title: Itertools equivalent of nested loop "for x in xs: for y in ys..."
body: <p>I have a nested loop to create all combinations in a set of conjugated verbs. The aim to to get all possible combinations of verb, person and tense, e.g. <code>[['to be', 'first person singular', 'future'],['to be', 'second person singular', 'future'], ...]</code>. </p>
  
  <pre><code>for v in verbs:
      for p in persons:
          for t in tenses:
              return [v, p, t]
  </code></pre>
  
  <p>Is there a way of reducing the nesting, perhaps using <code>itertools</code>?</p>