How are GoF patterns used in Java and Python?

In Java, GoF patterns are deeply embedded in the standard library and ecosystem. Singleton is used for Runtime.getRuntime(); Factory Method in Calendar.getInstance(); Abstract Factory in the DocumentBuilderFactory (XML API); Iterator in java.util.Iterator; Observer in java.util.EventListener; Decorator in java.io streams; Flyweight in Integer.valueOf() caching. In Python, the language's dynamic nature means many patterns are simpler or built-in: Iterator via __iter__/__next__, Observer via signals (Django) or callbacks, Decorator via Python's native @decorator syntax (though not exactly GoF Decorator), Singleton via module-level instances. Python's duck typing often replaces the need for explicit interface definitions that Java requires for patterns.