S3File python example

With the launch of Amazon S3 Files, you no longer need boto3 for basic object interaction. Once you have attached the S3 file system to your Lambda function (via the Configuration > File systems tab), you treat S3 objects as if they were on a local disk.

Python Example

This example assumes your mount path is configured as /mnt/s3data.

import os

def lambda_handler(event, context):
    mount_path = '/mnt/s3data'
    file_path = os.path.join(mount_path, 'example.txt')

    # Writing directly to S3
    with open(file_path, 'w', encoding='utf-8') as f:
        f.write("Hello from S3 Files!")

    # Reading directly from S3
    if os.path.exists(file_path):
        with open(file_path, 'r') as f:
            print(f"Content: {f.read()}")

    return {"status": "success", "files": os.listdir(mount_path)}

Technical Requirements:

• VPC & Security Groups: Lambda must be in the same VPC as the S3 Mount Target; allow NFS (Port 2049) in your Security Groups.
• IAM Permissions: The execution role needs s3files:ClientMount and s3files:ClientWrite, plus standard s3:GetObject permissions.
• Reference: See the official AWS News Blog (April 2026) titled "Launching S3 Files, making S3 buckets accessible as file systems" for the full architectural breakdown.

https://aws.amazon.com/blogs/aws/launching-s3-files-making-s3-buckets-accessible-as-file-systems/

https://aws.amazon.com/about-aws/whats-new/2026/04/amazon-s3-files/

Does that answer your question?

I don't have specific code examples for using the S3 Files feature with Lambda functions in Python from the available information. However, I can explain the general approach for configuring this feature.

S3 Files allows Lambda functions to access Amazon S3 objects as files using standard file system operations through a local mount path. To use this feature, you need to:

1. Set up prerequisites: Ensure you have an S3 file system with mount targets in the same VPC as your Lambda function, and configure the appropriate security groups to allow NFS traffic.

2. Configure IAM permissions: Your Lambda function's execution role needs permissions including s3files:ClientMount and s3files:ClientWrite to mount the file system, plus s3:GetObject and s3:GetObjectVersion to read from S3.

3. Attach the file system: In the Lambda console, go to your function's Configuration tab, select File systems, and attach your S3 file system by specifying a local mount path and selecting an access point if needed.

4. Access files in your code: Once configured, your Python Lambda function can access S3 objects through the local mount path using standard file operations, similar to how you would read/write files on a local file system.

The file system will be available the next time your Lambda function is invoked, allowing you to read large files, share data across invocations, or write output to persistent storage through the mounted path.
Sources
Mounting S3 file systems on AWS Lambda functions - Amazon Simple Storage Service
Configuring Amazon S3 Files access - AWS Lambda