title: operating over strings, python
body: <p>How to define a function that takes a string (sentence) and inserts an extra space after a period if the period is directly followed by a letter.</p>
  
  <pre><code>sent = "This is a test.Start testing!"
  def normal(sent):
      list_of_words = sent.split()
      ...
  </code></pre>
  
  <p>This should print out </p>
  
  <blockquote>
    <p>"This is a test. Start testing!"</p>
  </blockquote>
  
  <p>I suppose I should use <code>split()</code> to brake a string into a list, but what next?</p>
  
  <p><strong>P.S.</strong> The solution has to be as simple as possible.</p>