title: Import error, No module named xxxx
body: <p>I have a project having the structure</p>
  
  <pre><code>/example
  ../prediction
  ....__init__.py
  ....a.py
  </code></pre>
  
  <p>PYTHONPATH is pointed to /example</p>
  
  <p>now I open the python in terminal and type</p>
  
  <pre><code>import prediction
  </code></pre>
  
  <p>it succeeded, but if I type</p>
  
  <pre><code>import prediction.a
  </code></pre>
  
  <p>it returns error</p>
  
  <pre><code>ImportError: No module named 'prediction.a'; 'prediction' is not a package
  </code></pre>
  
  <p>why is that? isn't that already imported as a package</p>