"That Depends"

Dependency injection framework for Python inspired by dependency-injector.

It is production-ready and gives you the following:

• Simple async-first DI framework with IOC-container.
• Python 3.10-3.12 support.
• Full coverage by types annotations (mypy in strict mode).
• FastAPI and LiteStar compatibility.
• Overriding dependencies for tests.
• Injecting dependencies in functions and coroutines without wiring.
• Package with zero dependencies.

📚 Documentation

Projects with That Depends:

• fastapi-sqlalchemy-template - FastAPI template with sqlalchemy2 and PostgreSQL
• litestar-sqlalchemy-template - LiteStar template with sqlalchemy2 and PostgreSQL

Quickstart

Install

pip install that-depends

Describe resources and classes:

import dataclasses
import logging
import typing

logger = logging.getLogger(__name__)

# singleton provider with finalization
def create_sync_resource() -> typing.Iterator[str]:
    logger.debug("Resource initiated")
    try:
        yield "sync resource"
    finally:
        logger.debug("Resource destructed")

# same, but async
async def create_async_resource() -> typing.AsyncIterator[str]:
    logger.debug("Async resource initiated")
    try:
        yield "async resource"
    finally:
        logger.debug("Async resource destructed")

@dataclasses.dataclass(kw_only=True, slots=True)
class DependentFactory:
    sync_resource: str
    async_resource: str

Describe IoC-container

from that_depends import BaseContainer, providers

class DIContainer(BaseContainer):
    sync_resource = providers.Resource(create_sync_resource)
    async_resource = providers.Resource(create_async_resource)

    simple_factory = providers.Factory(SimpleFactory, dep1="text", dep2=123)
    dependent_factory = providers.Factory(
        sync_resource=sync_resource,
        async_resource=async_resource,
    )

Resolve dependencies in your code

# async resolving by default:
await DIContainer.simple_factory()

# sync resolving is also allowed if there is no uninitialized async resources in dependencies
DIContainer.simple_factory.sync_resolve()

# otherwise you can initialize resources beforehand one by one or in one call:
await DIContainer.init_resources()

Resolve dependencies not described in container

@dataclasses.dataclass(kw_only=True, slots=True)
class FreeFactory:
    dependent_factory: DependentFactory
    sync_resource: str

# this way container will try to find providers by names and resolve them to build FreeFactory instance
free_factory_instance = await DIContainer.resolve(FreeFactory)

Inject providers in function arguments

import datetime

from that_depends import inject, Provide

from tests import container

@inject
async def some_coroutine(
    simple_factory: container.SimpleFactory = Provide[container.DIContainer.simple_factory],
    dependent_factory: container.DependentFactory = Provide[container.DIContainer.dependent_factory],
    default_zero: int = 0,
) -> None:
    assert simple_factory.dep1
    assert isinstance(dependent_factory.async_resource, datetime.datetime)
    assert default_zero == 0

@inject
def some_function(
    simple_factory: container.SimpleFactory = Provide[container.DIContainer.simple_factory],
    default_zero: int = 0,
) -> None:
    assert simple_factory.dep1
    assert default_zero == 0