看一下線程的setDaemon()方法

import time import threading import ctypes import inspectdef sayHello():for i in range(10):print("hello")time.sleep(1)def _async_raise(tid, exctype):"""raises the exception, performs cleanup if needed"""tid = ctypes.c_long(tid)if not inspect.isclass(exctype):exctype = type(exctype)res = ctypes.pythonapi.PyThreadState_SetAsyncExc(tid, ctypes.py_object(exctype))if res == 0:raise ValueError("invalid thread id")elif res != 1:# """if it returns a number greater than one, you're in trouble,# and you should call it again with exc=NULL to revert the effect"""ctypes.pythonapi.PyThreadState_SetAsyncExc(tid, None)raise SystemError("PyThreadState_SetAsyncExc failed")def stop_thread(thread):_async_raise(thread.ident, SystemExit)if __name__ == '__main__':# sayHello()t = threading.Thread(target=sayHello, args=())t.setDaemon(True) # 主線程結束后停止子線程t.start()for i in range(3):print(t.is_alive())time.sleep(1)

上面的輸出是：

hello True True hello hello True hello

我們修改一下代碼：

''' 遇到問題沒人解答？小編創建了一個Python學習交流QQ群：778463939 尋找有志同道合的小伙伴，互幫互助,群里還有不錯的視頻學習教程和PDF電子書！ ''' import time import threading import ctypes import inspectdef sayHello():for i in range(10):print("hello")time.sleep(1)def _async_raise(tid, exctype):"""raises the exception, performs cleanup if needed"""tid = ctypes.c_long(tid)if not inspect.isclass(exctype):exctype = type(exctype)res = ctypes.pythonapi.PyThreadState_SetAsyncExc(tid, ctypes.py_object(exctype))if res == 0:raise ValueError("invalid thread id")elif res != 1:# """if it returns a number greater than one, you're in trouble,# and you should call it again with exc=NULL to revert the effect"""ctypes.pythonapi.PyThreadState_SetAsyncExc(tid, None)raise SystemError("PyThreadState_SetAsyncExc failed")def stop_thread(thread):_async_raise(thread.ident, SystemExit)if __name__ == '__main__':# sayHello()t = threading.Thread(target=sayHello, args=())t.setDaemon(False) # 主線程結束后不停止子線程t.start()for i in range(3):print(t.is_alive())time.sleep(1)

程序的輸出是：

hello True True hello hello True hello hello hello hello hello hello hello

可見，setDaemon()方法就是決定在主線程結束后是否結束子線程，如果為True時，會結束子線程，為False時，不會結束子線程。

我們再來看join()方法：

直接看代碼

''' 遇到問題沒人解答？小編創建了一個Python學習交流QQ群：778463939 尋找有志同道合的小伙伴，互幫互助,群里還有不錯的視頻學習教程和PDF電子書！ ''' import time import threading import ctypes import inspectdef sayHello():for i in range(10):print("hello")time.sleep(1)def _async_raise(tid, exctype):"""raises the exception, performs cleanup if needed"""tid = ctypes.c_long(tid)if not inspect.isclass(exctype):exctype = type(exctype)res = ctypes.pythonapi.PyThreadState_SetAsyncExc(tid, ctypes.py_object(exctype))if res == 0:raise ValueError("invalid thread id")elif res != 1:# """if it returns a number greater than one, you're in trouble,# and you should call it again with exc=NULL to revert the effect"""ctypes.pythonapi.PyThreadState_SetAsyncExc(tid, None)raise SystemError("PyThreadState_SetAsyncExc failed")def stop_thread(thread):_async_raise(thread.ident, SystemExit)if __name__ == '__main__':# sayHello()t = threading.Thread(target=sayHello, args=())t.setDaemon(False) # 主線程結束后不停止子線程t.start()for i in range(3):print(t.is_alive())time.sleep(1)# t.join()print("over")

輸出結果為：

hello True True hello True hello hello over hello hello hello hello hello hello

可以看到主線程結束時，打印出over，之后子線程還在繼續打印hello

修改代碼：

''' 遇到問題沒人解答？小編創建了一個Python學習交流QQ群：778463939 尋找有志同道合的小伙伴，互幫互助,群里還有不錯的視頻學習教程和PDF電子書！ ''' import time import threading import ctypes import inspectdef sayHello():for i in range(10):print("hello")time.sleep(1)def _async_raise(tid, exctype):"""raises the exception, performs cleanup if needed"""tid = ctypes.c_long(tid)if not inspect.isclass(exctype):exctype = type(exctype)res = ctypes.pythonapi.PyThreadState_SetAsyncExc(tid, ctypes.py_object(exctype))if res == 0:raise ValueError("invalid thread id")elif res != 1:# """if it returns a number greater than one, you're in trouble,# and you should call it again with exc=NULL to revert the effect"""ctypes.pythonapi.PyThreadState_SetAsyncExc(tid, None)raise SystemError("PyThreadState_SetAsyncExc failed")def stop_thread(thread):_async_raise(thread.ident, SystemExit)if __name__ == '__main__':# sayHello()t = threading.Thread(target=sayHello, args=())t.setDaemon(False) # 主線程結束后不停止子線程t.start()for i in range(3):print(t.is_alive())time.sleep(1)t.join()print("over")

輸出結果為：

hello True hello True True hello hello hello hello hello hello hello hello over

可以看到設置t.join()方法之后，主線程要等待t這個線程結束之后，才能繼續，也就是等hello打印完之后才打印over。

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