What is a Pythonic way for Dependency Injection?

Question

Introduction

For Java, Dependency Injection works as pure OOP, i.e. you provide an interface to be implemented and in your framework code accept an instance of a c

Answer 1

Some time ago I wrote dependency injection microframework with a ambition to make it Pythonic - Dependency Injector. That's how your code can look like in case of its usage:

"""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.UsersService,
                              logger=Platform.logger,
                              db=Platform.database)

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

    photos = providers.Factory(example.services.PhotosService,
                               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)

Here is a link to more extensive description of this example - http://python-dependency-injector.ets-labs.org/examples/services_miniapp.html

Hope it can help a bit. For more information please visit:

• GitHub https://github.com/ets-labs/python-dependency-injector
• Docs http://python-dependency-injector.ets-labs.org/