index.rst

Dependency Injector --- Dependency injection framework for Python

Dependency Injector is a dependency injection framework for Python.

It helps implementing the dependency injection principle.

Key features of the Dependency Injector:

• Providers. Provides Factory, Singleton, Callable, Coroutine, Object, List, Dict, Configuration, Resource, Dependency, and Selector providers that help assemble your objects. See :ref:`providers`.
• Overriding. Can override any provider by another provider on the fly. This helps in testing and configuring dev/stage environment to replace API clients with stubs etc. See :ref:`provider-overriding`.
• Configuration. Reads configuration from yaml, ini, and json files, pydantic settings, environment variables, and dictionaries. See :ref:`configuration-provider`.
• Resources. Helps with initialization and configuring of logging, event loop, thread or process pool, etc. Can be used for per-function execution scope in tandem with wiring. See :ref:`resource-provider`.
• Containers. Provides declarative and dynamic containers. See :ref:`containers`.
• Wiring. Injects dependencies into functions and methods. Helps integrate with other frameworks: Django, Flask, Aiohttp, Sanic, FastAPI, etc. See :ref:`wiring`.
• Asynchronous. Supports asynchronous injections. See :ref:`async-injections`.
• Typing. Provides typing stubs, mypy-friendly. See :ref:`provider-typing`.
• Performance. Fast. Written in Cython.
• Maturity. Mature and production-ready. Well-tested, documented, and supported.

from dependency_injector import containers, providers
from dependency_injector.wiring import Provide, inject


class Container(containers.DeclarativeContainer):

    config = providers.Configuration()

    api_client = providers.Singleton(
        ApiClient,
        api_key=config.api_key,
        timeout=config.timeout,
    )

    service = providers.Factory(
        Service,
        api_client=api_client,
    )


@inject
def main(service: Service = Provide[Container.service]) -> None:
    ...


if __name__ == "__main__":
    container = Container()
    container.config.api_key.from_env("API_KEY", required=True)
    container.config.timeout.from_env("TIMEOUT", as_=int, default=5)
    container.wire(modules=[__name__])

    main()  # <-- dependency is injected automatically

    with container.api_client.override(mock.Mock()):
        main()  # <-- overridden dependency is injected automatically

With the Dependency Injector, object assembling is consolidated in the container. Dependency injections are defined explicitly. This makes it easier to understand and change how the application works.

Explore the documentation to know more about the Dependency Injector.

Contents

.. toctree::
   :maxdepth: 2

   introduction/index
   examples/index
   tutorials/index
   providers/index
   containers/index
   wiring
   examples-other/index
   api/index
   main/feedback
   main/changelog