Print out "creation time" for EC2 instances (in reality, it's the first network interface attachement time)

ec2_instance_creation_time.py

import boto3
import datetime

# iterator over EC2 instances for region
def ec2_instances(region):
    client = boto3.client('ec2', region_name = region)
    for reservation in client.describe_instances().get('Reservations', []):
        for instance in reservation.get('Instances', []):
            yield instance

# iterator over EC2 regions
def ec2_regions():
    for region in boto3.client('ec2').describe_regions().get('Regions', []):
        yield region

# Name tag of EC2 instance
def instance_name(instance):
    tags = {t['Key']: t['Value'] for t in instance.get('Tags', [])}
    return tags.get('Name', 'NONAME')

# AttachTime for EC2 instance primary interface
def net_attach_time(instance):
    default_time = datetime.datetime.now()
    for interface in instance.get('NetworkInterfaces', []):
        attachement = interface.get('Attachment', {})
        if attachement.get('DeviceIndex') == 0:
            return attachement.get('AttachTime', default_time)
    return default_time
        
def lambda_handler(event, context):
    for region in (r['RegionName'] for r in ec2_regions()):
        print(region)
        for instance in ec2_instances(region):
            print(' %s: %s' % (instance_name(instance), net_attach_time(instance)))