import boto3
import datetime

s3_client = boto3.client('s3')
# ファイルを残す日数
retention_period = 2
# S3バケット名
bucket_name = 'bucket_name'
# プレフィックスリスト
prefix_list = ['aaa/', 'bbb/', 'ccc/']

###################################################################
# Handler
###################################################################
def lambda_handler(event, context):

    deleteFiles(bucket_name, False)

###################################################################
# Delete Files
###################################################################
def deleteFiles(bucket_name, dryrun=False):

    next_token = ''

    for prefix_name in prefix_list:
        while True:
            if next_token == '':
                response = s3_client.list_objects_v2(Bucket=bucket_name, Prefix=prefix_name)
            else:
                response = s3_client.list_objects_v2(Bucket=bucket_name, Prefix=prefix_name, ContinuationToken=next_token)

            if 'Contents' in response:
                contents = response['Contents']

                for content in contents:
                    obj = s3_client.get_object(Bucket=bucket_name, Key=content['Key'])
                    if prefix_name != content['Key'] : # プレフィックス（フォルダ）自体は削除対象から除外
                        gap = datetime.datetime.now(datetime.timezone.utc) - obj['LastModified']
                        if gap.days >= retention_period: #指定した日数以上のデータを削除対象とする
                            if not dryrun:
                                print("Deleting: s3://" + bucket_name + "/" + content['Key'])
                                s3_client.delete_object(Bucket=bucket_name, Key=content['Key'])
                            else:
                                print("DryRun: s3://" + bucket_name + "/" + content['Key'])

            if 'NextContinuationToken' in response:
                next_token = response['NextContinuationToken']
            else:
                break