Simple actions

Random number

var rng = RandomNumberGenerator.new()
rng.randomize()
var r = rng.randf_range(0.0, 1.0)
var k = rng.randi_range(1, 4) / 5.0

Float to string (display float in label)

var number: float = 42.0
$Label.text = number % "%.02f"
$Label.text = str(number).pad_decimals(2)
$Label.text = String.format("%.02f", number)

Concatenate strings from an array:

var array = ["a", "b", "c"]
var result = PoolStringArray(array).join(", ")

Find element in array (functional style)

func _find(arr: Array, f: FuncRef):
	for v in arr:
		if f.call_func(v):
			return true
	return false
	
func _lambda_player_in_room(a):
	return a.player_name != null

var player_in_room = _find(rooms, funcref(self, "_lambda_player_in_room"))

Parse custom command line arguments

var args = OS.get_cmdline_args()
for arg in args:
	if arg.begins_with("--window-size"):
		var size_string = arg.trim_prefix("--window-size")
		var sizes = size_string.split('x', false)

Read local file

const file_name = "user://user.conf"
var file = File.new()
if file.file_exists(file_name):
	file.open(file_name, File.READ)
	var line = file.get_line().rstrip('\n\r ')
	file.close()