title: How to generate random pairs
body: <p>I have an array like this:</p>
  
  <pre><code>a = [["A", "1"], ["B", "2"], ["C", "3"], ["D", "4"], ["E", "5"]]
  </code></pre>
  
  <p>I need to create a list of random pairs, removing the new ones that are similar to the previous ones.</p>
  
  <p>Example:</p>
  
  <pre><code>a = [["B", "4"], ["A", "2"], ["E", "3"], ["C", "5"]]
  </code></pre>
  
  <p>Not accepted : </p>
  
  <pre><code>["D", "4"]
  </code></pre>