守護線程

如果python線程是守護線程，那么以為著這個線程是“不重要”的，“不重要”意味著如果他的父進程結束了但該守護線程沒有運行完，守護進程就會被強制結束。如果線程是非守護線程，那么父進程只有等到守護線程運行完畢后才能結束。

在python中，線程通過threadName.setDaemon(True|False)來設置是否為守護線程

代碼實例

父進程中調用兩個線程，但父進程會瞬間運行完，觀察兩個線程的運行情況。

import time import threadingdef write(content):start_time = time.strftime("%Y/%m/%d-%H:%M:%S", time.localtime(time.time()))string = "start writting %s at %s" % (content, start_time)print(string)time.sleep(5)end_time = time.strftime("%Y/%m/%d-%H:%M:%S", time.localtime(time.time()))string = "start writting %s at %s" % (content, end_time)print(string)def watch(content):start_time = time.strftime("%Y/%m/%d-%H:%M:%S", time.localtime(time.time()))string = "start watching %s at %s" % (content, start_time)print(string)time.sleep(5)end_time = time.strftime("%Y/%m/%d-%H:%M:%S", time.localtime(time.time()))string = "start watching %s at %s" % (content, end_time)print(string)threads = [] t1 = threading.Thread(target=write, args=("poem",)) t2 = threading.Thread(target=watch, args=("video",)) threads.append(t1) threads.append(t2)def for_test():for thread in threads:thread.setDaemon(False)thread.start()print("main over")if __name__ == '__main__':for_test()

運行結果：

可以看到主線程瞬間結束，但是等待到子線程均運行完畢之后程序才退出。

import time import threadingdef write(content):start_time = time.strftime("%Y/%m/%d-%H:%M:%S", time.localtime(time.time()))string = "start writting %s at %s" % (content, start_time)print(string)time.sleep(5)end_time = time.strftime("%Y/%m/%d-%H:%M:%S", time.localtime(time.time()))string = "start writting %s at %s" % (content, end_time)print(string)def watch(content):start_time = time.strftime("%Y/%m/%d-%H:%M:%S", time.localtime(time.time()))string = "start watching %s at %s" % (content, start_time)print(string)time.sleep(5)end_time = time.strftime("%Y/%m/%d-%H:%M:%S", time.localtime(time.time()))string = "start watching %s at %s" % (content, end_time)print(string)threads = [] t1 = threading.Thread(target=write, args=("poem",)) t2 = threading.Thread(target=watch, args=("video",)) threads.append(t1) threads.append(t2)def for_test():for thread in threads:thread.setDaemon(True)thread.start()if __name__ == '__main__':print("main start a t %s" %(time.strftime("%Y/%m/%d-%H:%M:%S", time.localtime(time.time()))))for_test()print("main end at %s" %(time.strftime("%Y/%m/%d-%H:%M:%S", time.localtime(time.time()))))

運行結果：

我們可以看到主線程結束之后整個程序即退出了。

更新時間： 2019 11 12

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