python - 线程和信息传递——如何

Question

为了避免混淆，我编辑了问题:

一个.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从队列中放入和获取值，但在计数的情况下它不会反射(reflect)出来。

这是为什么？
我实际上在这里缺少什么要点？

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

Answer 1

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一种聪明方法，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，我们有一个清晰的示例，说明无论我们对 count 做什么，self.count 都是如何保持不变的。
这种行为的原因是调用:

dev = Dev(work_q, q_lock, count)

或

dev = Dev(work_q, q_lock, 1)

是一样的。

Arnold Moon向您展示了一种更改 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

在我们运行的代码中调用set_count会改变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()

我希望这能帮助你澄清一些疑问。