Step 4: Create the Lambda function that splits input data - Amazon Pinpoint

Step 4: Create the Lambda function that splits input data

The solution that's described in this tutorial uses three Lambda functions. The first Lambda function is triggered when you upload a file to a specific Amazon S3 bucket. This function reads the content of the input file, and then breaks it into smaller parts. Other functions (which you create later in this tutorial) process these incoming files concurrently. Processing the files concurrently reduces the amount of time that it takes to import all of the endpoints into Amazon Pinpoint.

Step 4.1: Create the function

To create the first Lambda function for this tutorial, you first have to upload the .zip file that you created in Step 3. Next, you set up the function itself.

To create the Lambda function

  1. Open the AWS Lambda console at

  2. Choose Create function.

  3. Choose Author from scratch. Under Basic information, do the following:

    • For Function name, enter CustomerImport_ReadIncomingAndSplit.

    • For Runtime, choose Python 3.7.

    • For Execution role, choose Use an existing role.

    • For Existing role, choose ImporterS3Role.

    • Choose Create function.

  4. Under Function code, for Code entry type, choose Upload a .zip file. Under Function package, choose Upload. Choose the file that you created in Step 3. After you select the file, choose Save.


    After you choose Save, you receive an error message stating that Lambda couldn’t open the file Dismiss this error—you create this file in the next step.

  5. In the function editor, on the File menu, choose New File. The editor creates a new file named Untitled1.

  6. Paste the following code in the editor:

    import os import boto3 import s3fs from botocore.exceptions import ClientError input_archive_folder = "input_archive" to_process_folder = "to_process" file_row_limit = 50 file_delimiter = ',' # S3 bucket info s3 = s3fs.S3FileSystem(anon=False) def lambda_handler(event, context): print("Received event: \n" + str(event)) for record in event['Records']: # Assign some variables that make it easier to work with the data in the # event record. bucket = record['s3']['bucket']['name'] key = record['s3']['object']['key'] input_file = os.path.join(bucket,key) archive_path = os.path.join(bucket,input_archive_folder,os.path.basename(key)) folder = os.path.split(key)[0] s3_url = os.path.join(bucket,folder) output_file_template = os.path.splitext(os.path.basename(key))[0] + "__part" output_path = os.path.join(bucket,to_process_folder) # Set a variable that contains the number of files that this Lambda # function creates after it runs. num_files = file_count(, 'r'), file_delimiter, file_row_limit) # Split the input file into several files, each with 50 rows. split(, 'r'), file_delimiter, file_row_limit, output_file_template, output_path, True, num_files) # Send the unchanged input file to an archive folder. archive(input_file,archive_path) # Determine the number of files that this Lambda function will create. def file_count(file_handler, delimiter, row_limit): import csv reader = csv.reader(file_handler, delimiter=delimiter) # Figure out the number of files this function will generate. row_count = sum(1 for row in reader) - 1 # If there's a remainder, always round up. file_count = int(row_count // row_limit) + (row_count % row_limit > 0) return file_count # Split the input into several smaller files. def split(filehandler, delimiter, row_limit, output_name_template, output_path, keep_headers, num_files): import csv reader = csv.reader(filehandler, delimiter=delimiter) current_piece = 1 current_out_path = os.path.join( output_path, output_name_template + str(current_piece) + "__of" + str(num_files) + ".csv" ) current_out_writer = csv.writer(, 'w'), delimiter=delimiter) current_limit = row_limit if keep_headers: headers = next(reader) current_out_writer.writerow(headers) for i, row in enumerate(reader): if i + 1 > current_limit: current_piece += 1 current_limit = row_limit * current_piece current_out_path = os.path.join( output_path, output_name_template + str(current_piece) + "__of" + str(num_files) + ".csv" ) current_out_writer = csv.writer(, 'w'), delimiter=delimiter) if keep_headers: current_out_writer.writerow(headers) current_out_writer.writerow(row) # Move the original input file into an archive folder. def archive(input_file, archive_path): s3.copy_basic(input_file,archive_path) print("Moved " + input_file + " to " + archive_path) s3.rm(input_file)
  7. In the function editor, on the File menu, choose Save As. Save the file as in the root directory of the function.

  8. At the top of the page, choose Save.

Step 4.2: Test the function

After you create the function, you should test it to make sure that it's set up correctly.

To test the Lambda function

  1. In a text editor, create a new file. In the file, paste the following text:

    Salutation,First Name,Last Name,Title,Mailing Street,Mailing City,Mailing State/Province,Mailing Zip/Postal Code,Mailing Country,Phone,Email,Contact Record Type,Account Name,Account Owner,Lead Source Mr.,Alejandro,Rosales,Operations Manager,414 Main Street,Anytown,AL,95762,United States,+18705550156,,Customer,Example Corp.,Richard Roe,Website Ms.,Ana Carolina,Silvia,Customer Service Representative,300 First Avenue,Any Town,AK,65141,United States,(727) 555-0128,,Qualified Lead,AnyCompany,Jane Doe,Seminar Mrs.,Juan,Li,Auditor,717 Kings Street,Anytown,AZ,18162,United States,768.555.0122,,Unqualified Lead,Example Corp.,Richard Roe,Phone Dr.,Arnav,Desai,Senior Analyst,782 Park Court,Anytown,AR,27084,United States,+17685550162,,Customer,Example Corp.,Richard Roe,Website Mr.,Mateo,Jackson,Sales Representative,372 Front Street,Any Town,CA,83884,United States,(781) 555-0169,,Customer,AnyCompany,Jane Doe,Seminar Mr.,Nikhil,Jayashankar,Executive Assistant,468 Fifth Avenue,Anytown,CO,75376,United States,384.555.0178,,Qualified Lead,Example Corp.,Jane Doe,Website Mrs.,Shirley,Rodriguez,Account Manager,287 Park Avenue,Any Town,CT,26715,United States,+12455550188,,Qualified Lead,Example Corp.,Richard Roe,Seminar Ms.,Xiulan,Wang,Information Architect,107 Queens Place,Anytown,DE,70710,United States,(213) 555-0192,,Unqualified Lead,Example Corp.,Richard Roe,Phone Miss,Saanvi,Sarkar,Director of Finance,273 Sample Boulevard,Any Town,FL,85431,United States,237.555.0121,,Customer,AnyCompany,Richard Roe,Referral Mr.,Wei,Zhang,Legal Counsel,15 Third Avenue,Any Town,GA,82387,United States,+18065550179,,Customer,AnyCompany,Jane Doe,Website

    Save the file as testfile.csv.


    This file contains fictitious contact records. You only use it to test the Lambda function that you create in this tutorial. Later, you can delete the segments that contain this fictitious data.

    For now, don't add or remove any columns to the file. After you implement the solution that's shown in this tutorial, you can modify it to meet your needs.

  2. Open the Amazon S3 console at

  3. In the list of buckets, choose the bucket that you created in Step 1, and then choose the input folder.

  4. Choose Upload. Upload the testfile.csv file that you just created.

  5. Open the AWS Lambda console at

  6. In the list of functions, choose the CustomerImport_ReadIncomingAndSplit function that you created earlier.

  7. Choose Test. On the Configure test event window, for Event name, enter TestEvent. Then, in the editor, paste the following code:

    { "Records": [ { "s3": { "bucket": { "name": "bucket-name", "arn": "arn:aws:s3:::bucket-name" }, "object": { "key": "input/testfile.csv" } } } ] }

    In the preceding example, replace bucket-name with the name of the Amazon S3 bucket that you created in Step 1. When you finish, choose Create.

  8. Choose Test again. The function executes with the test event that you provided.

    If the function runs as expected, proceed to the next step.

    If the function fails to complete, do the following:

    • Make sure that you specified the correct bucket name in the IAM policy that you created in Step 2: Create IAM roles.

    • Make sure that the Lambda test event that you created in step 7 of this section refers to the correct bucket and file name.

    • If you named the input file something other than testfile.csv, make sure that the file name doesn't contain any spaces.

  9. Return to the Amazon S3 console. Choose the bucket that you created in Step 1: Create an Amazon S3 bucket.

    Open the folders in the bucket and take note of the contents of each one. If all of the following statements are true, then the Lambda function worked as expected:

    • The input folder doesn't contain any files.

    • The input_archive folder contains the file that you uploaded in step 4 of this section.

    • The to_process folder contains a file named testfile__part1__of1.csv.

    Don't delete any of the newly generated files. The Lambda function that you create in the next step uses the files in the to_process folder.

Next: Create a Lambda function that processes the incoming records