[Python] How to inject a global httpx.AsyncClient session in FastAPI using dependency...

I'm using FastAPI and want to share an httpx.AsyncClient session across requests using dependency injection. I followed a pattern using FastAPI's lifespan function and storing the session in app.state as follows:

# Standard library imports
from contextlib import asynccontextmanager
from typing import AsyncGenerator, cast, Dict

# Third party library imports
import httpx
from fastapi import FastAPI, Request, Depends

@asynccontextmanager
async def lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
async with httpx.AsyncClient() as session:
app.state.session = session
yield

async def get_session(request: Request) -> httpx.AsyncClient:
return cast(httpx.AsyncClient, request.app.state.session)

app = FastAPI(lifespan=lifespan)

@app.get("/")
async def root(session: httpx.AsyncClient = Depends(get_session)) -> Dict[str, int]:
response = await session.get("https://www.stackoverflow.com")
return {"status": response.status_code}

if __name__ == "__main__":
import uvicorn
uvicorn.run(app)


This works well, but I’m wondering: are there alternative approaches to injecting a shared httpx.AsyncClient session in FastAPI? What are the potential drawbacks of this pattern?

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