想要獲取線程函數(shù)中Thread(target=fun, ...)中fun函數(shù)的返回值，根據(jù)網(wǎng)上的方法創(chuàng)建了一個(gè)類獲得：

但是不解的是，get_result()方法只能獲取到一個(gè)值，而run方法，print(self._result)是可以打印出所有的值的。
這是什么原因呢？請(qǐng)各位大佬指教。
下面附代碼：
import nmap
import sendemailtool as tool
from optparse import OptionParser
from threading import Thread

class CustomTask(Thread):

def __init__(self, tgthost, tgtport):
    Thread.__init__(self)
    self._result = None
    self.tgthost = tgthost
    self.tgtport = tgtport

def run(self):
    result = nmScan(self.tgthost, self.tgtport)
    self._result = result
    print(self._result)

def get_result(self):
    # print(self._result)
    return self._result

def nmScan(tgthost, tgtport):

whitelist = []
result = ''
nmscan = nmap.PortScanner()
tmp = nmscan.scan(tgthost, tgtport)
result = result + "<h2>ip地址:%s ...... %s</h2><hr>" % (tgthost, tmp['scan'][tgthost]['status']['state'])
try:
    ports = tmp['scan'][tgthost]['tcp'].keys()
    for port in ports:
        if port not in whitelist:
            info = '<strong><font color=red>Alert:非預(yù)期端口</font></strong>&nbsp;&nbsp;'
        else:
            info = '<strong><font color=green>Info:正常開放端口</font></strong>&nbsp;&nbsp;'
        portinfo = "%s <strong>port</strong> : %s &nbsp;&nbsp;<strong>state</strong> : %s &nbsp;&nbsp;<strong>product</strong> : %s <br>" % (info, port, tmp['scan'][tgthost]['tcp'][int(port)]['state'], tmp['scan'][tgthost]['tcp'][int(port)]['product'])
        result = result + portinfo
except KeyError as e:
    if whitelist:
         whitestr = ','.join(whitelist)
         result = result + "未掃到開放端口！請(qǐng)檢查%s端口對(duì)應(yīng)的服務(wù)狀態(tài)" % whitestr
    else:
        result = result + "掃描結(jié)果正常，無暴露端口"
return result

def main():

f1 = open('/home/angie/PycharmProjects/python_work/iplist.txt', 'ab')
parser = OptionParser()
parser.add_option('-H', dest='tgthost', type='string', help='specify target host')
parser.add_option('-f', dest='file', default='', help='host list', metavar='LIST')
(options, args) = parser.parse_args()
tgthost = options.tgthost
tgtports = [20, 21, 22, 23, 25, 69, 80, 109, 110, 139, 179, 443, 445, 544, 1080, 1433, 1434, 1521, 1158, 2100,3306, 3389, 7001, 8080, 8081, 9080, 9090]
if options.file == '':
    for tgtport in tgtports:
        ct = CustomTask(str(tgthost), str(tgtport))
        ct.start()
        ct.join()
    result = ct.get_result()
    # mailcontent = '<br>'.join(result)
    # print(result)
    tool.sendemail(result)
else:
    f = open(options.file, 'r')
    current_host = f.readline().strip()
    while (current_host):
        for tgtport in tgtports:
            ct = CustomTask(str(current_host), str(tgtport))
            ct.start()
            ct.join()
        current_host = f.readline().strip()
    # mailcontent = '<br>'.join(result)
    result = ct.get_result()
    f.close()
    # print(result)
    tool.sendemail(result)
f1.close()

if name == '__main__':

main()