s3-lambda-related-files.py

import os
import boto3
import traceback

s3_client = boto3.client('s3')
dynamodb = boto3.resource('dynamodb')
table_name = 'dynamodb-table'    

def import_file(bucket, key):
    filename, file_extension = os.path.splitext(key)
    s3_client.copy_object(Bucket='temp-bucket', Key='{}{}'.format(str(filename), file_extension), CopySource={'Bucket': bucket, 'Key': key})
    
    return (filename, file_extension)

def lambda_handler(event, context):
    table = dynamodb.Table(table_name)

    for record in event['Records']:
        bucket = record['s3']['bucket']['name']
        key = record['s3']['object']['key']
        
        filename, file_extension = import_file(bucket, key)
        
        try:
            response = table.get_item(Key={'filename': filename})
            item = response['Item'] if "Item" in response else None
            
            if item is None:
                # The item doesn't exist in the DynamoDB table, so this is the first file of the pair.
                # We need to create a new record and move on.
                item = {'filename': filename, 'status': 'loading'}
                table.put_item(TableName=table_name, Item=item)
            else:
                # The item does exist in the DynamoDB table, so this is the second file of the pair.
                # We need to update the status of the record and invoke the processing step.
                response = table.update_item(
                    Key={'filename': filename},
                    UpdateExpression="set #s = :s",
                     ExpressionAttributeNames={
                        "#s": "status"
                    },
                    ExpressionAttributeValues={
                        ':s': 'ready'
                    },
                    ReturnValues="UPDATED_NEW")
                    
                # Here we invoke the processing step passing the filename as an argument
                # invoke_processing_step(filename)
            
        except Exception as e:
            print(traceback.format_exc())

        return (bucket, key)