Python to Scala Syntax Mapping

Name: python-scala-syntax-mapping
Rating: 92
Author: KaiserWhoLearns

Variable Declarations

Python	Scala
`x = 5`	`val x = 5` (immutable) or `var x = 5` (mutable)
`x: int = 5`	`val x: Int = 5`
`x, y = 1, 2`	`val (x, y) = (1, 2)`

Prefer val over var unless mutation is required.

Type Mappings

Python	Scala
`int`	`Int`
`float`	`Double`
`str`	`String`
`bool`	`Boolean`
`None`	`None` (of type `Option`) or `null`
`list[T]`	`List[T]` or `Seq[T]`
`dict[K, V]`	`Map[K, V]`
`set[T]`	`Set[T]`
`tuple[A, B]`	`(A, B)` or `Tuple2[A, B]`
`Optional[T]`	`Option[T]`

Control Flow

Conditionals

python

# Python
if x > 0:
    result = "positive"
elif x < 0:
    result = "negative"
else:
    result = "zero"

scala

// Scala - if is an expression
val result = if (x > 0) "positive"
             else if (x < 0) "negative"
             else "zero"

Loops

python

# Python for loop
for i in range(10):
    print(i)

for item in items:
    process(item)

for i, item in enumerate(items):
    print(f"{i}: {item}")

scala

// Scala equivalents
for (i <- 0 until 10) println(i)

for (item <- items) process(item)

for ((item, i) <- items.zipWithIndex) println(s"$i: $item")

While loops

python

# Python
while condition:
    do_something()

scala

// Scala
while (condition) {
  doSomething()
}

Comprehensions

python

# Python list comprehension
squares = [x ** 2 for x in range(10)]
evens = [x for x in numbers if x % 2 == 0]
pairs = [(x, y) for x in xs for y in ys]

scala

// Scala for-comprehensions or map/filter
val squares = (0 until 10).map(x => x * x).toList
val evens = numbers.filter(_ % 2 == 0)
val pairs = for { x <- xs; y <- ys } yield (x, y)

Functions

python

# Python
def add(a: int, b: int) -> int:
    return a + b

# Lambda
square = lambda x: x ** 2

# Default arguments
def greet(name: str, greeting: str = "Hello") -> str:
    return f"{greeting}, {name}!"

scala

// Scala
def add(a: Int, b: Int): Int = a + b

// Lambda
val square: Int => Int = x => x * x
// or shorter: val square = (x: Int) => x * x

// Default arguments
def greet(name: String, greeting: String = "Hello"): String =
  s"$greeting, $name!"

String Formatting

Python	Scala
`f"Hello, {name}!"`	`s"Hello, $name!"`
`f"Value: {x:.2f}"`	`f"Value: $x%.2f"`
`f"{x + y}"`	`s"${x + y}"`

Common Operators

Python	Scala
`**` (power)	`math.pow(x, y)` or use `scala.math.pow`
`//` (floor div)	`x / y` (for Int) or `math.floor(x / y)`
`%` (modulo)	`%`
`and`, `or`, `not`	`&&`, `
`in`	`.contains()`
`is`	`eq` (reference equality)
`==`	`==` (value equality)

Exception Handling

python

# Python
try:
    result = risky_operation()
except ValueError as e:
    handle_error(e)
finally:
    cleanup()

scala

// Scala
import scala.util.{Try, Success, Failure}

// Pattern 1: try-catch
try {
  val result = riskyOperation()
} catch {
  case e: IllegalArgumentException => handleError(e)
} finally {
  cleanup()
}

// Pattern 2: Try monad (preferred for functional style)
val result = Try(riskyOperation()) match {
  case Success(value) => value
  case Failure(e) => handleError(e)
}

None/Null Handling

python

# Python
if value is None:
    return default
return process(value)

# Or
result = value if value is not None else default

scala

// Scala - use Option
val result = optionValue match {
  case Some(v) => process(v)
  case None => default
}

// Or more concisely
val result = optionValue.map(process).getOrElse(default)