registry

id	modern/registry
name	Registry
aliases	plugin-registry dispatch-table
guide_url
problem	Let implementations announce themselves by name, so dispatch is a lookup instead of an if/elif ladder.
symptoms	if/elif on a type string plugin system handlers by name adding a case means editing the dispatcher
verdict	pythonic
caveats	Registration at import time means the module defining a plugin must actually get imported — a plugin nobody imports doesn't exist. Decide the unknown-key policy (KeyError? default handler?) once, in the lookup, not at each call site.
stdlib_sightings	codecs.register functools.singledispatch atexit.register

Registry

Implementations announce themselves by name; dispatch is a lookup, and adding a case is writing one new function. Verdict: pythonic — the standard cure for if/elif dispatch.

Where	What
pattern/	The importable code: Registry, UnknownKeyError
docs/	Fundamentals · Implementation guide · External examples
examples/export_plugins/	Mini-project: self-registering exporters, one in a separate plugin module
tests/	Behavioral tests for the pattern and the mini-project

uv run python -m patterns.modern.registry.examples.export_plugins.main