Stop AWS instances with matching tags

myscript.py

#!/usr/bin/env python3
# Assumes you have Python 3 and boto3 installed in your [virtual]env
# Assumes we are taking positional parameters (this script could be longer with argparse)
# Assumes you have AWS_PROFILE and AWS_DEFAULT_REGION set and credentials are valid and not expired at ~/.aws/credentials

import boto3
import json
from sys import argv, exit

if len(argv) != 3:
    print("This script takes exactly two arguments, tag name and value")
    exit(1)

client = boto3.client("ec2")


def filter_hosts(tag_name, tag_value):
    response = client.describe_instances(
        Filters=[
            {
                "Name": f"tag:{tag_name}",
                "Values": [tag_value],
            },
            {
                "Name": "instance-state-name",
                "Values": ["running"],
            },
        ],
        MaxResults=1000,
    )

    try:
        instance_data = []
        for reservation in response["Reservations"]:
            instance_data.append(reservation["Instances"][0])
        return instance_data
    except IndexError:
        print("No matches for given tags")
        return None


def stop_instances(instances):
    for instance in instances:
        instance_id = instance["InstanceId"]
        private_ip_address = instance["PrivateIpAddress"]
        image_id = instance["ImageId"]
        try:
            client.stop_instances(
                InstanceIds=[
                    instance_id,
                ]
            )

            print(
                json.dumps(
                    {
                        "instance_id": instance_id,
                        "private_ip_address": private_ip_address,
                        "image_id": image_id,
                    }
                )
            )
        except:
            print(f"Stopping instance {instance_id} has failed")


def main(tag_name, tag_value):
    instances = filter_hosts(tag_name, tag_value)
    stop_instances(instances)


if __name__ == "__main__":
    tag_name = argv[1]
    tag_value = argv[2]
    main(tag_name, tag_value)