【Python】多线程编程

1、thread模块

2、threading模块

3、Queue模块与多线程互斥

简介：

thread和threading模块允许创建和管理线程，thread模块提供了基本的线程和锁的支持，而threading提供了更高级别，功能更强的线程管理功能，Queue模块

允许创建一个可以用于多个线程之间共享数据的队列数据结构

1.thread模块

Thread模块常用函数：

实例1：

# encoding:utf-8
'''
Created on 2014-6-23

@author: Administrator
'''

from time import ctime, sleep
import thread

loops = [4, 2]

def loop(index, nsecs, lock):
    print "start loop,%s at:%s" % (index, ctime())
    sleep(nsecs)
    print "loop %s done at:%s" % (index, ctime())
    lock.release()

def main():
    print "all starting at :%s" % ctime()
    locks = []

    nlocks = range(len(loops))
    for i in nlocks:
        lock = thread.allocate_lock()
        lock.acquire()
        locks.append(lock) 

    for i in nlocks:
        thread.start_new_thread(loop, (i, loops[i], locks[i]))

    for i in nlocks:
        while locks[i].locked():
            pass

    print "all done at:%s" % ctime()

if __name__ == "__main__":
    main()

2.threading模块

threading模块包含对象：

threading模块Thread类，常用函数：

使用threading.Thread类可以用多种方法创建线程：

一、创建一个Thread的实例，参数为一个函数

二、创建一个Thread的实例，参数为一个可调用的类对象

三、从Thread派生出一个子类，创建一个这个子类的实例

方法一：创建一个Thread的实例，参数为一个函数

# encoding:utf-8
'''
Created on 2014-6-23

@author: Administrator
'''

import threading
from time import ctime, sleep

loops = [4, 2]

def loop(nloop, nsec):
    print "strating loop %s at:%s" % (nloop, ctime())
    sleep(nsec)
    print "end loop %s at:%s" % (nloop, ctime())

def main():
    print threading.__file__
    print "all start at:%s" % ctime()
    threads = []
    nloops = range(len(loops))

    for i in nloops:
        t = threading.Thread(target=loop, args=(i, loops[i]))#创建一个Thread实例，传递一个函数
        threads.append(t)

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

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

    print "all end at:%s" % ctime()

if __name__ == "__main__":
    main()

方法二：创建一个Thread的实例，参数为一个可调用的类对象

# encoding:utf-8
'''
Created on 2014-6-24

@author: Administrator
'''

import threading
from time import sleep, ctime

loops = [4, 2]

class ThreadingCls(object):
    def __init__(self, func, args, name=''):
        self.name = name
        self.func = func
        self.args = args

    #python 可调用对象，重写__call__方法，通过ThreadingCls(...)调用
    def __call__(self):
        self.func(*self.args)   #函数调用，参数为元组*（...）

def loop(nloop, nsec):
    print "staring loop %s at:%s" % (nloop, ctime())
    sleep(nsec)
    print "end loop %s at:%s" % (nloop, ctime())

def main():
    print "all start at:%s" % ctime()
    threads = []
    nloops = range(len(loops))

    for i in nloops:
        t = threading.Thread(target=ThreadingCls(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 end at:%s" % ctime()

if __name__ == "__main__":
    main()

方法三：从Thread派生出一个子类，创建一个这个子类的实例

# encoding:utf-8
'''
Created on 2014-6-24

@author: Administrator
'''

import threading
from time import sleep, ctime

loops = [4, 2]

"""
    子类化Thread创建多线程:
    （1）构造函数__init__需要调用基类的构造函数
    （2）需要重写run方法
"""
class ThreadingDerived(threading.Thread):

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

    def run(self):
        print "%s running at:%s" % (self.name, ctime())
        self.func(*self.args)

def loop(nloop, nsec):
    print "staring loop %s at:%s" % (nloop, ctime())
    sleep(nsec)
    print "end loop %s at:%s" % (nloop, nsec) 

def main():
    print "all start at:%s" % ctime()
    threads = []
    nloops = range(len(loops))

    for i in nloops:
        t = ThreadingDerived(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 end at:%s" % ctime()

if __name__ == "__main__":
    main()

3、Queue模块与多线程互斥

Queue模块常用函数：

实例3. 生产者消费者

# encoding:utf-8
'''
Created on 2014-6-24

@author: Administrator
'''

from threading_subcls import ThreadingDerived
from Queue import Queue
from time import ctime, sleep
from random import randint

gl_queue = Queue(3)

def consumer():
    while True:
        if gl_queue.empty():
            sleep(2)
        else:
            print "consum %s at:%s" % (gl_queue.get(1), ctime())    #get函数，从队列中取一个对象，block=1，函数会一直阻塞直到队列有空间为止

def producer():
    while True:
        if gl_queue.full():
            sleep(2)
        else:
            pdata = randint(0, 3)
            gl_queue.put(pdata, 1)  #把pdata放入队列，block=1，函数会一直阻塞到队列有空间为止
            print "produce %s at:%s" % (pdata, ctime())

def main():
    funcs = [consumer, producer]
    ncount = range(len(funcs))
    threads = []

    for i in ncount:
        t = ThreadingDerived(funcs[i], (), funcs[i].__name__)
        threads.append(t)

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

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

if __name__ == "__main__":
    main()

线程互斥：Python主要有四种数据同步机制:互斥锁(Lock),条件变量(Condition), 信号量(Semaphore)和同步队列，在threading模块中锁对象用threading.Lock()创建

实例4.

# encoding:utf-8
'''
Created on 2014-6-24

@author: Administrator
'''

import threading
from threading_subcls import ThreadingDerived
from time import sleep 

gl_lock = threading.Lock()  #互斥锁
gl_count = 0
gl_max = 3

def consumer():
    global gl_count, gl_lock
    while True:
        gl_lock.acquire()
        if gl_count > 0:
            gl_count -= 1
            print "consume %s-->%s" % (gl_count + 1, gl_count)
            gl_lock.release()
        else:
            gl_lock.release()
            print "%s wait producer..." % threading.current_thread().getName()
            sleep(3)

def producer():
    global gl_count, gl_lock, gl_max
    while True:
        if gl_count >= gl_max:
            sleep(1)
            continue
        gl_lock.acquire()
        gl_count += 1
        print "produce %s-->%s" % (gl_count - 1, gl_count)
        gl_lock.release()

def main():
    funcs = [consumer, consumer, producer]
    ncount = range(len(funcs))
    threads = []

    for i in ncount:
        t = ThreadingDerived(funcs[i], (), "%s#%s" % (funcs[i].__name__, i))
        threads.append(t)

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

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

if __name__ == "__main__":
    main()