Local and Global Variables — GDScript

Skill codes on this page

Definition. A variable stores and labels data to be referenced and manipulated in a program. Its scope is the part of the program that can see it.

Quick check: is the line indented inside a func? Local.

C621 — Local variables

Definition. Variables defined inside a function that can only be accessed by that function.

func calculate_fare() -> void:
    # C621 — local variable: only calculate_fare() can see it
    var fare: float = 5.30
    balance -= fare

Parameters and loop variables are local too — in connect-go-dots/grid.gd, the parameter photo: Texture2D and the loop variable button exist only inside their function.

C631 — Global variables

Definition. Variables defined outside any function that can be accessed by all functions throughout the source code.

At the script level:

extends Control

# C631 — global variables: every func in this script can use them
var balance: float = 20.00
var is_concession: bool = false

Or using class_name with static for access from other scripts:

class_name GlobalVars

static var g_var = 20   # C631 — global via class_name

An autoload singleton is the Godot-idiomatic project-wide global — if you use one, name it as your C631 evidence in validation.

In connect-go-dots — the autoload in action (shared.gd, registered as Shared):

# connect-go-dots — shared.gd (autoload "Shared")
extends Node

## Handed from one screen to the next. Lives on root, so a scene change
## cannot touch it.
var photo: Texture2D   # C631 — global: both screens use it

Shared.photo = photo            # C631: grid.gd — one screen writes it
%Photo.texture = Shared.photo   # C631: detail.gd — the other reads it

The ## comment is model internal documentation: it says why the variable lives where it does.

C622 — Constants

Definition. A fixed value that, once defined, cannot be altered during the execution of a program.

# C622 — constant: the daily cap never changes while the program runs
const DAILY_CAP: float = 9.60

Earns the tick: const used for a value that genuinely never changes, named in CAPITALS. Showing Godot's error when you try to assign to it is a neat validation demo.

C628 and C634 — choosing the right data type

C621/C631 is that the variable exists. C628/C634 is that its data type suits the data — C628 for locals, C634 for globals.

extends Control

var trips_today: int = 0          # C634 — int: you cannot take half a trip
var balance: float = 20.00        # C634 — float: money needs decimal places
var is_concession: bool = false   # C634 — bool: only two possible answers
var card_id: String = ""          # C634 — String: digits never used in a calculation

func charge(zone: int) -> void:
    var fare: float = FARE_TABLE[zone]   # C628 — float: fares have cents
    balance -= fare

From tile-matching-game (deck.gd):

# tile-matching-game — deck.gd
var key: String = card["pair"]   # C628 — String: the pair label from the CSV

State the data type. var trips_today = 0 cannot earn C634 because no data type has been given for the marker to assess. Always write : int, : float, : bool or : String.

var trips_today := 0 is acceptable — GDScript works out the type for you — but name it in your comment so the marker can see it: # C634 — int: you cannot take half a trip.

Types go beyond int/float/bool/String: in connect-go-dots the global is var photo: Texture2D — same standard, # C634 — Texture2D: the value is an image.

The why in these comments doubles as your reasoning evidence (C629/C638) — see Data Types.

Check Your Understanding

1. var speed := 5 at script level — which code does it earn as written, and what more would C634 need?

2. Are function parameters local or global?

3. What three things make a C622 constant?