dependency-injector 2.0.0

Python dependency injection framework

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
Python versions and implementations
Builds and tests coverage

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:

"""Example of several Dependency Injector IoC containers."""

import sqlite3
import boto.s3.connection
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."""

    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,
                              db=Platform.database)

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

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

Next example demonstrates usage of @inject decorator with IoC containers defined above:

"""Dependency Injector @inject decorator example."""

import application
import dependency_injector.injections as injections


@injections.inject(users_service=application.Services.users)
@injections.inject(auth_service=application.Services.auth)
@injections.inject(photos_service=application.Services.photos)
def main(users_service, auth_service, photos_service):
    """Main function."""
    user = users_service.get_user('user')
    auth_service.authenticate(user, 'secret')
    photos_service.upload_photo(user['id'], 'photo.jpg')


if __name__ == '__main__':
    main()

Alternative definition styles

Dependecy Injector supports few other styles of dependency injections definition.

IoC containers from previous example could look like these:

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')


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

    users = providers.Factory(example.services.Users) \
        .add_kwargs(db=Platform.database)

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

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

or like this these:

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')


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

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

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

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

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!