AWS S3 + Python Flask - File Upload, Download, List, and Delete Example

To implement file upload, list, download, and delete operations for AWS S3 in a Flask app, you can follow the steps below.

This example will:

Upload files to an S3 bucket.
List files available in the S3 bucket.
Download files from the S3 bucket.
Delete files from the S3 bucket.

Step 1: Install Required Libraries

Make sure you have Flask and boto3 installed.

pip install Flask boto3

Step 2: AWS S3 Configuration

You will need AWS credentials and an S3 bucket. You can either:

Set the AWS credentials as environment variables (AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY).
Or use the default AWS credentials file located at ~/.aws/credentials.

Step 3: Flask Application with File Upload, List, Download, and Delete

Here's a simple Flask app that integrates with AWS S3 for file upload, listing, downloading, and deleting.

from flask import Flask, request, send_file, jsonify
import boto3
from botocore.exceptions import NoCredentialsError
import os

# Initialize Flask app
app = Flask(__name__)

# AWS S3 Configuration
AWS_BUCKET_NAME = "your-bucket-name"
AWS_ACCESS_KEY_ID = "your-access-key-id"
AWS_SECRET_ACCESS_KEY = "your-secret-access-key"
AWS_REGION = "your-region"

# Initialize S3 Client
s3_client = boto3.client(
    's3',
    aws_access_key_id=AWS_ACCESS_KEY_ID,
    aws_secret_access_key=AWS_SECRET_ACCESS_KEY,
    region_name=AWS_REGION
)

# Route to upload a file to S3
@app.route("/upload", methods=["POST"])
def upload_file():
    if "file" not in request.files:
        return "No file part", 400

    file = request.files["file"]
    
    if file.filename == "":
        return "No selected file", 400
    
    try:
        s3_client.upload_fileobj(file, AWS_BUCKET_NAME, file.filename)
        return f"File uploaded successfully: {file.filename}", 200
    except NoCredentialsError:
        return "Credentials not available", 403
    except Exception as e:
        return f"An error occurred: {str(e)}", 500

# Route to list files in the S3 bucket
@app.route("/list", methods=["GET"])
def list_files():
    try:
        response = s3_client.list_objects_v2(Bucket=AWS_BUCKET_NAME)
        if 'Contents' in response:
            file_names = [obj['Key'] for obj in response['Contents']]
            return jsonify({"files": file_names}), 200
        else:
            return jsonify({"message": "No files found"}), 404
    except Exception as e:
        return jsonify({"error": str(e)}), 500

# Route to download a file from S3
@app.route("/download/<filename>", methods=["GET"])
def download_file(filename):
    try:
        file_obj = s3_client.get_object(Bucket=AWS_BUCKET_NAME, Key=filename)
        return send_file(
            file_obj['Body'], 
            as_attachment=True, 
            download_name=filename
        )
    except Exception as e:
        return jsonify({"error": str(e)}), 500

# Route to delete a file from S3
@app.route("/delete/<filename>", methods=["DELETE"])
def delete_file(filename):
    try:
        s3_client.delete_object(Bucket=AWS_BUCKET_NAME, Key=filename)
        return jsonify({"message": f"File {filename} deleted successfully"}), 200
    except Exception as e:
        return jsonify({"error": str(e)}), 500

# Run the Flask app
if __name__ == "__main__":
    app.run(debug=True)

Explanation of Routes:

1. Upload a File (/upload):

Accepts a file upload using a POST request with the form field file.
Uses s3_client.upload_fileobj() to upload the file to your S3 bucket.
Returns a success message or error if it fails.

2. List Files (/list):

Lists all files in the S3 bucket using s3_client.list_objects_v2().
Returns a JSON response with the filenames in the bucket.

3. Download a File (/download/<filename>):

Downloads a file from the S3 bucket.
Uses send_file() to send the file to the client for download.

4. Delete a File (/delete/<filename>):

Deletes a file from the S3 bucket using s3_client.delete_object().
Returns a success message or an error.

Step 4: Running the Flask App

1. Start the Flask application:

python app.py

2. To test the API:

Upload a file (e.g., using curl):

curl -X POST -F "file=@path_to_your_file" http://localhost:5000/upload

List files:

curl http://localhost:5000/list

Download a file:

curl -O http://localhost:5000/download/your-file-name

Delete a file:

curl -X DELETE http://localhost:5000/delete/your-file-name

Final Notes:

Security: Make sure you don't hard-code your AWS credentials directly in the code. You can use environment variables, the AWS credentials file (~/.aws/credentials), or IAM roles (if deploying to AWS services like EC2).
File Size Consideration: If you're uploading large files, consider using multipart upload for efficiency.
Error Handling: The code catches general exceptions and provides error messages to the client, which can be expanded for more specific error types.

This should give you a full setup for working with AWS S3 in a Flask app for file upload, list, download, and delete operations. Let me know if you need further details!

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