Dependency Injector — Dependency injection framework for Python

Dependency Injector is a dependency injection framework for Python.

It helps implementing the dependency injection principle.

Key features of the Dependency Injector:

• Providers. Provides Factory, Singleton, Callable, Coroutine, Object, List, Dict, Configuration, Resource, Dependency, and Selector providers that help assemble your objects. See Providers.

• Overriding. Can override any provider by another provider on the fly. This helps in testing and configuring dev/stage environment to replace API clients with stubs etc. See Provider overriding.

• Configuration. Reads configuration from yaml, ini, and json files, pydantic settings, environment variables, and dictionaries. See Configuration provider.

• Resources. Helps with initialization and configuring of logging, event loop, thread or process pool, etc. Can be used for per-function execution scope in tandem with wiring. See Resource provider.

• Containers. Provides declarative and dynamic containers. See Containers.

• Wiring. Injects dependencies into functions and methods. Helps integrate with other frameworks: Django, Flask, Aiohttp, Sanic, FastAPI, etc. See Wiring.

• Asynchronous. Supports asynchronous injections. See Asynchronous injections.

• Typing. Provides typing stubs, mypy-friendly. See Typing and mypy.

• Performance. Fast. Written in Cython.

• Maturity. Mature and production-ready. Well-tested, documented, and supported.

from dependency_injector import containers, providers
from dependency_injector.wiring import Provide, inject


class Container(containers.DeclarativeContainer):

    config = providers.Configuration()

    api_client = providers.Singleton(
        ApiClient,
        api_key=config.api_key,
        timeout=config.timeout,
    )

    service = providers.Factory(
        Service,
        api_client=api_client,
    )


@inject
def main(service: Service = Provide[Container.service]) -> None:
    ...


if __name__ == "__main__":
    container = Container()
    container.config.api_key.from_env("API_KEY", required=True)
    container.config.timeout.from_env("TIMEOUT", as_=int, default=5)
    container.wire(modules=[__name__])

    main()  # <-- dependency is injected automatically

    with container.api_client.override(mock.Mock()):
        main()  # <-- overridden dependency is injected automatically

With the Dependency Injector, object assembling is consolidated in the container. Dependency injections are defined explicitly. This makes it easier to understand and change how the application works.

Explore the documentation to know more about the Dependency Injector.

Contents

• Introduction
  • Dependency injection and inversion of control in Python
  • Key features
  • Installation
• Examples
  • Application example (single container)
  • Application example (multiple containers)
  • Decoupled packages example (multiple containers)
  • Boto3 example
  • Django example
  • Flask example
  • Flask blueprints example
  • Aiohttp example
  • Sanic example
  • FastAPI example
  • FastAPI + Redis example
  • FastAPI + SQLAlchemy example
• Tutorials
  • Flask tutorial
  • Aiohttp tutorial
  • Asyncio daemon tutorial
  • CLI application tutorial
• Providers
  • Factory provider
  • Singleton provider
  • Callable provider
  • Coroutine provider
  • Object provider
  • List provider
  • Dict provider
  • Configuration provider
  • Resource provider
  • Aggregate provider
  • Selector provider
  • Dependency provider
  • Provider overriding
  • Injecting provided object attributes, items, or call its methods
  • Injecting container “self”
  • Creating a custom provider
  • Asynchronous injections
  • Typing and mypy
• Containers
  • Declarative container
  • Dynamic container
  • Specialization of the container provider type
  • Container overriding
  • Container copying
  • Reset container singletons
  • Check container dependencies
  • Container providers traversal
• Wiring
  • Decorator @inject
  • Markers
  • String identifiers
  • Making injections into modules and class attributes
  • Wiring with modules and packages
  • Wiring configuration
  • Asynchronous injections
  • Wiring of dynamically imported modules
  • Integration with other frameworks
• Other examples
  • Use cases example
  • Password hashing example
  • Chained Factories pattern
  • Factory of Factories pattern
• API Documentation
  • dependency_injector
  • dependency_injector.providers
  • dependency_injector.containers
  • dependency_injector.wiring
  • dependency_injector.errors
• Feedback
• Changelog
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