Question

我正在关注tutorialspoint，在他们的情况下，他们在我复制粘贴它时写它，但是当我试图在我的pycharm中重现它时，它给出了错误确实，IF不必要地缩进。因此，我缩减，但是当我这样做时，我没有得到同步线程只有线程3做了一些事情，线程1和2刚刚开始但从未执行任何工作，然后全部离开。但是，显然，它适用于教程作者，他们不会缩进IF。我正在使用python 3，所以我不得不小写队列导入。

import Queue
import threading
import time

exitFlag = 0

class myThread (threading.Thread):
   def __init__(self, threadID, name, q):
      threading.Thread.__init__(self)
      self.threadID = threadID
      self.name = name
      self.q = q
   def run(self):
      print "Starting " + self.name
      process_data(self.name, self.q)
      print "Exiting " + self.name

def process_data(threadName, q):
   while not exitFlag:
      queueLock.acquire()
         if not workQueue.empty(): #THIS IS THE ONE THEY INDENT
            data = q.get()
            queueLock.release()
            print "%s processing %s" % (threadName, data)
         else:
            queueLock.release()
         time.sleep(1)

threadList = ["Thread-1", "Thread-2", "Thread-3"]
nameList = ["One", "Two", "Three", "Four", "Five"]
queueLock = threading.Lock()
workQueue = Queue.Queue(10)
threads = []
threadID = 1

# Create new threads
for tName in threadList:
   thread = myThread(threadID, tName, workQueue)
   thread.start()
   threads.append(thread)
   threadID += 1

# Fill the queue
queueLock.acquire()
for word in nameList:
   workQueue.put(word)
queueLock.release()

# Wait for queue to empty
while not workQueue.empty():
   pass

# Notify threads it's time to exit
exitFlag = 1

# Wait for all threads to complete
for t in threads:
   t.join()
print "Exiting Main Thread"

Answer 1

您找到了答案，但仅举例说明，这是一个简化版本，不需要全局退出标志并删除不必要的锁定：

import queue
import threading
import time

def process_data():
    name = threading.current_thread().name
    print('Starting',name)
    while True:
        data = q.get()
        if data is None: # Check for exit special value
            break
        print(name,'processing',data)
        time.sleep(1)
        q.task_done()
    print('Exiting',name)

thread_count = 3
nameList = ["One", "Two", "Three", "Four", "Five"]
q = queue.Queue()

# Create new threads
threads = [threading.Thread(target=process_data) for _ in range(thread_count)]
for t in threads:
    t.start()

# Fill the queue
for word in nameList:
    q.put(word)

# Wait for queue to empty
q.join()

# Notify threads it's time to exit
for t in threads:
    q.put(None) # Special value put in queue indicating to exit

# Wait for all threads to complete
for t in threads:
    t.join()
print('Exiting main thread')

输出：

Starting Thread-1
Starting Thread-2
Starting Thread-3
Thread-1 processing One
Thread-3 processing Three
Thread-2 processing Two
Thread-3 processing Four
Thread-2 processing Five
Exiting Thread-1
Exiting Thread-3
Exiting Thread-2
Exiting main thread

Answer 2

嗯，结论是Tutorialspoint的例子在IF缩进时有错误。不应该有这样的事情。这意味着他们显示的结果明确地与代码不对应。

所以：

我做了两处改动：首先，我缩小了IF和其他人以及睡眠。其次，如果我还没有创建它，我无法看到我如何调用工作队列。所以我将队列创建的片段移到了调用之上。

这就是它在Python 3中的应用：

 import queue
    import threading
    import time

    exitFlag = 0

    class myThread (threading.Thread):
       def __init__(self, threadID, name, q):
          threading.Thread.__init__(self)
          self.threadID = threadID
          self.name = name
          self.q = q
       def run(self):
          print ("Starting" + self.name)
          process_data(self.name, self.q)
          print ("Exiting" + self.name)

    def process_data(threadName, q):
       while not exitFlag:
          queueLock.acquire()
          if not workQueue.empty():
                data = q.get()
                queueLock.release()
                print ("%s processing %s" % (threadName, data))
          else:
                queueLock.release()
          time.sleep(1)

    threadList = ["Thread-1", "Thread-2", "Thread-3"]
    nameList = ["One", "Two", "Three", "Four", "Five"]
    queueLock = threading.Lock()
    workQueue = queue.Queue(10)
    threads = []
    threadID = 1


    # Fill the queue
    queueLock.acquire()
    for word in nameList:
       workQueue.put(word)
    queueLock.release()


    # Create new threads
    for tName in threadList:
       thread = myThread(threadID, tName, workQueue)
       thread.start()
       threads.append(thread)
       threadID += 1


    # Wait for queue to empty
    while not workQueue.empty():
       pass

    # Notify threads it's time to exit
    exitFlag = 1

    # Wait for all threads to complete
    for t in threads:
       t.join()
    print ("Exiting Main Thread")

我得到的结果（看起来不错）是：

StartingThread-1
Thread-1 processing One                                                                                                                                                         
StartingThread-2                                                                                                                                                                
Thread-2 processing Two                                                                                                                                                         
StartingThread-3                                                                                                                                                                
Thread-3 processing Three                                                                                                                                                       
Thread-1 processing Four                                                                                                                                                        
Thread-2 processing Five                                                                                                                                                        
ExitingThread-3                                                                                                                                                                 
ExitingThread-1                                                                                                                                                                 
ExitingThread-2                                                                                                                                                                 
Exiting Main Thread

而python多线程，IF中的一个缩进改变了一切

2 个答案: