Getting Started

Install

Inlay requires Python 3.14 or newer.

pip install inlay

A minimal example

Declare what your code needs as an AppContext protocol, register concrete types for interfaces, and let Inlay assemble an implementation:

from typing import Protocol
from abc import ABCMeta
from inlay import Registry, compiled

class BaseDatabase(metaclass=ABCMeta):
    @property
    def url(self) -> str: ...

class PostgresDatabase(BaseDatabase):
    def __init__(self, url: str) -> None:
        self._url = url

    @property
    def url(self) -> str:
        return self._url

class UserService:
    def __init__(self, db: BaseDatabase) -> None:
        self.db = db

class AppContext(Protocol):
    @property
    def users(self) -> UserService: ...

registry = (
    Registry()
    .register(BaseDatabase)(PostgresDatabase)
)

@compiled(registry)
def make_app(url: str) -> AppContext: ...

app = make_app(url='postgres://localhost/app')
assert app.users.db.url == 'postgres://localhost/app'

A few things to notice:

• make_app has no body. The @compiled decorator inspects its signature, solves the dependency graph against registry, and replaces it with a generated implementation.
• url is a runtime parameter. It flows from the caller into Database.__init__ because the solver matched the parameter name and type to a constructor argument.
• The resolution happens once, at module import time. If anything is unsatisfiable or ambiguous, make_app fails to compile, so the program never starts in a partially-wired state.

Where to go next

• Features — explore full capabilities of the library.
• The gems-web example — a full Starlette application showing modular registries, qualifiers, async transitions, and pluggable backends.