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Python dependency injection framework

Project description

Dependency Injector is a Python dependency injection framework. 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:

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

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


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Dependency Injector library is available on PyPi:

pip install dependency_injector


Dependency Injector documentation is hosted on ReadTheDocs:


"""Pythonic way for Dependency Injection (example with Catalog)."""

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):
        self.db = db

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

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

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

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

    users = providers.Factory(UsersService,
    """:type: providers.Provider -> UsersService"""

    auth = providers.Factory(AuthService,
    """: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:
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:

# Overriding auth service provider and making some asserts:
class ExtendedAuthService(AuthService):
    """Extended version of auth service."""

    def __init__(self, db, users_service, ttl):
        self.ttl = ttl
        super(ExtendedAuthService, self).__init__(db=db,


auth_service = Services.auth()

assert isinstance(auth_service, ExtendedAuthService)

Authentication system example:

"""Pythonic way for Dependency Injection."""

from dependency_injector import providers
from dependency_injector import injections

def get_user_info(user_id):
    """Return user info."""
    raise NotImplementedError()

class AuthComponent(object):
    """Some authentication component."""

    def __init__(self, get_user_info):
        self.get_user_info = get_user_info

    def authenticate_user(self, token):
        """Authenticate user by token."""
        user_info = self.get_user_info(user_id=token + '1')
        return user_info

print AuthComponent
print get_user_info

def get_user_info(user_id):
    """Return user info."""
    return {'user_id': user_id}

print AuthComponent().authenticate_user(token='abc')
# {'user_id': 'abc1'}

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


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

Your feedback is quite important!

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