ClassRegistry

Contents:

ClassRegistry

At the intersection of the Registry and Factory patterns lies the ClassRegistry:

  • Define global factories that generate new class instances based on configurable keys.

  • Seamlessly create powerful service registries.

  • Integrate with setuptools’s entry_points system to make your registries infinitely extensible by 3rd-party libraries!

  • And more!

Upgrading from ClassRegistry v4

Important

ClassRegistry v5 introduces some changes that can break code that was previously using ClassRegistry v4. If you are upgrading from ClassRegistry v4 to ClassRegistry v5, please read Upgrading to ClassRegistry v5!

Getting Started

Create a registry using the class_registry.ClassRegistry class, then decorate any classes that you wish to register with its register method:

from class_registry import ClassRegistry

pokedex = ClassRegistry()

@pokedex.register('fire')
class Charizard(Pokemon):
    ...

@pokedex.register('grass')
class Bulbasaur(Pokemon):
    ...

@pokedex.register('water')
class Squirtle(Pokemon):
    ...

To create a class instance from a registry, use the subscript operator:

# Charizard, I choose you!
fighter1 = pokedex['fire']

# CHARIZARD fainted!
# How come my rival always picks the type that my pokémon is weak against??
fighter2 = pokedex['water']

Tip

If a ClassRegistry always returns objects derived from a particular base class, you can provide a type parameter to help with type checking, autocomplete, etc.:

# Add type parameter ``[Pokemon]``:
pokedex = ClassRegistry[Pokemon]()

# Your IDE will automatically infer that ``fighter1`` is a ``Pokemon``.
fighter1 = pokedex['fire']

Advanced Usage

There’s a whole lot more you can do with ClassRegistry, including:

  • Provide args and kwargs to new class instances.

  • Automatically register non-abstract classes.

  • Integrate with setuptools’s entry_points system so that 3rd-party libraries can add their own classes to your registries.

  • Wrap your registry in an instance cache to create a service registry.

  • And more!

To learn more about what you can do with ClassRegistry, keep reading!

Requirements

ClassRegistry is known to be compatible with the following Python versions:

  • 3.13

  • 3.12

  • 3.11

Note

I’m only one person, so to keep from getting overwhelmed, I’m only committing to supporting the 3 most recent versions of Python. ClassRegistry’s code is pretty simple, so it’s likely to be compatible with versions not listed here; there just won’t be any test coverage to prove it 😇

Installation

Install the latest stable version via pip:

pip install phx-class-registry

Important

Make sure to install phx-class-registry, not class-registry. I created the latter at a previous job years ago, and after I left they never touched that project again and stopped responding to my emails — so in the end I had to fork it 🤷