Modern DI

Welcome to the modern-di documentation!

modern-di is a Python dependency injection framework which supports the following:

• Automatic dependencies graph based on type annotations
• Also, explicit dependencies are allowed where needed
• Scopes and context management
• Python 3.10+ support
• Fully typed and tested
• Integrations with FastAPI, FastStream, LiteStar, Typer, and pytest

Usage examples:

• with LiteStar - litestar-sqlalchemy-template
• with FastAPI - fastapi-sqlalchemy-template

---

Quickstart

1. Install modern-di using your favorite tool:

If you need only modern-di without integrations:

uvpippoetry

uv add modern-di

pip install modern-di

poetry add modern-di

If you need to integrate with fastapi or litestar, then install modern-di-fastapi or modern-di-litestar accordingly.

2. Describe resources and classes:

import dataclasses
import logging
import typing


logger = logging.getLogger(__name__)


def create_singleton() -> str:
    return "some string"


@dataclasses.dataclass(kw_only=True, slots=True, frozen=True)
class SimpleFactory:
    dep1: str
    dep2: int


@dataclasses.dataclass(kw_only=True, slots=True, frozen=True)
class DependentFactory:
    simple_factory: SimpleFactory
    singleton: str

3. Describe dependencies groups

from modern_di import Group, Scope, providers


class Dependencies(Group):
    singleton = providers.Factory(
        scope=Scope.APP,  # scope is APP by default, can be missing
        creator=create_singleton,
        cache_settings=providers.CacheSettings()
    )

    # relation between dependent_factory and simple_factory will be defined based on type annotations
    simple_factory = providers.Factory(
        scope=Scope.REQUEST,
        creator=SimpleFactory,
        kwargs={"dep1": "text", "dep2": 123}
    )
    dependent_factory = providers.Factory(
        scope=Scope.REQUEST,
        creator=DependentFactory,
    )

4.1. Integrate with your framework

For now there are integrations for the following frameworks:

1. FastAPI
2. FastStream
3. LiteStar
4. Typer
5. Pytest

4.2. Or use modern-di without integrations

Create a container and resolve dependencies in your code

from modern_di import Container, Scope


ALL_GROUPS = [Dependencies]

# Initialize container of app scope
# Pass validate=True to detect circular dependencies at startup
container = Container(groups=ALL_GROUPS, validate=True)

# Resolve provider
instance1 = container.resolve_provider(Dependencies.singleton)

# You can also resolve by type if you've registered groups
instance2 = container.resolve(str)  # resolves the singleton

# Create container of request scope
with container.build_child_container(scope=Scope.REQUEST) as request_container:
    # Resolve factories of request scope
    instance3 = request_container.resolve_provider(Dependencies.simple_factory)
    instance4 = request_container.resolve_provider(Dependencies.dependent_factory)
    # Use your instances...
# Finalizers run automatically on `with` exit. In async code, use
# `async with container.build_child_container(...) as request_container:` instead.