This a demo on how we can use an IoC container with FastAPI. Checkout my full article here: https://medium.com/@mohammad.elmi/how-to-use-fastapi-with-an-ioc-framework-f32c67d8c59b

fastapi-ioc-demo.py

import functools
from typing import Annotated, Any, Callable, Protocol, Type, TypeVar
from fastapi import APIRouter, Depends, FastAPI, Request
import punq


# domain - no dependency to FastAPI or IoC

class Greeter(Protocol):
    def greet(self) -> str: ...


class WorldGreeter(Greeter):
    def greet(self) -> str:
        return 'Hello World!'


# IoC

def get_container() -> punq.Container:
    container = punq.Container()
    container.register(Greeter, WorldGreeter)
    return container


# Helper - No dependency to app or container

T = TypeVar('T')


def Service(t: Type[T]) -> Any:  # noqa: N802
    def resolver(t: Type[T], request: Request) -> Callable[[], T]:
        return request.app.state.ioc_container.resolve(t)
    return Depends(functools.partial(resolver, t))

# API - No dependency to app or container


router = APIRouter()


@router.get("/greet")
async def greet(greeter: Annotated[Greeter, Service(Greeter)]):
    return {"message": greeter.greet()}

# app

app = FastAPI()
app.state.ioc_container = get_container()
app.include_router(router)