Introduction

AWS Lambda provides a serverless computing environment that allows developers to run code without managing servers. One common use case for AWS Lambda is interacting with Amazon S3 buckets. In this article, we’ll discuss a simple Python code snippet that lists folders in an S3 bucket using the boto3 library.

Code Overview

import boto3
import botocore

def  list_files_in_folder(bucket_name, folder_prefix):
	s3 = boto3.client('s3')
		try:
			response = s3.list_objects(Bucket=bucket_name, Prefix=folder_prefix)
			if  'Contents'  in response:
				return [obj['Key'] for obj in response['Contents']]
			else:
				return []
		except botocore.exceptions.ClientError as e:
			print(f"Error listing files in the folder: {e}")
			return []

Explanation

Importing Required Libraries:

• The code begins by importing the necessary libraries, namely boto3 for interacting with AWS services and botocore for handling exceptions.

Function Definition:

• The list_files_in_folder function takes two parameters - bucket_name and folder_prefix.
• bucket_name represents the name of the S3 bucket, and folder_prefix is the prefix of the folder within the bucket.

AWS S3 Client Initialization:

• The code initializes an S3 client using boto3.client('s3').

Listing Objects in the Folder:

• The list_objects method is used to retrieve a list of objects in the specified S3 bucket and folder. The Prefix parameter ensures that only objects with the specified prefix (i.e., the folder) are included in the response.

Handling Response:

• The code checks if the response contains ‘Contents,’ indicating that objects were found in the specified folder. If objects are present, it extracts and returns a list of their keys (object identifiers). If no objects are found, an empty list is returned.

Exception Handling:

• In case of any errors during the API call, the code catches the botocore.exceptions.ClientError exception and prints an error message. It then returns an empty list.

Conclusion

This concise Python code demonstrates a straightforward way to list folders in an S3 bucket using AWS Lambda and the boto3 library. By providing the bucket name and folder prefix as inputs, developers can easily integrate this function into their serverless applications for efficient management of S3 resources. Keep in mind that this code can be extended or modified to suit specific requirements, such as filtering folders based on certain criteria or integrating it into a larger serverless workflow.