fastapi-standalone-di

Use FastAPI's dependency injection outside of any web/ASGI context.

FastAPI ships a powerful dependency injection system — Depends, sub-dependencies, yield teardown, per-resolution caching — but it is tightly coupled to the request/response cycle. fastapi-standalone-di reuses that exact machinery so you can resolve and invoke your dependencies from plain Python: CLI scripts, workers, cron jobs, tests — no HTTP server required.

Install

pip install fastapi-standalone-di
# or
uv add fastapi-standalone-di

Usage

Resolve any callable that uses Depends(), exactly as FastAPI would:

import asyncio

from fastapi import Depends

from fastapi_standalone_di import FastAPIContainer


def get_settings() -> dict[str, str]:
    return {"db_url": "postgres://localhost/app"}


class Database:
    def __init__(self, settings: dict[str, str] = Depends(get_settings)) -> None:
        self.url = settings["db_url"]


async def main() -> None:
    async with FastAPIContainer() as container:
        db = await container.get(Database)
        print(db.url)  # postgres://localhost/app


asyncio.run(main())

Sub-dependencies, yield teardown, caching, scopes, dependency overrides, registrable interfaces, per-package binding discovery, shared app state, application-lifetime singletons, loop-safe execution without a threadpool hop, standalone Request/Response stubs, and query/path/header/cookie parameters are all covered in the documentation.

Documentation

Full documentation is available at toilal.github.io/fastapi-standalone-di. The in-development docs (built from develop) are previewed at toilal.github.io/fastapi-standalone-di/dev/.

Requirements

• Python ≥ 3.11
• FastAPI ≥ 0.61

License

MIT © Rémi Alvergnat