线程和信息传递--如何

Threading and information passing -- how to(线程和信息传递--如何)

问题描述

为了避免混淆，我编辑了问题：

one.py

import threading
count = 5
dev = threading.Thread(name='dev', target=dev,args=(workQueue,count,))
dev.setDaemon(True)
dev.start()
workQueue = Queue.Queue(10)
queueLock.acquire()
workQueue.put(word)
queueLock.release()
count = 3
time.sleep(2)
count = 5

但我在这里的困惑是，我能够在线程之间放置和获取队列中的值，但在计数的情况下，它不会反映出来。

为什么？
我在这里到底遗漏了什么？

class dev ( threading.Thread ):
    def test(self):
        while 1:
            print count
            print self.EPP_Obj
            queueLock.acquire()
            if not self.workQueue.empty():
                data = self.workQueue.get()
                print data
                queueLock.release()
            else:
                queueLock.release()

    def __init__(self, workQueue, EPP_Obj):
        threading.Thread.__init__(self)
        self.workQueue = workQueue
        self.EPP_Obj = EPP_Obj

推荐答案

让我们从一个例子开始：

Thread子类：

import threading

class Dev(threading.Thread):

    def __init__(self, workQueue, queueLock, count):
        super(Dev, self).__init__()   # super() will call Thread.__init__ for you
        self.workQueue = workQueue
        self.queueLock= queueLock
        self.count = count

    def run(self):  # put inside run your loop
        data = ''
        while 1:
            with self.queueLock:
                if not self.workQueue.empty():
                    data = self.workQueue.get()
                    print data
                    print self.count

            if data == 'quit':
                break

with语句是获取和释放锁的智能方法，请查看doc。

现在运行代码：

import Queue
import time

work_q = Queue.Queue()     # first create your "work object"
q_lock = threading.Lock()
count = 1

dev = Dev(work_q, q_lock, count)  # after instantiate like this your Thread
dev.setDaemon(True)
dev.start()

time.sleep(1)
with q_lock:
    work_q.put('word')
# word
# 1

time.sleep(1)
count = 10
with q_lock:
    work_q.put('dog')
# dog
# 1

count = 'foo'
with q_lock:
    work_q.put('quit')
# quit
# 1

dev.join()   # This will prevent the main to exit
             # while the dev thread is still running

通过上面的代码，我们可以清楚地看到，无论对count执行什么操作，self.count如何保持不变。
此行为的原因是调用：

dev = Dev(work_q, q_lock, count)

或

dev = Dev(work_q, q_lock, 1)

是一样的。

Arnold Moon向您展示了更改self.count的方法。根据我们的示例进行调整：

class Dev(threading.Thread):

    def __init__(self, workQueue, queueLock, count):
        super(Dev, self).__init__()
        self.workQueue = workQueue
        self.queueLock= queueLock
        self.count = count

    def set_count(self, value):
        self.count = value

    def run(self):
        data = ''
        while 1:
            with self.queueLock:
                if not self.workQueue.empty():
                    data = self.workQueue.get()
                    print data
                    print self.count

            if data == 'quit':
                break

在我们的运行代码中调用set_count将更改self.count的值：

time.sleep(1)
with q_lock:
    work_q.put('word')
# word
# 1

time.sleep(1)
count = dev.count + 9
dev.set_count(count)
with q_lock:
    work_q.put('dog')
# dog
# 10

count = 'foo'
with q_lock:
    work_q.put('quit')
# quit
# 10
dev.join()

我希望这将帮助您澄清一些疑虑。

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