在安裝sklearn時報錯如下：
ERROR: Could not find a version that satisfies the requirement threadpoolctl>=2.0.0 (from scikit-learn->sklearn) (from versions: 1.0.0, 1.1.0)
ERROR: No matching distribution found for threadpoolctl>=2.0.0 (from scikit-learn->sklearn)
個人以為是threadpoolctl包的問題。
實際上經過查找是網絡不好，也就是源出了問題，我的源是 https://pypi.mirrors.ustc.edu.cn/simple/
解決辦法：pip install sklearn -i http://pypi.douban.com/simple/ --trusted-host pypi.douban.com