title: Unknown python expression filename=r'/path/to/file'
body: <p>I found this potentially very useful python <a href="http://quickscriptfixes.blogspot.co.uk/" rel="noreferrer">script</a>, but came across these expressions which I've never seen before:</p>
  
  <pre><code>inputfilename = r'/path/to/infile'
  outputfilename = r'/path/to/outfile'
  </code></pre>
  
  <p>I can't find a way to search for it. what does the <code>r'...'</code> do?</p>
  
  <p>Thanks for your help!</p>