title: Testing whether a string has repeated characters
body: <p>I am trying to figure out the lightest method for determining whether a string has any repeated characters, in the lightest way possible. I have tried searching for similar questions, but cant find any. It also needs to be the shorted way possible, as i will be checking quite a few strings (I can handle putting this into a loop, etc.) </p>
  
  <p>For example:</p>
  
  <pre><code>a = "12348546478"
  #code to check multiple characters
  print(result) 
  </code></pre>
  
  <p>Results: 8 was repeated, 4 was repeated</p>
  
  <p>The code will check what character was repeated and print out what was repeated. I don't need to know how many times it was repeated, just whether it was or was not repeated.</p>