解决使用pip无法安装包、无限依赖警告

安装Spyder，使用清华镜像，总是提示

INFO: pip is looking at multiple versions of sanic to determine which version is compatible with other requirements. This could take a while.
INFO: This is taking longer than usual. You might need to provide the dependency resolver with stricter constraints to reduce runtime. If you want to abort this run, you can press Ctrl + C to do so. To improve how pip performs, tell us what happened here: https://pip.pypa.io/surveys/backtracking

参考：https://blog.csdn.net/weixin_35757704/article/details/122269142，改为如下，很快安装完成！

pip3 install -U --user pip && pip3 install spyder -i https://pypi.org/simple

Spyder5.4.3 现在也很吃内存！Spyder+4个Python进程，占用了886.89M。
8G内存的机器不够看了！

另一个参考：
https://blog.csdn.net/weixin_47542175/article/details/122380430