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Engin 🏎️

Engin is a lightweight application framework powered by dependency injection. It helps you build and maintain everything from large monoliths to hundreds of microservices.

Features

Engin provides:

  • A fully-featured dependency injection system.
  • A robust runtime with lifecycle hooks and supervised background tasks.
  • Zero-boilerplate code reuse across applications.
  • Integrations for popular frameworks like FastAPI.
  • Full asyncio support.
  • A CLI for development utilities.

Installation

uv add engin

poetry add engin

pip install engin

Example

Here’s a minimal example showing how Engin wires dependencies, manages background tasks, and handles graceful shutdown.

import asyncio
from httpx import AsyncClient
from engin import Engin, Invoke, Lifecycle, OnException, Provide, Supervisor


def httpx_client_factory(lifecycle: Lifecycle) -> AsyncClient:
    client = AsyncClient()
    lifecycle.append(client)  # easily manage the AsyncClient's lifecycle concerns
    return client


async def main(httpx_client: AsyncClient, supervisor: Supervisor) -> None:
    async def long_running_task():
        while True:
            await httpx_client.get("https://example.org/")
            await asyncio.sleep(1.0)

    supervisor.supervise(long_running_task)  # let the app run the task in a supervised manner


engin = Engin(Provide(httpx_client_factory), Invoke(main))  # define our modular application

asyncio.run(engin.run())  # run it!

Expected output (with logging enabled):

[INFO]  engin: starting engin
[INFO]  engin: startup complete
[INFO]  engin: supervising task: long_running_task
[INFO]  httpx: HTTP Request: GET https://example.org/ "HTTP/1.1 200 OK"
[INFO]  httpx: HTTP Request: GET https://example.org/ "HTTP/1.1 200 OK"
[INFO]  httpx: HTTP Request: GET https://example.org/ "HTTP/1.1 200 OK"
[DEBUG] engin: received signal: SIGINT
[DEBUG] engin: supervised task 'long_running_task' was cancelled
[INFO]  engin: stopping engin
[INFO]  engin: shutdown complete