一、原因
出现这个的原因是我们把yum给删除掉或者卸载掉了 ，这时候我们只需要重新安装即可，具体步骤如下：
二、查看系统新建目录
1、查看自己的系统版本
RedHat系列：
常见系统有：Redhat、Centos、Fedora等
我的是centos 查看系统命令如下：
cat /etc/redhat-release
2、新建目录
1 mkdir /usr/local/src/python
2 mkdir /usr/local/src/yum
3、下载yum源
cd /usr/local/src/yum
rpm -ivh --nodeps http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
rpm -ivh --nodeps http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.31-54.el7_8.noarch.rpm
rpm -ivh --nodeps http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-3.4.3-168.el7.centos.noarch.rpm
4、下载python依赖
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
三、安装python和yum
1、安装python
rpm -ivh python-* rpm-python-*
#可能会出现以下报错
root@node2 python\]# rpm -ivh python-\* rpm-python-\* 错误：依赖检测失败： rpm = 4.11.3-17.el7 被 rpm-python-4.11.3-17.el7.x86_64 需要
2、忽略依赖安装
rpm -ivh python-* rpm-python-* --nodeps --force # --nodeps --force为不考虑依赖包，强制安装。
安装完后即可运行python
3、安装yum
cd /usr/local/src/yum
rpm -ivh yum-*
如果提示缺少依赖包
同上安装python一样 强制前安装即可
rpm -ivh yum-* --nodeps --force
运行yum,问题完美解决
