title: Order of variables in python using the .update method of sets
body: <p>How are the order of variables decided when updating a set?</p>
  
  <pre><code>A = {1, 2, 3, 4, 5}
  
  A.add(8)
  print(A)
  
  A.update({-1, -2, -3})
  print(A)
  </code></pre>
  
  <p>Why is the order <code>{1, 2, 3, 4, 5, 8, -2, -3, -1}</code> and not <code>{1, 2, 3, 4, 5, 8, -1, -2, -3}</code>?</p>