title: avoid break when choosing item from list
body: <p>Considering a list, and wanting to select the first item from it that is not in a second list, and then stop searching, what is the most efficient way to do this (without breaking):</p>
  
  <pre><code>aa = [11,22,33,44,55,66]
  bb = [11,12,22,23,33,34,88,66]
  
  for x in aa:
      if x not in bb:
          bb.append(x)
          break
  print(f'{aa} \n{bb}')
  </code></pre>
  
  <p>Like this but in a efficient way.</p>