import boto3

s3 = boto3.resource('s3')

def human_size(bytes, units=[' bytes','KB','MB','GB','TB', 'PB', 'EB']):
    return str(bytes) + units[0] if bytes < 1024 else human_size(bytes>>10, units[1:])

def get_bucket_size(balde):
    bucket = s3.Bucket(balde)
    total_size = 0
    for k in bucket.objects.all():
        total_size += k.size
    return total_size


for bucket in s3.buckets.all():
    bucket_size = human_size(get_bucket_size(bucket.name))
    print('%s: %s' % (bucket.name, bucket_size))