title: Python - ValueError: unknown url type
body: <p>I'm trying to extract sources from <code>&lt;iframes&gt;</code> attributes like these:</p>
  
  <pre><code>   iframes =  [&lt;iframe frameborder="no" height="160px" scrolling="no" src="https://w.soundcloud.com/player/?url=https%3A//api.soundcloud.com/tracks/308197184%3Fsecret_token%3Ds-VtArH&amp;amp;auto_play=false&amp;amp;hide_related=false&amp;amp;show_comments=true&amp;amp;show_user=true&amp;amp;show_reposts=false&amp;amp;visual=true" width="100%"&gt;&lt;/iframe&gt;, &lt;iframe allowtransparency="true" frameborder="0" scrolling="no" src="//www.facebook.com/plugins/likebox.php?href=https%3A%2F%2Fwww.facebook.com%2FPauseMusicale&amp;amp;width=300&amp;amp;height=62&amp;amp;show_faces=false&amp;amp;colorscheme=light&amp;amp;stream=false&amp;amp;show_border=false&amp;amp;header=false" style="border:none; overflow:hidden; width:300px; height:62px;"&gt;&lt;/iframe&gt;, &lt;iframe allowfullscreen="" frameborder="0" height="169" src="//www.youtube.com/embed/videoseries?list=PLNKCTdT9YSESoQnj5tPP4P9kaIwBCx7F1" width="100%"&gt;&lt;/iframe&gt;]
  </code></pre>
  
  <p>but when I try to extract it:</p>
  
  <pre><code>for iframe in iframes:
      url = urllib2.urlopen(iframe.attrs['src'])
      print (url)
  </code></pre>
  
  <p>I get the following error:</p>
  
  <pre><code>   url = urllib2.urlopen(iframe.attrs['src'])
    File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 154, in urlopen
      return opener.open(url, data, timeout)
    File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 423, in open
      protocol = req.get_type()
    File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib2.py", line 285, in get_type
      raise ValueError, "unknown url type: %s" % self.__original
  ValueError: unknown url type: //www.facebook.com/plugins/likebox.php?href=https%3A%2F%2Fwww.facebook.com%2FPauseMusicale&amp;width=300&amp;height=62&amp;show_faces=false&amp;colorscheme=light&amp;stream=false&amp;show_border=false&amp;header=false
  </code></pre>
  
  <p>why am I getting url with no <code>http</code> before the <code>//www</code>?</p>
  
  <p>Is there some workaround this?</p>