This script based on the .json data files provided by Instagram creates a file called noback.txt that gives you the list of all the people who don't follow you back.
First of all create a new directory and place inside that directory the main.py script and the files provided in the data JSON files downloaded from Instagram which can be found inside the folder "followers_and_following" renamed to following.json and followers.json.
Navigate to the script directory and run:
python3 main.pyThe script will create two outputs: following.txt and followers.txt files which you consult to get a .txt following or followers list and then the most important output which is the noback.txt that contains all the usernames of the people that don't follow you back.