template.py

from cfn_flip import to_yaml
from troposphere import Ref, Template, Select, GetAZs, Output, GetAtt
import troposphere.ec2 as ec2
import troposphere.elasticloadbalancing as lb
import troposphere.autoscaling as asg

t = Template()

def subnet(vpc, i, az, classC, public=True):
    return ec2.Subnet(
        "{0}Subnet{1}".format("Public" if public else "Private", az),
        CidrBlock = "10.{0}.{1}.0/24".format(classC, i),
        MapPublicIpOnLaunch = public,
        VpcId = Ref(vpc),
        AvailabilityZone = Select(az, GetAZs())
    )

vpc = ec2.VPC(
    "VPC",
    CidrBlock = "10.0.0.0/16",
    EnableDnsSupport = True,
    EnableDnsHostnames = True,
    InstanceTenancy = "default"
)

t.add_resource(vpc)

for subnet in (map(lambda i: subnet(vpc, i, i / 2, 0, i % 2 == 0), range(0, 4))):
    t.add_resource(subnet)
    t.add_output(Output(subnet.title, Value=Ref(subnet)))

print(to_yaml(t.to_json()))

# Produces following output
# Outputs:
#   PrivateSubnet0:
#     Value: !Ref 'PrivateSubnet0'
#   PrivateSubnet1:
#     Value: !Ref 'PrivateSubnet1'
#   PublicSubnet0:
#     Value: !Ref 'PublicSubnet0'
#   PublicSubnet1:
#     Value: !Ref 'PublicSubnet1'
# Resources:
#   PrivateSubnet0:
#     Properties:
#       AvailabilityZone: !Select [0, !GetAZs '']
#       CidrBlock: 10.0.1.0/24
#       MapPublicIpOnLaunch: 'false'
#       VpcId: !Ref 'VPC'
#     Type: AWS::EC2::Subnet
#   PrivateSubnet1:
#     Properties:
#       AvailabilityZone: !Select [1, !GetAZs '']
#       CidrBlock: 10.0.3.0/24
#       MapPublicIpOnLaunch: 'false'
#       VpcId: !Ref 'VPC'
#     Type: AWS::EC2::Subnet
#   PublicSubnet0:
#     Properties:
#       AvailabilityZone: !Select [0, !GetAZs '']
#       CidrBlock: 10.0.0.0/24
#       MapPublicIpOnLaunch: 'true'
#       VpcId: !Ref 'VPC'
#     Type: AWS::EC2::Subnet
#   PublicSubnet1:
#     Properties:
#       AvailabilityZone: !Select [1, !GetAZs '']
#       CidrBlock: 10.0.2.0/24
#       MapPublicIpOnLaunch: 'true'
#       VpcId: !Ref 'VPC'
#     Type: AWS::EC2::Subnet
#   VPC:
#     Properties:
#       CidrBlock: 10.0.0.0/16
#       EnableDnsHostnames: 'true'
#       EnableDnsSupport: 'true'
#       InstanceTenancy: default
#     Type: AWS::EC2::VPC