An AWS lambda_function that will stop running ec2 instances when triggered.

lambda_function.py

import json
import boto3
import logging
from botocore.exceptions import ClientError

ec2 = boto3.client('ec2')
logger = logging.getLogger()
logger.setLevel(logging.INFO)
send_sns = False

def lambda_handler(event, context):
    global send_sns
    logger.info('Function {} has started execution.'.format(context.function_name))
    # Collect Instance ids for running instances
    response = ec2.describe_instances()
    ids = []
    for i in response['Reservations']:
        if i['Instances'][0]['State']['Name'] == 'running':
            ids.append(i['Instances'][0]['InstanceId'])

    # Stop running instances
    if ids:
        try:
            ec2.stop_instances(InstanceIds=ids, DryRun=False)
            logger.info('Function {} has successfully executed.'.format(context.function_name))
            send_sns = True
        except ClientError as e:
            logger.info('Function {} has failed.'.format(context.function_name))
            print(e)
    else:
        logger.info('function {} could not find any running instances.'.format(context.function_name))

    # Send SNS Email
    if send_sns:
        sns = boto3.client('sns')
        arn = 'YOUR SNS ARN'
        notification = f'{len(ids)} of your EC2 instances with the following Instance ids have been successfully shutdown: {ids}'

        response = sns.publish(
            TargetArn=arn,
            Message=json.dumps({'default': notification}),
            MessageStructure='json'
        )
        return {
    'statusCode': 200,
    'body': json.dumps(response)
        }