title: Download huge number of files in chunks
body: <p>I'm trying to download a bunch (some thousands) of files using Python Selenium in Firefox by giving an input list. I'm downloading successfully. </p>
  
  <p>Since there are thousands of files I want to download, I was wondering if you could suggest a way to start downloading 10 files, wait until they are completed and start next 10. How can I do that?</p>
  
  <p>I tried <code>fp.set_preference("browser.download.manager.closeWhenDone", True)</code> to close the browser after download finishes. But it doesn't close. </p>