Python 多线程

Threading

Python的标准库提供了两个模块：thread和threading，thread是低级模块，threading是高级模块，对thread进行了封装。绝大多数情况下，我们只需要使用threading这个高级模块。

启动一个线程就是把一个函数传入并创建Thread实例，然后调用start()开始执行：

import time,threading
def loop():
    print 'thread %s is running...'%threading.current_thread().name
    n = 0 
    while n<5:
        n= n+1
        print 'thread %s >>> %s'%(threading.current_thread().name,n)
        time.sleep(1)
    print 'thread %s end.' %threading.current_thread().name
print 'thread %s in running...' % threading.current_thread().name
t = threading.Thread(target = loop,name = 'LoopThread')
t.start()
t.join()

print 'thread %s end.' %threading.current_thread().name

输出结果：

thread MainThread is running…
thread LoopThread is running…
thread LoopThread >>> 1
thread LoopThread >>> 2
thread LoopThread >>> 3
thread LoopThread >>> 4
thread LoopThread >>> 5
thread LoopThread ended.
thread MainThread ended.

由于任何进程默认就会启动一个线程，我们把该线程称为主线程，主线程又可以启动新的线程，Python的threading模块有个current_thread()函数，它永远返回当前线程的实例。主线程实例的名字叫MainThread，子线程的名字在创建时指定，我们用LoopThread命名子线程。名字仅仅在打印时用来显示，完全没有其他意义，如果不起名字Python就自动给线程命名为Thread-1，Thread-2……

Lock

import threading
# 3.lock
# 假定这是你的银行存款:
balance = 0
lock = threading.Lock()
def change_it(n):
    # 先存后取，结果应该为0:
    global balance
    balance = balance + n
    balance = balance - n

def run_thread(n):
    for i in range(100000):
        lock.acquire()
        try:
            change_it(n)
        finally:
            lock.release()

t1 = threading.Thread(target=run_thread, args=(5,))
t2 = threading.Thread(target=run_thread, args=(8,))
t1.start()
t2.start()
t1.join()
t2.join()
print balance

Queue

from random import randint
from time import sleep
from Queue import Queue
from myThread import MyThread

def writeQ(queue):
    print 'producing object for Q...',
    queue.put('xxx', 1)
    print "size now", queue.qsize()

def readQ(queue):
    val = queue.get(1)
    print 'consumed object from Q... size now', \
        queue.qsize()

def writer(queue, loops):
    for i in range(loops):
        writeQ(queue)
        sleep(randint(1, 3))

def reader(queue, loops):
    for i in range(loops):
        readQ(queue)
        sleep(randint(2, 5))

funcs = [writer, reader]
nfuncs = range(len(funcs))

def main():
    nloops = randint(2, 5)
    q = Queue(32)
    threads = []
    for i in nfuncs:
        t = MyThread(funcs[i], (q, nloops), \
            funcs[i].__name__)
        threads.append(t)

    for i in nfuncs:
        threads[i].start()

    for i in nfuncs:
        threads[i].join()

    print 'all DONE'

if __name__ == '__main__':
    main()

>

starting writer at: Mon Mar 06 16:34:51 2017
add for Q… size now= 1
starting reader at: Mon Mar 06 16:34:51 2017
sub from Q… size now= 0
add for Q… size now= 1
sub from Q… size now= 0
add for Q… size now= 1
add for Q… size now= 2
writer finished at: Mon Mar 06 16:34:57 2017
sub from Q… size now= 1
sub from Q… size now= 0
reader finished at: Mon Mar 06 16:35:06 2017
all DONE

参考文献：
http://www.tuicool.com/articles/vqQNbiz