04·Strategy, Command, Template Method, Iterator

Introduction

Four behavioural GoF patterns, yet every average Python implementation is shorter than the UML diagrams in the books. Strategy = a function as an argument. Command = a @dataclass or functools.partial. Template Method = ABC with abstractmethod. Iterator = yield. Plus orthogonal tools: itertools.chain/islice for streams, functools.singledispatch as a Pythonic Visitor, yield from for delegation. This lesson shows when classical classes still pay off and when functional composition is cleaner.