Python入门-多线程

╰半橙微兮° 2022-06-03 08:15 246阅读 0赞

本文介绍Python的多线程：

1、使用\_thread模块

import _thread
    import time
    
    def print_time(threadName,delay):
        count=1;
        while count<5:
            time.sleep(delay)
            count+=1
            print(threadName+time.ctime(time.time()))
        
    try:
        _thread.start_new_thread(print_time,("thread-1",2))
        _thread.start_new_thread(print_time,("thread-2",4))
    except Exception as e:
        print("错误"+str(e))
    
    while 1:
        pass    #空语句

2、使用threading模块

import threading
    import time
    
    def print_time(threadName,delay):
        count=1;
        while count<5:
            time.sleep(delay)
            count+=1
            print(threadName+time.ctime(time.time()))
    
    class myThread(threading.Thread):    #继承Thread类，并重写run方法
        threadId1=0
        name1=""
        def __init__(self,threadId,name):
            threading.Thread.__init__(self)   #调用父类
            self.threadId1=threadId
            self.name1=name
            return
    
        def run(self):
            print("开始线程"+self.name1)
            print_time(self.name1,2)
            print("结束线程"+self.name1)
    
    t1=myThread(1,"t1")
    t2=myThread(2,"t2")
    t1.start()
    t2.start()
    t1.join()
    t2.join()
    while 1:
        pass

3、线程同步问题

import threading
    import time
    
    myList=[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
    class MyThread(threading.Thread):
        threadName=''
        flag=0   # 0表示做读，1表示做写1
        threadLock=threading.Lock()   #获取锁的对象
        def __init__(self,threadName,flag):
            threading.Thread.__init__(self)  # 调用父类
            self.threadName=threadName
            self.flag=flag
    
        def run(self):
            print("线程开始"+self.threadName)
           MyThread.threadLock.acquire()    #获取锁
            MyThread.change(self,self.threadName,self.flag)
           MyThread.threadLock.release()    #释放锁
            print("线程结束"+self.threadName)
    
        def change(self,threadName,flag):
            if flag==0:
                for a in myList:  #读操作
                    print(a)
                    time.sleep(1)
            elif flag==1:
                co=0
                while co<len(myList):  #不断地把0变为1
                    myList[co]=1
                    #print(myList[co])
                    time.sleep(1)
                    co+=1
    
    tMy1=MyThread("t1",0)   #做读操作
    tMy2=MyThread("t2",1)   #做写操作
    tMy1.start()
    tMy2.start()
    tMy1.join()
    tMy2.join()

说明：线程tMy1去读List，线程tMy2去把List的内容改为1,；

当注释掉“获取锁”和“释放锁”的代码时，可以看到，tMy1读出了1,；当不注释，必须先读完才能再去修改