title: Keeping Python packages with the same top-level name in different directories
body: <p>I have several Python packages that I'd like to keep on separate filesystems but which unfortunately share the same top-level module name.</p>
  
  <p>To illustrate, the directory structure looks like this:</p>
  
  <pre><code>/fs1
    /top
      __init__.py
      /sub1
        __init__.py
  
  /fs2
    /top
      __init__.py
      /sub2
        __init__.py
  </code></pre>
  
  <p>In Python 2.7, is there any way I can set up my <code>PYTHONPATH</code> so that I could import both <code>top.sub1</code> and <code>top.sub2</code> into the same script? Adding both <code>/fs1</code> and <code>/fs2</code> doesn't work, since it only allows one of the two submodules to be imported (whichever comes first on <code>PYTHONPATH</code>).</p>
  
  <p>I could copy/symlink the two trees into one, but for practical reasons I'd rather not do that.</p>