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http resolver local

Http Resolver (Local Development)

Local Development Only

HttpResolverLocal is intended for local development and testing only. The API may change in future releases. Do not use in production environments.

When developing locally, you can use HttpResolverLocal to run your API with any ASGI server like uvicorn. It implements the ASGI specification, is lightweight with no external dependencies, and the same code works on any compute platform, including Lambda.

If your Lambda is behind Lambda Web Adapter or any other HTTP proxy that speaks the HTTP protocol, it works seamlessly.

All existing resolver features work out of the box: routing, middleware, validation, OpenAPI/Swagger, CORS, exception handling, and more.

Install uvicorn:

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pip install uvicorn

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from aws_lambda_powertools.event_handler import HttpResolverLocal

app = HttpResolverLocal()


@app.get("/hello/<name>")
def hello(name: str):
    return {"message": f"Hello, {name}!"}


# Lambda handler - same code works in Lambda
handler = app

Run locally: uvicorn app:app --reload

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from pydantic import BaseModel

from aws_lambda_powertools.event_handler import HttpResolverLocal


class User(BaseModel):
    name: str
    age: int


app = HttpResolverLocal(enable_validation=True)

app.enable_swagger(
    title="My API",
    version="1.0.0",
)


@app.post("/users")
def create_user(user: User) -> dict:
    return {"id": "123", "user": user.model_dump()}


handler = app

Access Swagger UI at http://localhost:8000/swagger

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from aws_lambda_powertools.event_handler import HttpResolverLocal, Response

app = HttpResolverLocal()


class NotFoundError(Exception):
    def __init__(self, resource: str):
        self.resource = resource


@app.exception_handler(NotFoundError)
def handle_not_found_error(exc: NotFoundError):
    return Response(
        status_code=404,
        content_type="application/json",
        body={"error": "Not Found", "resource": exc.resource},
    )


@app.not_found
def handle_not_found(exc: Exception):
    return Response(
        status_code=404,
        content_type="application/json",
        body={"error": "Route not found", "path": app.current_event.path},
    )


@app.get("/users/<user_id>")
def get_user(user_id: str):
    if user_id == "0":
        raise NotFoundError(f"User {user_id}")
    return {"user_id": user_id}


handler = app