strategy

id	behavioral/strategy
name	Strategy
aliases	policy
guide_url
problem	Make an algorithm interchangeable at runtime without the caller knowing which variant it got.
symptoms	swap algorithm at runtime pricing rules pluggable policy if/elif chain choosing behavior
verdict	prefer-alternative
caveats	In Python a strategy is just a function passed as an argument — the class-per-algorithm hierarchy is Java's workaround for lacking first-class functions. Reach for the class form only when a strategy carries its own state or several related methods.
stdlib_sightings	sorted list.sort functools.cmp_to_key

Strategy

Swap the algorithm without touching the caller. Verdict: prefer an alternative — in Python a strategy is a function passed as an argument; the registry below is for families that grow.

Where	What
pattern/	The importable code: StrategyRegistry, UnknownStrategyError
docs/	Fundamentals · Implementation guide · External examples
examples/promotions/	Mini-project: checkout pricing rules built on pattern/
tests/	Behavioral tests for the pattern and the mini-project

uv run python -m patterns.behavioral.strategy.examples.promotions.main