title: What is __path__ useful for?
body: <p>I had never noticed the <code>__path__</code> attribute that gets defined on some of my packages before today.  According to the documentation:</p>
  
  <blockquote>
    <p>Packages support one more special
    attribute, <code>__path__</code>. This is
    initialized to be a list containing
    the name of the directory holding the
    package’s <code>__init__.py</code> before the code
    in that file is executed. This
    variable can be modified; doing so
    affects future searches for modules
    and subpackages contained in the
    package.</p>
    
    <p>While this feature is not often
    needed, it can be used to extend the
    set of modules found in a package.</p>
  </blockquote>
  
  <p>Could somebody explain to me what exactly this means and why I would ever want to use it?</p>