title: Ubuntu add directory to Python path
body: <p>I want to run third part tool written in python on my ubuntu machine (<a href="https://github.com/pkerpedjiev/corgy" rel="noreferrer">corgy tool</a>).  </p>
  
  <p>However I don't know how to add additional modules to Python path.  </p>
  
  <pre><code>cat doc/download.rst         
  There is currently no setup.py, so you need to manually add
  the download directory to your PYTHON_PATH environment variable.
  </code></pre>
  
  <p>How can I add directory to PYTHON_PATH?</p>
  
  <p><strong>I have tried:</strong><br>
  <code>export PYTHON_PATH=/home/user/directory:$PYTHON_PATH &amp;&amp; source .bashrc</code><br>
  <code>export PATH=/home/user/directory:$PATH &amp;&amp; source .bashrc</code>  </p>
  
  <p><code>python<br>
   import sys<br>
   sys.path.append("/home/user/directory/")</code></p>
  
  <p>But when I try to run this tool I get:  </p>
  
  <pre><code>Traceback (most recent call last):
  File "examples/dotbracket_to_bulge_graph.py", line 4, in &lt;module&gt;
  import corgy.graph.bulge_graph as cgb
  ImportError: No module named corgy.graph.bulge_graph
  </code></pre>