Python: UnboundLocalError：引用前未赋值的局部变量

Question

我这里有一段用Python写的线程代码（服务器），但是当我运行客户端时，出现了一个错误：“UnboundLocalError: 在赋值之前引用了局部变量'stop'”。

import threading
import msvcrt

stop = False
Buffer= 1024

class ChatServer(threading.Thread):
   def __init__(self,channel,addr,counter):
       self.channel = channel
       self.addr = addr
       self.counter = counter
       threading.Thread.__init__(self)
       self.start()

   def run(self):
       # press s to trigger
       if msvcrt.kbhit():
           if msvcrt.getch() == 's':
               stop = True
               print "Login is closed closed.\n"
       while 1:
           if (stop == False):
               print "\nClient connection received!\n"
               self.channel.send("Status: Server connection received")

counter = 0                   
server = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
server.bind(("",500))
server.listen(20)

while True:
    print "\nServer awaiting connections....\n"
    channel, addr = server.accept()
    counter += 1
    ChatServer(channel,addr,counter)

Answer 1

你只在非常特定的情况下设置了变量 stop，而且从来没有把它设置为 False。在 run() 函数的开头加上一个明确的 stop = False。

def run(self):
   stop = False
   # press s to trigger
   if msvcrt.kbhit():
       if msvcrt.getch() == 's':
           stop = True
           print "Login is closed closed.\n"
   while 1:
       if (stop == False):
           print "\nClient connection received!\n"
           self.channel.send("Status: Server connection received")

你 可能 想在 while 循环的某个时刻设置 stop，因为现在的情况是，如果达到了 stop = True，程序将永远不会停止。