make_all_public.py

import boto3
client = boto3.client('s3')
s3 = boto3.resource('s3')

paginator = client.get_paginator('list_objects')

count = 0
for page in paginator.paginate(Bucket='data.example', Prefix='images', MaxKeys=10000):
    for key in page['Contents']:
        object_acl = s3.ObjectAcl('data.example', key['Key'])
        object_acl.put(ACL='public-read')
        count += 1

print(count)