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What is ``Dependency Injector``?
================================

``Dependency Injector`` is a dependency injection framework for Python.

Why do I need it?
=================

``Dependency Injector`` helps you **improve application structure**.

With ``Dependency Injector`` you keep your **application structure in one place**. This place is called **container**. In the container you see all application components and their dependencies.

*The container is like a map of your application.*

Example:

.. code-block:: python

    import sqlite3

    import boto3
    from dependency_injector import containers, providers
    
    from .example import services


    class Application(containers.DeclarativeContainer):
        """Application container."""

        config = providers.Configuration()

        # Gateways

        database_client = providers.Singleton(sqlite3.connect, config.database.dsn)

        s3_client = providers.Singleton(
            boto3.client, 's3',
            aws_access_key_id=config.aws.access_key_id,
            aws_secret_access_key=config.aws.secret_access_key,
        )

        # Services

        users_service = providers.Factory(
            services.UsersService,
            db=database_client,
        )

        auth_service = providers.Factory(
            services.AuthService,
            token_ttl=config.auth.token_ttl,
            db=database_client,
        )

        photos_service = providers.Factory(
            services.PhotosService,
            db=database_client,
            s3=s3_client,
        )


Run the application:

.. code-block:: python

    import sys

    from .application import Application
    
    
    def main(uid, password, photo):
       """Run application."""
       application = Application()
       application.config.from_yaml('config.yml')
       
       users_service = application.users_service()
       auth_service = application.auth_service()
       photos_service = application.photos_service()
        
       user = users_service.get_user_by_id(uid)
       auth_service.authenticate(user, password)
       photos_service.upload_photo(user['uid'], photo)


    if __name__ == '__main__':
        main(*sys.argv[1:])

You can find more *Dependency Injector* examples in the ``/examples`` directory
on our GitHub:

    https://github.com/ets-labs/python-dependency-injector


How to install?
---------------

``Dependency Injector`` is available on `PyPi`_:

    pip install dependency-injector

Where is the docs?
------------------

Documentation is on the `Read The Docs <http://python-dependency-injector.ets-labs.org/>`_

Have a question?
----------------

- Open a `Github Issue <https://github.com/ets-labs/python-dependency-injector/issues>`_


.. _Dependency injection: http://en.wikipedia.org/wiki/Dependency_injection
.. _Inversion of control: https://en.wikipedia.org/wiki/Inversion_of_control
.. _PyPi: https://pypi.org/project/dependency-injector/