title: Again looping issue
body: <p>I just wrote a simple bunch of code, which had to remove duplicates in list, but there was an issue.
  Can somebody explain me why it is skipping number 3 ?</p>
  <pre><code>lis = [1, 1, 3, 4, 5, 5, 5, 6, 1, 1, 3, 6, 6, 6, 1, 4, 7, 6, 5]
  for i in lis:
      while lis.count(i) &gt; 1:
          print(f'removing {i} ... ')
          lis.remove(i)
          print(lis.count(i))
  print(lis)
  </code></pre>