title: It takes more than 1 runs to remove some values
body: <p>I want to remove the tuples that first and second values same. But It needs more than 1 run. After 3 runs I'm getting the result that I want.</p>
  <pre><code>list1 = [(1, 1), (1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (2, 2), (2, 4), (2, 6), (3, 3), (3, 6), (4, 4), (5, 5), (6, 6)]
  
  for x,y in list1:
      if x == y:
          list1.remove((x,y))
  </code></pre>