[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/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> **エラー内容** ```shell 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