title: How to convert array of array into set in Python 3?
body: <p>What I have as input:         </p>
  
  <pre><code>list: [[2, 4], [2, 6], [2, 8]]
  </code></pre>
  
  <p>What I want as output:       </p>
  
  <pre><code>set: 2,4,6,8
  </code></pre>
  
  <p>What I'm currently doing(not working):         </p>
  
  <pre><code>def convert(input_list):
      all_nums = set([arr[0], arr[1]] for arr in input_list)
      return all_nums
  </code></pre>
  
  <p>I know I can manually iterate through parent array and add contents of child array to the <code>set</code> like this:      </p>
  
  <pre><code>def convert(input_list):
      all_nums = set()
      for inner_list in input_list:
          all_nums.add(inner_list[0])
          all_nums.add(inner_list[1])
      return all_nums
  </code></pre>
  
  <ul>
  <li>How to do do that in <strong>pythonic</strong> way?</li>
  <li>In second approach can I do something like <code>all_nums.add(inner_list[0], inner_list[1])</code>?</li>
  </ul>