- https://pythonprogramming.net/matplotlib-intro-tutorial/
- https://matplotlib.org/gallery.html
- [Python数据可视化分析 matplotlib](https://www.bilibili.com/video/av6989413)
$ python3 -m venv venv3
$ . venv3/bin/activate
(venv3)$ pip3 install -r requirements.txt
...
(venv3)$ deactivate