Tweepy - Unfollow people don't follow you back

unfollow.py

#! /usr/bin/env python

# Based on Jamieson Becker's unfollow script http://pastebin.com/CxUDMtMi
# Python 3 compatible.

import time
import tweepy
import sys

auth = tweepy.auth.OAuthHandler(
        consumer_key='APITOKEN',
        consumer_secret='APITOKEN_SECRET')
auth.set_access_token(
        'ACCESS_TOKEN',
        'ACCESS_TOKEN_SECRET')

api = tweepy.API(auth_handler=auth, wait_on_rate_limit=True, wait_on_rate_limit_notify=True)

print("Loading followers..")
followers = api.followers_ids("USERNAME")

print("Found %s followers, finding friends.." % len(followers))
following = api.friends_ids("USERNAME")


no_followers = set(following) - set(followers)
total_unfollowed = 0

print("Unfollowing %s people who don't follow you back" % len(no_followers))
print("This will take approximately %s minutes." % (len(no_followers) / 60.0))
answer = input("Are you sure? [Y/n]").lower()
if answer and answer[0] != "y":
    sys.exit(1)

for nf in no_followers:
    print("Unfollowing %s" % nf)
    try:
        api.destroy_friendship(nf)
        total_unfollowed += 1
    except (tweepy.RateLimitError, tweepy.TweepError) as e:
        print(e)
    print(" .. completed, sleeping for 1 second.")
    time.sleep(1)

print(str(total_unfollowed) + 'Unfollowed')