镜像安装可以加快python包的下载速度

pip install python_lib -i https://pypi.tuna.tsinghua.edu.cn/simple

## for example
pip install numpy -i https://pypi.tuna.tsinghua.edu.cn/simple

设置永久镜像源

pip install --upgrade pip
pip config set global.index-url https://pypi.tuna.tsinghua.edu.cn/simple