title: How to get every string permutation where each letter is from a different string
body: <p>I have this block of code in python3:</p>
  <pre><code>keyLetters = []
  for coset in cosets:
      keyLetters.append(Counter(coset).most_common(8))
  </code></pre>
  <p>Where <code>cosets</code> is a list of gibberish strings, and <code>keyLetters</code> are a list of the most common letters from each string.</p>
  <p>My goal is to get every letter combination as a series of strings from their most common letters, where each position of the string is from a different coset.</p>
  <p>So if the top three most frequent letters from three cosets are:</p>
  <pre><code>c1 = {'D', 'K', 'M'}
  c2 = {'L', 'D', 'J'}
  c3 = {'Z', 'B', 'F'}
  </code></pre>
  <p>I need the strings:</p>
  <pre><code>s1 = 'DDF'
  s2 = 'DJF'
  s3 = 'ZDM'
  etc
  </code></pre>
  <p>How do I achieve this?</p>