DynamoDBLambda Lab | Python Fiddle

import boto3

DDB = boto3.resource('dynamodb').Table('DynamoDBLambdaLab')

def lambda_handler(event, context):
   records = event['Records']
   print("Received %s records" % len(records))

for record in records:
       print(record)

# if new record or update
       if record['eventName'].upper() in {'INSERT', 'MODIFY'}:

# primary key
           record_id = record['dynamodb']['Keys']['Id']['S']

# init local vars
           old_email = old_is_personal = new_email = new_is_personal = None

# new and old images
           old_image = record['dynamodb'].get('OldImage') or {}
           new_image = record['dynamodb'].get('NewImage') or {}

# old values (optional, only on update)
           if 'Email' in old_image:
               old_email = old_image['Email']['S']
           if 'IsPersonalEmail' in old_image:
               old_is_personal = old_image['IsPersonalEmail']['BOOL']

# new values
           if 'Email' in new_image:
               new_email = new_image['Email']['S']
               new_is_personal = is_personal_email(new_email)

# avoid recursion on update and write only if strictly needed
           if old_email != new_email and old_is_personal != new_is_personal:
               update_record(record_id, new_is_personal)

print("Processed %s records" % len(records))

def update_record(record_id, is_personal):
   print("Updating %s: IsPersonalEmail=%s" % (record_id, is_personal))
   DDB.update_item(
       Key={'Id': record_id},
       UpdateExpression='SET IsPersonalEmail = :val',
       ExpressionAttributeValues={':val': is_personal or False},
   )

def is_personal_email(email):
   domains = {"gmail.com", "outlook.com", "hotmail.com"}
   return any(email.endswith(domain) for domain in domains)

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