python-scala-oop

Python to Scala OOP Translation

Basic Classes

# Python
class Person:
    def __init__(self, name: str, age: int):
        self.name = name
        self.age = age

    def greet(self) -> str:
        return f"Hello, I'm {self.name}"

// Scala
class Person(val name: String, val age: Int) {
  def greet: String = s"Hello, I'm $name"
}

// Usage
val person = new Person("Alice", 30)  // 'new' required for class

Data Classes → Case Classes

# Python
from dataclasses import dataclass

@dataclass
class Point:
    x: float
    y: float

@dataclass(frozen=True)
class ImmutablePoint:
    x: float
    y: float

// Scala - case class is idiomatic
case class Point(x: Double, y: Double)

// Case classes are immutable by default
// They auto-generate: equals, hashCode, toString, copy, apply

// Usage
val p = Point(1.0, 2.0)  // No 'new' needed for case class
val p2 = p.copy(x = 3.0)  // Creates new instance with x changed

Properties

# Python
class Circle:
    def __init__(self, radius: float):
        self._radius = radius

    @property
    def radius(self) -> float:
        return self._radius

    @radius.setter
    def radius(self, value: float):
        if value < 0:
            raise ValueError("Radius must be non-negative")
        self._radius = value

    @property
    def area(self) -> float:
        return 3.14159 * self._radius ** 2

// Scala
class Circle(private var _radius: Double) {
  require(_radius >= 0, "Radius must be non-negative")

  def radius: Double = _radius

  def radius_=(value: Double): Unit = {
    require(value >= 0, "Radius must be non-negative")
    _radius = value
  }

  def area: Double = math.Pi * _radius * _radius
}

// Idiomatic Scala: prefer immutable case class
case class Circle(radius: Double) {
  require(radius >= 0, "Radius must be non-negative")
  def area: Double = math.Pi * radius * radius
}

Inheritance

# Python
class Animal:
    def __init__(self, name: str):
        self.name = name

    def speak(self) -> str:
        raise NotImplementedError

class Dog(Animal):
    def speak(self) -> str:
        return f"{self.name} says woof!"

class Cat(Animal):
    def speak(self) -> str:
        return f"{self.name} says meow!"