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