【python学习】多线程锁 生产者和消费者问题

#!/usr/bin/env python
# -*- coding:utf-8 -*-

import threading
import random, time, Queue

MAX_SIZE = 5
SHARE_Q = []  #模拟共享队列
CONDITION = threading.Condition()

class Producer(threading.Thread) :

    def run(self) :
        products = range(5)
        global SHARE_Q
        while True :
            CONDITION.acquire()
            if len(SHARE_Q) == 5 :
                print "Queue is full.."
                CONDITION.wait()
                print "Consumer have comsumed something"
            product = random.choice(products)
            SHARE_Q.append(product)
            print "Producer : ", product
            CONDITION.notify()
            CONDITION.release()
            time.sleep(random.random())

class Consumer(threading.Thread) :

    def run(self) :
        global SHARE_Q
        while True:
            CONDITION.acquire()
            if not SHARE_Q :
                print "Queue is Empty..."
                CONDITION.wait()
                print "Producer have producted something"
            product = SHARE_Q.pop(0)
            print "Consumer :", product
            CONDITION.notify()
            CONDITION.release()
            time.sleep(random.random())

def main() :
    producer = Producer()
    consumer = Consumer()
    producer.start()
    consumer.start()

if __name__ == '__main__':
    main()

Condition

条件变量中有acquire()和release方法用来调用锁的方法, 有wait(), notify(), notifyAll()方法, 后面是三个方法必须在获取锁的情况下调用, 否则产生RuntimeError错误.

• 当一个线程获得锁后, 发现没有期望的资源或者状态, 就会调用wait()阻塞, 并释放已经获得锁, 知道期望的资源或者状态发生改变
• 当一个线程获得锁, 改变了资源或者状态, 就会调用notify()和notifyAll()去通知其他线程,