title: Optimal solution to extend a python list by adding the at the beginning of the list instead of tail?
body: <p>You have </p>
  
  <pre><code>x = ['a', 'b', 'c']
  y = [1, 2, 3]
  </code></pre>
  
  <p>And want to insert list <code>y</code> at the beginning of <code>x</code>:</p>
  
  <pre><code>x = [1, 2, 3, 'a', 'b', 'c']
  </code></pre>
  
  <p>What is the optimal solution to do this in Python?</p>