run2-python-scala-dataclass

name	run2_python-scala-dataclass
description	Translating Python @dataclass and Enum to Scala case class and Enumeration/Sealed Traits safely

Dataclass and Enum to Scala Case Class and Sealed Trait

Python uses @dataclass for concise data records and Enum for enumerations. In Scala, we use case class and sealed abstract class / trait with case object.

Python Enum

class TokenType(Enum):
    STRING = "string"
    NUMERIC = "numeric"

Scala Enum Equivalent (Scala 2.13)

While Scala 3 has enum, in Scala 2.13 we implement Algebraic Data Types explicitly using sealed abstract class (or sealed trait). Abstract class allows taking parameters in constructor.

sealed abstract class TokenType(val value: String)
object TokenType {
  case object STRING extends TokenType("string")
  case object NUMERIC extends TokenType("numeric")
}

Python Dataclass

@dataclass(frozen=True)
class Token:
    value: str
    token_type: TokenType
    metadata: dict[str, Any] = field(default_factory=dict)

Scala Case Class

Case classes are immutable and come with an out-of-the-box copy method.

case class Token(
  value: String,
  tokenType: TokenType,
  metadata: Map[String, Any] = Map.empty
) {
  // Using .copy to create a modified clone
  def withMetadata(kwargs: (String, Any)*): Token = {
    this.copy(metadata = this.metadata ++ kwargs)
  }
}

Notes

• Python's default_factory translates simply to = Map.empty as default parameters in Scala are evaluated dynamically upon invocation.
• Python dict translates safely to Scala's immutable Map. For mutability, use scala.collection.mutable.Map.