Python lightweight dependency injection library

Last update: Dec 16, 2022

Overview

pythondi

pythondi is a lightweight dependency injection library for python

Support both sync and async functions

Installation

pip3 install pythondi

Usage

First, you have to binding classes to provider.

There is three different ways to binding.

Binding one by one

from pythondi import Provider


provider = Provider()
provider.bind(Repo, SQLRepo)
provider.bind(Usecase, CreateUsecase)

Binding at initialization

from pythondi import Provider


provider = Provider(cls=Repo, new_cls=SQLRepo)

Binding at initialization with dictionary

from pythondi import Provider


provider = Provider(classes={Repo: SQLRepo, Usecase: CreateUsecase})

After binding, you need to configure it to container

from pythondi import configure, configure_after_clear


# Inject with configure
configure(provider=provider)

# Or if you want to fresh inject, use `configure_after_clear`
configure_after_clear(provider=provider)

Import inject

from pythondi import inject

Add type annotations that you want to inject dependencies

class Usecase:
    def __init__(self, repo: Repo):
        self.repo = repo

Add decorator

class Usecase:
    @inject()
    def __init__(self, repo: Repo):
        self.repo = repo

Initialize class with no arguments

usecase = Usecase()

Or, you can also inject manually through decorator arguments

class Usecase:
    @inject(repo=SQLRepo)
    def __init__(self, repo):
        self.repo = repo

In this case, do not have to configure providers and type annotation.

For test

In case of test codes, you probably want to use mock objects.

In that case, you must use keyword arguments.

class MockRepo:
    pass


@inject()
def test(repo: Repo):
    return repo

Yes:

test(repo=MockRepo())

No:

test(MockRepo())
test(MockRepo)

Note

At the moment of inject, class is automatically initialized.

So you don't have to initialize your class inside of code.

Yes:

@inject()
def __init__(self, repo: Repo):
    self.repo = repo

No:

@inject()
def __init__(self, repo: Repo):
    self.repo = repo()

General example

import abc

from pythondi import Provider, configure, configure_after_clear, inject


class Repo:
    """Interface class"""
    __metaclass__ = abc.ABCMeta

    @abc.abstractmethod
    def get(self):
        pass


class SQLRepo(Repo):
    """Impl class"""
    def get(self):
        print('SQLRepo')


class Usecase:
    @inject()
    def __init__(self, repo: Repo):
        self.repo = repo


if __name__ == '__main__':
    # Init provider
    provider = Provider()

    # Bind `Impl` class to `Interface` class
    provider.bind(Repo, SQLRepo)

    # Inject with configure
    configure(provider=provider)

    # Or if you want to fresh injection, use `configure_after_clear`
    configure_after_clear(provider=provider)

    # Init class without arguments
    u = Usecase()

FastAPI example

from fastapi import FastAPI, APIRouter

from pythondi import Provider, configure, inject
import abc

router = APIRouter()


class Repo:
    """Interface class"""
    __metaclass__ = abc.ABCMeta

    @abc.abstractmethod
    def get(self):
        pass


class SQLRepo(Repo):
    """Impl class"""
    def __init__(self):
        pass

    def get(self):
        print('SQLRepo')


@router.route('/')
def home():
    usecase = Usecase()
    usecase.repo.get()
    return {'hello': 'world'}


class Usecase:
    @inject()
    def __init__(self, repo: Repo):
        self.repo = repo


def create_app():
    provider = Provider()
    provider.bind(Repo, SQLRepo)
    configure(provider=provider)
    app = FastAPI()
    app.include_router(router)
    return app


if __name__ == '__main__':
    app = create_app()
    app.run(debug=True)

Flask example

from flask import Flask, Blueprint, jsonify

from pythondi import Provider, configure, inject
import abc

bp = Blueprint('home', __name__)


class Repo:
    """Interface class"""
    __metaclass__ = abc.ABCMeta

    @abc.abstractmethod
    def get(self):
        pass


class SQLRepo(Repo):
    """Impl class"""
    def __init__(self):
        pass

    def get(self):
        print('SQLRepo')


@bp.route('/')
def home():
    usecase = Usecase()
    usecase.repo.get()
    return jsonify({'hello': 'world'})


class Usecase:
    @inject()
    def __init__(self, repo: Repo):
        self.repo = repo


def create_app():
    provider = Provider()
    provider.bind(Repo, SQLRepo)
    configure(provider=provider)
    app = Flask(__name__)
    app.register_blueprint(bp)
    return app


if __name__ == '__main__':
    app = create_app()
    app.run(debug=True)

Sanic example

import abc

from sanic import Sanic, Blueprint
from sanic.response import json

from pythondi import Provider, configure, inject


class Repo:
    """Interface class"""
    __metaclass__ = abc.ABCMeta

    @abc.abstractmethod
    def get(self):
        pass


class SQLRepo(Repo):
    """Impl class"""
    def __init__(self):
        pass

    def get(self):
        print('SQLRepo')


bp = Blueprint('home', url_prefix='/')


@bp.route('/')
async def home(request):
    usecase = Usecase()
    usecase.repo.get()
    return json({'hello': 'world'})


class Usecase:
    @inject()
    def __init__(self, repo: Repo):
        self.repo = repo


def create_app():
    provider = Provider()
    provider.bind(Repo, SQLRepo)
    configure(provider=provider)
    app = Sanic(__name__)
    app.blueprint(bp)
    return app


if __name__ == '__main__':
    app = create_app()
    app.run(debug=True)

Django example

"""
In case of django, just put the initializing code inside of django startup

You can use project folder's __init__.py or urls.py
"""

Python lightweight dependency injection library

Related tags

Overview

pythondi

Installation

Usage

For test

Note

General example

FastAPI example

Flask example

Sanic example

Django example

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