deps-injection

Injection

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Easy dependency injection for all, works with Python 3.8-3.12. Main features and advantages:

• support Python 3.8-3.12;
• works with FastAPI, Litestar, Flask and Django REST Framework;
• support dependency injection via Annotated in FastAPI;
• the code is fully typed and checked with mypy;
• no third-party dependencies;
• no wiring;
• the life cycle of objects (scope) is implemented by providers;
• overriding dependencies for testing;
• 100% code coverage;
• good documentation;
• intuitive and almost identical api with dependency-injector, which will allow you to easily migrate to injection (see migration from dependency injector);

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Installation

pip install deps-injection

Compatibility between web frameworks and injection features

Framework	Dependency injection with @inject	Overriding providers	Dependency injection with @autoinject
FastAPI	✅	✅	➖
Flask	✅	✅	✅
Django REST Framework	✅	✅	✅
Litestar	✅	⚠️	➖

Using example with FastAPI

from typing import Annotated
from unittest.mock import Mock

import pytest
from fastapi import APIRouter, Depends, FastAPI
from fastapi.testclient import TestClient
from injection import DeclarativeContainer, Provide, inject, providers


class Settings:
    redis_url: str = "redis://localhost"
    redis_port: int = 6379


class Redis:
    def __init__(self, *, url: str, port: int):
        self.uri = url + ":" + str(port)
        self.url = url
        self.port = port

    def get(self, key):
        return key


class Container(DeclarativeContainer):
    settings = providers.Singleton(Settings)
    redis = providers.Singleton(
        Redis,
        port=settings.provided.redis_port,
        url=settings.provided.redis_url,
    )


router = APIRouter(prefix="/api")


def create_app():
    app = FastAPI()
    app.include_router(router)
    return app


RedisDependency = Annotated[Redis, Depends(Provide[Container.redis])]


@router.get("/values")
@inject
def some_get_endpoint_handler(redis: RedisDependency):
    value = redis.get(299)
    return {"detail": value}

Testing example with overriding providers for above FastAPI example

@pytest.fixture(scope="session")
def app():
    return create_app()


@pytest.fixture(scope="session")
def container():
    return Container.instance()


@pytest.fixture()
def test_client(app):
    client = TestClient(app)
    return client


def test_override_providers(test_client, container):
    def mock_get_method(_):
        return "mock_get_method"

    mock_redis = Mock()
    mock_redis.get = mock_get_method

    providers_to_override = {"redis": mock_redis}

    with container.override_providers(providers_to_override):
        response = test_client.get("/api/values")

    assert response.status_code == 200
    body = response.json()
    assert body["detail"] == "mock_get_method"