title: Using a regular expression to replace upper case repeated letters in python with a single lowercase letter
body: <p>I am trying to replace any instances of uppercase letters that repeat themselves twice in a string with a single instance of that letter in a lower case. I am using the following regular expression and it is able to match the repeated upper case letters, but I am unsure as how to make the letter that is being replaced lower case.</p>
  
  <pre><code>import re
  s = 'start TT end'
  re.sub(r'([A-Z]){2}', r"\1", s)
  &gt;&gt;&gt; 'start T end'
  </code></pre>
  
  <p>How can I make the "\1" lower case? Should I not be using a regular expression to do this?</p>