kink 0.5.0

Dependency injection for python.

Kink

Dependency injection made for python

Features

• Easy to use interface
• Extensible with custom dependency resolvers
• Automatic dependency injection
• Lightweight
• Support for async with asyncio

Installation

pip install kink

Usage

Adding service to dependency injection container

Dependency container is a dict-like object, adding new service to dependency container is as simple as the following example:

from kink import di
from os import getenv

di["db_name"] = getenv("DB_NAME")
di["db_password"] = getenv("DB_PASSWORD")

Adding service factory to dependency injection container

Kink also supports on-demand service creation. In order to define such a service, lambda function should be used:

from kink import di
from sqlite3 import connect

di["db_connection"] = lambda di: connect(di["db_name"])

In this scenario connection to database will not be established until service is requested.

Adding factorised services to dependency injection

Factorised services are services that are instantiated every time they are requested.

from kink import di
from sqlite3 import connect

di.factories["db_connection"] = lambda di: connect(di["db_name"])

connection_1 = di["db_connection"]
connection_2 = di["db_connection"]

connection_1 != connection_2

In the above example we defined factorised service di_connection, and below by accessing the service from di we created two separate connection to database.

Requesting services fromm dependency injection container

from kink import di
from sqlite3 import connect

# Setting services
di["db_name"] = "test_db.db"
di["db_connection"] = lambda di: connect(di["db_name"])


# Getting service

connection = di["db_connection"] # will return instance of sqlite3.Connection
assert connection == di["db_connection"] # True

Autowiring dependencies

from kink import di, inject
from sqlite3 import connect, Connection


di["db_name"] = "test_db.db"
di["db_connection"] = lambda di: connect(di["db_name"])

# Inject connection from di, connection is established once function is called.
@inject
def get_database(db_connection: Connection):
    ...


connection = get_database()
connection_with_passed_connection = get_database(connect("temp.db")) # will use passed connection

Constructor injection

from kink import inject, di
import MySQLdb

# Set dependencies
di["db_host"] = "localhost"
di["db_name"] = "test"
di["db_user"] = "user"
di["db_password"] = "password"
di["db_connection"] = lambda di: MySQLdb.connect(host=di["db_host"], user=di["db_user"], passwd=di["db_password"], db=di["db_name"])

@inject
class AbstractRepository:
    def __init__(self, db_connection):
        self.connection = db_connection


class UserRepository(AbstractRepository):
    ...


repository = UserRepository()
repository.connection # mysql db connection is resolved and available to use.

When class is annotated by inject annotation it will be automatically added to the container for future use (eg autowiring).

Services aliasing

When you registering service with @inject decorator you can attach your own alias name, please consider the following example:

from kink import inject
from typing import Protocol

class IUserRepository(Protocol):
    ...

@inject(alias=IUserRepository)
class UserRepository:
    ...


assert di[IUserRepository] == di[UserRepository] # returns true

For more examples check tests directory

Clearing di cache

from kink import inject, di

... # set and accesss your services

di.clear_cache() # this will clear cache of all services inside di container that are not factorised services