independency 1.3

Dependency injection container

Independency

Independency is a DI container library. Unlike many other Python DI containers Independency operates in the local scope. It's inspired by punq, so the API is very similar.

Independency supports generics and other specific typings.

Installation

pip install independency

Usage

Independency avoids global state, so you must explicitly create a container in the entrypoint of your application:

import independency

builder = independency.ContainerBuilder()
# register application dependencies
container = builder.build()
obj: SomeRegisteredClass = container.resolve(SomeRegisteredClass)

Registering Dependencies

builder.register(User, User)  # creates new object on each `resolve`
builder.singleton(User, User)  # creates object only once
builder.singleton(Storage[int], Storage[int])  # use generics
builder.singleton('special_storage', Storage[int])  # or literals to register dependency

The second argument is a factory, so you can provide not only a class __init__ function:

def create_db(config: Config) -> Database:
    return Database(config.dsn)

builder.singleton(Config, Config)
builder.singleton(Database, create_db)

If you need to pass some specific dependency as an argument to a factory, use Dependency:

from independency import Dependency as Dep

builder.singleton(SpecificConnection, SpecificConnection)
builder.singleton(Storage, conn=Dep(SpecificConnection))

Examples

import requests

from independency import Container, ContainerBuilder


class Config:
    def __init__(self, url: str):
        self.url = url


class Getter:
    def __init__(self, config: Config):
        self.config = config

    def get(self):
        return requests.get(self.config.url)


def create_container() -> Container:
    builder = ContainerBuilder()
    builder.singleton(Config, Config, url='http://example.com')
    builder.singleton(Getter, Getter)
    return builder.build()


def main():
    container = create_container()
    getter: Getter = container.resolve(Getter)
    print(getter.get().status_code)


if __name__ == '__main__':
    main()

Suppose we need to declare multiple objects of the same type and use them correspondingly.

from independency import Container, ContainerBuilder, Dependency as Dep


class Queue:
    def __init__(self, url: str):
        self.url = url

    def pop(self):
        ...

    
class Consumer:
    def __init__(self, q: Queue):
        self.queue = q

    def consume(self):
        while True:
            message = self.queue.pop()
            # process message


def create_container() -> Container:
    builder = ContainerBuilder()
    builder.singleton('first_q', Queue, url='http://example.com')
    builder.singleton('second_q', Queue, url='http://example2.com')
    builder.singleton('c1', Consumer, q=Dep('first_q'))
    builder.singleton('c2', Consumer, q=Dep('second_q'))
    return builder.build()


def main():
    container = create_container()
    consumer: Consumer = container.resolve('c1')
    consumer.consume()


if __name__ == '__main__':
    main()

Contributing

If you find a bug or have a feature request, please open an issue on GitHub. Pull requests are also welcome!