import boto3
import csv

client = boto3.client('rds')

response = client.describe_db_instances()
instances = response['DBInstances']
instances_arns = []

for each_instance in instances:
    instances_arns.append({'DBInstanceArn': each_instance['DBInstanceArn']})

for each_instance in instances_arns:
    response = client.list_tags_for_resource(
    ResourceName=each_instance['DBInstanceArn'])
    tags = response['TagList']
    for each_tag in tags:
        if each_tag['Key'] == 'terraformed':
            each_instance['terraformed'] = each_tag['Value']
        if each_tag['Key'] == 'application_family':
            each_instance['application_family'] = each_tag['Value']

columns = ['DBInstanceArn',  'terraformed', 'application_family']
with open('rds_resources.csv', 'w') as csvfile:
    writer = csv.DictWriter(csvfile, fieldnames=columns)
    writer.writeheader()
    writer.writerows(instances_arns)