import boto3


def all_users():
    iam = boto3.client('iam')

    paginator = iam.get_paginator('list_users')

    for response in paginator.paginate():
        for user in response['Users']:
            username = user['UserName']
            Arn = user['Arn']
            print('Username : {} Arn : {}'.format(username, Arn))


all_users()