Python unique followers count calc

gistfile1.py

import sys
import tweepy

CONSUMER_SECRET = 'xx'
CONSUMER_KEY = 'xx'

# Run this code first to get your auth keys from Twitter
# auth_url = auth.get_authorization_url()
#
# print 'Please authorise: ' + auth_url
# verifier = raw_input('PIN: ').strip()
# auth.get_access_token(verifier)
#
# print "ACCESS_KEY = '%s'" % auth.access_token.key
# print "ACCESS_SECRET = '%s'" % auth.access_token.secret

ACCESS_KEY = 'xxx
ACCESS_SECRET = 'xxx'

auth = tweepy.OAuthHandler(CONSUMER_KEY, CONSUMER_SECRET)
auth.set_access_token(ACCESS_KEY, ACCESS_SECRET)
api = tweepy.API(auth)

status_id = 198348823318380544
status = api.get_status(status_id)

print "Searching against status %(id)d: %(text)s" % {'id': status_id, 'text': status.text}
retweets = status.retweets()

witnesses = []
witness_count = 0

for tweet in retweets: 
  retweeter = tweet.user
  followers = api.followers(retweeter.screen_name)
  witness_count += retweeter.followers_count
  print "%(user)s has %(followers)d followers..." % {'user': retweeter.screen_name, 'followers': retweeter.followers_count}

  for follower in retweeter.friends():
    witnesses.append(follower.screen_name)

witnesses_set = set(witnesses)
unique_witnesses = list(witnesses_set)

print "---"
print "Total %d followers" % witness_count
print "Unique witness count: %d" % len(unique_witnesses)