title: recursively create tuples from lists
body: <p>I have a list of lists such as:<br>
        <code>[[1,2,3],[4,5,6],[7,8,9]]</code>
  I'm trying to create tuples of the form <code>(1,4),(1,5),(1,6),(1,7),(1,8),(1,9),(2,4),(2,5),(4,7),(4,8),...</code></p>
  
  <p>In other words, items in the first list should be tuples with items in subsequent lists, items in the second list, tuples with items from its subsequent lists and so on, until we get to the last list.</p>
  
  <p>I'm a bit unsure of how a list comprehension in python here would work. Any ideas?</p>
  
  <p>Thanks.</p>