tinyinject

tinyinject

A minimalistic protocol driven dependency injection framework for python.

Installation

python -m pip install tinyinject

Examples

Registering implementation to the DI registry

# package/protocols.py
from typing import Protocol


class Arithmetic(Protocol):
    def sum(self, a: int, b: int) -> int:
        ...


# package/providers.py
from tinyinject import di
from protocols import Arithmetic


@di.implements(interface=Arithmetic)
class _ArithmeticImplementation:
    def sum(self, a: int, b: int) -> int:
        return a + b


# package/__init__.py
# IMPORTANT: this ensures provider gets registered in the DI
from . import providers  # noqa

Requesting dependencies via Require descriptor

# main.py
from tinyinject import di
from package.protocols import Arithmetic


class App:
    _dependency: Arthmetic = di.Require(Arithmetic)

    def format_sum(self, a: int, b: int):
        print(f"Sum of {a} and {b} is {self._dependency.sum(a, b)}")

Requesting dependencies via request_kwargs decorator

# main.py
from tinyinject import di
from package.protocols import Arithmetic


@di.require_kwargs(dependency=Arithmetic)
def format_sum(self, a: int, b: int, *, dependency: Arithmetic):
    print(f"Sum of {a} and {b} is {dependency.sum(a, b)}")

Dependency Injection of functions

# package/protocols.py
from typing import Protocol


class Sum(Protocol):
    def __call__(self, a: int, b: int) -> int:
        ...


# package/providers.py
from tinyinject import di
from .protocols import Sum


@di.implements(interface=Sum)
def sum_func(a: int, b: int) -> int:
    return a + b


# package/__init__.py
from . import providers  # noqa


# main.py
from tinyinject import di
from package.protocols import Sum


class App:
    _sum: Sum = di.Require(Sum)

    def format_sum(self, a: int, b: int) -> int:
        print(f"Sum of {a} and {b} is {self._sum(a, b)}")

Using override context manager

This is written with testing in mind, however it will work in any use case where temporary replacement of the provider is necessary.

# test_sum.py
from unittest import mock
from tinyinject import di
from src.package.protocols import Arithmetic
from src.main import App


class TestSum:
    def test_app_format_sum_always_call_sum_with_correct_parameters(self):
        spy = mock.MagicMock()

        with di.override(Arithmetic, using=spy):
            App().format_sum(1, 2)

        spy.sum.assert_called_with(1, 2)