python-scala-oop

name	python-scala-oop
description	Translating Python classes, inheritance, and generic variance to Scala equivalents.

Python to Scala OOP and Generics

This skill covers the translation of object-oriented concepts from Python to Scala.

Classes and Inheritance

Data Classes

• Python: @dataclass(frozen=True)
• Scala: case class (immutable by default, comes with copy and structural equality).

Abstract Base Classes

• Python: ABC and @abstractmethod
• Scala: abstract class or trait. Use trait when multiple inheritance is needed.

Methods

• Python: def my_method(self, arg):
• Scala: def myMethod(arg: Type): ReturnType = { ... }

Enums

• Python: class Color(Enum):
• Scala: object Color extends Enumeration { val Red, Green, Blue = Value } or (better) sealed trait Color.

Generics and Variance

Python	Scala	Notes
Generic[T]	[T]	Invariant
Generic[T_co]	[+T]	Covariant (can return subtypes)
Generic[T_contra]	[-T]	Contravariant (can accept supertypes)

Covariance (+T)

Useful for read-only containers (e.g., List[+A]).

class Container[+T](val item: T)

Contravariance (-T)

Useful for consumers or sinks.

trait Sink[-T] { def consume(item: T): Unit }

Structural Typing (Protocols)

• Python: @runtime_checkable class Protocol:
• Scala: trait or structural types type MyType = { def method(): Unit }. Usually, explicit traits are preferred.