python 归纳 _线程_threading.Thread

Posted 2021-01-04 sunzebo

总结:

1. 默认父线程跑完,子线程并不会马上退出,不像 thread.start_threadXXXX
2. 父线程跑完了，并没有退出，一直在那里
3. 线程启动速度很快，不占多少开销，不到1毫秒

代码:

# -*- coding: utf-8 -*-
"""
学习 并发
linux下执行
"""
from threading import Thread
from multiprocessing import Process
import time
import os
import psutil
def work():
    print(‘%s,%f: sub begin %d‘ % (time.strftime(‘%M:%S‘,time.localtime(time.time())),time.time(),os.getpid()))
    print "%s,%f: sub %d,%d,%d" % (time.strftime(‘%M:%S‘,time.localtime(time.time())),time.time(),os.getpid(),os.getppid(), psutil.Process(os.getpid()).num_threads())

    time.sleep(5)

    print "%s,%f: sub %d,%d,%d" % (time.strftime(‘%M:%S‘,time.localtime(time.time())),time.time(),os.getpid(),os.getppid(), psutil.Process(os.getpid()).num_threads())
    print(‘%s,%f: sub end %d‘ % (time.strftime(‘%M:%S‘,time.localtime(time.time())),time.time(),os.getpid()))

if __name__ == ‘__main__‘:

    print "%s,%f: main begin" % (time.strftime(‘%M:%S‘,time.localtime(time.time())),time.time())
    print "%s,%f: main %d,%d,%d" % (time.strftime(‘%M:%S‘,time.localtime(time.time())),time.time(),os.getpid(),os.getppid(), psutil.Process(os.getpid()).num_threads())
    # 开启子线程
    t=Thread(target=work)
    t.start()
    print  ‘%s,%f: main 线程‘ %  (time.strftime(‘%M:%S‘,time.localtime(time.time())),time.time())
    print "%s,%f: main %d,%d,%d" % (time.strftime(‘%M:%S‘,time.localtime(time.time())),time.time(),os.getpid(),os.getppid(), psutil.Process(os.getpid()).num_threads())

    # 开启子进程
    # t=Process(target=work)
    # t.start()
    # print "
main %d,%d,%d" % (os.getpid(),os.getppid(), psutil.Process(os.getpid()).num_threads())
    # print(‘
main 进程‘)

    print "%s,%f: main end" % (time.strftime(‘%M:%S‘,time.localtime(time.time())),time.time())

　　

输出：

格式说明：

小时 :秒，时间戳,     <当前进程ID,  [父 进程ID,当前进程线程数量]>

[email protected]:~/python# python test_threadprocess1.py

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

03:04,1536397384.349529: main begin
03:04,1536397384.349605: main 3604,2692,1
03:04,1536397384.350838: sub begin 3604
03:04,1536397384.350939: main 线程
03:04,1536397384.351009: sub 3604,2692,2
03:04,1536397384.351310: main 3604,2692,2
03:04,1536397384.352097: main end
03:09,1536397389.357353: sub 3604,2692,2   

03:09,1536397389.358372: sub end 3604

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

输出解读:

1. 黄色 标记的中间 输出部分 ，是启动 子线程期间，这段 时间非常快，说明启动线程的速度很快
2. 红色标记，此时main线程的逻辑 代码跑完了，但是还是显示有2个线程，对比开始，说明main线程并 没有退出