title: Nested For Loops Using List Comprehension
body: <p>If I had two strings, <code>'abc'</code> and <code>'def'</code>, I could get all combinations of them using two for loops:</p>
  
  <pre><code>for j in s1:
    for k in s2:
      print(j, k)
  </code></pre>
  
  <p>However, I would like to be able to do this using list comprehension. I've tried many ways, but have never managed to get it. Does anyone know how to do this?</p>