AWS Lamdba python 3.8 script that automatically adds public Cache-Control for 1 year. don't forget to grant iam permission and s3 event trigger.

lambda-s3-auto-add-cache-control-header

import json
import boto3
from botocore.exceptions import ClientError


def lambda_handler(event, context):
    bucket_name =  event['Records'][0]['s3']['bucket']['name']
    s3_file = event['Records'][0]['s3']['object']['key']
    print(bucket_name, s3_file)
    s3 = boto3.client('s3')
    try:
        t = s3.copy_object(Key=s3_file, Bucket=bucket_name,
               CopySource={"Bucket": bucket_name, "Key": s3_file},
               CacheControl="max-age=31536000, public",
               MetadataDirective="REPLACE")
        print(t)
    except ClientError as e:
        raise(e)
    lambda_output = {'status': 200}
    return lambda_output