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In this tutorial, you’ll learn how to create, deploy, and test a simple AWS Lambda function written in Python. We’ll cover the entire workflow from the AWS Management Console to verifying your function’s output and logs.

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Prerequisites

  • An AWS account with permissions to create Lambda functions
  • Basic knowledge of Python

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1. Navigate to the AWS Lambda Console

  1. Sign in to the AWS Management Console.
  2. In the search bar, type Lambda and select AWS Lambda.
The image shows the AWS Management Console with a search for "lamb" displaying services like AWS Lambda, CodeBuild, and AWS Signer.

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2. Create a New Function

  1. Click Create function.
  2. Select Author from scratch.
  3. Enter a name, e.g., MyFirstFunction.
  4. Choose Python 3.7 for the runtime.
  5. Under Permissions, leave the default to let AWS create a new IAM role with basic Lambda permissions.
  6. Click Create function.
The image shows a screenshot of the AWS Lambda console, where a user is configuring a function with Python 3.7, selecting architecture options, and setting permissions for execution roles.
Once provisioning is complete, you’ll see the function’s configuration page:
The image shows an AWS Lambda console with a function named "myfirstfunction" displayed. The interface includes options for testing, monitoring, configuration, aliases, and versions.

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3. Add and Deploy Your Code

Scroll to the Code source section, remove the default boilerplate, and paste the following handler: 
def lambda_handler(event, context):
    name = event.get("name")
    if name == "KodeKloud":
        return "Success"
    else:
        return "No"
Click Deploy to save your changes.
The function returns a simple string based on the name parameter. You can expand this logic to handle more complex business rules.

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4. Test Your Lambda Function

  1. Switch to the Test tab.
  2. Click Create new test event.
  3. Configure the event:
    • Event name: ColdStartTest
    • Template: Hello World
    • Event JSON: 
      {
  "name": "KodeKloud"
}
  4. Click Create and then Test.
A successful run will display the output "Success" and execution details:
The image shows an AWS Lambda console with a successful execution result for a test event. It includes options to create or edit a test event and displays JSON formatting options.

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Review CloudWatch Logs

Under Monitor, click View logs in CloudWatch to inspect log entries similar to: 
START RequestId: ... Version: $LATEST
END RequestId: ...
REPORT RequestId: ... Duration: 1.90 ms Billed Duration: 2 ms Memory Size: 128 MB Max Memory Used: 36 MB Init Duration: 137.57 ms

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5. Test the Else Branch

Create a second test event: 
{
  "name": "Other"
}
  • Event name: OtherTest
Run the test again. The function should return "No".

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6. Summary of Test Events

Event NameInput JSONExpected Output
ColdStartTest{"name": "KodeKloud"}”Success”
OtherTest{"name": "Other"}”No”

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Next Steps

You’ve successfully created, configured, and tested a Python-based AWS Lambda function. In upcoming lessons, we’ll explore:
  • Advanced Lambda configurations
  • Integrating event source triggers (S3, SNS, API Gateway)
  • Environment variables and layers

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References

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