Code:
img=requests.get('http:////files.explosm.net/comics/Rob/chainsaw.png')
Error Message:
requests.exceptions.InvalidURL: Invalid URL u'http://files.explosm.net/comics/Rob/chainsaw.png': No host supplied
What's wrong with the url? files.explosm.net/comics/Rob/chainsaw.png
You have a few too many '/'s in the URL:
Hope that helps.