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247 lines
8.2 KiB
ReStructuredText
.. figure:: https://raw.githubusercontent.com/wiki/ets-labs/python-dependency-injector/img/logo.svg
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:target: https://github.com/ets-labs/python-dependency-injector
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.. image:: https://img.shields.io/pypi/v/dependency_injector.svg
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:target: https://pypi.org/project/dependency-injector/
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:alt: Latest Version
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.. image:: https://img.shields.io/pypi/l/dependency_injector.svg
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:target: https://pypi.org/project/dependency-injector/
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:alt: License
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.. image:: https://img.shields.io/pypi/pyversions/dependency_injector.svg
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:target: https://pypi.org/project/dependency-injector/
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:alt: Supported Python versions
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.. image:: https://img.shields.io/pypi/implementation/dependency_injector.svg
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:target: https://pypi.org/project/dependency-injector/
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:alt: Supported Python implementations
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.. image:: https://pepy.tech/badge/dependency-injector
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:target: https://pepy.tech/project/dependency-injector
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:alt: Downloads
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.. image:: https://pepy.tech/badge/dependency-injector/month
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:target: https://pepy.tech/project/dependency-injector
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:alt: Downloads
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.. image:: https://pepy.tech/badge/dependency-injector/week
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:target: https://pepy.tech/project/dependency-injector
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:alt: Downloads
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.. image:: https://img.shields.io/pypi/wheel/dependency-injector.svg
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:target: https://pypi.org/project/dependency-injector/
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:alt: Wheel
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.. image:: https://travis-ci.org/ets-labs/python-dependency-injector.svg?branch=master
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:target: https://travis-ci.org/ets-labs/python-dependency-injector
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:alt: Build Status
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.. image:: http://readthedocs.org/projects/python-dependency-injector/badge/?version=latest
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:target: http://python-dependency-injector.ets-labs.org/
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:alt: Docs Status
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.. image:: https://coveralls.io/repos/github/ets-labs/python-dependency-injector/badge.svg?branch=master
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:target: https://coveralls.io/github/ets-labs/python-dependency-injector?branch=master
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:alt: Coverage Status
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What is ``Dependency Injector``?
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================================
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``Dependency Injector`` is a dependency injection framework for Python.
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It helps you implement the dependency injection principle.
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What is dependency injection?
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-----------------------------
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Dependency injection is a principle that helps to decrease coupling and increase cohesion. Your
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code becomes more flexible, clear and it is easier to test it.
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How to implement dependency injection?
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--------------------------------------
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Objects do not create each other anymore. They provide a way to inject the needed dependency
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instead.
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Before:
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.. code-block:: python
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class ApiClient:
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def __init__(self):
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self.api_key = os.getenv('API_KEY')
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self.timeout = os.getenv('TIMEOUT')
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class Service:
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def __init__(self):
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self.api_client = ApiClient()
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After:
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.. code-block:: python
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class ApiClient:
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def __init__(self, api_key: str, timeout: int):
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self.api_key = api_key
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self.timeout = timeout
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class Service:
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def __init__(self, api_client: ApiClient):
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self.api_client = api_client
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Who creates the objects now? Look at the next section.
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What does Dependency Injector do?
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---------------------------------
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``Dependency Injector`` provides you with the container and the providers that help you build
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your application objects when you apply dependency injection principle:
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.. code-block:: python
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from dependency_injector import containers, providers
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from unittest import mock
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from .example_di import ApiClient, Service
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class Container(containers.DeclarativeContainer):
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config = providers.Configuration()
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api_client = providers.Singleton(
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ApiClient,
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api_key=config.api_key,
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timeout=config.timeout,
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)
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service = providers.Factory(
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Service,
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api_client=api_client,
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)
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if __name__ == '__main__':
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container = Container()
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container.config.from_yaml('config.yml')
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service = container.service()
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assert isinstance(service.api_client, ApiClient)
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with container.api_client.override(mock.Mock()):
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service = container.service()
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assert isinstance(service.api_client, mock.Mock)
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`More examples <https://github.com/ets-labs/python-dependency-injector/tree/master/examples>`_
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Installation
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------------
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The package is available on the `PyPi`_::
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pip install dependency-injector
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Documentation
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-------------
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The documentation is available on the `Read The Docs <http://python-dependency-injector.ets-labs.org/>`_
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Tutorials
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---------
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Choose one of the following:
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- `Flask web application tutorial <http://python-dependency-injector.ets-labs.org/tutorials/flask.html>`_
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- `Aiohttp REST API tutorial <http://python-dependency-injector.ets-labs.org/tutorials/aiohttp.html>`_
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- `Asyncio monitoring daemon tutorial <http://python-dependency-injector.ets-labs.org/tutorials/asyncio-daemon.html>`_
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- `CLI application tutorial <http://python-dependency-injector.ets-labs.org/tutorials/cli.html>`_
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Concept
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-------
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``Dependency Injector`` stands on two principles:
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- Explicit is better than implicit (PEP20).
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- Do no magic to your code.
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How does it different from the other frameworks?
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- **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)*.
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- **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.
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``Dependency Injector`` makes a simple contract with you:
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- You tell the framework how to build you code
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- The framework does it for you
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The power of the ``Dependency Injector`` is in its simplicity and straightforwardness. It is a simple tool for the powerful concept.
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Frequently asked questions
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--------------------------
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What is the dependency injection?
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- dependency injection is a principle that decreases coupling and increases cohesion
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Why should I do the dependency injection?
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- your code becomes more flexible, testable and clear
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- you have no problems when you need to understand how it works or change it 😎
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How do I start doing the dependency injection?
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- you start writing the code following the dependency injection principle
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- you register all of your application components and their dependencies in the container
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- when you need a component, you get it from the container
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Why do I need a framework for this?
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- you need the framework for this to not create it by your own
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- this framework gives you the container and the providers
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- the container is like a dictionary with the batteries 🔋
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- the providers manage the lifetime of your components, you will need factories, singletons, smart config object etc
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What price do I pay and what do I get?
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- you need to explicitly specify the dependencies in the container
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- it will be extra work in the beginning
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- it will payoff when project grows or in two weeks 😊 (when you forget what project was about)
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What features does the framework have?
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- building objects graph
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- smart configuration object
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- providers: factory, singleton, thread locals registers, etc
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- positional and keyword context injections
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- overriding of the objects in any part of the graph
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What features the framework does NOT have?
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- autowiring / autoresolving of the dependencies
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- the annotations and ``@inject``-like decorators
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Have a question?
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- Open a `Github Issue <https://github.com/ets-labs/python-dependency-injector/issues>`_
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Found a bug?
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- Open a `Github Issue <https://github.com/ets-labs/python-dependency-injector/issues>`_
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Want to help?
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- |star| Star the ``Dependency Injector`` on the `Github <https://github.com/ets-labs/python-dependency-injector/>`_
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- |new| Start a new project with the ``Dependency Injector``
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- |tell| Tell your friend about the ``Dependency Injector``
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Want to contribute?
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- |fork| Fork the project
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- |pull| Open a pull request to the ``develop`` branch
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.. _PyPi: https://pypi.org/project/dependency-injector/
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.. |star| unicode:: U+2B50 U+FE0F .. star sign1
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.. |new| unicode:: U+1F195 .. new sign
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.. |tell| unicode:: U+1F4AC .. tell sign
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.. |fork| unicode:: U+1F500 .. fork sign
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.. |pull| unicode:: U+2B05 U+FE0F .. pull sign
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