title: correctly strip : char with Regex
body: <p>I want to get words in a text string in python</p>
  
  <pre><code>s = "The saddest aspect of life right now is: science gathers knowledge faster than society gathers wisdom."
  
  result = re.sub("\b[^\w\d_]+\b", " ",  s ).split()
  print result  
  </code></pre>
  
  <p>I am getting:</p>
  
  <pre><code>['The', 'saddest', 'aspect', 'of', 'life', 'right', 'now', 'is:', 'science', 'gathers', 'knowledge', 'faster', 'than', 'society', 'gathers', 'wisdom.']
  </code></pre>
  
  <p>How can I get "is" and not "is:" on strings that happen to contain <code>:</code> ?
  I thought using <code>\b</code> would be enough...</p>