title: Is there a way to determine the filename passed to a map job in Hadoop/Dumbo/Mrjob?
body: <p>All,</p>
  
  <p>I am working on creating an interface for dealing with some massive data and generating arff files for doing some machine learning stuff with.  I can currently collect the features- but I have no way of associating them with the files they were derived from.  I am currently using Dumbo</p>
  
  <pre><code>def mapper(key, value):
      #do stuff to generate features
  </code></pre>
  
  <p>Is there any convenient method for determining the filename that was opened and had its contents passed to the mapper function?</p>
  
  <p>Thanks again.
  -Sam</p>