python lambda function to detect empty s3 buckets

empty-s3-bucket.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import json
import boto3

s3 = boto3.client('s3')


# creates a generator for files in bucket, this is a fast approach is not reading each object name.
def keys(bucket_name, prefix='/', delimiter='/'):
    prefix = prefix[1:] if prefix.startswith(delimiter) else prefix
    bucket = boto3.resource('s3').Bucket(bucket_name)
    return (_.key for _ in bucket.objects.filter(Prefix=prefix))


def lambda_handler(event, context):
    # Call S3 to list current buckets
    response = s3.list_buckets()
    # Get a list of all bucket names from the response
    buckets = [bucket['Name'] for bucket in response['Buckets']]
    # Print out the bucket list
    print(f"Bucket List: {buckets}")
    for bucket in buckets:
        _exhausted = object()
        try:
            if next(keys(bucket), _exhausted) == _exhausted:
                print(f"{bucket}: generator is empty")
        except Exception as e:
            print(f"Error: {bucket} - {e}")
    return {
        'body': json.dumps(f"Scanned {len(buckets)} buckets")
}