title: What is generator.throw() good for?
body: <p><a href="http://www.python.org/dev/peps/pep-0342/" rel="noreferrer">PEP 342 (Coroutines via Enhanced Generators)</a> added a <code>throw()</code> method to generator objects, which allows the caller to raise an exception <em>inside</em> the generator (as if it was thrown by the <code>yield</code> expression).</p>
  
  <p>I am wondering what the use cases for this feature are.</p>