Dependency Injector

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 assembling your objects. See 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 Provider overriding.

  • Configuration. Reads configuration from yaml & ini files, pydantic settings, environment variables, and dictionaries. See Configuration provider.

  • Containers. Provides declarative and dynamic containers. See Containers.

  • 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 Resource provider.

  • Wiring. Injects dependencies into functions and methods. Helps integrating with other frameworks: Django, Flask, Aiohttp, Sanic, FastAPI, etc. See Wiring.

  • Asynchronous. Supports asynchronous injections. See Asynchronous injections.

  • Typing. Provides typing stubs, mypy-friendly. See Typing and mypy.

  • 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 inject, Provide

    class Container(containers.DeclarativeContainer):

      config = providers.Configuration()
      api_client = providers.Singleton(
      service = providers.Factory(

    def main(service: Service = Provide[Container.service]):

    if name == 'main':
    container = Container()

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

When you call main() function the Service dependency is assembled and injected automatically.

When doing a testing you call the container.api_client.override() to replace the real API client with a mock. When you call main() the mock is injected.

You can override any provider with another provider.

It also helps you in configuring project for the different environments: replace an API client with a stub on the dev or stage.

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

Visit the docs to know more about the Dependency injection and inversion of control in Python.