title: Python - Find characters in list of strings that are not duplicates
body: <p>I'm having difficulty with finding a non-duplicate value in a dictionary.</p>
  
  <pre><code>my_dict = {(1, 1):'2345', (1, 2):'234', (1, 3):'5678', (1, 4):'2387'}
  </code></pre>
  
  <p>What I need is to be able to find out is, what character is not a duplicate and what key it is a value of.
  For this dictionary I would need to return the following:</p>
  
  <pre><code>&gt;&gt;&gt; {(1, 3):'6'} 
  </code></pre>
  
  <p>6 is the only value that does not appear in any of the other values, so I would need to be returned the key ((1, 3)) and the non-duplicate (6).</p>
  
  <p>Any help would be greatly appreciated.</p>