url shortener unshortener (resolves url)

url_unshortener.py

# this code handles redirects, failed requests, etc. can be tweaked to return some non-final url as well.

from urllib.parse import urlsplit
import requests
headers = {'headers':'Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:51.0) Gecko/20100101 Firefox/51.0'}
def resolve_url_req(url):
    """ if `url` is redirected returns the new url, otherwise None is returned """
    try:
        r = requests.head(url, headers=headers, allow_redirects=False, timeout=10)
        if r.status_code in [301, 302]:
            location = r.headers.get('Location', None)
            # handle the special case of local redirect
            if location is not None and location.startswith('/'):
                base = "{0.scheme}://{0.netloc}".format(urlsplit(r.url))
                location = base + location
            return location
    except: pass
    return None

def resolve_url(url):
    """ given a `url` traverse the chain of redirects and return the last url it was resolved to, even if it responds with error. This is useful for discovering where url shortners point to, even if the destination no longer exists 
    return: last resolved url (which could be the original url)
    """
    redirect_url = resolve_url_req(url)
    if redirect_url is not None: 
        # add other special cases here:        
        # * for t.co shortner we want the link before the suspension url
        if redirect_url == 'https://twitter.com/account/suspended': return url
        return resolve_url(redirect_url)
    return url

# test run:
urls = [
    'https://t.co/RbbnjkoqUD',
    'https://t.co/VgzGOK5k3S',
    'http://t.co/cIrTVml9Vp',
    'http://t.co/y7sIPKB1kd'
]
for u in urls: resolve_url(u)
#'https://vine.co/v/eHzipDIO5x7'
#'https://twitter.com/OfficialWith1D/status/629090990486237184'
#'https://www.youtube.com/watch?v=NnnSS0_-xoA'
#'https://twitter.com/JoshPainter2154/status/629274422952620033/photo/1'