Code to go with http://blog.macuyiko.com/post/2017/cleaning-up-a-gmail-inbox.html
First run fill_database.py to fill / update the emails database. Warning: this will take a while with a large inbox, due to the Gmail API being limited in its list() and get() calls (feel free to let me know if there's a way to speed this up).
Next, use the flask_app.py to start cleaning.
You'll need to create a Gmail API in your Google API console and obtain the client_secret JSON file.