Suppose you have a function which is used to search files in a directory. This function will take a long time to finish.
For example, when you press Find button, we will start a python thread (search_thread_1) to search files in a directory.
However, we may press Find button again to start a new thread (search_thread_2) to search files before search_thread_1 thread is finished. At that situation, we should stop search_thread_1 before starting to run search_thread_2.
The example is below:
import threading import time import inspect import ctypes def searchFiles(dir): print("start to search files in "+dir) for i in range(100): time.sleep(1) print("get file "+ str(i)+ " in "+ dir) print("search files end in "+ dir) search_thread_1 = threading.Thread(target=searchFiles, args=["C:\\"]) search_thread_1.start() time.sleep(10) search_thread_2 = threading.Thread(target=searchFiles, args=["E:\\"])
In this code, we define a searchFiles() function to show files found in a directory. First we create and start search_thread_1 thread to search files in C:\.
Then we create a new thread search_thread_2 to search E:\. However, we should stop search_thread_1 before starting to run search_thread_2.
How to stop a python thread initiatively?
It is a pity that python does not provide functions to stop a running thread, we have to use other ways.
In this tutorial, we define a stop function to stop a running python thread.
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)
How to use stop_thread()?
You can stop a running thread like this:
After we stop a running thread search_thread_1, we can start to run search_thread_2.
Run this python code, we can find the result is:
From the result, we can find search_thread_1 is stop successfully by us.