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Showing content from https://docs.aws.amazon.com/lambda/latest/dg/getting-started.html below:

Create your first Lambda function

Create your first Lambda function

To get started with Lambda, use the Lambda console to create a function. In a few minutes, you can create and deploy a function and test it in the console.

As you carry out the tutorial, you'll learn some fundamental Lambda concepts, like how to pass arguments to your function using the Lambda event object. You'll also learn how to return log outputs from your function, and how to view your function's invocation logs in Amazon CloudWatch Logs.

To keep things simple, you create your function using either the Python or Node.js runtime. With these interpreted languages, you can edit function code directly in the console's built-in code editor. With compiled languages like Java and C#, you must create a deployment package on your local build machine and upload it to Lambda. To learn about deploying functions to Lambda using other runtimes, see the links in the Additional resources and next steps section.

Prerequisites

If you do not have an AWS account, complete the following steps to create one.

To sign up for an AWS account

  1. Open https://portal.aws.amazon.com/billing/signup.

  2. Follow the online instructions.

    Part of the sign-up procedure involves receiving a phone call or text message and entering a verification code on the phone keypad.

    When you sign up for an AWS account, an AWS account root user is created. The root user has access to all AWS services and resources in the account. As a security best practice, assign administrative access to a user, and use only the root user to perform tasks that require root user access.

AWS sends you a confirmation email after the sign-up process is complete. At any time, you can view your current account activity and manage your account by going to https://aws.amazon.com/ and choosing My Account.

After you sign up for an AWS account, secure your AWS account root user, enable AWS IAM Identity Center, and create an administrative user so that you don't use the root user for everyday tasks.

Sign in as the user with administrative access Assign access to additional users

  1. In IAM Identity Center, create a permission set that follows the best practice of applying least-privilege permissions.

    For instructions, see Create a permission set in the AWS IAM Identity Center User Guide.

  2. Assign users to a group, and then assign single sign-on access to the group.

    For instructions, see Add groups in the AWS IAM Identity Center User Guide.

Create a Lambda function with the console

In this example, your function takes a JSON object containing two integer values labeled "length" and "width". The function multiplies these values to calculate an area and returns this as a JSON string.

Your function also prints the calculated area, along with the name of its CloudWatch log group. Later in the tutorial, you’ll learn to use CloudWatch Logs to view records of your functions’ invocation.

To create a Hello world Lambda function with the console

  1. Open the Functions page of the Lambda console.

  2. Choose Create function.

  3. Select Author from scratch.

  4. In the Basic information pane, for Function name, enter myLambdaFunction.

  5. For Runtime, choose either Node.js 22 or Python 3.13.

  6. Leave architecture set to x86_64, and then choose Create function.

In addition to a simple function that returns the message Hello from Lambda!, Lambda also creates an execution role for your function. An execution role is an AWS Identity and Access Management (IAM) role that grants a Lambda function permission to access AWS services and resources. For your function, the role that Lambda creates grants basic permissions to write to CloudWatch Logs.

Use the console's built-in code editor to replace the Hello world code that Lambda created with your own function code.

Node.js
To modify the code in the console

  1. Choose the Code tab.

    In the console's built-in code editor, you should see the function code that Lambda created. If you don't see the index.mjs tab in the code editor, select index.mjs in the file explorer as shown on the following diagram.

  2. Paste the following code into the index.mjs tab, replacing the code that Lambda created.

    export const handler = async (event, context) => {
  
  const length = event.length;
  const width = event.width;
  let area = calculateArea(length, width);
  console.log(`The area is ${area}`);
        
  console.log('CloudWatch log group: ', context.logGroupName);
  
  let data = {
    "area": area,
  };
    return JSON.stringify(data);
    
  function calculateArea(length, width) {
    return length * width;
  }
};

  3. In the DEPLOY section, choose Deploy to update your function's code:

Understanding your function code

Before you move to the next step, let's take a moment to look at the function code and understand some key Lambda concepts.

Python
To modify the code in the console

  1. Choose the Code tab.

    In the console's built-in code editor, you should see the function code that Lambda created. If you don't see the lambda_function.py tab in the code editor, select lambda_function.py in the file explorer as shown on the following diagram.

  2. Paste the following code into the lambda_function.py tab, replacing the code that Lambda created.

    import json
import logging

logger = logging.getLogger()
logger.setLevel(logging.INFO)

def lambda_handler(event, context):
    
    # Get the length and width parameters from the event object. The 
    # runtime converts the event object to a Python dictionary
    length = event['length']
    width = event['width']
    
    area = calculate_area(length, width)
    print(f"The area is {area}")
        
    logger.info(f"CloudWatch logs group: {context.log_group_name}")
    
    # return the calculated area as a JSON string
    data = {"area": area}
    return json.dumps(data)
    
def calculate_area(length, width):
    return length*width

  3. In the DEPLOY section, choose Deploy to update your function's code:

Understanding your function code

Before you move to the next step, let's take a moment to look at the function code and understand some key Lambda concepts.

Invoke the Lambda function using the console code editor

To invoke your function using the Lambda console code editor, create a test event to send to your function. The event is a JSON formatted document containing two key-value pairs with the keys "length" and "width".

To create the test event

  1. In the TEST EVENTS section of the console code editor, choose Create test event.

  2. For Event Name, enter myTestEvent.

  3. In the Event JSON section, replace the default JSON with the following:

    {
  "length": 6,
  "width": 7
}

  4. Choose Save.

To test your function and view invocation records

In the TEST EVENTS section of the console code editor, choose the run icon next to your test event:

When your function finishes running, the response and function logs are displayed in the OUTPUT tab. You should see results similar to the following:

Node.js 
Status: Succeeded
Test Event Name: myTestEvent

Response
"{\"area\":42}"

Function Logs
START RequestId: 5c012b0a-18f7-4805-b2f6-40912935034a Version: $LATEST
2024-08-31T23:39:45.313Z	5c012b0a-18f7-4805-b2f6-40912935034a	INFO	The area is 42
2024-08-31T23:39:45.331Z	5c012b0a-18f7-4805-b2f6-40912935034a	INFO	CloudWatch log group:  /aws/lambda/myLambdaFunction
END RequestId: 5c012b0a-18f7-4805-b2f6-40912935034a
REPORT RequestId: 5c012b0a-18f7-4805-b2f6-40912935034a	Duration: 20.67 ms	Billed Duration: 21 ms	Memory Size: 128 MB	Max Memory Used: 66 MB	Init Duration: 163.87 ms

Request ID
5c012b0a-18f7-4805-b2f6-40912935034a
Python 
Status: Succeeded
Test Event Name: myTestEvent

Response
"{\"area\": 42}"

Function Logs
START RequestId: 2d0b1579-46fb-4bf7-a6e1-8e08840eae5b Version: $LATEST
The area is 42
[INFO]	2024-08-31T23:43:26.428Z	2d0b1579-46fb-4bf7-a6e1-8e08840eae5b	CloudWatch logs group: /aws/lambda/myLambdaFunction
END RequestId: 2d0b1579-46fb-4bf7-a6e1-8e08840eae5b
REPORT RequestId: 2d0b1579-46fb-4bf7-a6e1-8e08840eae5b	Duration: 1.42 ms	Billed Duration: 2 ms	Memory Size: 128 MB	Max Memory Used: 39 MB	Init Duration: 123.74 ms

Request ID
2d0b1579-46fb-4bf7-a6e1-8e08840eae5b

When you invoke your function outside of the Lambda console, you must use CloudWatch Logs to view your function's execution results.

To view your function's invocation records in CloudWatch Logs

  1. Open the Log groups page of the CloudWatch console.

  2. Choose the log group for your function (/aws/lambda/myLambdaFunction). This is the log group name that your function printed to the console.

  3. Scroll down and choose the Log stream for the function invocations you want to look at.

    You should see output similar to the following:

    Node.js 
    INIT_START Runtime Version: nodejs:22.v13    Runtime Version ARN: arn:aws:lambda:us-west-2::runtime:e3aaabf6b92ef8755eaae2f4bfdcb7eb8c4536a5e044900570a42bdba7b869d9
START RequestId: aba6c0fc-cf99-49d7-a77d-26d805dacd20 Version: $LATEST
2024-08-23T22:04:15.809Z    5c012b0a-18f7-4805-b2f6-40912935034a  INFO	The area is 42
2024-08-23T22:04:15.810Z    aba6c0fc-cf99-49d7-a77d-26d805dacd20  INFO  CloudWatch log group:  /aws/lambda/myLambdaFunction
END RequestId: aba6c0fc-cf99-49d7-a77d-26d805dacd20
REPORT RequestId: aba6c0fc-cf99-49d7-a77d-26d805dacd20    Duration: 17.77 ms    Billed Duration: 18 ms    Memory Size: 128 MB    Max Memory Used: 67 MB    Init Duration: 178.85 ms
    Python 
    INIT_START Runtime Version: python:3.13.v16    Runtime Version ARN: arn:aws:lambda:us-west-2::runtime:ca202755c87b9ec2b58856efb7374b4f7b655a0ea3deb1d5acc9aee9e297b072
START RequestId: 9d4096ee-acb3-4c25-be10-8a210f0a9d8e Version: $LATEST
The area is 42
[INFO]	2024-09-01T00:05:22.464Z	9315ab6b-354a-486e-884a-2fb2972b7d84	CloudWatch logs group: /aws/lambda/myLambdaFunction
END RequestId: 9d4096ee-acb3-4c25-be10-8a210f0a9d8e 
REPORT RequestId: 9d4096ee-acb3-4c25-be10-8a210f0a9d8e    Duration: 1.15 ms    Billed Duration: 2 ms    Memory Size: 128 MB    Max Memory Used: 40 MB
Clean up

When you're finished working with the example function, delete it. You can also delete the log group that stores the function's logs, and the execution role that the console created.

To delete the Lambda function

  1. Open the Functions page of the Lambda console.

  2. Select the function that you created.

  3. Choose Actions, Delete.

  4. Type confirm in the text input field and choose Delete.

To delete the log group

  1. Open the Log groups page of the CloudWatch console.

  2. Select the function's log group (/aws/lambda/myLambdaFunction).

  3. Choose Actions, Delete log group(s).

  4. In the Delete log group(s) dialog box, choose Delete.

To delete the execution role

  1. Open the Roles page of the AWS Identity and Access Management (IAM) console.

  2. Select the function's execution role (for example, myLambdaFunction-role-31exxmpl).

  3. Choose Delete.

  4. In the Delete role dialog box, enter the role name, and then choose Delete.

Additional resources and next steps

Now that you’ve created and tested a simple Lambda function using the console, take these next steps:

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