ididi 0.1.2

A dependency injection library for Python, Optimized for serverless applications

ididi

Introduction

ididi is a zero-configuration, minimal-code-intrusiveness dependency injection library for Python that works out of the box.

It allows you to define dependencies in a declarative way without any boilerplate code.

Install

pip install ididi

Usage

Decorate your top level dependencies and leave the rest to ididi

from didi import DependencyGraph

dg = DependencyGraph()

class Config:
    def __init__(self, env: str = "prod"):
        self.env = env


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


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


class UserRepository:
    def __init__(self, db: Database, cache: Cache):
        self.db = db
        self.cache = cache


class AuthService:
    def __init__(self, db: Database):
        self.db = db

@dg.node
class UserService:
    def __init__(self, repo: UserRepository, auth: AuthService):
        self.repo = repo
        self.auth = auth

@dg.node
def auth_service_factory(database: Database) -> AuthService:
    return AuthService(db=database)

service = dg.resolve(UserService)
assert isinstance(service.repo.db, Database)
assert isinstance(service.repo.cache, Cache)
assert isinstance(service.auth.db, Database)
assert service.auth.db is service.repo.db

Visualize the dependency graph(beta)

from ididi import DependencyGraph, Visualizer
dg = DependencyGraph()
vs = Visualizer(dg)

class ConfigService:
    def __init__(self, env: str = "test"):
        self.env = env


class DatabaseService:
    def __init__(self, config: ConfigService):
        self.config = config


class CacheService:
    def __init__(self, config: ConfigService):
        self.config = config


class BaseService:
    def __init__(self, db: DatabaseService):
        self.db = db


class AuthService(BaseService):
    def __init__(self, db: DatabaseService, cache: CacheService):
        super().__init__(db)
        self.cache = cache


class UserService:
    def __init__(self, auth: AuthService, db: DatabaseService):
        self.auth = auth
        self.db = db


class NotificationService:
    def __init__(self, config: ConfigService):
        self.config = config


class EmailService:
    def __init__(self, notification: NotificationService, user: UserService):
        self.notification = notification
        self.user = user

dg.resolve(EmailService)
vs.view # In jupyter notebook, or use save(path) otherwise

Runtime override is also supported

dg = DependencyGraph()

class Inner:
    def __init__(self, value: str = "inner"):
        self.value = value

@dg.node
class Outer:
    def __init__(self, inner: Inner):
        self.inner = inner

# Override nested dependency
instance = dg.resolve(Outer, inner=Inner(value="overridden"))
assert instance.inner.value == "overridden"

Features

• Automatically resolve dependencies
• Circular dependencies detection
• Support Forward References

Resolve Rules

• If a node has a factory, it will be used to create the instance.
• Otherwise, the node will be created using the __init__ method.
  • Parent's __init__ will be called if no __init__ is defined in the node.
• bulitin types are not resolvable by nature, it requires default value to be provided.
• runtime override with dg.resolve