[Python] マルチスレッド

python でのスレッドの作成、開始、終了の方法です。いつもどうだったっけ？となるので、出来るだけシンプルなコードでメモしておきます。 <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEid9G04i6Yw-BNUi16o0RaiCkd5c-N6A0QO2MO6n6tlGlZ2zj5fKVqkS2Xcr7KPr-vp319pWmtet6B0pjx7eEMoKMvDGUohyphenhyphen9QiDHR8pp9pS8u3tyUKFersSJVNbCmigzoaYE2ndNcfpfk/s0/2048px-Python-logo-notext.svg.png" hidden><img alt="" border="0" data-original-height="200" data-original-width="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEid9G04i6Yw-BNUi16o0RaiCkd5c-N6A0QO2MO6n6tlGlZ2zj5fKVqkS2Xcr7KPr-vp319pWmtet6B0pjx7eEMoKMvDGUohyphenhyphen9QiDHR8pp9pS8u3tyUKFersSJVNbCmigzoaYE2ndNcfpfk/s0/2048px-Python-logo-notext.svg.png"/></a> ## 環境 - Python 3.8.10 ## スレッドの起動と停止 ```py import time from threading import Thread from datetime import datetime class Sample: def __init__(self): self.__is_running = False def start(self): print('start') self.__is_running = True self.__thread = Thread(target=self.__run) self.__thread.start() def stop(self): print('stopping') self.__is_running = False self.__thread.join() print('stopped') def __run(self): while self.__is_running: print(f'{datetime.now()} running') time.sleep(1) if __name__ == '__main__': sample = Sample() sample.start() time.sleep(10) sample.stop() ``` ### 排他処理 上記をベースに、スレッドを複数開始しないように排他をかけてみます。 ```py import time from threading import Thread, Lock from datetime import datetime class Sample: def __init__(self): self.__lock = Lock() self.__is_running = False def start(self): if self.__is_running: print('already running') else: with self.__lock: print('start') self.__is_running = True self.__thread = Thread(target=self.__run) self.__thread.start() def stop(self): if not self.__is_running: print('not running') else: with self.__lock: print('stopping') self.__is_running = False self.__thread.join() print('stopped') def __run(self): while self.__is_running: print(f'{datetime.now()} running') time.sleep(1) if __name__ == '__main__': sample = Sample() sample.start() sample.start() sample.start() time.sleep(10) sample.stop() sample.stop() sample.stop() ``` `with` の代わりに `acquire` と `release` を使ってもいいです。 ** 出力結果 ** ``` start already running already running 2022-02-14 14:29:16.802901 running ... stopping stopped not running not running ``` ### 既にスレッド起動中の場合は一度停止してから再起動 上記の `print('already running')` のところで `self.stop()` をコールすればよいです。 ## 参考 URL - https://qiita.com/tag1216/items/2dcb112f8018eb19a999 - https://qiita.com/GRGSIBERIA/items/5e5d6d7afb40a7fc5c34 - https://udemyfun.com/python-threading-lock/