title: python can't find mpi4py in command line but can import it in interpreter mode
body: <p>So I need to use mpi4py to run a module. After manually installed mpi4py and add the path to mpi4py package to python search path through <code>sys.path.append()</code> command in .pythonrc. And I tried to import mpi4py in the interpreter and it works fine, no matter where the interpreter is invoked:</p>
  
  <pre><code>$ python
  Python 2.7.4 (default, May 23 2013, 17:15:02) 
  [GCC 4.6.3] on linux2
  Type "help", "copyright", "credits" or "license" for more information.
  &gt;&gt;&gt; from mpi4py import MPI
  &gt;&gt;&gt; MPI
  &lt;module 'mpi4py.MPI' from '/home/XXXX/yt-x86_64/src/mpi4py-1.3/build/lib.linux-x86_64-2.7/mpi4py/MPI.so'&gt;
  </code></pre>
  
  <p>Then I tried to run from command line which a python script containing <code>from mpi4py import MPI</code>. It can't find the module:</p>
  
  <pre><code>$ python run_rockstar2.py
  Traceback (most recent call last):
    File "run_rockstar2.py", line 1, in &lt;module&gt;
      from mpi4py import MPI
  ImportError: No module named mpi4py
  </code></pre>
  
  <p>I've checked that I'm using the same python in the two cases. Anyone has a clue about this?</p>
  
  <p>Thanks in advance.</p>