关于python线程threading使用的学习笔记

爱被打了一巴掌 2023-02-20 05:00 22阅读 0赞

至于线程和进程，看了好多网文，但各有不同论断，还没太明白究竟如何。

(有博文初看不错,待细看学习:[https://blog.csdn.net/weixin\_42134789/article/details/82992326][https_blog.csdn.net_weixin_42134789_article_details_82992326])

看代码帮助理解方法功能：

import threading
    import time
    threading.active_count() #获取已激活的线程数
    threading.enumerate() #查看所有线程信息
    threading.current_thread() #查看现在正在运行的线程
    
    def thread_job():
        print('T1 start\n')
        #让 T1 线程工作的耗时增加:
        for i in range(10):
            time.sleep(0.1)  #任务间隔0.1s
        print('T1 finsh\n')
                
    def main():
        #添加线程(定义一个线程)，threading.Thread()接收参数target代表这个线程要完成的任务，需自行定义
        added_thread=threading.Thread(target=thread_job,name='T1')  #此处thread_job后面不带括号
        added_thread.start() #让线程开始工作
        print('all done\n')
        
    if __name__ == '__main__':
        main()

输出:

T1 start
    
    all done
    
    T1 finsh

本想:

T1 start
    T1 finish
    all done

计算不等人.

可用join帮助控制执行顺序:

def main():
        #添加线程(定义一个线程)，threading.Thread()接收参数target代表这个线程要完成的任务，需自行定义
        added_thread=threading.Thread(target=thread_job,name='T1')
        added_thread.start() #让线程开始工作
        added_thread.join() #在启动线程后,调用join
        print('all done\n')

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FobWN3dA_size_16_color_FFFFFF_t_70][]

又例:join控制执行顺序:  
**(1)未加join:**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FobWN3dA_size_16_color_FFFFFF_t_70 1][]

**(2)加join后:**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FobWN3dA_size_16_color_FFFFFF_t_70 2][]

**join()控制,让已经start()了的线程，运行完之后,再运行其后的线程**

**如果**:

![20200623173324343.png][]

**显示结果如下:**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FobWN3dA_size_16_color_FFFFFF_t_70 3][]

--------------------

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FobWN3dA_size_16_color_FFFFFF_t_70 4][]

贴出 代码便于复制验证:

import threading
    import time
    def T1_job():
        print("T1 start\n")
        for i in range(10):
            time.sleep(0.1)
        print("T1 finish\n")
        global T1_end
        T1_end=time.time()
        print('T1 结束时间:{}'.format(T1_end))
        
    def T2_job():
        print("T2 start\n")
        for i in range(10):
            time.sleep(0.1)
        print("T2 finisth\n")
        global t3
        t3=time.time()
        print('t2 结束时间:{}'.format(t3))
        
    thread_1=threading.Thread(target=T1_job,name='T1')
    thread_2=threading.Thread(target=T2_job,name='T2')
    
    thread_1.start() # start T1
    t1=time.time()
    print('T1开始时间:',t1)
    
    thread_2.start() # start T2
    t4=time.time()
    print('T2开始时间:{}'.format(t4))
    
    thread_2.join() # join for T2
    thread_1.join() # join for T1
    print("all done\n")
    print('线程1运行时长:',T1_end-t1)
    print('线程2运行时长:',t3-t4)

T1 start
    T1开始时间:
     1592942923.562432
    T2 start
    T2开始时间:1592942923.5654247
    T1 finish
    T1 结束时间:1592942924.5682905
    T2 finisth
    t2 结束时间:1592942924.5732422
    all done
    线程1运行时长: 1.0058584213256836
    线程2运行时长: 1.0078175067901611

如若,在join()之前都已start(),则join语句的先后顺序，不决定运算结果秩序，起决定作用的还是看谁运行结束。所以，通常推荐采用如下这种`1221`的V型排布：

thread_1.start() # start T1
    thread_2.start() # start T2
    thread_2.join() # join for T2
    thread_1.join() # join for T1
    print("all done\n")
    
    """
    T1 start
    T2 start
    T2 finish
    T1 finish
    all done
    """

--------------------

参考： [https://morvanzhou.github.io/tutorials/python-basic/threading/3-join/][https_morvanzhou.github.io_tutorials_python-basic_threading_3-join]

[https_blog.csdn.net_weixin_42134789_article_details_82992326]: https://blog.csdn.net/weixin_42134789/article/details/82992326
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FobWN3dA_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200623160913820.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FobWN3dA==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FobWN3dA_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20200623163428473.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FobWN3dA==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FobWN3dA_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20200623172556403.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FobWN3dA==,size_16,color_FFFFFF,t_70
[20200623173324343.png]: https://img-blog.csdnimg.cn/20200623173324343.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FobWN3dA_size_16_color_FFFFFF_t_70 3]: https://img-blog.csdnimg.cn/20200623174415690.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FobWN3dA==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FobWN3dA_size_16_color_FFFFFF_t_70 4]: https://img-blog.csdnimg.cn/20200624034302324.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FobWN3dA==,size_16,color_FFFFFF,t_70
[https_morvanzhou.github.io_tutorials_python-basic_threading_3-join]: https://morvanzhou.github.io/tutorials/python-basic/threading/3-join/