title: Pairwise crossproduct in Python
body: <p>How can I get the list of cross product <em>pairs</em> from a list of arbitrarily long lists in Python?</p>
  
  <h2>Example</h2>
  
  <pre><code>a = [1, 2, 3]
  b = [4, 5, 6]
  </code></pre>
  
  <p><code>crossproduct(a,b)</code> should yield <code>[[1, 4], [1, 5], [1, 6], ...]</code>.</p>