How do I create a 2D array ?

Question

I can create a 1-dimensional array as follows:

var list = []

How would I create a 2-dimensional array? I can't seem to find an obvious example in the docs or project examples. In Python I think it would be:

var matrix = [[0 for x in range(width)] for y in range(height)] 

but this returns an error in Godot.

Answer 1

godotscript is not python and doesn't follow the pythonic way. Simply do it the old fashion way:

var matrix=[]
for x in range(width):
    matrix[x]=[]
    for y in range(height):
        matrix[x][y]=0

Comments

This approach is returning an error " Invalid set index '0' (on base: 'Array'). " at the first step

matrix[x] = []

---

Strange. I did try it yesterday. Anyway, maybe using

matrix.append([])

does the trick. The theory for the n dimensional matrix doesn't change.

---

Thank you , that seems to fix the problem:

var matrix = []
for x in range(width):
    matrix.append([])
    matrix[x]=[]        
    for y in range(height):
        matrix[x].append([])
        matrix[x][y]=0

---

Almost, I fixed it for you. Your method had some redundancies that slowed it down.

var matrix = []
for x in range(width):
    matrix.append([])
    for y in range(height):
        matrix[x].append(0)

matrix[x]=[]

this sets the [] you just appended into a []

matrix[x].append([])

matrix[x][y]=0

these append a [] and then set the [] to a 0, which is weird and inefficient

the cleaned up method simply starts with a [], then adds [] as rows, ex: [ [],[],[] ]
then adds 0's into the rows, ex: [ [0,0,0],[0,0,0],[0,0,0] ]

one last side note: if you are making a very large 2D array (300x300 or higher), it seems to be faster to use a while loop instead of the for each loop with the range method, because the range method does something along the lines of building an array, ex: range(3) makes an array = [0,1,2]. This is slower than simply having an increment counter, ex: int x = 0, while(x<3), x += 1

---

very helpful, thanks for the advice and improvements!

---

Use append_array() for arrays, efficient for it expects specifically an array.
Examples:

array1.append_array(array2)

Answer 2

Or such:

func create_map(w, h):
    var map = []

    for x in range(w):
        var col = []
        col.resize(h)
        map.append(col)

    return map

Return Null-filled array.

Answer 3

This is the way I create 2d arrays in godot:

var array_a = [1,2,3,4]
var array_b = [5,6,7,8]

var array_2d = [array_a, array_b]

And then, to read:

array_2d[0,1] -> 2
array_2d[1,2] -> 7

Comments

I believe the correct way to read/write is (now):

array_2d[0][1] -> 2 

etc...

At least that's what i experienced in Godot 3.0

Answer 4

Seeing these awful answers; this is the most performance-friendly way of creating it:

func create_2d_array(width, height, value):
    var a = []

    for y in range(height):
        a.append([])
        a[y].resize(width)

        for x in range(width):
            a[y][x] = value

    return a

To be used as array[y][x].

Comments

This comment is ancient now, but why did you put y before x? That seems pretty programmer-unfriendly, considering that every other time coordinates are used, they go in alphabetical order (x,y)

---

@Davi-Danger, that isn't always true. It comes down to row-major vs. column major, which very much depends on the application of the 2D array. If I'm modeling something like a matrix, it isn't uncommon at all to have y first; and in some APIs it's the standard to do it that way.

After all, it doesn't just affect how the programmer sees it, it affects how it's arranged in memory.

---

2D Arrays are still not listed in documentation.

Answer 5

#creating 2D Arrays in GDscript
var my_array = [[]]

var width = 5
var height = 5

func _ready():
#setting 2D Array size
for x in width:
    my_array.resize(width)

    for y in height:
        my_array[x].resize(y)

#setting a value
my_array[0][0] = 1

Comments

Isn't it that the function _ready() should be replaced with _init() because the following code is initialization rather than something to do after entering the tree?

Answer 6

The simplest way is probably:

var r = [0,0,0,0,0,0,0,0,0,0,0,0,0]#r for row
var matrix = [r,r,r,r,r,r,r,r,r,r,r,r,r,r,r]

Comments

Unfortunately your answer will lead to a serious problem if you change any one of the elements in matrix. Say you assign matrix[0][0] = 1, then matrix will become something like

[
    1, 0,0,0,0,0,0,0,0,0,0,0,0
    1, 0,0,0,0,0,0,0,0,0,0,0,0
    ...
    1, 0,0,0,0,0,0,0,0,0,0,0,0
]

Since you have repeated appended the same r to matrix, the underlying elements in matrix is referencing the same memory block, i.e., matrix[0] and matrix[1] is pointing to the same memory block which is also referenced by var r.

This is because r is shallowly copied into matrix. You should use deep copy instead.

Answer 7

extends Node2D
var AilList = Array()
func _onButtonpressed():
$Label.text=str("hi")
AilList = make2darray()
print(AilList)
print(AilList[0][3])

func make2darray():
var array1 = Array()
var ihei =[0,1 ,2 ,3 ,4, 5, 6 ,7 ,8 ,9 ,10 ,11 ,12 ,13 ,14 ,15 ,16]
var width = 4
var height = 4
var counok = 0
for i in width:
var array2 = Array()
for j in height:
array2.append(ihei[counok])
counok += 1
array1.append(array2)
return array_1

Answer 8

                X1      X2
var Arr2D = [[y1,y2],[y1,y2]]

you dont need a code to do it , its just that easy!!!

look here is an Example :

var Arr2D = [[1,3],[2,4]]
print(Arr2D[0][1])

will print 3

Answer 9

I get that a lot of these are joke answers because the real answer is really simple, but in case someone actually doesn't know.

var matrix = [[],[]]

append as needed