title: upgrading default python version or install another python version in Linux
body: <p>I want to upgrade python's default version i.e <code>/usr/bin/python</code> in Linux.</p>
  
  <p>I have multiple python versions installed as </p>
  
  <pre><code>/usr/bin/python2.7   
  /usr/bin/python3.3
  </code></pre>
  
  <p>However, <code>python</code> command still returns <code>python2.7</code></p>
  
  <pre><code># python
  Python 2.7 
  Type "help", "copyright", "credits" or "license" for more information.
  &gt;&gt;&gt;
  </code></pre>
  
  <p>Now, I have installed a module, which got installed in the default version <code>2.7</code>.</p>
  
  <p>That's why I can't use <code>python3.3 script.py</code>, as it returns error for missing module.</p>
  
  <p>How to update this default version to <code>3.3</code>? </p>
  
  <p>Is there a way to install the module in <code>/usr/bin/python3.3</code> as well? </p>
  
  <p><strong>Added:</strong> Module is <code>pexpect-2.3</code>.</p>