Pydantic でどのように設定を管理しますか？

from pydantic_settings import BaseSettings

class Settings(BaseSettings):
    app_name: str = "My API"
    database_url: str                       # required — must be provided
    secret_key: str                          # required (a secret)
    debug: bool = False
    max_connections: int = 10

    class Config:
        env_file = ".env"                    # also read from a .env file

settings = Settings()                        # reads & VALIDATES env vars at startup

from functools import lru_cache
from fastapi import Depends

@lru_cache                              # create the Settings once (cached)
def get_settings():
    return Settings()

@app.get("/info")
def info(settings: Settings = Depends(get_settings)):
    return {"app": settings.app_name, "debug": settings.debug}

# .env — local config, GITIGNORED (never commit secrets)
DATABASE_URL=postgresql://localhost/mydb
SECRET_KEY=dev-secret
DEBUG=true

✓ Keep secrets in env vars / .env (gitignored); commit a .env.example documenting keys
✓ In production, inject config via the platform's environment / secret manager
✓ Validation at startup catches misconfiguration immediately (not deep in a request)