总体解决思路就是卸载和删除python、yum的残留文件，再下载自己系统版本对应的python、yum包进行安装。
一、彻底卸载python和yum
删除python已安装程序及其关联
rpm -qa|grep python|xargs rpm -ev --allmatches --nodeps
删除残余python文件
whereis python |xargs rm -frv
验证删除，返回为无结果
whereis python
删除现有yum
rpm -qa|grep yum|xargs rpm -ev --allmatches --nodeps
删除残余yum文件
whereis yum |xargs rm -frv
二、下载安装包
创建目录python和yum用以存放rpm包
mkdir /usr/local/src/python
mkdir /usr/local/src/yum
下载python以及yum的rpm包
需要注意的是centos8已经停止维护了，所以要从centos8-stream找替代的安装包：https://pkgs.org/ 可以在此网站上搜索相关安装包
#python
cd /usr/local/src/python
wget http://mirror.centos.org/centos/8-stream/BaseOS/x86_64/os/Packages/python3-asn1crypto-0.24.0-3.el8.noarch.rpm
wget http://mirror.centos.org/centos/8-stream/BaseOS/x86_64/os/Packages/python3-dnf-4.7.0-4.el8.noarch.rpm
wget http://mirror.centos.org/centos/8-stream/BaseOS/x86_64/os/Packages/python3-gpg-1.13.1-9.el8.x86_64.rpm
wget http://mirror.centos.org/centos/8-stream/BaseOS/x86_64/os/Packages/python3-hawkey-0.63.0-3.el8.x86_64.rpm
wget http://mirror.centos.org/centos/8-stream/BaseOS/x86_64/os/Packages/python3-libcomps-0.1.16-2.el8.x86_64.rpm
wget http://mirror.centos.org/centos/8-stream/BaseOS/x86_64/os/Packages/python3-libdnf-0.63.0-3.el8.x86_64.rpm
wget http://mirror.centos.org/centos/8-stream/BaseOS/x86_64/os/Packages/python3-libs-3.6.8-41.el8.x86_64.rpm
wget http://mirror.centos.org/centos/8-stream/BaseOS/x86_64/os/Packages/python3-rpm-4.14.3-19.el8.x86_64.rpm
wget http://mirror.centos.org/centos/8-stream/BaseOS/x86_64/os/Packages/platform-python-3.6.8-41.el8.x86_64.rpm
#yum
cd /usr/local/src/yum
wget http://mirror.centos.org/centos/8-stream/BaseOS/x86_64/os/Packages/yum-4.7.0-4.el8.noarch.rpm
wget http://mirror.centos.org/centos/8-stream/BaseOS/x86_64/os/Packages/yum-utils-4.0.21-3.el8.noarch.rpm
三、安装
安装python以及yum的rpm包
#安装Python
cd /usr/local/src/python
#Centos7
rpm -ivh python-* rpm-python-* --nodeps --force
#Centos8
rpm -ivh python3-* platform-python-* --nodeps --force
#安装yum
cd /usr/local/src/yum
rpm -ivh yum-*
大功告成！
参考文档：
https://www.mxlong.com/14.html
注意：本文归作者所有，未经作者允许，不得转载