component-injector

A modern component / dependency injector for python 3.6+.

This library provides a framework-agnostic component (or dependency) injector that injects registered components into your function calls. The components to insert are identified by looking at the called function argument annotations.

When registering a component, all its base classes are registered as well unless you explicitly disable that. You can also choose to only register base classes that are not already registered with the injector.

It provides local scopes where you can register additional components or override existing components. After exiting the scope, the registry will return to the state it was in before entering the scope.

Compatibility

component-injector is compatible with python 3.6+ using the backported contextvars and dataclasses packages.

The scopes are thread-safe and when using python 3.7 also safe for for use with asyncio tasks.

Installation

component-injector is available from pypi:

pip install component-injector

Usage example

Here's a small demo on how to use the injector:

from component_injector import Injector

injector = Injector()

class O:
    pass

@injector.inject
def consumer_of_o(o: O) -> None:
    print(o)

injector.register(O())
consumer_of_o()  # 'o' wil be the registered instance.

consumer_of_o(O())  # 'o' will be this new instance.

For more examples and usage, please refer to demo.py and async_demo.py.

Development setup

For development purposes, you can clone the repository and use poetry to install and maintain the dependencies. There is no test suite. The project comes with a set of pre-commit hooks that can format (isort, black) and check your code (mypy, flake8) automatically.

git clone git@github.com:iksteen/component-injector.git
cd component-injector
poetry run pre-commit install

Release History

• Next version

  • Support overriding the component type.
  • Support for forward declaration annotations.
  • Support types that don't have an MRO (like the result from typing.NewType).

• 1.1.1

  • Fix incorrect type registration when not registering bases.
  • Fix typo in documentation (thanks @trbs!).

• 1.1.0

  • Add documentation.
  • Add support for component factories. Asynchronous factories are supported as well when injecting into asynchronous functions.

• 1.0.2

  • Fix bug where already bound arguments were overwritten.

• 1.0.1

  • Fix links to examples.

• 1.0.0

  • Initial Release.

Meta

Ingmar Steen – @iksteen

Distributed under the MIT license. See LICENSE for more information.

https://github.com/iksteen/

Contributing

1. Fork it (https://github.com/iksteen/component-injector/fork)
2. Create your feature branch (git checkout -b feature/fooBar)
3. Commit your changes (git commit -am 'Add some fooBar')
4. Push to the branch (git push origin feature/fooBar)
5. Create a new Pull Request