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FastAPI Dependency Injection for Settings

Provide shared settings through a FastAPI dependency so handlers receive a configured object and tests can override it cleanly.

PythonConfig Management

Code

snippet
import os
from functools import lru_cache
from typing import Annotated

from fastapi import Depends, FastAPI
from pydantic import BaseModel

app = FastAPI()


class Settings(BaseModel):
    service_name: str
    max_page_size: int = 100


@lru_cache
def get_settings() -> Settings:
    return Settings(service_name=os.environ.get("SERVICE_NAME", "api"))


@app.get("/health")
def health(settings: Annotated[Settings, Depends(get_settings)]) -> dict:
    return {"status": "ok", "service": settings.service_name}

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