title: Non-alphanumeric list order from os.listdir()
body: <p>I often use python to process directories of data. Recently, I have noticed that the default order of the lists has changed to something almost nonsensical. For example, if I am in a current directory containing the following subdirectories: run01, run02, ... run19, run20, and then I generate a list from the following command:</p>
  
  <pre><code>dir = os.listdir(os.getcwd())
  </code></pre>
  
  <p>then I usually get a list in this order:</p>
  
  <pre><code>dir = ['run01', 'run18', 'run14', 'run13', 'run12', 'run11', 'run08', ... ]
  </code></pre>
  
  <p>and so on. The order used to be alphanumeric. But this new order has remained with me for a while now.</p>
  
  <p>What is determining the (displayed) order of these lists?</p>