Python 多线程

2019-11-06 06:36:52

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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,threadingdef 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().nameprint 'thread %s in running...' % threading.current_thread().namet = 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 = 0lock = threading.Lock()def change_it(n): # 先存后取，结果应该为0: global balance balance = balance + n balance = balance - ndef 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 randintfrom time import sleepfrom Queue import Queuefrom myThread import MyThreaddef 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

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