determine how many bytes of storage are used in all S3 buckets in account

bktsize.py

#!/usr/bin/env python3

from datetime import datetime, timedelta
import sys

import boto3

cloudwatch = boto3.client('cloudwatch')
paginator = cloudwatch.get_paginator('list_metrics')
s3 = boto3.client("s3")

buckets = s3.list_buckets()['Buckets']
buckets = [x['Name'] for x in buckets]

total = 0

for bucket_name in buckets:
    if not bucket_name.startswith("fh-pi-"):
        continue
    cloudwatch = boto3.client('cloudwatch')
    response = cloudwatch.get_metric_statistics(
        Namespace="AWS/S3",
        MetricName="BucketSizeBytes",
        Dimensions=[
            {
                "Name": "BucketName",
                "Value": bucket_name
            },
            {
                "Name": "StorageType",
                "Value":  "StandardStorage"
            }
        ],
        StartTime=datetime.now() - timedelta(days=1),
        EndTime=datetime.now(),
        Period=86400,
        Statistics=['Average']
    )

    if not response['Datapoints']:
        print("NO DATAPOINTS FOR {}".format(bucket_name))
        continue
    bucket_size_bytes = response['Datapoints'][-1]['Average']
    total += bucket_size_bytes
    print("{} has {} bytes".format(bucket_name, bucket_size_bytes))

print("total is {}".format(total))