Python多线程编程

原文

运行几个线程和同时运行几个不同的程序类似，它有以下好处：

•  一个进程内的多个线程和主线程分享相同的数据空间，比分开不同的过程更容易分享信息或者彼此通信。
•  线程有时叫做轻量化过程，而且他们不要求更多的内存开支；它们比过程便宜。

•  它可以被抢占（中断）
•  它能暂时被挂起（也叫做休眠），而别的线程在运行--这也叫做yielding（让步）。

开始一个新线程：

import thread
import time

# Define a function for the thread
def print_time( threadName, delay):
   count = 0
   while count < 5:
      time.sleep(delay)
      count += 1
      print "%s: %s" % ( threadName, time.ctime(time.time()) )

# Create two threads as follows
try:
   thread.start_new_thread( print_time, ("Thread-1", 2, ) )
   thread.start_new_thread( print_time, ("Thread-2", 4, ) )
except:
   print "Error: unable to start thread"


while 1:
   pass

Thread-1: Thu Jan 22 15:42:17 2009
Thread-1: Thu Jan 22 15:42:19 2009
Thread-2: Thu Jan 22 15:42:19 2009
Thread-1: Thu Jan 22 15:42:21 2009
Thread-2: Thu Jan 22 15:42:23 2009
Thread-1: Thu Jan 22 15:42:23 2009
Thread-1: Thu Jan 22 15:42:25 2009
Thread-2: Thu Jan 22 15:42:27 2009
Thread-2: Thu Jan 22 15:42:31 2009
Thread-2: Thu Jan 22 15:42:35 2009

尽管对于低级别的线程，它是非常有效的，然而thread模块与较新的线程模块相比，其功能还是非常有限的。

Threading模块：

•  threading.activeCount():返回激活的线程对象的数目
•  theading.currentThread():返回调用者的线程控制中线程对象的数目
•  threading.enumerate(): 返回当前活动的线程对象列表

•  run():线程的入口点
•  start():调用run方法启动线程
•  join(time):等待线程结束
•  isAlive():检查一个线程是否仍旧在执行
•  getName():返回线程的名字
•  setName():设置一个线程的名字

使用Threading模块创建线程：

•   定义Thread类的一个子类。
•  重写__init__(self,[,args])方法以增加额外的参数
•  然后，重写run(self[,args])方法以实现线程启动后要做的事情

#!/usr/bin/python

import threading
import time

exitFlag = 0

class myThread (threading.Thread):
    def __init__(self, threadID, name, counter):
        threading.Thread.__init__(self)
        self.threadID = threadID
        self.name = name
        self.counter = counter
    def run(self):
        print "Starting " + self.name
        print_time(self.name, self.counter, 5)
        print "Exiting " + self.name

def print_time(threadName, delay, counter):
    while counter:
        if exitFlag:
            thread.exit()
        time.sleep(delay)
        print "%s: %s" % (threadName, time.ctime(time.time()))
        counter -= 1

# Create new threads
thread1 = myThread(1, "Thread-1", 1)
thread2 = myThread(2, "Thread-2", 2)

# Start new Threads
thread1.start()
thread2.start()

print "Exiting Main Thread"

Starting Thread-1
Starting Thread-2
Exiting Main Thread
Thread-1: Thu Mar 21 09:10:03 2013
Thread-1: Thu Mar 21 09:10:04 2013
Thread-2: Thu Mar 21 09:10:04 2013
Thread-1: Thu Mar 21 09:10:05 2013
Thread-1: Thu Mar 21 09:10:06 2013
Thread-2: Thu Mar 21 09:10:06 2013
Thread-1: Thu Mar 21 09:10:07 2013
Exiting Thread-1
Thread-2: Thu Mar 21 09:10:08 2013
Thread-2: Thu Mar 21 09:10:10 2013
Thread-2: Thu Mar 21 09:10:12 2013
Exiting Thread-2

同步线程：
Python提供的threading模块包括一个易于实现的锁定机制，以允许你同步线程。创建一个新锁通过调用Lock()实现，它也返回这个新锁。
新锁对象的accquire(blocking)方法，用来强制线程同步运行。可选的blocking参数使你能够控制线程是否请求锁。
如果blocking设置为0，线程在不能获取锁时立即返回0值；而blocking设置为1时，线程获取锁以后返回1值。如果blocking设置为1，线程将会阻塞，一直等到锁释放。
新锁对象的release()方法用来释放不再需要的锁。


例子：

#!/usr/bin/python

import threading
import time

class myThread (threading.Thread):
    def __init__(self, threadID, name, counter):
        threading.Thread.__init__(self)
        self.threadID = threadID
        self.name = name
        self.counter = counter
    def run(self):
        print "Starting " + self.name
        # Get lock to synchronize threads
        threadLock.acquire()
        print_time(self.name, self.counter, 3)
        # Free lock to release next thread
        threadLock.release()

def print_time(threadName, delay, counter):
    while counter:
        time.sleep(delay)
        print "%s: %s" % (threadName, time.ctime(time.time()))
        counter -= 1

threadLock = threading.Lock()
threads = []

# Create new threads
thread1 = myThread(1, "Thread-1", 1)
thread2 = myThread(2, "Thread-2", 2)


# Start new Threads
thread1.start()
thread2.start()

# Add threads to thread list
threads.append(thread1)
threads.append(thread2)

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

Starting Thread-1
Starting Thread-2
Thread-1: Thu Mar 21 09:11:28 2013
Thread-1: Thu Mar 21 09:11:29 2013
Thread-1: Thu Mar 21 09:11:30 2013
Thread-2: Thu Mar 21 09:11:32 2013
Thread-2: Thu Mar 21 09:11:34 2013
Thread-2: Thu Mar 21 09:11:36 2013
Exiting Main Thread

多线程优先级 队列：

• get():从队列移除一个项目并返回它
• put():把项目放入队列
• qsize():返回当前队列中项目的数量
• empty():如果队列为空，返回True，反之为False
• full():如果队列满了返回True，反之为False

#!/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"

Python多线程编程,布布扣,bubuko.com

Python多线程编程

原文：http://blog.csdn.net/fengyu09/article/details/26393873