Python多线程编程

来源：互联网发布：grpc java 编辑：程序博客网时间：2024/05/16 06:51

  Python多线程编程

退出线程： 可以调用thread.exit(),sys.exit()或抛出一个SystemExit异常等，但不可以kill掉一个线程

Python提供的用于多线程编程的模块：thread,threading,Queue.

threading模块对象：

Thread， Lock, RLock, Condition, Event, Semaphore BoundedSemaphore, Timer

Thread对象的函数：

start(), run(), join(timeout = None), getName(), setName(name), isAlive, isDaemon(),setDaemon(daemonic)

用Thread类创建线程的三种方法：

* 创建一个Thread的实例，传给它一个函数

* 创建一个Thread的实例，传给它一个可调用的类对象

* 从Thread派生出一个子类，创建一个这个子类的实例

########################################################################################################

import threading

from time import sleep,ctime

loops = [4,2]

def loop(nloop,nsec):

    print('start loop ',nloop,'at: ',ctime())

    sleep(nsec)

    print('loop ',nloop,'done at: ',ctime())

def main():

    print ('starting at: ',ctime())

    threads = []

    nloops = range(len(loops))

    for i in nloops:

        t = threading.Thread(target = loop,args = (i,loops[i]))

        threads.append(t)

    for i in nloops:

        threads[i].start()

    for i in nloops:

        threads[i].join()

    print('all Done at: ',ctime())

if __name__ == '__main__':

    main()

运行结果：

starting at:  Tue Nov  4 12:59:46 2014

start loop start loop   01  at: at:   Tue Nov  4 12:59:46 2014Tue Nov  4 12:59:46 2014

loop  1 done at:  Tue Nov  4 12:59:48 2014

loop  0 done at:  Tue Nov  4 12:59:50 2014

all Done at:  Tue Nov  4 12:59:50 2014

###############################################################################################

import threading

from time import sleep,ctime

loops = [4,2]

class ThreadFunc(object):

    def __init__(self,func,args,name = ''):

        self.name = name

        self.func = func

        self.args = args

    def __call__(self):

        self.func(*self.args)

def loop(nloop,nsec):

    print ('start loop',nloop,'at: ',ctime())

    sleep(nsec)

    print('loop',nloop,'done at: ',ctime())

def main():

    print('strarting at: ',ctime)

    threads = []

    nloops = range(len(loops))

    for i in nloops:

        t = threading.Thread(target = ThreadFunc(loop,(i,loops[i]),

                            loop.__name__))

        threads.append(t)

    for i in nloops:

        threads[i].start()

    for i in nloops:

        threads[i].join()

    print('all Done at:',ctime())

if __name__ == '__main__':

    main()

运行结果：

strarting at:  <built-in function ctime>

start loopstart loop  01  at: at:   Tue Nov  4 14:30:49 2014Tue Nov  4 14:30:49 2014

loop 1 done at:  Tue Nov  4 14:30:51 2014

loop 0 done at:  Tue Nov  4 14:30:53 2014

all Done at: Tue Nov  4 14:30:53 2014

###########################################################################################

###createdb.py

import threading

from time import ctime

class MyThread(threading.Thread):

    def __init__(self,func,args,name = ''):

        threading.Thread.__init__(self)

        self.name = name

        self.func = func

        self.args = args

    def getResult(self)        :

        return self.res

    def run(self):

        print('starting',self.name,'at:',ctime())

        self.res = self.func(*self.args)

        print (self.name,'finished at:',ctime())

###mul.py

from createdb import MyThread

from time import ctime,sleep

def fib(x):

    sleep(0.005)

    if x < 2:

        return 1

def fac(x):

    sleep(0.1)

    if x < 2:

        return 1

    return (x * fac(x - 1))

def sum(x):

    sleep(0.1)

    if x < 2:

        return 1

funcs = [fib,fac,sum]

n = 12

def main():

    nfuncs = range(len(funcs))

    print('*** SINGLE THREAD')

    for i in nfuncs:

        print('starting',funcs[i].__name__,'at:',ctime())

        print(funcs[i](n))

        print (funcs[i].__name__,'finished at:',ctime())

    print('\n*** MULTIPLE THREADS')

    threads = []

    for i in nfuncs:

        t = MyThread(funcs[i],(n,),funcs[i].__name__)

        threads.append(t)

    for i in nfuncs:

            threads[i].start()

    for i in nfuncs:

        threads[i].join()

        print(threads[i].getResult())

    print('all done')

if __name__ == '__main__':

    main()

运行结果：

*** SINGLE THREAD

starting fib at: Wed Nov  5 01:16:46 2014

None

fib finished at: Wed Nov  5 01:16:46 2014

starting fac at: Wed Nov  5 01:16:46 2014

479001600

fac finished at: Wed Nov  5 01:16:48 2014

starting sum at: Wed Nov  5 01:16:48 2014

None

sum finished at: Wed Nov  5 01:16:48 2014

*** MULTIPLE THREADS

startingstartingstarting   fibfacsum   at:at:at:   Wed Nov  5 01:16:48 2014Wed Nov  5 01:16:48 2014Wed Nov  5 01:16:48 2014

fib finished at: Wed Nov  5 01:16:48 2014

None

sum finished at: Wed Nov  5 01:16:48 2014

fac finished at: Wed Nov  5 01:16:49 2014

479001600

None

all done

###################################################################################################

除了各种同步对象和线程对象外，threading模块中的其他函数：

activeCount()

currentThread()

enumerate()

settrace(func): 为所有线程设置一个跟踪函数

setprofile(func): 为所有线程设置一个profile函数

###################################################################################################

利用Queue模块解决生产者——消费者问题

常用的Queue模块的属性：

Queue模块函数：

    queue(size): 创建一个大小为size的Queue对象

Queue对象函数：

    qsize(): 返回队列的大小(由于在返回的时候，队列可能会被其他线程修改，所以是近似值)

    empty()

    full()

    put(item,block = 0): 如果block非0，函数会一致阻塞到队列中有空间为止。

    get(block = 0): 同上

Queue模块可以用来进行线程间通讯，让各个线程之间共享数据。

from random import randint

from time import sleep

from queue import Queue

from createdb 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()

运行结果：

startingstarting  writerreader  at:at:  Wed Nov  5 01:39:44 2014Wed Nov  5 01:39:44 2014

producing object for Q...consumed object from Q... size now  None0

size now 0

producing object for Q... None

size now 1

consumed object from Q... size now 0

producing object for Q... None

size now 1

producing object for Q... None

size now 2

consumed object from Q... size now 1

consumed object from Q... size now 0

writer finished at: Wed Nov  5 01:39:52 2014

reader finished at: Wed Nov  5 01:39:56 2014

all done

0 0