How can I unshorten a URL?

Question

I want to be able to take a shortened or non-shortened URL and return its un-shortened form. How can I make a python program to do this?

Additional Clarification:

Answer 1

Using requests:

import requests

session = requests.Session()  # so connections are recycled
resp = session.head(url, allow_redirects=True)
print(resp.url)