First, login to your AWS console and open the Lambda console. Click on “Create Function”, give it a name and choose “Create a custom role”.

Keep the role with the default policy document since our “Hello World” function will not need any special permission.

Click on “Allow” and make sure to choose “lambda_basic_execution” as a role.

Now let’s add this Node.js Hello World function:

exports.handler = (event, context, callback) => {
    // Succeed with the string "Hello world!"
    callback(null, 'Hello world!');
};

Click on “Test”:

Our test event, once executed will call the Lambda Hello World function. Click on “Create” followed by “Test” and you will notice the execution results:

You can use another language like Python. In order to do this, let’s first remove the first function, so go back to your dashboard and click on “Action” then “Delete”:

Now, create a new function and choose Python 3.6 as a runtime.

The Python Hello World function is the following:

def lambda_handler(event, context):
    return 'Hello from Lambda'

This function will return the string “Hello from Lambda” and exits.

Note: Note that the function handler should be configured correctly in this form file_name.function_name

The file name should not also contain the extension of the file.

In my example, my file is called lambda_function.py and my function is defined as lambda_handler. The handler will be:

lambda_function.lambda_handler