Python的线程模块错误：“NoneType”对象不是可调用

Question

我的屏幕显示<type 'exceptions.TypeError'>: 'NoneType' object is not callable当我运行下面这段代码：

import threading 
import urllib2 
import Queue 
import time 

hosts = ["http://baidu.com", "http://yahoo.com"] 

queue = Queue.Queue() 

class ThreadUrl(threading.Thread): 
    """ Threaded Url Grab """ 
    def __init__(self, queue): 
     threading.Thread.__init__(self) 
     self.queue = queue 

    def run(self): 
     while True: 
      #grabs host from queue 
      host = self.queue.get() 

      #grabs urls of hosts and prints first 1024 byte of page 
      url = urllib2.urlopen(host) 

      #signals to queue job is done 
      self.queue.task_done() 

start = time.time() 
def main(): 
    for i in range(2): 
     t = ThreadUrl(queue) 
     t.setDaemon(True) 
     t.start() 

     for host in hosts: 
      queue.put(host) 

    queue.join() 

main() 
print "Elapsed Time: %s" % (time.time() - start) 

这是错误的详细信息：

Exception in thread Thread-3 (most likely raised during interpreter shutdown): 
Traceback (most recent call last): 
File "/usr/local/lib/python2.7/threading.py", line 808, in __bootstrap_inner 
File "url_thread.py", line 21, in run 
File "/usr/local/lib/python2.7/Queue.py", line 168, in get 
File "/usr/local/lib/python2.7/threading.py", line 332, in wait 
<type 'exceptions.TypeError'>: 'NoneType' object is not callable 

这有什么错我的代码？非常感谢。

Answer 1

这是一个python 2.7 bug - Shutdown exception in daemon thread。 你可以让线程非deamon，并通过队列传递一个标记来指示它们退出，然后将它们从主线程中加入。

import threading 
import urllib2 
import Queue 
import time 

hosts = ["http://baidu.com", "http://yahoo.com"] 

queue = Queue.Queue() 

class ThreadUrl(threading.Thread): 
    """ Threaded Url Grab """ 
    def __init__(self, queue): 
     threading.Thread.__init__(self) 
     self.queue = queue 

    def run(self): 
     while True: 
      #grabs host from queue 
      host = self.queue.get() 
      if host is None: 
       self.queue.task_done() 
       return 

      #grabs urls of hosts and prints first 1024 byte of page 
      url = urllib2.urlopen(host) 

      #signals to queue job is done 
      self.queue.task_done() 

start = time.time() 
def main(): 
    threads = [ThreadUrl(queue) for _ in range(2)] 
    map(lambda t: t.start() threads) 
    for i in range(2): 
     for host in hosts: 
      queue.put(host) 
    for t in threads: 
     queue.put(None) 
    queue.join() 
    map(lambda t: t.join() threads) 

main() 
print "Elapsed Time: %s" % (time.time() - start)