gladi 0.1.0

A simple dependency injection library for Python

sdi

Overview

Import the injector. This is the only import needed.

from sdi import inject

The library provides 4 decorators:

• @inject.singleton: creates a singleton from a callable that instantiates the class in its return type
• @inject.scoped: same as singleton, but the callable gets called once per request
• @inject.transient: same as singleton, but it gets called on every request
• @inject.resolve: signals to the library that dependencies in parameters need to be resolved
  • using @inject.singleton, @inject.scoped or @inject.transient implies this

Simple Usage

Assuming we have a class to inject,

class Database: ...

create a function (or callable) with no user-provided arguments that returns a Database instance.

def get_database() -> Database:
	return Database(
		host=...,
		port=...,
	)

Mark the callable with a decorator. In this case, a singleton would be appropriate.

@inject.singleton
def get_database() -> Database: ...

Database class is now an injectable (as a singleton).

async retrieve_user(
	user_id: int,
	database = inject(Database),
): ...

Lastly, signal that the retrieve_user function needs its dependencies to be resolved with the @inject.resolve decorator.

@inject.resolve
async retrieve_user(
	user_id: int,
	database = inject(Database),
): ...

await retrieve_user(33)