AWS Lambda function for deleting files from S3 bucket, filename contains timestamp. Clean up for everything older then 7 days. Triggered once a week by a CloudWatch Event.

cleanup_s3_policy.py

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

def lambda_handler(event, context):
    # Set up logging
    logging.basicConfig(level=logging.DEBUG,
                        format='%(levelname)s: %(asctime)s: %(message)s')
                        
    bucket_name = 'bucket_name'
    s3 = boto3.client('s3')
    
    objects = list_bucket_objects(bucket_name)
    if objects is not None:
        # List the object names
        logging.info(f'Objects in {bucket_name}')
        count = len(objects)
        print(f'Backup count: {count}')
        last = '0'
        
        for obj in objects:
            if count <= 56: # For not deleting from the last 7 days! (Backup every 3 hours per day, 24/3 * 7 = 56) 
                return True
                
            count = count - 1 # For not deleting from the last 7 days!  
            print(f'{count}')    
            
            # Start Policy for everything older then one week
            date = obj["Key"].replace('prefix_before_time', '')
            dateArray = date.split("T")
            date = dateArray[0]
            hour = dateArray[1].split(":")[0]
            print(f'  {date} - {hour}')

            if last == '0':
                last = date
                print(f'last==0')
            elif last == date:
                print(f'delete: {obj["Key"]}')
                try:
                    s3.delete_object(Bucket=bucket_name, Key='prefix' + obj["Key"])
                except ClientError as e:
                    logging.error(e)
            else:
                print(f'last = {obj["Key"]}')
                last = date
    return True

def list_bucket_objects(bucket_name):
    # Retrieve the list of bucket objects
    s3 = boto3.client('s3')
    try:
        response = s3.list_objects_v2(Bucket=bucket_name)
    except ClientError as e:
        logging.error(e)
        return None
    return response['Contents']

hmmm.... Line 30.... "date = obj["Key"].replace('prefix_before_time', '')" Why are we assuming that the key of the object contains the date?

Well it does say that in the script description "AWS Lambda function for deleting files from S3 bucket, filename contains timestamp"