modern-di-flask 3.1.1

Modern-DI integration for Flask.

Full guide: Flask integration docs

Usage example: examples/

Installation

uv add modern-di-flask      # or: pip install modern-di-flask

Usage

Flask has no dependency-injection system of its own, so modern-di-flask pairs an @inject decorator with inert FromDI markers (there is no Depends). setup_di installs a before_request/teardown_appcontext pair that builds a per-request Scope.REQUEST child container and closes it once the request finishes. Resolution is sync-only — the child container is closed with close_sync().

import typing

from flask import Flask
from modern_di import Container, Group, Scope, providers
from modern_di_flask import FromDI, inject, setup_di


class Settings:
    def __init__(self) -> None:
        self.greeting = "hello"


class Dependencies(Group):
    settings = providers.Factory(scope=Scope.APP, creator=Settings)


app = Flask(__name__)


@app.route("/hello/<name>")
@inject
def hello(name: str, settings: typing.Annotated[Settings, FromDI(Dependencies.settings)]) -> str:
    return f"{settings.greeting}, {name}"


# call setup_di AFTER registering routes (required when using auto_inject) —
# it registers flask_request_provider, so validate after it rather than before
container = Container(groups=[Dependencies])
setup_di(app, container)
container.validate()  # optional fail-fast; flask_request_provider is registered by now

Pass auto_inject=True to setup_di to wire every registered view (app and blueprint routes alike) without a per-view @inject; because it walks app.view_functions at call time, setup_di must run after all routes are registered. flask.Request is resolvable within DI via the pre-built flask_request_provider context provider. Flask has no application-startup/shutdown hook, so the root container's shutdown is yours to own. As of modern-di 3.1 a container is open from construction, so no .open() call is needed before serving. Validation is explicit in 3.1: if you want boot-time fail-fast, call .validate() after setup_di (which registers flask_request_provider) — validating first would fail any provider with a non-optional flask.Request dependency, because that provider does not exist yet. Call fetch_di_container(app).close_sync() at your process-shutdown point; that half is still yours, since Flask has no shutdown hook to attach to.

API

📦 PyPI

📝 License

Part of modern-python

Built on modern-di, a dependency-injection framework with IoC container and scopes.

Browse the full list of templates and libraries in modern-python — see the org profile for the categorized index.