Hack to fetch all bucket sizes in S3

s3size.py

from datetime import timedelta, datetime
import math
import boto3

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

def get_bucket_size(bucket):
    try:
        return cloudwatch.get_metric_statistics(
            Namespace='AWS/S3', MetricName='BucketSizeBytes',
            StartTime=datetime.utcnow() - timedelta(days=2) ,
            EndTime=datetime.utcnow(), Period=86400,
            Statistics=['Average'], Unit='Bytes',
            Dimensions=[
                {'Name': 'BucketName', 'Value': bucket},
                {u'Name': 'StorageType', u'Value': 'StandardStorage'}
            ])['Datapoints'][0]['Average']
    except IndexError:
        return 0

def convertSize(size):
    if size == 0:
        return '0B'
    size_name = ("B", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB")
    i = int(math.floor(math.log(size,1024)))
    p = math.pow(1024,i)
    s = round(size/p,2)
    if (s > 0):
        return '%s %s' % (s,size_name[i])
    else:
        return '0B'

buckets = list(s3.buckets.all())
for bucket in buckets:
    print bucket.name, convertSize(get_bucket_size(bucket.name))