svcs 23.12.0

A Flexible Service Locator

A Flexible Service Locator for Python.

WARNING ☠️ Not ready yet! ☠️

This project is only public to gather feedback, and everything can and will change until the project is proclaimed stable.

The code has 100% test and type coverage, and the shipped Flask and Pyramid integrations have been in production for years, but the API details can still change.

svcs (pronounced services) is a dependency container for Python. It gives you a central place to register factories for types/interfaces and then imperatively request instances of those types with automatic cleanup and health checks.

It's a flexible Inversion of Control container suitable for dependency injection or service location, while not requiring global state, decorators, or mangling of function signatures.

Benefits:

• Eliminates tons of repetitive boilerplate code,
• unifies acquisition and cleanups of services,
• provides full static type safety for them,
• simplifies testing through loose coupling,
• and allows for easy health checks across all services.

The goal is to minimize the code for acquiring pluggable services to:

from svcs.your_framework import svcs_from

def view(request):
    db, api, cache = svcs_from(request).get(Database, WebAPIClient, Cache)

To a type checker like Mypy, db has the type Database, api has the type WebAPIClient, and cache has the type Cache.

svcs comes with seamless integration for the Flask and Pyramid web frameworks and has first-class async support.

While svcs has first-class support for static typing, it is strictly optional and will always remain so. svcs also doesn't check your types at runtime.

It only forwards the type you have asked for to the type checker. If you don't use a type checker, that information is ignored without any runtime overhead.

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Read on in Why?, if you find that intriguing!

Project Links

• PyPI
• Source Code
• Documentation
• Changelog

Release Information

Added

• svcs now logs registrations at debug level along with a stacktrace. So if you ever get confused where your factories are coming from, set the log level to debug and trace your registrations!

Changed

• Ooof. It's obvious in hindsight, but accessing anything directly on a request object like in the request.svcs.get() examples erases type information and everything becomes a big soup of Any.

  Therefore, we've added a new "best practice" for integrations to have a svcs_from() function that extracts containers from request objects (or from thread locals in the case of Flask).

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→ Full Changelog

Credits

svcs is written by Hynek Schlawack and distributed under the terms of the MIT license.

The development is kindly supported by my employer Variomedia AG and all my fabulous GitHub Sponsors.

The Bestagon radar logo is made by Lynn Root, based on an Font Awesome icon. svcs has started out as a wrapper around wired by Michael Merickel and has been heavily influenced by it.