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Dependency Injector is a dependency injection framework for Python.

It helps implementing the dependency injection principle.

Key features of theDependency Injector:

• Providers. ProvidesFactory,Singleton,Callable,Coroutine,Object,List,Dict,Configuration,Resource,Dependency andSelector providersthat help assembling your objects.SeeProviders.
• Overriding. Can override any provider by another provider on the fly. This helps in testingand configuring dev / stage environment to replace API clients with stubs etc. SeeProvider overriding.
• Configuration. Reads configuration fromyaml &ini files,pydantic settings,environment variables, and dictionaries.SeeConfiguration provider.
• Containers. Provides declarative and dynamic containers.SeeContainers.
• Resources. Helps with initialization and configuring of logging, event loop, threador process pool, etc. Can be used for per-function execution scope in tandem with wiring.SeeResource provider.
• Wiring. Injects dependencies into functions and methods. Helps integrating withother frameworks: Django, Flask, Aiohttp, Sanic, FastAPI, etc.SeeWiring.
• Asynchronous. Supports asynchronous injections.SeeAsynchronous injections.
• Typing. Provides typing stubs,mypy-friendly.SeeTyping and mypy.
• Performance. Fast. Written inCython.
• Maturity. Mature and production-ready. Well-tested, documented and supported.

fromdependency_injectorimportcontainers,providersfromdependency_injector.wiringimportinject,ProvideclassContainer(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,    )@injectdefmain(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()# <-- dependency is injected automaticallywithcontainer.api_client.override(mock.Mock()):main()# <-- overridden dependency is injected automatically

When you callmain() function theService dependency is assembled and injected automatically.

When doing a testing you call thecontainer.api_client.override() to replace the real APIclient with a mock. When you callmain() 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 clientwith a stub on the dev or stage.

With theDependency 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 theDependency injection and inversion of control in Python.

The package is available on thePyPi:

pip install dependency-injector

The documentation is availablehere.

Choose one of the following:

• Application example (single container)
• Application example (multiple containers)
• Decoupled packages example (multiple containers)
• Boto3 example
• Django example
• Flask example
• Aiohttp example
• Sanic example
• FastAPI example
• FastAPI + Redis example
• FastAPI + SQLAlchemy example

Choose one of the following:

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

The framework stands on thePEP20 (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 aGithub Issue

Found a bug?

• Open aGithub Issue

Want to help?

• ⭐️ Star theDependency Injector on theGithub
• 🆕 Start a new project with theDependency Injector
• 💬 Tell your friend about theDependency Injector

Want to contribute?

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