bridge

id	structural/bridge
name	Bridge
aliases	abstraction-implementor
guide_url
problem	Let an abstraction and its implementation vary independently, instead of multiplying subclasses across both axes.
symptoms	two hierarchies multiplying shapes times renderers device times remote backend swappable under a stable front
verdict	prefer-alternative
caveats	In Python the Bridge collapses into ordinary composition with dependency injection — hold the implementor as an attribute, pass it in. The pattern's real lesson survives: name the two axes, give each its own small hierarchy (or set of callables), and connect them with one reference.
stdlib_sightings	logging.Logger with logging.Handler

Bridge

Two independent axes (what to do × how to carry it out) joined by one injected reference, instead of a subclass per combination. Verdict: prefer an alternative — composition with dependency injection is the bridge.

Where	What
pattern/	The importable code: Transport protocol, transports, AlertNotifier, DigestNotifier
docs/	Fundamentals · Implementation guide · External examples
examples/notification_center/	Mini-project: team alert/digest routing over per-team transports
tests/	Behavioral tests for the pattern and the mini-project

uv run python -m patterns.structural.bridge.examples.notification_center.main