python 的多线程以及锁定

下面的代码主要是使用一个类对外部数据（myList）进行修改，由于两个线程同时对myList修改，在不加锁的情况下，可能导致数据被不安全修改。
读者可尝试将“开启锁”和“释放锁”注释，重运行，看效果。

#!/usr/local/bin/python
# coding: utf-8

import threading
import time

class ChangeVal(threading.Thread):
    # 继承threading.Thread并初始化，相当于构造函数
    def __init__(self, myList, changeType, threadLock):
        threading.Thread.__init__(self)
        # self.myList 会指向外部传入的myList的同一个物理地址。相当于传入了C++的引用类型。
        self.myList = myList
        self.changeType = changeType
        self.threadLock = threadLock

    # 重写run
    def run(self):
        # 开启锁
        self.threadLock.acquire()
        if self.changeType:
            self.change1()
        else:
            self.change2()
        # 释放锁
        self.threadLock.release()

    # 将myList数据全部改为1
    def change1(self):
        for i in range(len(self.myList)):
            time.sleep(1)
            self.myList[i] = 1
        print "in change1:" + str(self.myList)

    # 将myList数据全部改为2
    def change2(self):
        for i in range(len(self.myList)):
            time.sleep(1)
            self.myList[i] = 2
        print "in change2:" + str(self.myList)

if __name__ == "__main__":
    # 初始化用于给多个线程操作的数据
    myList = [0 for i in range(10)]
    # 初始化锁的对象
    threadLock = threading.Lock()
    thread1 = ChangeVal(myList, True, threadLock)
    thread2 = ChangeVal(myList, False, threadLock)

    threads = [thread1, thread2]
    print "origin is:" + str(myList)
    thread1.start()
    thread2.start()

    # 等待所有线程结束
    for t in threads:
        t.join()
    print "all threads exit"