dynamo.py

import boto3
import json
sts=boto3.client('sts')
crossRoleArn = "arn:aws:iam::XX:role/cross"
stsresponse = sts.assume_role(RoleArn=crossRoleArn,RoleSessionName='dynamocross')

src_client = boto3.client('dynamodb', region_name="us-east-1")
dest_client = boto3.client('dynamodb', region_name="us-east-1",aws_access_key_id=stsresponse["Credentials"]["AccessKeyId"],aws_secret_access_key=stsresponse["Credentials"]["SecretAccessKey"],aws_session_token=stsresponse["Credentials"]["SessionToken"])

srcTableName="src"
destTableName="dest"

def putDynamo(items):
    for item in items:
        dest_client.put_item(TableName=destTableName, Item=item)
def lambda_handler(event, context):
    first_page = True
    nextToken="NA"
    while True:
        response = src_client.scan(TableName=srcTableName)
        putDynamo(response['Items'])
        try:
            nextToken = response['LastEvaluatedKey']
        except Exception as e:
            print(e)
        if nextToken != "NA":
            response = src_client.scan(TableName=srcTableName, ExclusiveStartKey = response['LastEvaluatedKey'])
            putDynamo(response['Items'])
        else:
            print("No new entrines. exiting")
            break