title: How to sort a list of tuples according to another list
body: <p>There is a list:</p>
  
  <pre><code>a = [("ax", 1), ("ec", 3), ("bk", 5)]
  </code></pre>
  
  <p>another list: </p>
  
  <pre><code>b = ["ec", "ax", "bk"]
  </code></pre>
  
  <p>I want to sort <code>a</code> according to <code>b</code>:</p>
  
  <pre><code>sort_it(a, b)
  
  a = [("ec", 3), ("ax", 1), ("bk", 5)]
  </code></pre>
  
  <p>How to do this?</p>