title: How to know which python is running under ipython?
body: <p>I have several versions of python installed on my computer:</p>
  
  <pre><code>$ which ipython
  /usr/local/share/python/ipython
  $ ipython
  Python 2.7.3 (default, Nov 28 2012, 13:43:07) 
  
  $ which python
  /usr/bin/python
  $ python
  Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49) 
  </code></pre>
  
  <p>I would like to locate the python bin running under my ipython.
  thanks for your help</p>