关于python的单线程和多线程

单线程

比如两件事，要相继执行，而不是一起执行

'''学习一下单线程和多线程的问题'''from time import ctime,sleep
'''单线程'''
print('单线程开始：')
def music_single(name):for i in range(2):print('i was listening to music %s. %s' %(name,ctime()))sleep(1)
def move_single(name):for i in range(2):print('i was at the movies %s! %s' %(name,ctime()))sleep(5)
if __name__=="__main__":music_single(u'夜空中最亮的星')move_single(u'谍影重重')print('all over %s' %ctime())

输出结果：

单线程开始：
i was listening to music 夜空中最亮的星. Mon Aug 27 21:24:03 2018
i was listening to music 夜空中最亮的星. Mon Aug 27 21:24:04 2018
i was at the movies 谍影重重! Mon Aug 27 21:24:05 2018
i was at the movies 谍影重重! Mon Aug 27 21:24:10 2018
all over Mon Aug 27 21:24:15 2018

多线程

即边听歌边看电影，python中有thread和threading用来实现多线程，在这里使用threading。

'''多线程'''
print('****************')
print('多线程开始：')
from time import ctime,sleep
import threadingdef music_mutil(name):for i in range(2):print('i was listening to music %s. %s' %(name,ctime()))sleep(1)
def move_mutil(name):for i in range(2):print('i was at the movies %s! %s' %(name,ctime()))sleep(5)threads=[]
t1=threading.Thread(target=music_mutil,args=(u'夜空中最亮的星',)) # 创建线程t1
threads.append(t1)
t2=threading.Thread(target=move_mutil,args=(u'谍影重重',)) # 创建线程t2
threads.append(t2)if __name__=='__main__':for t in threads: # 遍历线程数组t.setDaemon(True) # 将线程声明为守护线程，必须在start()之前设置，如果不设置为守护线程，那么程序会被无限挂起。t.start() # 开始线程    t.join()print('all over %s' %ctime())

输出结果：

****************
多线程开始：
i was listening to music 夜空中最亮的星. Mon Aug 27 21:24:15 2018
i was at the movies 谍影重重! Mon Aug 27 21:24:15 2018
i was listening to music 夜空中最亮的星. Mon Aug 27 21:24:16 2018
i was at the movies 谍影重重! Mon Aug 27 21:24:20 2018
all over Mon Aug 27 21:24:25 2018

注意：
倘若没有join()语句，那么输出结果为

****************
多线程开始：
i was listening to music 夜空中最亮的星. Mon Aug 27 21:27:29 2018
i was at the movies 谍影重重! Mon Aug 27 21:27:29 2018
all over Mon Aug 27 21:27:29 2018

分析：
以上，从运行结果看，子线程(music_mutil,move_mutil)和主线程(print(all over %s) %ctime())一起启动，但是主线程结束导致子线程也终止。在这里可以在主线程前面加上t.join(),其作用是在子线程完成运行之前，子线程的父线程将一直被阻塞。注意，join()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。

多线程进阶

重写一下代码，写一个player，根据文件类型来选择操作。

from time import ctime,sleep
import threadingdef music(name):for i in range(2):print('start playing %s. %s' %(name,ctime()))sleep(2)def move(name):for i in range(2):print('start playing %s. %s' %(name,ctime()))sleep(5)def player(func):rc=func.split('.')[1]if rc=='mp3':music(func)else:if rc=='mp4':move(func)else:print('error type of file!')alist=['夜空中最亮的星.mp3','谍影重重.mp4']
length=len(alist)
threads=[]
# 创建线程
for i in range(length):t=threading.Thread(target=player,args=(alist[i],))threads.append(t)
if __name__=='__main__':# 启动线程for i in range(length):threads[i].start()for i in range(length):threads[i].join()# 主线程print('all over at %s' %(ctime()))

输出：

start playing 夜空中最亮的星.mp3. Mon Aug 27 21:52:50 2018
start playing 谍影重重.mp4. Mon Aug 27 21:52:50 2018
start playing 夜空中最亮的星.mp3. Mon Aug 27 21:52:52 2018
start playing 谍影重重.mp4. Mon Aug 27 21:52:55 2018
all over at Mon Aug 27 21:53:00 2018

继续修改：

from time import ctime,sleep
import threadingdef super_player(name,time0):for i in range(2):print('now we are playing %s. %s' %(name,ctime()))sleep(time0)
# 
alist={'飞鸟.mp3':3,'阿凡达.mp4':4,'我和你.mp3':4}threads=[]
files=range(len(alist))# 创建线程
for file,time in alist.items():t=threading.Thread(target=super_player,args=(file,time))threads.append(t)if __name__=='__main__':# 启动线程for i in files:threads[i].start()for i in files:threads[i].join()# 主线程print('end: %s' %ctime())

输出：

now we are playing 飞鸟.mp3. Mon Aug 27 21:57:02 2018
now we are playing 阿凡达.mp4. Mon Aug 27 21:57:02 2018
now we are playing 我和你.mp3. Mon Aug 27 21:57:02 2018
now we are playing 飞鸟.mp3. Mon Aug 27 21:57:05 2018
now we are playing 我和你.mp3. Mon Aug 27 21:57:06 2018
now we are playing 阿凡达.mp4. Mon Aug 27 21:57:06 2018
end: Mon Aug 27 21:57:10 2018

继续创建：

'''创建自己的多线程类'''#coding=utf-8
import threading
from time import sleep,ctimeclass MyThread(threading.Thread):def __init__(self,func,args,name=''):threading.Thread.__init__(self)self.name=nameself.func=funcself.args=argsdef run(self):# apply(self.func,self.args) # python2的用法self.func(*self.args) # python3没有了apply()的全局用法。用self.func(*self.args)。def super_play(file,time):for i in range(2):print('start playing: %s! %s' %(file,ctime()))sleep(time)alist={'红日.mp3':3,'阿凡达.mp4':5}# 创建线程
threads=[]
files=range(len(alist))for k,v in alist.items():t=MyThread(super_play,(k,v),super_play.__name__)threads.append(t)if __name__=='__main__':# 启动线程for i in files:threads[i].start()for i in files:threads[i].join()# 主线程print('end: %s' %ctime())

输出：

start playing: 红日.mp3! Mon Aug 27 21:58:48 2018
start playing: 阿凡达.mp4! Mon Aug 27 21:58:48 2018
start playing: 红日.mp3! Mon Aug 27 21:58:51 2018
start playing: 阿凡达.mp4! Mon Aug 27 21:58:53 2018
end: Mon Aug 27 21:58:58 2018