typewirepy 0.1.2

Lightweight, container-agnostic dependency injection for Python — typed, explicit, composable.

typewirepy

Lightweight, container-agnostic dependency injection for Python — typed, explicit, composable.

Features

• Zero runtime dependencies — only stdlib
• Fully typed — strict mypy + pyright out of the box
• Async-first — native async/await; sync wrappers included
• Immutable wires — safe to share across threads and modules
• Scopes — singleton (default) and transient
• Generator lifecycle — yield-based creators with automatic cleanup
• FastAPI integration — WireDepends() bridges wires to FastAPI's Depends()

Installation

pip install typewirepy

With FastAPI support:

pip install typewirepy[fastapi]

Quick Start

Async (primary)

from typewirepy import Scope, TypeWireContainer, type_wire_group_of, type_wire_of

config_wire = type_wire_of(token="Config", creator=lambda: {"db_url": "sqlite://"})

db_wire = type_wire_of(
    token="Database",
    imports={"config": config_wire},
    create_with=lambda *, config: f"db({config['db_url']})",
)

app_wires = type_wire_group_of([config_wire, db_wire])

async def main():
    async with TypeWireContainer() as container:
        await app_wires.apply(container)
        db = await db_wire.get_instance(container)
        print(db)  # "db(sqlite://)"

Sync

from typewirepy import TypeWireContainer, type_wire_of

wire = type_wire_of(token="Greeting", creator=lambda: "hello")

with TypeWireContainer.sync() as container:
    wire.apply_sync(container)
    print(wire.get_instance_sync(container))  # "hello"

Key Concepts

Wires

A wire is an immutable description of a dependency — its token (name), how to create it, and what it depends on. Create wires with type_wire_of():

• Leaf wire — uses creator (zero-arg callable)
• Composed wire — uses create_with + imports to receive resolved dependencies

Imports

Imports declare which other wires a composed wire depends on. They're passed as a dict[str, TypeWire] and delivered to create_with as keyword arguments:

# Keyword-only parameters (works with lambdas too)
type_wire_of(token="Svc", imports={"db": db_wire}, create_with=lambda *, db: Service(db))

# Named function
def create_svc(*, db: Database) -> Service: ...
type_wire_of(token="Svc", imports={"db": db_wire}, create_with=create_svc)

Scopes

• Scope.SINGLETON (default) — resolved once, cached for the container's lifetime
• Scope.TRANSIENT — resolved fresh on every call

Groups

A TypeWireGroup bundles wires together for batch application:

group = type_wire_group_of([config_wire, db_wire, service_wire])
await group.apply(container)

Override wires for testing with with_extra_wires():

test_group = group.with_extra_wires([service_wire.with_creator(lambda _ctx: mock_svc)])

Use the 2-arg form of with_creator to spy on or decorate the original creator:

async def spy(ctx, original_creator):
    instance = await original_creator()  # zero-arg closure
    instance.log = MagicMock(wraps=instance.log)
    return instance

test_group = group.with_extra_wires([service_wire.with_creator(spy)])

Introspection

Every wire exposes read-only properties for inspecting the dependency graph at runtime:

wire = type_wire_of(
    token="UserService",
    imports={"db": db_wire},
    create_with=lambda *, db: UserService(db),
    scope=Scope.TRANSIENT,
)

wire.token_label  # "UserService"
wire.scope        # Scope.TRANSIENT
wire.imports      # {"db": TypeWire(...)}  (shallow copy — safe to mutate)

Use these to build dependency graphs, generate documentation, or debug resolution order.

FastAPI Integration

from contextlib import asynccontextmanager

from fastapi import FastAPI
from typewirepy import TypeWireContainer, type_wire_group_of, type_wire_of
from typewirepy.integrations.fastapi import WireDepends

db_wire = type_wire_of(token="DB", creator=lambda: "db_connection")
app_wires = type_wire_group_of([db_wire])

@asynccontextmanager
async def lifespan(app: FastAPI):
    async with TypeWireContainer() as container:
        await app_wires.apply(container)
        app.state.typewire_container = container
        yield

app = FastAPI(lifespan=lifespan)

@app.get("/")
async def root(db: str = WireDepends(db_wire)):
    return {"db": db}

Contributing

See CONTRIBUTING.md.

License

MIT