感谢分享：http://www.cnblogs.com/PHPandMysqL/p/7066399.html
网上看到有同学yum不能使用的消息，出现了下面的结果
无赖的使用了网上的很多方法，还是不行。
于是我卸载了python和yum，觉得自己重新安装python和yum。
步骤1：卸载python
rpm -qa|grep python|xargs rpm -e --allmatches --nodeps whereis python|xargs rm -fr
步骤2：卸载yum
grep yum|rm -rf /etc/yum.repos.d/*
whereis yum|xargs rm -fr
步骤3：安装python
在任何一个镜像站中找到你系统对应版本的python rpm包（我的是centos 6.9的64位系统，使用的镜像是http://mirrors.163.com/centos/6.9/os/x86_64/Packages/）
mkdir /usr/local/src/python wget http://mirrors.163.com/centos/6.9/os/x86_64/Packages/python-2.6.6-66.el6_8.x86_64.rpm mirrors.163.com/centos/6.9/os/x86_64/Packages/python-iniparse-0.3.1-2.1.el6.noarch.rpm mirrors.163.com/centos/6.9/os/x86_64/Packages/python-pycurl-7.19.0-9.el6.x86_64.rpm mirrors.163.com/centos/6.9/os/x86_64/Packages/python-devel-2.6.6-66.el6_8.x86_64.rpm mirrors.163.com/centos/6.9/os/x86_64/Packages/python-libs-2.6.6-66.el6_8.x86_64.rpm mirrors.163.com/centos/6.9/os/x86_64/Packages/python-urlgrabber-3.9.1-11.el6.noarch.rpm mirrors.163.com/centos/6.9/os/x86_64/Packages/rpm-python-4.8.0-55.el6.x86_64.rpm
切换到/usr/local/src/python路径下
rpm -ivh python-* rpm-python-*
如果中间过程出现了类似下面的代码，这是包与包之间的依赖关系，只需要卸载已经安装的包（rpm -e 包名（没有.rpm后缀）），然后先安装依赖包
如：
rpm -e yum-Metadata-parser-1.1.2-16.el6.x86_64 rpm -ivh /16.el6.x86_64.rpm
步骤4：安装yum
mkdir /usr/local/src/yum
mirrors.163.com/centos/6.9/os/x86_64/Packages/yum-3.2.29-81.el6.centos.noarch.rpm
mirrors.163.com/centos/6.9/os/x86_64/Packages/yum-Metadata-parser-1.1.2-16.el6.x86_64.rpm
mirrors.163.com/centos/6.9/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.30-40.el6.noarch.rpm
rpm -ivh yum-*
