title: Removing rows from 2d list
body: <p>I am confused why this short snippet to remove specific pairs from a list fails:</p>
  
  <pre><code>g = [[7, 11], [7, 8], [3, 10], [3, 8], [8, 9], [11, 10], [11, 2], 
  [11, 9]]
  u = 3
  g_cpy = g
  for e in g_cpy:
      if u == e[0]:
          g.remove(e)
  print g
  </code></pre>
  
  <p>It does not remove the entry [3,8], but it does remove [3,10]. What am I missing?</p>