List all folder and size within a s3 bucket

s3-get-folder-size.py

import boto3
import sys
import decimal


def main():
    bucket = sys.argv[1]
    client = boto3.client('s3')
    result = client.list_objects_v2(Bucket=bucket, Delimiter='/')
    for o in result.get('CommonPrefixes'):
        sub_prefix = o.get('Prefix')
        objects = client.list_objects_v2(Bucket=bucket, Prefix=sub_prefix)
        totalSize = sum(obj['Size'] for obj in objects['Contents'])
        print(
            sub_prefix[:-1] + ': {:.3f} MB'.format(decimal.Decimal(
                totalSize)/decimal.Decimal(1024)/decimal.Decimal(1024)))


if __name__ == "__main__":
    try:
        main()
    except Exception as error:
        print('Error occurred. Please make sure that: \n - You have sys, decimal & boto3 lib installed. \n - You pass your bucket name in the parameter list. E.g. python3 s3-get-folder-size.py my-bucket\n')
        print('***Error detail:')
        raise error