title: How to move old libraries of previous version python to new version of python
body: <p>I am using Ubuntu. I install newer version of python. But all my installed libraries such as imdbPy, NumPy, Cython etc. can run in previous version of python whose version number is 2.6.6. </p>
  
  <p>When I import Cython in 2.6.6, tt works, but I try same thing in 2.7.0+ version of python</p>
  
  <pre><code>import cython
  </code></pre>
  
  <p>occurs an error as following:</p>
  
  <pre><code>import cython
  ImportError: No module named cython
  </code></pre>
  
  <p>What I need is to change default version of python which is used in bash. I think, I can handle it by modifying bash profile file. I also want to move all of these libs to appropriate place so that new version of python can reach them permanently.</p>