python 使用matplotlib，import matplotlib.pyplot as plt，某次开始弹出警告

font_manager.py:273: UserWarning: Matplotlib is building the font cache using fc-list. This may take a moment.
  warnings.warn('Matplotlib is building the font cache using fc-list. This may take a moment.')

Google一下之后，stackoverflow的回答：

As tom suggested in the comment above, deleting the files:

fontList.cache
fontList.py3k.cache
tex.cache
solve the problem. In my case the files were under:

~/.matplotlib
EDITED

A couple of days ago the message appeared again, I deleted the files in the locations mention above without any success. I found that as suggested here by T Mudau there’s an extra location with text cache files is: ~/.cache/fontconfig

删除缓存文件。亲测有效，只会再出现一次警告，之后运行都没有警告了
The warning should now appear only the next time that matplotlib.pyplot is imported, and not afterwards.