1.创建目录python和yum用以存放rpm包：

mkdir /usr/local/src/python
mkdir /usr/local/src/yum

2.使用wget分别下载python以及yum的rpm包（注意：一定要和系统的版本号对应）地址：http://vault.centos.org

（1）下载python的rpm包：

 cd /usr/local/src/python 
wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/python-2.7.5-34.el7.x86_64.rpm
wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/python-iniparse-0.4-9.el7.noarch.rpm
wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/python-pycurl-7.19.0-17.el7.x86_64.rpm
wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/python-devel-2.7.5-34.el7.x86_64.rpm
wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/python-libs-2.7.5-34.el7.x86_64.rpm
wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/python-urlgrabber-3.10-7.el7.noarch.rpm
wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/rpm-python-4.11.3-17.el7.x86_64.rpm

 （2）下载yum的rpm包：

cd /usr/local/src/yum
wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/yum-3.4.3-132.el7.centos.0.1.noarch.rpm
wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
wget http://vault.centos.org/7.2.1511/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.31-34.el7.noarch.rpm

3.安装python以及yum的rpm包

（1）安装python:

rpm -ivh python-*   rpm-python-* --nodeps --force
--nodeps --force     为不考虑依赖包，强制安装。

  （2）安装yum:

cd /usr/local/src/yum
rpm -ivh yum-*

yum重新安装成功