Organizationsでアカウント作成し、デフォルトVPCを削除するためのLambda関数を記載
import boto3
import os
import logging
import time
from datetime import datetime

region = os.environ.get("AWS_REGION", "ap-northeast-1")
logs_client = boto3.client('logs', region_name=region)
logger = logging.getLogger()
logger.setLevel(logging.INFO)

formatter = logging.Formatter('[%(levelname)s] - %(message)s')
handler = logging.StreamHandler()
handler.setFormatter(formatter)
logger.handlers.clear()
logger.addHandler(handler)

# CloudWatchログに特定のキーワードが出力されたか確認
def confirm_log_written(log_group_name, log_stream_name, keyword="CloudWatch Logs Output Check"):
    logger.info(f"{keyword}")

    for _ in range(5):
        try:
            events = logs_client.get_log_events(
                logGroupName=log_group_name,
                logStreamName=log_stream_name,
                startFromHead=True
            )['events']

            messages = [e['message'] for e in events]
            if any(keyword in m for m in messages):
                logger.info("CloudWatch Logs Output OK")
                return True

            time.sleep(2)
        except logs_client.exceptions.ResourceNotFoundException:
            time.sleep(2)
        except Exception as e:
            logger.error("Log Write Failed", exc_info=True)
            return False

    return False

# 指定アカウントのIAMロールを引き受けて一時クレデンシャルを取得
def assume_role(account_id):
    sts = boto3.client('sts')
    role_arn = f"arn:aws:iam::{account_id}:role/OrganizationAccountAccessRole"
    creds = sts.assume_role(RoleArn=role_arn, RoleSessionName='delete-vpc-session')['Credentials']
    return creds

# 指定アカウントで利用可能なEC2リージョンを取得
def get_regions(account_id):
    creds = assume_role(account_id)
    ec2 = boto3.client(
        "ec2",
        aws_access_key_id=creds["AccessKeyId"],
        aws_secret_access_key=creds["SecretAccessKey"],
        aws_session_token=creds["SessionToken"]
    )
    regions = ec2.describe_regions()["Regions"]
    region_names = []
    for region in regions:
        region_names.append(region["RegionName"])
    return region_names

# 指定VPCに関連付けられているサブネットを削除
def delete_subnets(ec2, vpc_id, region_name):
    try:
        subnets = ec2.describe_subnets(Filters=[{'Name': 'vpc-id', 'Values': [vpc_id]}])['Subnets']
        for subnet in subnets:
            subnet_id = subnet['SubnetId']
            ec2.delete_subnet(SubnetId=subnet_id)
            logger.info(f"Deleted Subnet: {subnet_id} in {region_name}")
    except Exception as e:
        logger.error(f"Failed to delete subnets for VPC {vpc_id} in {region_name}: {e}")
        raise

# 指定VPCに関連付けられているインターネットゲートウェイをデタッチして削除
def detach_and_delete_igws(ec2, vpc_id, region_name):
    try:
        igws = ec2.describe_internet_gateways(Filters=[{'Name': 'attachment.vpc-id', 'Values': [vpc_id]}])['InternetGateways']
        for igw in igws:
            igw_id = igw['InternetGatewayId']
            ec2.detach_internet_gateway(InternetGatewayId=igw_id, VpcId=vpc_id)
            ec2.delete_internet_gateway(InternetGatewayId=igw_id)
            logger.info(f"Detached and Deleted Internet Gateway: {igw_id} in {region_name}")
    except Exception as e:
        logger.error(f"Failed to delete internet gateways for VPC {vpc_id} in {region_name}: {e}")
        raise

# 各リージョンでデフォルトVPCを検出し、関連リソースを削除後にVPCを削除
def delete_default_vpcs(account_id, regions):
    creds = assume_role(account_id)
    for region_name in regions:
        ec2 = boto3.client(
            'ec2',
            region_name=region_name,
            aws_access_key_id=creds['AccessKeyId'],
            aws_secret_access_key=creds['SecretAccessKey'],
            aws_session_token=creds['SessionToken']
        )
        try:
            vpcs = ec2.describe_vpcs(Filters=[{"Name": "isDefault", "Values": ["true"]}])['Vpcs']
            if vpcs:
                vpc_id = vpcs[0]['VpcId']
                logger.info(f"Default VPC found in {region_name}: {vpc_id}")
                delete_subnets(ec2, vpc_id, region_name)
                detach_and_delete_igws(ec2, vpc_id, region_name)
                ec2.delete_vpc(VpcId=vpc_id)
                logger.info(f"Deleted default VPC in {region_name}")
            else:
                logger.info(f"Default VPC does not exist in {region_name}")
        except Exception as e:
            logger.error(f"{account_id} - Failed to delete default VPC in {region_name}: {e}")
            raise

# Lambda関数のエントリポイント
def lambda_handler(event, context):
    # ログストリーム名取得
    log_stream_name = context.log_stream_name
    # CloudWatch Logs にログが出力されたか確認
    if not confirm_log_written(context.log_group_name, log_stream_name):
        return {
            "status": "error",
            "message": "CloudWatch Logs output not found",
            "logname": f"{log_stream_name}"
        }

    # イベントからアカウントIDを取得し、フォーマットチェック
    try:
        logger.info("Input argument Check")
        account_id = event.get('account_id')
        if not account_id or not account_id.isdigit() or len(account_id) != 12:
            raise ValueError('Invalid input argument')
        logger.info("Input argument is valid")
    except ValueError as e:
        logger.error(f"{account_id} - {e}")
        return {
            "status": "error",
            "error_code": "401",
            "message": "Invalid input argument",
            "logname": f"{log_stream_name}"
        }
    except Exception as e:
        logger.error(f"{account_id} - Error occurred during input validation: {e}")
        return {
            "status": "error",
            "message": f"Error occurred during input validation: {e}",
            "logname": f"{log_stream_name}"
        }

    # 全リージョンを取得
    try:
        regions = get_regions(account_id)
    except Exception as e:
        logger.error(f"{account_id} - Failed to retrieve regions: {e}")
        return {
            "status": "error",
            "message": "Failed to retrieve regions",
            "logname": f"{log_stream_name}"
        }

    # 全リージョンでデフォルトVPCを削除
    try:
        delete_default_vpcs(account_id, regions)
        logger.info(f"{account_id} - Lambda executed successfully: Default VPC deleted")
    except Exception as e:
        return {
            "status": "error",
            "error_code": "401",
            "message": f"Failed to delete default VPCs: {e}",
            "logname": f"{log_stream_name}"
        }

    return {
        "status": "success",
        "message": "Default VPCs deleted successfully",
        "logname": f"{log_stream_name}"
    }