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Dependency Injector - Python dependency injection framework
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*Dependency Injector* is a Python dependency injection framework. It was 
designed to be unified, developer-friendly tool for managing any kind
of Python objects and their dependencies in formal, pretty way.

*Dependency Injector* framework key features are:

+ Easy, smart, pythonic style.
+ Obvious, clear structure.
+ Extensibility and flexibility.
+ Memory efficiency.
+ Thread safety.
+ Documentation.
+ Semantic versioning.

Status
------

+---------------------------------------+----------------------------------------------------------------------------------------+
| *PyPi*                                | .. image:: https://img.shields.io/pypi/v/dependency_injector.svg                       |
|                                       |    :target: https://pypi.python.org/pypi/dependency_injector/                          |
|                                       |    :alt: Latest Version                                                                |
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|                                       |    :alt: License                                                                       |
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|                                       |    :target: https://pypi.python.org/pypi/dependency_injector/                          |
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|                                       |    :target: https://pypi.python.org/pypi/dependency_injector/                          |
|                                       |    :alt: Supported Python implementations                                              |
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| *Builds and tests coverage*           | .. image:: https://travis-ci.org/ets-labs/python-dependency-injector.svg?branch=master |
|                                       |    :target: https://travis-ci.org/ets-labs/python-dependency-injector                  |
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Installation
------------

*Dependency Injector* library is available on PyPi_::

    pip install dependency_injector

Example
-------

Brief example below demonstrates usage of *Dependency Injector* containers and 
providers for definition of several IoC containers for some microservice 
system that consists from several business and platform services:

.. code-block:: python

    """Example of dependency injection in Python."""

    import logging
    import sqlite3

    import boto.s3.connection

    import example.main
    import example.services

    import dependency_injector.containers as containers
    import dependency_injector.providers as providers


    class Platform(containers.DeclarativeContainer):
        """IoC container of platform service providers."""

        logger = providers.Singleton(logging.Logger, name='example')

        database = providers.Singleton(sqlite3.connect, ':memory:')

        s3 = providers.Singleton(boto.s3.connection.S3Connection,
                                 aws_access_key_id='KEY',
                                 aws_secret_access_key='SECRET')


    class Services(containers.DeclarativeContainer):
        """IoC container of business service providers."""

        users = providers.Factory(example.services.Users,
                                  logger=Platform.logger,
                                  db=Platform.database)

        auth = providers.Factory(example.services.Auth,
                                 logger=Platform.logger,
                                 db=Platform.database,
                                 token_ttl=3600)

        photos = providers.Factory(example.services.Photos,
                                   logger=Platform.logger,
                                   db=Platform.database,
                                   s3=Platform.s3)


    class Application(containers.DeclarativeContainer):
        """IoC container of application component providers."""

        main = providers.Callable(example.main.main,
                                  users_service=Services.users,
                                  auth_service=Services.auth,
                                  photos_service=Services.photos)

Next example demonstrates usage of IoC containers & providers defined above:

.. code-block:: python

    """Run dependency injection example application.

    Instructions for running:

        python run.py 1 secret photo.jpg
    """

    import sys
    import logging

    from containers import Platform, Application


    if __name__ == '__main__':
        # Configure platform logger:
        Platform.logger().addHandler(logging.StreamHandler(sys.stdout))

        # Run application:
        Application.main(uid=sys.argv[1],
                         password=sys.argv[2],
                         photo=sys.argv[3])

        # Previous call is an equivalent of next operations:
        #
        # logger = logging.Logger(name='example')
        # database = sqlite3.connect(':memory:')
        # s3 = boto.s3.connection.S3Connection(aws_access_key_id='KEY',
        #                                      aws_secret_access_key='SECRET')
        #
        # example.main.main(uid=sys.argv[1],
        #                   password=sys.argv[2],
        #                   photo=sys.argv[3],
        #                   users_service=example.services.Users(logger=logger,
        #                                                        db=database),
        #                   auth_service=example.services.Auth(logger=logger,
        #                                                      db=database,
        #                                                      token_ttl=3600),
        #                   photos_service=example.services.Photos(logger=logger,
        #                                                          db=database,
        #                                                          s3=s3))
        #
        # Output:
        #
        # User 1 has been found in database
        # User 1 has been successfully authenticated
        # Photo photo.jpg has been successfully uploaded by user 1
   
Alternative definition styles
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

*Dependecy Injector* supports few other styles of dependency injections 
definition.

IoC containers from previous example could look like these:

.. code-block:: python

    class Platform(containers.DeclarativeContainer):
        """IoC container of platform service providers."""

        database = providers.Singleton(sqlite3.connect) \
            .add_args(':memory:')

        s3 = providers.Singleton(boto.s3.connection.S3Connection) \
            .add_kwargs(aws_access_key_id='KEY',
                        aws_secret_access_key='SECRET')

or like this these:

.. code-block:: python

    class Platform(containers.DeclarativeContainer):
        """IoC container of platform service providers."""

        database = providers.Singleton(sqlite3.connect)
        database.add_args(':memory:')

        s3 = providers.Singleton(boto.s3.connection.S3Connection)
        s3.add_kwargs(aws_access_key_id='KEY',
                      aws_secret_access_key='SECRET')

You can get more *Dependency Injector* examples in ``/examples`` directory on
GitHub:

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

Documentation
-------------

*Dependency Injector* documentation is hosted on ReadTheDocs:

- `User's guide`_ 
- `API docs`_

Feedback
--------

Feel free to post questions, bugs, feature requests, proposals etc. on
*Dependency Injector*  GitHub Issues:

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

Your feedback is quite important!


.. _PyPi: https://pypi.python.org/pypi/dependency_injector
.. _User's guide: http://python-dependency-injector.ets-labs.org/en/stable/
.. _API docs: http://python-dependency-injector.ets-labs.org/en/stable/api/
.. _SLOC: http://en.wikipedia.org/wiki/Source_lines_of_code
.. _SOLID: http://en.wikipedia.org/wiki/SOLID_%28object-oriented_design%29
.. _IoC: http://en.wikipedia.org/wiki/Inversion_of_control
.. _dependency injection: http://en.wikipedia.org/wiki/Dependency_injection