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What is ``Dependency Injector``?
================================
``Dependency Injector`` is a dependency injection framework for Python.
It 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.
Example
=======
With the ``Dependency Injector`` you keep **application structure in one place**.
This place is called **the container**. You use the container to manage all the components of the
application. All the component dependencies are defined explicitly. This provides the control on
the application structure. It is **easy to understand and change** it.
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*The container is like a map of your application. You always know what depends on what.*
Example application container:
.. code-block:: python
import logging
import sys
from dependency_injector import containers, providers
from . import http, monitors, dispatcher
class ApplicationContainer(containers.DeclarativeContainer):
config = providers.Configuration()
configure_logging = providers.Callable(
logging.basicConfig,
stream=sys.stdout,
level=config.log.level,
format=config.log.format,
)
http_client = providers.Factory(http.HttpClient)
example_monitor = providers.Factory(
monitors.HttpMonitor,
http_client=http_client,
options=config.monitors.example,
)
httpbin_monitor = providers.Factory(
monitors.HttpMonitor,
http_client=http_client,
options=config.monitors.httpbin,
)
dispatcher = providers.Factory(
dispatcher.Dispatcher,
monitors=providers.List(
example_monitor,
httpbin_monitor,
),
)
Example of running of such application:
.. code-block:: python
from .containers import ApplicationContainer
def main() -> None:
container = ApplicationContainer()
container.config.from_yaml('config.yml')
container.configure_logging()
dispatcher = container.dispatcher()
dispatcher.run()
if __name__ == '__main__':
main()
Tutorials
=========
Tutorial is a good point to start.
Choose one of the following:
- `Flask web application tutorial <http://python-dependency-injector.ets-labs.org/tutorials/flask.html>`_
- `Aiohttp REST API tutorial <http://python-dependency-injector.ets-labs.org/tutorials/aiohttp.html>`_
- `Asyncio monitoring daemon tutorial <http://python-dependency-injector.ets-labs.org/tutorials/asyncio-daemon.html>`_
Installation
============
- The package is available on the `PyPi`_::
pip install dependency-injector
Documentation
=============
- The documentation is available on the `Read The Docs <http://python-dependency-injector.ets-labs.org/>`_
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 <https://github.com/ets-labs/python-dependency-injector/issues>`_
Found a bug?
- Open a `Github Issue <https://github.com/ets-labs/python-dependency-injector/issues>`_
Want to help?
- |star| Star the ``Dependency Injector`` on the `Github <https://github.com/ets-labs/python-dependency-injector/>`_
- |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
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.. |tell| unicode:: U+1F4AC .. tell sign
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.. |pull| unicode:: U+2B05 U+FE0F .. pull sign
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