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Dependency injection framework for Python projects

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

Below is a list of some key features and points of Dependency Injector framework:

  • Easy, smart, pythonic style.
  • Obvious, clear structure.
  • Memory efficiency.
  • Thread safety.
  • Semantic versioning.

Main idea of Dependency Injector is to keep dependencies under control.

Installation

Dependency Injector library is available on PyPi:

pip install dependency_injector

Documentation

Dependency Injector documentation is hosted on ReadTheDocs:

Examples

"""Concept example of `Dependency Injector`."""

import sqlite3

from dependency_injector import catalogs
from dependency_injector import providers
from dependency_injector import injections


class UsersService(object):
    """Users service, that has dependency on database."""

    def __init__(self, db):
        """Initializer."""
        self.db = db


class AuthService(object):
    """Auth service, that has dependencies on users service and database."""

    def __init__(self, db, users_service):
        """Initializer."""
        self.db = db
        self.users_service = users_service


class Services(catalogs.DeclarativeCatalog):
    """Catalog of service providers."""

    database = providers.Singleton(sqlite3.connect,
                                   injections.Arg(':memory:'))
    """:type: providers.Provider -> sqlite3.Connection"""

    users = providers.Factory(UsersService,
                              injections.KwArg('db', database))
    """:type: providers.Provider -> UsersService"""

    auth = providers.Factory(AuthService,
                             injections.KwArg('db', database),
                             injections.KwArg('users_service', users))
    """:type: providers.Provider -> AuthService"""


# Retrieving catalog providers:
users_service = Services.users()
auth_service = Services.auth()

# Making some asserts:
assert users_service.db is auth_service.db is Services.database()
assert isinstance(auth_service.users_service, UsersService)
assert users_service is not Services.users()
assert auth_service is not Services.auth()


# Making some "inline" injections:
@injections.inject(users_service=Services.users)
@injections.inject(auth_service=Services.auth)
@injections.inject(database=Services.database)
def example(users_service, auth_service, database):
    """Example callback."""
    assert users_service.db is auth_service.db
    assert auth_service.db is database
    assert database is Services.database()


# Making a call of decorated callback:
example()

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

https://github.com/rmk135/dependency_injector

Feedback

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

https://github.com/rmk135/dependency_injector/issues

Your feedback is quite important!

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