How do I trigger inline lambda function within cloudformation template during stack creation?

Hello, So you can use a lambda function that takes and event as input which can contain a "bucket_name" field with the name you want. Then using the native boto3 library, create an s3 client and check if it exists already by calling the "head_bucket" method. If it doesn't exist, have the function create it with the "create_bucket" api call. finally, you can add a statement to just print the bucket name if it already exists. Feel free to reference the code below as a base:

*You will need to replace the "event" and "context" parameters with the desired event and objects for when the function is called.

Hope this helps!

import boto3

def create_s3_bucket(event, context):
    # Get the bucket name from the event data
    bucket_name = event['bucket_name']
    
    # Create an S3 client
    s3 = boto3.client('s3')
    
    # Check if the bucket already exists
    try:
        s3.head_bucket(Bucket=bucket_name)
    except s3.exceptions.NoSuchBucket:
        # Create the bucket if it does not exist
        s3.create_bucket(Bucket=bucket_name)
        print(f'Bucket {bucket_name} created')
    else:
        print(f'Bucket {bucket_name} already exists')

What are you using as an event trigger for Lambda? CloudTrail or EventBridge?