多线程-threading

1.多线程

import threadingimport timedef say():    print("Hello！How are you?")    time.sleep(1)if __name__=='__main__':    for i in range(5):        t=threading.Thread(target=say)        t.start() #启动线程，即让线程开始执行

1. 使用了多线程并发的操作，花费时间要短很多
2. 创建好的线程，需要调用start()方法来启动

2.主线程等待所有子线程结束或后结束

#coding=utf-8import threadingfrom time import sleep,ctimedef sing():    for i in range(3):        print("正在唱歌...%d"%i)        sleep(1)def dance():    for i in range(3):        print("正在跳舞...%d"%i)        sleep(1)if __name__ == '__main__':    print('---开始---:%s'%ctime())    t1 = threading.Thread(target=sing)    t2 = threading.Thread(target=dance)    t1.start()    t2.start()    #sleep(5) # 屏蔽此行代码，主线程会立即结束    print('---结束---:%s'%ctime())

3.查看线程数

#coding=utf-8import threadingfrom time import sleep,ctimedef sing():    for i in range(3):        print("正在唱歌...%d"%i)        sleep(1)def dance():    for i in range(3):        print("正在跳舞...%d"%i)        sleep(1)if __name__ == '__main__':    print('---开始---:%s'%ctime())    t1 = threading.Thread(target=sing)    t2 = threading.Thread(target=dance)    t1.start()    t2.start()    while True:        length = len(threading.enumerate())        print('当前运行的线程数为：%d' % length)        if length <= 1:            break        sleep(0.5)