title: Python - order list of lists by multiple column indexes
body: <p>Let's say I've the following list x in Python</p>
  
  <pre><code>[['a',6,'aa']
  ['d',7,'bb']]
  ['c',1,'cc']
  ['a',4,'dd']
  ['d',2,'ee']]
  </code></pre>
  
  <p>and I want to sort its elements in order to obtain the following result</p>
  
  <pre><code>[['a',4,'dd']
  ['a',6,'aa']
  ['c',1,'cc']
  ['d',2,'ee']
  ['d',7,'bb']]
  </code></pre>
  
  <p>that is I want to sort it by two columns, the first one (the most important) and the second one (the less important). This is probably a duplicate question but I haven't been able to find the solution...</p>