title: How to cast string back into a list
body: <p>I have a list:</p>
  
  <pre><code>ab = [1, 2, a, b, c]
  </code></pre>
  
  <p>I did:</p>
  
  <pre><code>strab = str(ab).
  </code></pre>
  
  <p>So <code>strab</code> is now a string.</p>
  
  <p>I want to cast that string back into a list.</p>
  
  <p>How can I do that?</p>