title: Finding common letters in list of words
body: <p>I am new to python this is what i am trying to achieve: </p>
  
  <pre><code>letter = 4
  word = "Demo Deer Deep Deck Cere Reep Creep Creeps"
  split_word = word.split()   
  </code></pre>
  
  <p>I am trying to achieve words that can be formed by any 4 common letters for example: </p>
  
  <pre><code>Deer Deep Reep [these can be formed by 4 letters d, e, r &amp; p]
  Creep Cere Reep [these can be formed by 4 letters c, r, e, p]
  </code></pre>
  
  <p>Is there easy way to do this in python without using regex.</p>