stop-running-instances.py

import boto3
import pprint

def lambda_handler(event, context):
    ec2 = boto3.client('ec2')
    resp = ec2.describe_instances(
        Filters=[
            {
                'Name': 'instance-state-name',
                'Values': [
                    'running'
                ]
            }
        ]
    )

    for reservation in resp['Reservations']:
        pprint.pprint('stopping ' + reservation['Instances'][0]['InstanceId'])
        ec2.stop_instances(InstanceIds=[reservation['Instances'][0]['InstanceId']])