yum安装pip
参考文档：https://www.cnblogs.com/ermao0423/p/9596617.html
1、安装epel扩展源：yum -y install epel-release
2、安装pip：yum -y install python-pip
升级pip：pip install --upgrade pip

pip源提示“not a trusted or secure host” 解决
参考文档：https://www.cnblogs.com/shenfei2031/p/10854566.html
问题：
The repository located at mirrors.aliyun.com is not a trusted or secure host and is being ignored. If this repository is available via HTTPS we recommend you use HTTPS instead, otherwise you may silence this warning and allow it anyway with '--trusted-host mirrors.aliyun.com'. Could not find a version that satisfies the requirement proxy (from versions: ) No matching distribution found for proxy
答案：
http://mirrors.aliyun.com/pypi/simple/
改成
https://mirrors.aliyun.com/pypi/simple/

问题：
Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None))

原文链接：https://blog.csdn.net/nahanai/article/details/96435128

解决：
pip install pymysql -i url（ 其他pip源）

国内几个pip源如下：

阿里云 http://mirrors.aliyun.com/pypi/simple/

中国科技大学 https://pypi.mirrors.ustc.edu.cn/simple/

豆瓣(douban) http://pypi.douban.com/simple/

清华大学 https://pypi.tuna.tsinghua.edu.cn/simple/

中国科学技术大学 http://pypi.mirrors.ustc.edu.cn/simple/

例：安装pymysql

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