.. figure:: https://raw.githubusercontent.com/wiki/ets-labs/python-dependency-injector/img/logo.svg :target: https://github.com/ets-labs/python-dependency-injector | .. image:: https://img.shields.io/pypi/v/dependency_injector.svg :target: https://pypi.org/project/dependency-injector/ :alt: Latest Version .. image:: https://img.shields.io/pypi/l/dependency_injector.svg :target: https://pypi.org/project/dependency-injector/ :alt: License .. image:: https://img.shields.io/pypi/pyversions/dependency_injector.svg :target: https://pypi.org/project/dependency-injector/ :alt: Supported Python versions .. image:: https://img.shields.io/pypi/implementation/dependency_injector.svg :target: https://pypi.org/project/dependency-injector/ :alt: Supported Python implementations .. image:: https://pepy.tech/badge/dependency-injector :target: https://pepy.tech/project/dependency-injector :alt: Downloads .. image:: https://pepy.tech/badge/dependency-injector/month :target: https://pepy.tech/project/dependency-injector :alt: Downloads .. image:: https://pepy.tech/badge/dependency-injector/week :target: https://pepy.tech/project/dependency-injector :alt: Downloads .. image:: https://img.shields.io/pypi/wheel/dependency-injector.svg :target: https://pypi.org/project/dependency-injector/ :alt: Wheel .. image:: https://travis-ci.org/ets-labs/python-dependency-injector.svg?branch=master :target: https://travis-ci.org/ets-labs/python-dependency-injector :alt: Build Status .. image:: http://readthedocs.org/projects/python-dependency-injector/badge/?version=latest :target: http://python-dependency-injector.ets-labs.org/ :alt: Docs Status .. image:: https://coveralls.io/repos/github/ets-labs/python-dependency-injector/badge.svg?branch=master :target: https://coveralls.io/github/ets-labs/python-dependency-injector?branch=master :alt: Coverage Status What is ``Dependency Injector``? ================================ ``Dependency Injector`` is a dependency injection framework for Python. It helps you implement the dependency injection principle. What is dependency injection? ----------------------------- Dependency injection is a principle that helps to decrease coupling and increase cohesion. Your code becomes more flexible, clear and it is easier to test it. How to implement dependency injection? -------------------------------------- Objects do not create each other anymore. They provide a way to inject the needed dependency instead. Before: .. code-block:: python class ApiClient: def __init__(self): self.api_key = os.getenv('API_KEY') self.timeout = os.getenv('TIMEOUT') class Service: def __init__(self): self.api_client = ApiClient() After: .. code-block:: python 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 Who creates the objects now? Look at the next section. What does Dependency Injector do? --------------------------------- ``Dependency Injector`` provides you with the container and the providers that help you build your application objects when you apply dependency injection principle: .. code-block:: python 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| Star the ``Dependency Injector`` on the `Github `_ - |new| Start a new project with the ``Dependency Injector`` - |tell| Tell your friend about the ``Dependency Injector`` Want to contribute? - |fork| Fork the project - |pull| Open a pull request to the ``develop`` branch .. _PyPi: https://pypi.org/project/dependency-injector/ .. |star| unicode:: U+2B50 U+FE0F .. star sign1 .. |new| unicode:: U+1F195 .. new sign .. |tell| unicode:: U+1F4AC .. tell sign .. |fork| unicode:: U+1F500 .. fork sign .. |pull| unicode:: U+2B05 U+FE0F .. pull sign