title: Using list comprehension to get count of all files in multiple sub directories
body: <p>I have a folder which contains multiple sub directories, each of those containing several files. I would like to get the sum total of all files in all sub directories. The following list comprehension works quite well:</p>
  
  <pre><code>sum_total = len([file for file in os.listdir(current_directory)])
  </code></pre>
  
  <p>How would I modify this to include counting all files in all sub directories (not just the current_directory)? Or do I have to use a traditional for loop and counter? Is there something similar to the following that I could use?</p>
  
  <pre><code>sum_total = len([file in os.listdir(current_directory + '\\' + folder) for folder in os.listdir(current_directory)])
  </code></pre>