title: Python: How to remove certain words in a string
body: <p>I have the following string: </p>
  
  <blockquote>
    <p>right then the treasure be right on that island right where we left it
    then when ye left me</p>
  </blockquote>
  
  <p>My task is to delete everything except the reoccurring words. So the output would be:</p>
  
  <p><code>&gt;&gt;&gt;right right then left</code></p>
  
  <p>I have managed to get the following output:</p>
  
  <p><code>&gt;&gt;&gt;['right', 'then', 'the', 'treasure', 'be', 'on', 'that', 'island', 'where', 'we', 'left', 'it', 'when', 'ye', 'me']</code></p>
  
  <p>Now if i manage to delete the above words from the original string, I will be left the the correct output. How do i do this?</p>