Python to Scala Syntax Mapping

Enums

Python Enum -> Scala sealed trait + case objects or Enumeration:

// Preferred: sealed trait for pattern matching exhaustiveness
sealed abstract class TokenType(val value: String)
object TokenType {
  case object STRING extends TokenType("string")
  case object NUMERIC extends TokenType("numeric")
}

Dataclasses (frozen=True) -> Case Classes

// Python: @dataclass(frozen=True) with default fields
// Scala: case class (immutable by default)
case class Token(value: String, tokenType: TokenType, metadata: Map[String, Any] = Map.empty)

TypeVar -> Type Parameters

// Python: T = TypeVar("T")           -> [T]
// Python: T_co = TypeVar(covariant)  -> [+T]
// Python: T_contra = TypeVar(contra) -> [-T]
// Python: NumericT = TypeVar("NumericT", int, float, Decimal) -> type class or union

Protocol -> Trait (structural typing)

// Python Protocol -> Scala trait
trait Tokenizable {
  def toToken: String
}

Optional / Union

// Python: Optional[X] -> Scala: Option[X]
// Python: X | None -> Scala: Option[X]
// Python: Union[A, B] -> Scala: Either[A, B] or sealed trait or overloaded methods

Default Mutable Args

Python allows mutable defaults (anti-pattern). Scala avoids this:

// Python: def __init__(self, opts: dict = {}):
// Scala:  def this(opts: Map[String, Any] = Map.empty)