Quick Start

pip install "dynamic-config-py[fastapi]"

from dataclasses import dataclass

from fastapi import Depends, FastAPI

from dynamic_config import DynamicConfig
from dynamic_config_web.fastapi import config_dependency, setup


@dataclass
class Database:
    host: str = "localhost"
    port: int = 5432


config = DynamicConfig(Database, key="db").file("config.toml").env("APP_")

app = FastAPI()
setup(app, config)                     # lifecycle + request scope + routes
database = config_dependency(config)


@app.get("/")
def index(db: Database = Depends(database)) -> dict[str, str]:
    return {"host": db.host}

Run it — uvicorn main:app — and you have:

setup did four things: loaded before the first request (a broken document fails startup, not traffic), started the watcher and stops it on shutdown, opened a request scope around every request, and mounted the routes above. Every adapter here is those same four things through its own framework's seams — the Introduction has the table of nine.

Edit config.toml while it serves: the next request answers with the new document, and no request ever straddles the change — that is the request scope, and The Rules is the page that spells out what it promises and what it refuses to.

Diagnostics (/_config/explain, /_config/check) exist only when you pass a guard: setup(app, config, guard=token_guard("s3cret")) — see Diagnostics.