get_vpc_subnets.py

import argparse
import sys

import boto3

from netaddr import IPNetwork

parser = argparse.ArgumentParser()
parser.add_argument('--vpc-id', required=True)
parser.add_argument('--region', default='us-east-1')

args = parser.parse_args()

client = boto3.client('ec2', region_name=args.region)

subnets = client.describe_subnets(
    Filters=[
        {
            'Name': 'vpc-id',
            'Values': [
                args.vpc_id
            ]
        }
    ]
)

vpc_subnets = subnets['Subnets']
if len(vpc_subnets) == 0:
    sys.exit("Could not find any subnets for VPC {}".format(args.vpc_id))

for vpc_subnet in vpc_subnets:
    try:
        subnet_name = [
            t for t in vpc_subnet['Tags'] if t['Key'] == 'Name'][0]['Value']
    except IndexError:
        subnet_name = "<none>"
    print "\tChoice: {index} -- {subnet_name} - {subnet_id}".format(
        index=vpc_subnets.index(vpc_subnet),
        subnet_name=subnet_name,
        subnet_id=vpc_subnet['SubnetId'])

try:
    choice_input = raw_input
except NameError:
    choice_input = input

choice = choice_input('Choose a subnet (a for all):')

try:
    choice_number = int(choice)
    if (choice_number < 0) or ((choice_number + 1) > len(vpc_subnets)):
        sys.exit("{} not a vaild choice".format(choice))
    vpc_subnets = [vpc_subnets[choice_number]]
except ValueError:
    if choice == "a":
        pass
    else:
        sys.exit("{} not a vaild choice".format(choice))

print "\n"

for vpc_subnet in vpc_subnets:
    try:
        subnet_name = [
            t for t in vpc_subnet['Tags'] if t['Key'] == 'Name'][0]['Value']
    except IndexError:
        subnet_name = "<none>"

    # this list consists of IPAddress objects
    addresses = list(IPNetwork(vpc_subnet['CidrBlock']))
    # clean up first 4 and last 1 (reserved)
    del addresses[0:4]
    del addresses[-1]

    # create a list of strings containing ip addresses
    raw_addresses = [str(i) for i in addresses]

    eni_response = client.describe_network_interfaces(
        Filters=[
            {
                'Name': 'vpc-id',
                'Values': [
                    args.vpc_id,
                ]
            },
            {
                'Name': 'subnet-id',
                'Values': [
                    vpc_subnet['SubnetId']
                ]
            },
        ]
    )
    enis = eni_response['NetworkInterfaces']
    for eni in enis:
        for ip in eni['PrivateIpAddresses']:
            if ip['PrivateIpAddress'] in raw_addresses:
                raw_addresses.remove(ip['PrivateIpAddress'])

    print "\n-----"
    print "Subnet Name: {} - Subnet ID: {} - AZ: {}".format(
        subnet_name,
        vpc_subnet['SubnetId'],
        vpc_subnet['AvailabilityZone']
    )
    print "Available Addresses Count: {}".format(
        vpc_subnet['AvailableIpAddressCount'])

    print "Available Addresses:\n{}".format(', '.join(raw_addresses))
    print "-----\n"