list_unused_security_groups.py

#!/usr/bin/env python

import boto3


ec2 = boto3.resource('ec2')


FMT = '{sg.group_id},{sg.group_name},"{sg.description}"'


def unused_security_groups():
    sgs_in_use = set(
        sg['GroupId']
        for instance in ec2.instances.all()
        for sg in instance.security_groups)
    unused_sgs = (sg for sg in ec2.security_groups.all() if sg.id not in sgs_in_use)
    return unused_sgs


def main():
    for sg in unused_security_groups():
        print(FMT.format(sg=sg))


if __name__ == '__main__':
    main()