title: only download new files (wget -N) in python
body: <p>I am trying to use a python package to download new files. All I can do is download like</p>
  
  <pre><code>outdir = ""
  url = ""
  filename = wget.download(url, out=outdir)
  </code></pre>
  
  <p>but how can I tell wget to only download new files?
  In the command line I did it with </p>
  
  <pre><code>wget -N url
  </code></pre>
  
  <p>which only downloads the new files. The python package wget does not seem to have any equivalent to the -N flag? 
  Does anybody know whether there is a way to do this with wget for python or is there another python package which can do that?</p>