title: Twisted: event for a new file in directory
body: <p>I have the application, which runs when new file appears in specific directory.
  For this purpose I use nncron (cron for windows), an example </p>
  
  <pre><code>#(
  500 VALUE MonitorDirTimeout
  WatchDir: "c:\directory" WatchSubtree
  WATCH-CHANGE-LAST-WRITE
  Action:
          StartIn: "c:\directory"
          SWHide   NormalPriority
          START-APP: c:\app.py
  )#
  </code></pre>
  
  <p>I want to use event-driven programming and Twisted, and want to execute callback when new file appears in directory.
  Of course, I can monitor directory by using <a href="http://twistedmatrix.com/documents/8.1.0/api/twisted.internet.task.LoopingCall.html" rel="nofollow" title="LoopingCall">LoopingCall</a>, but its not event-driven.</p>