python 多线程

刚开始时候，cpu不支持多任务，所以是顺序执行的，比如先听歌，再看电影

from time import ctime,sleep

def music():
    for i in range(2):
        print("I was listening to music. %s",ctime())
        sleep(1)

def move():
    for i in range(2):
        print("I was at the movies! %s",str(ctime()))
        sleep(5)

if __name__ == '__main__':
    music()
    move()
    print("all over %s" %ctime())

后来，cpu支持了多任务，那我们就可以一边听歌，一边看电影了，两个程序同时是运行状态的。下面的例子是非阻塞的。

#coding=utf-8
import threading
from time import ctime,sleep


def music(func):
    for i in range(2):
        print("I was listening to {0}. {1}" .format(func,ctime()))
        sleep(1)

def move(func):
    for i in range(2):
        print ("I was at the {0}! {1}".format(func,ctime()))
        sleep(5)

threads = []
t1 = threading.Thread(target=music,args=(u'爱情买卖',))
threads.append(t1)
t2 = threading.Thread(target=move,args=(u'阿凡达',))
threads.append(t2)

if __name__ == '__main__':
    for t in threads:
        t.setDaemon(False)
        t.start()

    print("all over %s" %ctime())

输出

I was listening to 爱情买卖. Fri Jan 18 14:36:20 2019
I was at the 阿凡达! Fri Jan 18 14:36:20 2019               
all over Fri Jan 18 14:36:20 2019                           
I was listening to 爱情买卖. Fri Jan 18 14:36:21 2019       
I was at the 阿凡达! Fri Jan 18 14:36:25 2019               
[Program finished]

阻塞模式，由于主线程执行完毕，子线程不再继续执行

#coding=utf-8
import threading
from time import ctime,sleep


def music(func):
    for i in range(2):
        print("I was listening to {0}. {1}" .format(func,ctime()))
        sleep(1)

def move(func):
    for i in range(2):
        print ("I was at the {0}! {1}".format(func,ctime()))
        sleep(5)

threads = []
t1 = threading.Thread(target=music,args=(u'爱情买卖',))
threads.append(t1)
t2 = threading.Thread(target=move,args=(u'阿凡达',))
threads.append(t2)

if __name__ == '__main__':
    for t in threads:
        t.setDaemon(True)
        t.start()

    print("all over %s" %ctime())

输出

I was listening to 爱情买卖. Fri Jan 18 14:38:36 2019
I was at the 阿凡达! Fri Jan 18 14:38:36 2019               
all over Fri Jan 18 14:38:36 2019                           
[Program finished]

我们只对上面的程序加了个join()方法，用于等待线程终止。join（）的作用是，在子线程完成运行之前，这个子线程的父线程将一直被阻塞。

　　注意:  join()方法的位置是在for循环外的，也就是说必须等待for循环里的两个进程都结束后，才去执行主进程。

#coding=utf-8
import threading
from time import ctime,sleep


def music(func):
    for i in range(2):
        print("I was listening to {0}. {1}" .format(func,ctime()))
        sleep(1)

def move(func):
    for i in range(2):
        print ("I was at the {0}! {1}".format(func,ctime()))
        sleep(5)

threads = []
t1 = threading.Thread(target=music,args=(u'爱情买卖',))
threads.append(t1)
t2 = threading.Thread(target=move,args=(u'阿凡达',))
threads.append(t2)

if __name__ == '__main__':
    for t in threads:
        t.setDaemon(True)
        t.start()
    t.join()
    print("all over %s" %ctime())

输出

I was listening to 爱情买卖. Fri Jan 18 14:47:26 2019
I was at the 阿凡达! Fri Jan 18 14:47:26 2019               
I was listening to 爱情买卖. Fri Jan 18 14:47:27 2019       
I was at the 阿凡达! Fri Jan 18 14:47:31 2019               
all over Fri Jan 18 14:47:36 2019                           
[Program finished]