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, Configuration, 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. Read configuration from yaml & ini files, environment variables and dictionaries. See Configuration provider.
• Containers. Provides declarative and dynamic containers. See Containers.
• Wiring. Injects container providers into functions and methods. Helps integrating with other frameworks: Django, Flask, Aiohttp, etc. See Wiring.
• 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 Provide class Container(containers.DeclarativeContainer): config = providers.Configuration() api_client = providers.Singleton( ApiClient, api_key=config.api_key, timeout=config.timeout.as_int(), ) service = providers.Factory( Service, api_client=api_client, ) def main(service: Service = Provide[Container.service]): ... if __name__ == '__main__': container = Container() container.config.api_key.from_env('API_KEY') container.config.timeout.from_env('TIMEOUT') container.wire(modules=[sys.modules[__name__]]) main()

With the Dependency Injector you explicitly define and inject the dependencies. 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.

The package is available on the PyPi:

pip install dependency-injector 

The documentation is available on the Read The Docs

Choose one of the following:

• Application example (single container)
• Application example (multiple containers)
• Decoupled packages example (multiple containers)

Choose one of the following:

• Flask web application tutorial
• Aiohttp REST API tutorial
• Asyncio monitoring daemon tutorial
• CLI application tutorial

The framework stands on the PEP20 (The Zen of Python) principle:

Explicit is better than implicit 

You need to specify how to assemble and where to inject the dependencies explicitly.

The power of the framework is in a simplicity. Dependency Injector is a simple tool for the powerful concept.

What is the dependency injection?

• dependency injection is a principle that decreases coupling and increases cohesion

Why should I do the dependency injection?

• your code becomes more flexible, testable and clear 😎

How do I start doing the dependency injection?

• you start writing the code following the dependency injection principle
• you register all of your application components and their dependencies in the container
• when you need a component, you specify where to inject it or get it from the container

What price do I pay and what do I get?

• you need to explicitly specify the dependencies
• it will be extra work in the beginning
• it will payoff as the project grows

Have a question?

• Open a Github Issue

Found a bug?

• Open a Github Issue

Want to help?

• ⭐️ Star the Dependency Injector on the Github
• 🆕 Start a new project with the Dependency Injector
• 💬 Tell your friend about the Dependency Injector

Want to contribute?

• 🔀 Fork the project
• ⬅️ Open a pull request to the develop branch