title: Subclassing file class in Python raises NameError
body: <p>I have to do a very simple project in python where I add error checking to the built in file class.  So far, I've got:</p>
  
  <pre><code>class RobustFile(file):
      def __init__(self,name,mode):
          file.__init__(self,name,mode)
  </code></pre>
  
  <p>I'm just starting out, but to make sure I hadn't messed anything up, I ran it.  Well, right off the bat, I raised a NameError because it didn't recognize file.  I tried tweaking it, I looked it up on the internet, I copied examples using the same format, and...all NameError.  Can anyone shed some light on how exactly to subclass file?</p>