Prerequisites Create the function Invoke the function Clean up Next steps

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 to 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.

Tip

To learn how to build serverless solutions, check out the Serverless Developer Guide.

Prerequisites

If you do not have an Amazon Web Services account, use the following procedure to create one.

To sign up for Amazon Web Services

Open http://www.amazonaws.cn/ and choose Sign Up.
Follow the on-screen instructions.

Amazon 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 http://www.amazonaws.cn/ and choosing My Account.

After you sign up for an Amazon Web Services account, safeguard your administrative user by turning on multi-factor authentication (MFA). For instructions, see Enable a virtual MFA device for an IAM user (console) in the IAM User Guide.

To give other users access to your Amazon Web Services account resources, create IAM users. To secure your IAM users, turn on MFA and only give the IAM users the permissions needed to perform their tasks.

For more information about creating and securing IAM users, see the following topics in the IAM 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

Open the Functions page of the Lambda console.
Choose Create function.
Select Author from scratch.
In the Basic information pane, for Function name, enter myLambdaFunction.
For Runtime, choose either Node.js 22.x or Python 3.13.
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 Amazon Identity and Access Management (IAM) role that grants a Lambda function permission to access Amazon Web Services 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

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.

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;
  }
};

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.

The Lambda handler:

Your Lambda function contains a Node.js function named handler. A Lambda function in Node.js can contain more than one Node.js function, but the handler function is always the entry point to your code. When your function is invoked, Lambda runs this method.

When you created your Hello world function using the console, Lambda automatically set the name of the handler method for your function to handler. Be sure not to edit the name of this Node.js function. If you do, Lambda won’t be able to run your code when you invoke your function.

To learn more about the Lambda handler in Node.js, see Define Lambda function handler in Node.js.
The Lambda event object:

The function handler takes two arguments, event and context. An event in Lambda is a JSON formatted document that contains data for your function to process.

If your function is invoked by another Amazon Web Services service, the event object contains information about the event that caused the invocation. For example, if your function is invoked when an object is uploaded to an Amazon Simple Storage Service (Amazon S3) bucket, the event contains the name of the bucket and the object key.

In this example, you’ll create an event in the console by entering a JSON formatted document with two key-value pairs.
The Lambda context object:

The second argument that your function takes is context. Lambda passes the context object to your function automatically. The context object contains information about the function invocation and execution environment.

You can use the context object to output information about your function's invocation for monitoring purposes. In this example, your function uses the logGroupName parameter to output the name of its CloudWatch log group.

To learn more about the Lambda context object in Node.js, see Using the Lambda context object to retrieve Node.js function information.
Logging in Lambda:

With Node.js, you can use console methods like console.log and console.error to send information to your function's log. The example code uses console.log statements to output the calculated area and the name of the function's CloudWatch Logs group. You can also use any logging library that writes to stdout or stderr.

To learn more, see Log and monitor Node.js Lambda functions. To learn about logging in other runtimes, see the 'Building with' pages for the runtimes you're interested in.

Python

To modify the code in the console

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.

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

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.

The Lambda handler:

Your Lambda function contains a Python function named lambda_handler. A Lambda function in Python can contain more than one Python function, but the handler function is always the entry point to your code. When your function is invoked, Lambda runs this method.

When you created your Hello world function using the console, Lambda automatically set the name of the handler method for your function to lambda_handler. Be sure not to edit the name of this Python function. If you do, Lambda won’t be able to run your code when you invoke your function.

To learn more about the Lambda handler in Python, see Define Lambda function handler in Python.
The Lambda event object:

The function lambda_handler takes two arguments, event and context. An event in Lambda is a JSON formatted document that contains data for your function to process.

If your function is invoked by another Amazon Web Services service, the event object contains information about the event that caused the invocation. For example, if your function is invoked when an object is uploaded to an Amazon Simple Storage Service (Amazon S3) bucket, the event contains the name of the bucket and the object key.

In this example, you’ll create an event in the console by entering a JSON formatted document with two key-value pairs.
The Lambda context object:

The second argument that your function takes is context. Lambda passes the context object to your function automatically. The context object contains information about the function invocation and execution environment.

You can use the context object to output information about your function's invocation for monitoring purposes. In this example, your function uses the log_group_name parameter to output the name of its CloudWatch log group.

To learn more about the Lambda context object in Python, see Using the Lambda context object to retrieve Python function information.
Logging in Lambda:

With Python, you can use either a print statement or a Python logging library to send information to your function's log. To illustrate the difference in what's captured, the example code uses both methods. In a production application, we recommend that you use a logging library.

To learn more, see Log and monitor Python Lambda functions. To learn about logging in other runtimes, see the 'Building with' pages for the runtimes you're interested in.

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

In the TEST EVENTS section of the console code editor, choose Create test event.
For Event Name, enter myTestEvent.
In the Event JSON section, replace the default JSON with the following:
```
{
  "length": 6,
  "width": 7
}
```
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:

Run test event button in the Lambda console code editor

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

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

Open the Log groups page of the CloudWatch console.
Choose the log group for your function (/aws/lambda/myLambdaFunction). This is the log group name that your function printed to the console.

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

List of log streams for a Lambda function.

You should see output similar to the following:

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

Open the Functions page of the Lambda console.
Select the function that you created.
Choose Actions, Delete.
Type delete in the text input field and choose Delete.

To delete the log group

Open the Log groups page of the CloudWatch console.
Select the function's log group (/aws/lambda/myLambdaFunction).
Choose Actions, Delete log group(s).
In the Delete log group(s) dialog box, choose Delete.

To delete the execution role

Open the Roles page of the Amazon Identity and Access Management (IAM) console.
Select the function's execution role (for example, myLambdaFunction-role-31exxmpl).
Choose Delete.
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:

Learn to add dependencies to your function and deploy it using a .zip deployment package. Choose your preferred language from the following links.

Node.js

Deploy Node.js Lambda functions with .zip file archives

Typescript

Deploy transpiled TypeScript code in Lambda with .zip file archives

Python

Working with .zip file archives for Python Lambda functions

Ruby

Deploy Ruby Lambda functions with .zip file archives

Java

Deploy Java Lambda functions with .zip or JAR file archives

Go

Deploy Go Lambda functions with .zip file archives

C#

Build and deploy C# Lambda functions with .zip file archives
To learn how to invoke a Lambda function using another Amazon Web Services service, see Tutorial: Using an Amazon S3 trigger to invoke a Lambda function.
Choose one of the following tutorials for more complex examples of using Lambda with other Amazon Web Services services.
- Tutorial: Using Lambda with API Gateway: Create an Amazon API Gateway REST API that invokes a Lambda function.
- Using a Lambda function to access an Amazon RDS database: Use a Lambda function to write data to an Amazon Relational Database Service (Amazon RDS) database through RDS Proxy.
- Using an Amazon S3 trigger to create thumbnail images: Use a Lambda function to create a thumbnail every time an image file is uploaded to an Amazon S3 bucket.

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What is Amazon Lambda?

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