AWS Chalice

Warnings

• gotcha Chalice automatically generates IAM policies for your Lambda functions. While convenient, these auto-generated policies can sometimes be overly permissive. For production environments, it's recommended to review the generated policies (in `.chalice/policy.json`) and manually refine them or disable auto-generation using `manage_iam_role=False` in `config.json` or the `--no-autogen-policy` flag during deployment for fine-grained control.
  Fix: Manually review `.chalice/policy.json` and refine permissions, or use `manage_iam_role=False` in `.chalice/config.json` and provide your own IAM role ARN.
• gotcha When using `chalice local` for local development and testing, the application runs in your local environment and uses your configured AWS CLI credentials, not the IAM role that would be assumed by the Lambda function in AWS. Ensure your local AWS profile has the necessary permissions to access any AWS services (e.g., DynamoDB, S3) your application interacts with during local testing.
  Fix: Ensure your local AWS CLI profile (e.g., `~/.aws/credentials`, `~/.aws/config`) has sufficient permissions for all AWS services your Chalice app uses.
• breaking The `@app.on_s3_event` decorator, used for triggering Lambda functions from S3 events, is incompatible with the `chalice package` command. If your application uses S3 event sources, you cannot use `chalice package` to generate a CloudFormation/SAM template; you must deploy directly using `chalice deploy`.
  Fix: If using `@app.on_s3_event`, use `chalice deploy` for direct deployment rather than `chalice package`.
• gotcha AWS Lambda has specific Python runtime versions it supports. While Chalice aims to support these, always verify that your local Python environment matches a supported AWS Lambda runtime (e.g., Python 3.9 through 3.13 are currently supported) to avoid deployment issues or unexpected behavior.
  Fix: Check AWS Lambda's current Python runtime support and ensure your development environment and `runtime` configuration in `.chalice/config.json` are compatible.

Install

• pip install chalice Install Chalice

Imports

• Chalice

  from chalice import Chalice

• Response

  from chalice import Response

  Used for customizing HTTP responses (status codes, headers, non-JSON bodies).
• Rate, Cron

  from chalice import Rate, Cron

  Used with @app.schedule decorator for defining scheduled events.

Quickstart

This quickstart demonstrates how to define a basic REST API with Chalice. After installing Chalice and configuring AWS credentials, create a new project using `chalice new-project <project-name>`, then update `app.py` with the provided code. Deploy the application to AWS Lambda and API Gateway with `chalice deploy`.

import os
from chalice import Chalice

# Configure AWS credentials if not already set up via AWS CLI
# os.environ['AWS_ACCESS_KEY_ID'] = os.environ.get('AWS_ACCESS_KEY_ID', 'YOUR_ACCESS_KEY')
# os.environ['AWS_SECRET_ACCESS_KEY'] = os.environ.get('AWS_SECRET_ACCESS_KEY', 'YOUR_SECRET_KEY')
# os.environ['AWS_DEFAULT_REGION'] = os.environ.get('AWS_DEFAULT_REGION', 'us-east-1')

app = Chalice(app_name='my-first-chalice-app')

@app.route('/')
def index():
    return {'hello': 'world'}

@app.route('/greet/{name}')
def greet_name(name):
    return {'message': f'Hello, {name}!'}

# To deploy:
# 1. Ensure AWS CLI is configured with credentials.
# 2. Run `chalice new-project my-first-chalice-app`
# 3. Replace the generated `app.py` content with the code above.
# 4. Run `chalice deploy` in your project directory.
# To test locally: `chalice local`
# To delete: `chalice delete`