[Python] matplotlib で plot する際に "Tcl_AsyncDelete: async handler deleted by the wrong thread" というエラーがでる

matplotlib を使って画像を作成する場合に、たまに以下のようなエラーが表示されます。 <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhy1CH-vAtyu44KWe-z1Asd4NHXP62IrNbpe2zO3HR5pQHAYTPkPjHXd67T32ELdx18N9fxe8zRXnm_Zupfrs1mAG3bnfH6Rp1WOM7Uxv65ouxxP-h61HVVumDuv_qpdFDOK7P34i8vhfQ/s1600/6375fc39bf885c1ec9d99445f8720127f1f728ac.png" imageanchor="1" hidden><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhy1CH-vAtyu44KWe-z1Asd4NHXP62IrNbpe2zO3HR5pQHAYTPkPjHXd67T32ELdx18N9fxe8zRXnm_Zupfrs1mAG3bnfH6Rp1WOM7Uxv65ouxxP-h61HVVumDuv_qpdFDOK7P34i8vhfQ/s320/6375fc39bf885c1ec9d99445f8720127f1f728ac.png" width="320" height="320" data-original-width="500" data-original-height="500" /></a> **エラー内容** ```sh Exception ignored in: <function Image.__del__ at 0x000002ABF39B1310>Traceback (most recent call last): File "C:\Users\username\AppData\Local\Programs\Python\Python38\lib\tkinter\__init__.py", line 4014, in __del__ self.tk.call('image', 'delete', self.name) RuntimeError: main thread is not in main loop Exception ignored in: <function Image.__del__ at 0x000002ABF39B1310>Traceback (most recent call last): File "C:\Users\username\AppData\Local\Programs\Python\Python38\lib\tkinter\__init__.py", line 4014, in __del__ self.tk.call('image', 'delete', self.name) RuntimeError: main thread is not in main loop Exception ignored in: <function Image.__del__ at 0x000002ABF39B1310>Traceback (most recent call last): File "C:\Users\username\AppData\Local\Programs\Python\Python38\lib\tkinter\__init__.py", line 4014, in __del__ self.tk.call('image', 'delete', self.name) RuntimeError: main thread is not in main loop Exception ignored in: <function Image.__del__ at 0x000002ABF39B1310>Traceback (most recent call last): File "C:\Users\username\AppData\Local\Programs\Python\Python38\lib\tkinter\__init__.py", line 4014, in __del__ self.tk.call('image', 'delete', self.name) RuntimeError: main thread is not in main loop Tcl_AsyncDelete: async handler deleted by the wrong thread ``` ググってみたところ、`matplotlib.use('Agg')` を追加すればよいそうなので、以下のようにして追加しました。 ```py import matplotlib matplotlib.use('Agg') import matplotlib.pyplot as plt ``` とりあえず今のところ、このエラーは表示されなくなりました。 ## 参考 URL - https://catdance124.hatenablog.jp/entry/2019/09/20/113202 - https://stackoverflow.com/questions/50848127/python-plot-image-save-error - https://qiita.com/TomokIshii/items/3a26ee4453f535a69e9e