patos 0.0.4

Typed Python design and dispatch patterns, pip one in or copy one in and own the file

A flock of typed, zero-dependency Python design patterns. Each pattern is a single self-contained pato (a duck you adopt), fully typed, standard library only, and small enough to read in one sitting.

Install

pip install patos

Or copy a single duck. Open its docs page, copy the source from the Source section, and paste it into your own project. No dependency, no version pin, no tool, just one module you own.

Patterns

Creational

pato	description	docs
Singleton	one instance per class, __init__ runs once	docs
FlyweightMeta	a metaclass that interns instances by constructor args, build-once and immutable	docs

Dispatch & selection

pato	description	docs
Registry	self-registering class hierarchies via __init_subclass__, with try-each dispatch	docs
Strategy	a named family of interchangeable implementations, with first_available()	docs
value_dispatch	dispatch on a value the way singledispatch dispatches on a type	docs

Command-line

pato	description	docs
StrFlag	an enum Flag whose members carry a literal string, OR-combinable and iterable	docs

Example

from patos import Singleton


class Settings(Singleton):
    def __init__(self) -> None:
        self.debug = False


a = Settings()
a.debug = True
b = Settings()      # same object, __init__ did not run again

assert a is b and b.debug

Documentation

Full documentation lives at phvv.me/patos.

Development

This project uses uv.

• Install: uv sync --extra dev
• Lint: uv run ruff check . && uv run ruff format --check .
• Typecheck: uv run pyrefly check
• Test: uv run pytest
• Docs: uv run --extra docs mkdocs build
• Build: uv build