url_update.py

# Do this to update URL documents (assuming you already have url_dic and all other lists and dicts)

for user in collection.find():
    for tweet in user['tweets']:        
        urls = tweet['urls']
        for url in urls:
            
            url_string = url['url']             # DO NOT FORGET THIS. url is the url OBJECT, not the url string
            
            if url_string in short_urls:
    			long_url = url_dic[url_string]
			else:
			    long_url = url_string
            domain = get_url_domain(url_string)
            affiliation = get_url_affilation(url_string)
            
            url['resolved_url'] = long_url
            url['domain'] = domain
            url['affiliation'] = affiliation
        
        collection.update(
            {"id": user['id'], "tweets.id": tweet['id']}, 
            {"$set": {"tweets.$.urls": urls}}
            )