terraform scripts are in s3 bucket, lambda will install terraform, download the zipped scripts into /tmp directory and run terraform apply...

run_terraform_in_lambda.py

import os
import subprocess
import urllib
import boto3
import botocore
import commands


# Version of Terraform that we're using
TERRAFORM_VERSION = '0.8.5'

# Download URL for Terraform
TERRAFORM_DOWNLOAD_URL = (
    'https://releases.hashicorp.com/terraform/%s/terraform_%s_linux_amd64.zip'
    % (TERRAFORM_VERSION, TERRAFORM_VERSION))

# Paths where Terraform should be installed
TERRAFORM_DIR = os.path.join('/tmp', 'terraform_%s' % TERRAFORM_VERSION)
TERRAFORM_PATH = os.path.join(TERRAFORM_DIR, 'terraform')



def check_call(args):
    """Wrapper for subprocess that checks if a process runs correctly,
    and if not, prints stdout and stderr.
    """
    proc = subprocess.Popen(args,
        stdout=subprocess.PIPE,
        stderr=subprocess.PIPE,
        cwd='/tmp')
    stdout, stderr = proc.communicate()
    if proc.returncode != 0:
        print(stdout)
        print(stderr)
        raise subprocess.CalledProcessError(
            returncode=proc.returncode,
            cmd=args)


def install_terraform():
    """Install Terraform on the Lambda instance."""
    # http://docs.aws.amazon.com/lambda/latest/dg/lambda-introduction.html
    if os.path.exists(TERRAFORM_PATH):
        return

    urllib.urlretrieve(TERRAFORM_DOWNLOAD_URL, '/tmp/terraform.zip')

    # Flags:
    #   '-o' = overwrite existing files without prompting
    #   '-d' = output directory
    check_call(['unzip', '-o', '/tmp/terraform.zip', '-d', TERRAFORM_DIR])

    check_call([TERRAFORM_PATH, '--version'])

    print ("TERRAFORM_DIR : " + TERRAFORM_DIR)
    print("TERRAFORM_PATH : " + TERRAFORM_PATH)


def apply_terraform_plan():
    """Download a Terraform plan from S3 and run a 'terraform apply'.

    :param s3_bucket: Name of the S3 bucket where the plan is stored.
    :param path: Path to the Terraform planfile in the S3 bucket.

    """
    
    BUCKET_NAME = 'terraform007'
    KEY = 'files/ec2.zip'
    
    s3_client = boto3.client('s3')
    #Download private key file from secure S3 bucket
    s3_client.download_file(BUCKET_NAME, KEY, '/tmp/ec2.zip')

    # UNZIP CODEBASE
    print(commands.getstatusoutput('unzip /tmp/ec2.zip -d /tmp'))
    print("list /tmp")
    print(commands.getstatusoutput('ls /tmp'))

    print(commands.getstatusoutput('/tmp/terraform_0.8.5/terraform init /tmp/'))
    print(commands.getstatusoutput('/tmp/terraform_0.8.5/terraform plan /tmp/'))
    print(commands.getstatusoutput('/tmp/terraform_0.8.5/terraform apply -input=false /tmp/'))



def handler(event, context):

    install_terraform()
    apply_terraform_plan()