Process either S3 event notifications or SNS messages with python in AWS Lambda

lambda_handler.py

import urllib

def lambda_handler(event, context):
    for record in event['Records']:
        try:
            if 'aws:sns' == record['EventSource'] and record['Sns']['Message']:
                record = json.loads(record['Sns']['Message'])['Records'][0]
         except KeyError:
            pass
         bucket = record['s3']['bucket']['name']
         key = urllib.unquote(record['s3']['object']['key'])