title: How can I download just thumbnails using youtube-dl?
body: <p>I've been trying to download the thumbnails of a list of URL's (youtube videos) I have.</p>
  
  <p>I've been using youtube-dl and I've worked it out to this so far:</p>
  
  <pre><code>     import os
  
       with open('results.txt') as f:
            for line in f:
                os.system("youtube-dl " + "--write-thumbnail " + line)
  </code></pre>
  
  <p>Like this I'm able to download the thumbnails but I'm forced to downloading the youtube videos as well.</p>
  
  <p>How can I just download the thumbnail?</p>