hdmi 0.2.1

A dependency injection framework for Python with dynamic late-binding resolution

hdmi - Dependency Management Interface

Warning: Pre-Alpha Software

hdmi is experimental software in active development. Breaking changes may occur until version 1.0. Use with care in production environments.

A lightweight dependency injection framework for Python 3.13+ with:

• Type-driven dependency discovery - Uses Python's standard type annotations
• Scope-aware validation - Prevents lifetime bugs at build time
• Lazy instantiation - Services created just-in-time
• Early error detection - Configuration errors caught at build time

Quick Example

Simple Example (Singleton Services)

import asyncio
from hdmi import ContainerBuilder

# Define your services
class DatabaseConnection:
    def __init__(self):
        self.connected = True

class UserRepository:
    def __init__(self, db: DatabaseConnection):
        self.db = db

class UserService:
    def __init__(self, repo: UserRepository):
        self.repo = repo

async def main():
    # Configure the container (all singletons by default)
    builder = ContainerBuilder()
    builder.register(DatabaseConnection)
    builder.register(UserRepository)
    builder.register(UserService)

    # Build validates the dependency graph
    container = builder.build()

    # Resolve services lazily - dependencies are auto-wired!
    user_service = await container.get(UserService)

asyncio.run(main())

Using Scoped Services

import asyncio
from hdmi import ContainerBuilder

async def main():
    # For request-scoped services (e.g., web requests)
    builder = ContainerBuilder()
    builder.register(DatabaseConnection)  # singleton (default)
    builder.register(UserRepository, scoped=True)  # One per request
    builder.register(UserService, transient=True)   # New each time

    container = builder.build()

    # Scoped services must be resolved within a scope context
    async with container.scope() as scoped:
        user_service = await scoped.get(UserService)
        # All scoped dependencies share the same instance within this scope

asyncio.run(main())

Key Features

Two-Phase Architecture

1. ContainerBuilder (Configuration): Register services and define scopes
2. Container (Runtime): Validated, immutable graph for lazy resolution

Scope Safety

Services have four lifecycles that are validated at build time:

• Singleton (default): One instance per container
• Scoped: One instance per scope (e.g., per request)
• Transient: New instance every time
• Scoped Transient: New instance every time, requires scope

Validation Rules (Simplified): The only invalid dependency is when a non-scoped service (singleton or transient) depends on a scoped service.

# Valid: Scoped -> Singleton
builder = ContainerBuilder()
builder.register(DatabaseConnection)  # singleton (default)
builder.register(UserRepository, scoped=True)

# Invalid: Singleton -> Scoped (raises ScopeViolationError)
builder = ContainerBuilder()
builder.register(RequestHandler, scoped=True)
builder.register(SingletonService)  # singleton depends on scoped!
container = builder.build()  # ScopeViolationError!

Type-Driven Dependencies

Dependencies are automatically discovered from type annotations:

class ServiceA:
    def __init__(self, dep: DependencyType):
        self.dep = dep

No decorators or manual wiring required!

Installation

pip install hdmi  # Coming soon

Development

This project uses uv for dependency management and follows strict TDD methodology.

# Run all checks (linting, type checking, tests)
make test

# Build documentation
make docs

# See all available commands
make help

License

MIT License - see LICENSE file for details.