dependency-injector 3.30.1

Dependency injection microframework for Python

What is Dependency Injector?

Dependency Injector is a dependency injection framework for Python.

It provides you with the container and the providers that help you build your application objects:

from dependency_injector import containers, providers


class ApiClient:

    def __init__(self, api_key: str, timeout: int):
        self.api_key = api_key
        self.timeout = timeout


class Service:

    def __init__(self, api_client: ApiClient):
        self.api_client = api_client


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,
    )


if __name__ == '__main__':
    container = Container()
    container.config.from_yaml('config.yml')

    service = container.service()

    assert isinstance(service.api_client, ApiClient)

More examples

Installation

The package is available on the PyPi:

pip install dependency-injector

Documentation

The documentation is available on the Read The Docs

Tutorials

Choose one of the following:

• Flask web application tutorial

• Aiohttp REST API tutorial

• Asyncio monitoring daemon tutorial

• CLI application tutorial

Concept

Dependency Injector stands on two principles:

• Explicit is better than implicit (PEP20).

• Do no magic to your code.

How does it different from the other frameworks?

• No autowiring. The framework does NOT do any autowiring / autoresolving of the dependencies. You need to specify everything explicitly. Because “Explicit is better than implicit” (PEP20).

• Does not pollute your code. Your application does NOT know and does NOT depend on the framework. No @inject decorators, annotations, patching or any other magic tricks.

Dependency Injector makes a simple contract with you:

• You tell the framework how to build you code

• The framework does it for you

The power of the Dependency Injector is in its simplicity and straightforwardness. It is a simple tool for the powerful concept.

Frequently asked questions

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

• you have no problems when you need to understand how it works or change it 😎

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 get it from the container

Why do I need a framework for this?

• you need the framework for this to not create it by your own

• this framework gives you the container and the providers

• the container is like a dictionary with the batteries 🔋

• the providers manage the lifetime of your components, you will need factories, singletons, smart config object etc

What price do I pay and what do I get?

• you need to explicitly specify the dependencies in the container

• it will be extra work in the beginning

• it will payoff when project grows or in two weeks 😊 (when you forget what project was about)

What features does the framework have?

• building objects graph

• smart configuration object

• providers: factory, singleton, thread locals registers, etc

• positional and keyword context injections

• overriding of the objects in any part of the graph

What features the framework does NOT have?

• autowiring / autoresolving of the dependencies

• the annotations and @inject-like decorators

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