headers['User-Agent'] = (
    """Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.17 (KHTML, like Gecko) Chrome/24.0.1312.27 Safari/537.17"""
    )
r = requests.get(
    'http://www.google.com/searchbyimage?image_url=http://i.imgur.com/j3shP.jpg'
    , headers=headers)
Sending GET requests for a Google reverse image search