python - 使用多线程在不同的运行中获得不同的结果

Question

为什么代码执行时，每次结果都不一样？

我试图跟踪代码是如何执行的，但我很困惑，我觉得这没有意义。

结果每次都是随机出现的

#!/usr/bin/python

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

# 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"

代码来源 http://www.tutorialspoint.com/python/python_multithreading.htm

<小时/>

更新

抱歉，我的意思是结果的顺序

像这样:

Starting Thread-1
Starting Thread-2
Starting Thread-3
Thread-3 processing One
Thread-2 processing Two
Thread-1 processing Three
Thread-3 processing Four
Thread-2 processing Five
Exiting Thread-1
Exiting Thread-3
Exiting Thread-2
Exiting Main Thread
[Finished in 3.0s]

再试一次，结果

Starting Thread-1
Starting Thread-2
Starting Thread-3
Thread-3 processing One
Thread-2 processing Two
Thread-1 processing Three
Thread-3 processing Four
Thread-3 processing Five
Exiting Thread-1
Exiting Thread-2
Exiting Thread-3
Exiting Main Thread
[Finished in 3.0s]

Answer 1

我认为，“结果”指的是执行顺序。 多线程背后的一个想法是，除非您想明确指定，否则您不必关心执行顺序。你完全依赖于底层操作系统、系统负载……等等。