How to get redirect url?

I am using urllib.request to perform a sequence of http calls in python 3.6. I need to retrieve the value of a 302 http redirect that is returned in response to a urllib.request.urlopen call like so...

import urllib.request

... many previous http calls ...

post_data = {'foo': 'bar', 'some': 'otherdata'}
encoded = urllib.parse.urlencode(post_data).encode('utf-8')
req = urllib.request.Request('https://some-url', encoded)
redirected_url = urllib.request.urlopen(req).geturl()

I get an error like...

urllib.error.HTTPError: HTTP Error 302: Found - Redirection to url 'gibberish://login_callback?code=ABCD......' is not allowed

What I need is to actually get the url that is being returned in the 302 as the .geturl() method should provide, but instead I get an error.

Please no answers like "Hey use this other library that I'm super into right now" as we've spent a long time building this script using urllib2 and we have very little python knowledge.

Thanks for your help.

Solution

If you dont want to use the requests library (which is almost part of the core libs at this point), you need to write a custom HTTPRedirectHandler using urllib2.

import urllib2

class CustomHTTPRedirectHandler(urllib2.HTTPRedirectHandler):
    def http_error_302(self, req, fp, code, msg, headers):
        ### DO YOUR STUFF HERE
        return urllib2.HTTPRedirectHandler.http_error_302(self, req, fp, code, msg, headers)

    http_error_301 = http_error_303 = http_error_307 = http_error_302

opener = urllib2.build_opener(CustomHTTPRedirectHandler)
post_data = {'foo': 'bar', 'some': 'otherdata'}
encoded = urllib.parse.urlencode(post_data).encode('utf-8')
req = urllib.request.Request('https://some-url', encoded)
opener.urlopen(req)