python多线程怎么使用

最近用到了多线程的调用，看前辈们的自动化用例实在是看不懂。所以网上搜了些资料学习，整理如下。

首先，需要知道要import哪些包

python2有3个可用：

                import thread

                import threading

                import multiprocessing（进程）

python3新增了一个concurrent.futures，也是超好用的

其次，举个小例子演示怎么使用

场景：有个打印当前时间的函数print_time，想要并发执行,

1、import thread

调用方式：thread.start_new_thread(print_time, ("Thread-1", 2,))，拷贝下方代码，可以直接运行

#-*- coding: utf-8 -*-

import thread

import time

# 为线程定义一个函数

def print_time(threadName, delay):

count =0

    while count <5:

time.sleep(delay)

count +=1

        print "%s: %s" % (threadName, time.ctime(time.time()))

if __name__ =='__main__':

# 创建两个线程-----------使用thread

    try:

thread.start_new_thread(print_time, ("Thread-1", 2,))

thread.start_new_thread(print_time, ("Thread-2", 4,))

except:

print "Error: unable to start thread"

    while 1:

pass

2、import threading

调用方法1：直接使用threading.Thread调用；方法2：改写threading.Thread的执行方法

方法1：

#-*- coding: utf-8 -*-

# import thread

import time

import threading

exitFlag =0

def print_time(threadName, delay):

count =0

    while count <5:

if exitFlag:

(threading.thread).exit()

time.sleep(delay)

count +=1

        print "%s: %s" % (threadName, time.ctime(time.time()))

if __name__ =='__main__':

threads = []

thread1 = threading.Thread(target=print_time,args = ("thread-1",2))

thread2 = threading.Thread(target=print_time, args=("thread-2", 2))

threads.append(thread1)

threads.append(thread2)

for threadin threads:

thread.start()

for threadin threads:

thread.join()

方法2：

#-*- coding: utf-8 -*-

# import thread

import time

import threading

exitFlag =0

class myThread(threading.Thread):

def __init__(self,threadID,name,delay):

threading.Thread.__init__(self)

self.threadID = threadID

self.name = name

self.delay = delay

def run(self):#把要执行的代码写到run函数里面 线程在创建后会直接运行run函数

        print "Starting "+self.name

print_time(self.name,self.delay)

print "Exiting "+self.name

def print_time(threadName, delay):

count =0

    while count <5:

if exitFlag:

# threading.thread.exit()

            (threading.thread).exit()

time.sleep(delay)

count +=1

        print "%s: %s" % (threadName, time.ctime(time.time()))

if __name__ =='__main__':

# 使用threading.thread------------------

    thread1 = myThread(1,"thread-1",1)

thread2 = myThread(2,"thread-2",2)

thread1.start()

thread2.start()

3、import multiprocessing

#-*- coding: utf-8 -*-

import time

import multiprocessing

exitFlag =0

def print_time(threadName, delay):

count =0

    while count <5:

if exitFlag:

# threading.thread.exit()

            (threading.thread).exit()

time.sleep(delay)

count +=1

        print "%s: %s" % (threadName, time.ctime(time.time()))

if __name__ =='__main__':

# 使用multiprocessing---------------

    threads = []

thread1 = multiprocessing.Process(target=print_time,args = ("thread-1",2))

thread2 = multiprocessing.Process(target=print_time, args=("thread-2", 2))

threads.append(thread1)

threads.append(thread2)

for threadin threads:

thread.start()

for threadin threads:

thread.join()

总结

进程和线程怎么选取，菜鸟教程上有个帖子写的特别好：CPU密集型选择多进程；IO密集型选择多线程。原文如下：

资料显示，如果多线程的进程是CPU密集型的，那多线程并不能有多少效率上的提升，相反还可能会因为线程的频繁切换，导致效率下降，推荐使用多进程；如果是IO密集型，多线程进程可以利用IO阻塞等待时的空闲时间执行其他线程，提升效率。（引自：https://www.runoob.com/w3cnote/python-single-thread-multi-thread-and-multi-process.html）