s] separated by comma')
    (options, args) = parser.parse_args()
    tgtHost = options.tgtHost
    tgtPorts = str(options.tgtPort).split(',')
    if (tgtHost == None) | (tgtPorts[0] == None):
        print parser.usage
        exit(0)
    for tgtPort in tgtPorts:
        nmapScan(tgtHost, tgtPort)

if __name__ == '__main__':
    main()

错误如下：

File "nmapScan.py", line 24, in <module>
    main()
File "nmapScan.py", line 21, in main
    nmapScan(tgtHost, tgtPort)
File "nmapScan.py", line 7, in nmapScan
    state = nmScan[tgtHost]['tcp'][int(tgtPort)]['state']
File "build/bdist.linux-x86_64/egg/nmap/nmap.py", line 567, in __getitem__
KeyError:'10.50.60.125'

Answer 1

nmap中的KeyError表示无法访问ip。你应该验证ip是否真的启动了。

如果您不总是确定主机是否会启动，则需要try/except:

try:
    state = nmScan[tgtHost]['tcp'][int(tgtPort)]['state']
except KeyError as e:
   print(e)
   return

Answer 2

无法访问此主机10.50.60.125。

ping 10.50.60.125
PING 10.50.60.125 (10.50.60.125): 56 data bytes
Request timeout for icmp_seq 0
Request timeout for icmp_seq 1

尝试使用一些可访问的主机，如：127.0.0.1。

Answer 3

这是因为nmap没有扫描端口的信息，你可以用查询

nmScan = nmap.PortScanner()
data = nmScan.scan(tgtHost,tgtPort)
print(data.get(tgtHost))

你会发现输出值是空的

从来源cod，我们可以知道：nmScan[tgtHost]等于data.get(tgtHost)[tgtHost]

更好的方法是用data.get(tgtHost)[tgtHost]或data.get(tgtHost).get(tgtHost, {})