centos yum出现no module named yum

运行yum出现如下错误

There was a problem importing one of the Python modules  
required to run yum. The error leading to this problem was:  
  
   No module named yum  
  
Please install a package which provides this module, or  
verify that the module is installed correctly.  
  
It's possible that the above module doesn't match the  
current version of Python, which is:  
2.7.5 (default, Nov  8 2012, 23:03:00)   
[GCC 4.1.2 20080704 (Red Hat 4.1.2-48)]  
  
If you cannot solve this problem yourself, please go to   
the yum faq at:  
  http://wiki.linux.duke.edu/YumFaq  

修改yum工具默认的python版本。vi /usr/bin/yum

将第一行#!/usr/bin/python改为/usr/bin下的版本