Resource (Python)

Access linked resources in Python Lambda functions

The Python SDK provides access to linked resources through the Resource class.

Installation

pip install sst

Import

from sst import Resource

Usage

Access linked resources by name:

from sst import Resource
import boto3

# Access a bucket
s3 = boto3.client('s3')
bucket_name = Resource.MyBucket.name

# Access a table
dynamodb = boto3.resource('dynamodb')
table_name = Resource.MyTable.name
table = dynamodb.Table(table_name)

# Access an API
api_url = Resource.MyApi.url

Lambda Handler Example

lambda.py

from sst import Resource
import boto3
import json

s3 = boto3.client('s3')

def handler(event, context):
    # Use linked bucket
    s3.put_object(
        Bucket=Resource.MyBucket.name,
        Key='file.txt',
        Body=b'Hello from Python'
    )
    
    return {
        'statusCode': 200,
        'body': json.dumps({'message': 'Success'})
    }

DynamoDB Example

from sst import Resource
import boto3
from decimal import Decimal

dynamodb = boto3.resource('dynamodb')

def handler(event, context):
    table = dynamodb.Table(Resource.MyTable.name)
    
    # Put item
    table.put_item(
        Item={
            'id': '123',
            'data': 'Hello World',
            'count': Decimal('42')
        }
    )
    
    # Get item
    response = table.get_item(Key={'id': '123'})
    item = response.get('Item')
    
    return {
        'statusCode': 200,
        'body': json.dumps(item, default=str)
    }

SQS Example

from sst import Resource
import boto3
import json

sqs = boto3.client('sqs')

def handler(event, context):
    # Send message to linked queue
    sqs.send_message(
        QueueUrl=Resource.MyQueue.url,
        MessageBody=json.dumps({
            'action': 'process',
            'data': 'example'
        })
    )
    
    return {
        'statusCode': 200,
        'body': json.dumps({'message': 'Message sent'})
    }

Secrets Example

from sst import Resource
import requests

def handler(event, context):
    # Access secret value
    api_key = Resource.StripeSecret.value
    
    # Use the secret
    response = requests.post(
        'https://api.stripe.com/v1/charges',
        headers={'Authorization': f'Bearer {api_key}'},
        data={'amount': 1000, 'currency': 'usd'}
    )
    
    return {
        'statusCode': 200,
        'body': response.text
    }

App Metadata

Access app information:

from sst import Resource

def handler(event, context):
    app_name = Resource.App.name
    stage = Resource.App.stage
    
    print(f"Running in {app_name} on {stage} stage")
    
    return {
        'statusCode': 200,
        'body': f'App: {app_name}, Stage: {stage}'
    }

How It Works

The Python SDK reads resource information from environment variables:

import os
import json

# SST sets these automatically
resource_data = os.environ.get('SST_RESOURCE_MyBucket')
bucket_info = json.loads(resource_data)
bucket_name = bucket_info['name']

# Or use the SDK wrapper
from sst import Resource
bucket_name = Resource.MyBucket.name  # Simpler

Error Handling

from sst import Resource
import boto3
from botocore.exceptions import ClientError

s3 = boto3.client('s3')

def handler(event, context):
    try:
        s3.put_object(
            Bucket=Resource.MyBucket.name,
            Key='file.txt',
            Body=b'Hello'
        )
        return {'statusCode': 200}
    except ClientError as e:
        print(f"Error: {e}")
        return {
            'statusCode': 500,
            'body': 'Internal server error'
        }

Type Hints

Use type hints for better IDE support:

from sst import Resource
from typing import Dict, Any
import boto3

def handler(event: Dict[str, Any], context: Any) -> Dict[str, Any]:
    bucket_name: str = Resource.MyBucket.name
    
    s3 = boto3.client('s3')
    s3.put_object(
        Bucket=bucket_name,
        Key='file.txt',
        Body=b'Hello'
    )
    
    return {
        'statusCode': 200,
        'body': 'Success'
    }

Best Practices

Reuse Boto3 Clients

Create clients outside the handler for reuse:

from sst import Resource
import boto3

# ✓ Good - client reused across invocations
s3 = boto3.client('s3')

def handler(event, context):
    s3.put_object(
        Bucket=Resource.MyBucket.name,
        Key='file.txt',
        Body=b'Hello'
    )

Handle Missing Resources

from sst import Resource

def handler(event, context):
    try:
        bucket_name = Resource.MyBucket.name
    except AttributeError:
        return {
            'statusCode': 500,
            'body': 'Bucket not linked'
        }

Use Environment Variables for Configuration

import os
from sst import Resource

DEBUG = os.environ.get('DEBUG', 'false').lower() == 'true'

def handler(event, context):
    if DEBUG:
        print(f"Using bucket: {Resource.MyBucket.name}")

Related

Linking

Learn how to link resources to Python functions

Function Component

Deploy Python Lambda functions with SST