Format Strings¶

A format string is a string prefixed with $ that can embed expressions inside { }.

name = "Alice"
age = 30
write($"Hello {name}, you are {age} years old!")

Syntax¶

$"text {expression} more text"

Any valid Luz expression can go inside { }:

write($"2 + 2 = {2 + 2}")                  # 2 + 2 = 4
write($"uppercase: {uppercase(name)}")      # uppercase: ALICE
write($"list length: {len([1, 2, 3])}")    # list length: 3
write($"null value: {null}")               # null value: null
write($"condition: {10 > 5}")              # condition: true

Nested expressions¶

Expressions can call functions, access attributes, do math — anything that returns a value:

class Point {
    function init(self, x, y) {
        self.x = x
        self.y = y
    }
}

p = Point(3, 4)
write($"Point is at ({p.x}, {p.y})")   # Point is at (3, 4)

Escape sequences¶

Escape sequences in format strings work the same as in regular strings, but only outside { }:

write($"line one\nline two")
write($"tab\there")

Difference from regular strings¶

	Regular string	Format string
Prefix	none	`$`
Embed expressions	no	yes, with `{ }`
Escape sequences	yes	yes (outside `{ }`)