title: How to add files to a ZIP archive without deleting everything in it
body: <p>So, whenever I'd add a file to the ZIP archive, it would paste it in, but delete everything previously added.
  Example: 
  <code>
  zf = zipfile.ZipFile(os.getenv('localappdata') + '/test.zip')</code>
  <code>
  zf.write(os.getenv('appdata') + '/test.txt')</code></p>
  
  <p>Like I said, it would paste the test.txt and delete everything else in the .zip</p>