title: Python regular Expressions -- 3 adjacent digits
body: <p>I am trying to write a regular expression that will find 3 adjacent digits, and only 3.</p>
  
  <pre><code>s = "1234sss" = no match
  x = "rrr123rrr" = match
  g = fff12ggg" = no match
  </code></pre>
  
  <p>I have played around with this: </p>
  
  <pre><code>m = re.search(r"(\d+)","Hello1234rrr")
  m.group(0)
  '1234'
  </code></pre>
  
  <p>I am not sure how to just return 3 digits no more or less</p>