Python to Scala Syntax Mapping
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
if x > 0:
result = "positive"
elif x < 0:
result = "negative"
else:
result = "zero"
// Scala - if is an expression
val result = if (x > 0) "positive"
else if (x < 0) "negative"
else "zero"
Loops
# 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 equivalents
for (i <- 0 until 10) println(i)
for (item <- items) process(item)
for ((item, i) <- items.zipWithIndex) println(s"$i: $item")
While loops
# Python
while condition:
do_something()
// Scala
while (condition) {
doSomething()
}
Comprehensions
# Python list comprehension
squares = [x ** 2 for x in range(10)]
evens = [x for x in numbers if x % 2 == 0]
pairs = [(x, y) for x in xs for y in ys]
// Scala for-comprehensions or map/filter
val squares = (0 until 10).map(x => x * x).toList
val evens = numbers.filter(_ % 2 == 0)
val pairs = for { x <- xs; y <- ys } yield (x, y)
Functions
# Python
def add(a: int, b: int) -> int:
return a + b
# Lambda
square = lambda x: x ** 2
# Default arguments
def greet(name: str, greeting: str = "Hello") -> str:
return f"{greeting}, {name}!"
// Scala
def add(a: Int, b: Int): Int = a + b
// Lambda
val square: Int => Int = x => x * x
// or shorter: val square = (x: Int) => x * x
// Default arguments
def greet(name: String, greeting: String = "Hello"): String =
s"$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
try:
result = risky_operation()
except ValueError as e:
handle_error(e)
finally:
cleanup()
// 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
if value is None:
return default
return process(value)
# Or
result = value if value is not None else default
// 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)
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