Python script that collects data about your AWS VPCs. This can be used to determine if you have VPCs that are no longer used.

scan-vpcs.py

import boto3
import sys
import csv
import ipaddress

def describe_regions(session):
    try:
        aws_regions = []
        ec2_client = session.client('ec2')
        response_regions = ec2_client.describe_regions()['Regions']
        for region in response_regions:
            aws_regions.append(region['RegionName'])
        return aws_regions
    except Exception:
        print("Unexpected error:", sys.exc_info()[0])


def describe_vpc(ec2,aws_region,writer):
    try:
        response_vpc = ec2.describe_vpcs()['Vpcs']
        for vpc in response_vpc:
            print('=' * 50)
            count = 0
            filters = [
                {'Name': 'vpc-id',
                'Values': [vpc['VpcId']]}
            ]

            response_subnets = ec2.describe_subnets(Filters=filters)['Subnets']

            for subnets in response_subnets:
                count += 1
                total_count = (ipaddress.ip_network(subnets['CidrBlock']).num_addresses) - 5
                Used_IP = total_count - subnets['AvailableIpAddressCount']
                writer.writerow({"VpcId": vpc['VpcId'], "VpcCidr": vpc['CidrBlock'], "Region": aws_region,
                            "Subnet": subnets['CidrBlock'], "SubnetId": subnets['SubnetId'], "AvailableIPv4": subnets['AvailableIpAddressCount'], "Total_Network_IP": str(total_count),
                            "AvailabilityZone": subnets['AvailabilityZone'],"Used_IP": str(Used_IP)})
                print({"VpcId": vpc['VpcId'], "VpcCidr": vpc['CidrBlock'], "Region": aws_region,
                            "Subnet": subnets['CidrBlock'], "SubnetId": subnets['SubnetId'], "AvailableIPv4": subnets['AvailableIpAddressCount'], "Total_Network_IP": str(total_count),
                            "AvailabilityZone": subnets['AvailabilityZone'],"Used_IP": str(Used_IP)})
            print('='*50)
    except Exception:
        print("Unexpected error:", sys.exc_info()[0])


def main():
    try:

          session = boto3.session.Session()
          file_name = "results"
          print("File Name: " +file_name)
          with open(file_name + ".csv", "w", newline="") as csvfile:
              fieldnames = [
                  "Account", "VpcId",
                  "VpcCidr", "Region",
                  "Subnet", "SubnetId",
                  "AvailableIPv4","Total_Network_IP",
                  "AvailabilityZone","Used_IP"
              ]
              writer = csv.DictWriter(csvfile, fieldnames=fieldnames)
              writer.writeheader()
              aws_regions = describe_regions(session)
              for aws_region in aws_regions:
                  ec2 = session.client('ec2', region_name=aws_region)
                  print("Scanning region: {}".format(aws_region))
                  describe_vpc(ec2,aws_region, writer)

    except Exception:
        print("Unexpected error:", sys.exc_info()[0])
        raise


if __name__ == "__main__":
    main()