API

The stable public surface of patos. Every name here is importable straight from the top-level package.

from patos import (
    Singleton,
    FlyweightMeta,
    Registry,
    Strategy,
    value_dispatch,
    type_dispatch,
    Decorator,
    Pipeline,
    Lifecycle,
    DerivedCache,
    StrFlag,
)

Two ways to use a pato

Install the flock and import what you want.

pip install patos

from patos import Registry, Singleton

Or copy a single duck. Open its 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.

The SQL namespace is an optional extension rather than a top level import. Install its extra and import the namespace when a project uses PostgreSQL.

pip install "patos[sql]"

from patos import sql

The flock

Creational

pato	exports	what it does
singleton	Singleton	one instance per class, __init__ runs once
flyweight	FlyweightMeta	intern instances by constructor args, build-once and immutable

Dispatch & selection

pato	exports	what it does
registry	Registry	self-registering class hierarchies via __init_subclass__, with dispatch, select and first_available
strategy	Strategy	a named family of interchangeable implementations, with first_available()
dispatch	value_dispatch, type_dispatch	dispatch on a value, or on the first argument's type the way singledispatch does

Structural & lifecycle

pato	exports	what it does
decorator	Decorator	a transparent wrapper forwarding everything to the wrapped object but its overrides
pipeline	Pipeline, Reversible	a reversible stack of stages, applied forward and unwound in reverse
lifecycle	Lifecycle, IllegalTransition	a typed state machine that permits only the transitions it declares
cache	DerivedCache	a load-once cache of a derived value keyed by exactly what it depends on

Command-line

pato	exports	what it does
strflag	StrFlag	an enum Flag whose members carry a literal string, OR-combinable and iterable

Optional extensions

extension	exports	what it does
sql	sql.Column, sql.PGEnum, sql.TypedJSONB, sql.CosineHalfvec, SQL expression helpers	concise typed PostgreSQL and SQLModel building blocks installed through patos[sql]