Python线程的join和setDaemon探究

一、前言

　　由于查阅资料众口不一，故决定自己写代码，来证实正确结果，此文根据一段代码，来探究Python的线程运行情况，读者可运行代码自己调试理解。

　　系统环境Win10，运行环境Python3.6，运行工具Pycharm。

 

二、实现思路

　　1.通过改变每个线程的sleep()时长，以及setDaemon()和join()的属性，来改变结果

　　1.通过控制台打印时间和线程的结果变化来分析线程运行情况

 

三、源码设计

import threading
import time


# 返回当前时间年月日+时分秒+毫秒
def getcurrenttime():
    tt = time.time()
    local_time = time.localtime(tt)
    data_head = time.strftime("%Y-%m-%d %H:%M:%S", local_time)
    data_secs = (tt - int(tt)) * 1000000
    return "%s %06d" % (data_head, data_secs)


# 返回一个包含正在运行的线程的list。正在运行指线程启动后、结束前，不包括启动前和终止后的线程
def getallthread():
    return threading.enumerate()


def printmsg(puple):  # 打印结果
    print("There is running %s %s %s %s" % puple)


def task0(tag):
    while True:
        printmsg((tag, getcurrenttime(), threading.current_thread().getName(), getallthread()))
        time.sleep(1)


def task1(tag):
    for i in range(2):
        printmsg((tag, getcurrenttime(), threading.current_thread().getName(), ""))
        time.sleep(5)


def task2(tag):
    for i in range(2):
        printmsg((tag, getcurrenttime(), threading.current_thread().getName(), ""))
        time.sleep(3)


def threadsstart():
    t0 = threading.Thread(target=task0, name="task0", args=(u'task0',))
    # 默认继承父级属性：True父线程结束子线程立即结束；False子线程结束父线程才会退出
    t0.setDaemon(True)
    t0.start()

    t1 = threading.Thread(target=task1, name="task1", args=(u'task1',))
    t1.setDaemon(False)
    t1.start()
    # 主线程等待最多7秒，等待过程后面子线程t2不会执行
    t1.join(7)

    t2 = threading.Thread(target=task2, name="task2", args=(u'task2',))
    t2.setDaemon(True)
    t2.start()


if __name__ == '__main__':
    threadsstart()
    printmsg(("end00", getcurrenttime(), threading.current_thread().getName(), ""))

部分打印结果

D:\Python\python.exe E:/Python/Demo/venv/thread_test/threading_test.py
There is running task0 2018-11-29 16:28:52 600983 task0 [<_MainThread(MainThread, started 8904)>, <Thread(task0, started daemon 9024)>]
There is running task1 2018-11-29 16:28:52 601979 task1 
There is running task0 2018-11-29 16:28:53 602678 task0 [<_MainThread(MainThread, started 8904)>, <Thread(task0, started daemon 9024)>, <Thread(task1, started 2280)>]
There is running task0 2018-11-29 16:28:54 603651 task0 [<_MainThread(MainThread, started 8904)>, <Thread(task0, started daemon 9024)>, <Thread(task1, started 2280)>]
There is running task0 2018-11-29 16:28:55 604120 task0 [<_MainThread(MainThread, started 8904)>, <Thread(task0, started daemon 9024)>, <Thread(task1, started 2280)>]
There is running task0 2018-11-29 16:28:56 604486 task0 [<_MainThread(MainThread, started 8904)>, <Thread(task0, started daemon 9024)>, <Thread(task1, started 2280)>]
There is running task1 2018-11-29 16:28:57 603277 task1 
There is running task0 2018-11-29 16:28:57 605237 task0 [<_MainThread(MainThread, started 8904)>, <Thread(task0, started daemon 9024)>, <Thread(task1, started 2280)>]
There is running task0 2018-11-29 16:28:58 606382 task0 [<_MainThread(MainThread, started 8904)>, <Thread(task0, started daemon 9024)>, <Thread(task1, started 2280)>]
There is running task2 2018-11-29 16:28:59 603960 task2 
There is running end00 2018-11-29 16:28:59 603960 MainThread 
There is running task0 2018-11-29 16:28:59 606956 task0 [<_MainThread(MainThread, stopped 8904)>, <Thread(task0, started daemon 9024)>, <Thread(task1, started 2280)>, <Thread(task2, started daemon 8028)>]
There is running task0 2018-11-29 16:29:00 607855 task0 [<_MainThread(MainThread, stopped 8904)>, <Thread(task0, started daemon 9024)>, <Thread(task1, started 2280)>, <Thread(task2, started daemon 8028)>]
There is running task0 2018-11-29 16:29:01 608642 task0 [<_MainThread(MainThread, stopped 8904)>, <Thread(task0, started daemon 9024)>, <Thread(task1, started 2280)>, <Thread(task2, started daemon 8028)>]

Process finished with exit code 0

 

四、分析总结

　　1.打印结果有时间秒数，有线程及属性，不断更改设置，查看不同的结果，总结如下：

　　(a)join(time=60)，父线程会在此线程最多阻塞60s，join后的线程不会运行，join前已经运行的线程不受影响

　　(b)setDaemon(False)，此子线程为非守护线程，所有非守护子线程结束，父线程才会退出

　　(c)setDaemon(True)，此子菜鸟仓为守护线程，父线程退出，所有守护子线程立即结束