Lists

The same rules apply for lists as for variables regarding **for all sprites** and **for this sprite only**.

Declaration

list list_name;

list type_name list_name;

Operations

Add item to list

add value to list_name;

Delete item from list at index

delete list_name[index];

Delete all items from list

delete list_name;

Insert item at index in list

insert value at list_name[index];

Replace item at index in list

list_name[index] = value;

Get item at index in list

value = list_name[index];

Get index of item in list

index in item

Get length of list

len = length list_name;

Check if item is in list

if value in list_name {
    ...
}

Show/Hide List Monitor

show list_name;

hide list_name;

Get random/last item in list

value = list_name["random"];

value = list_name["last"];

Compound Assignment

+---------------------------+--------------------------------------------------+
|         Operator          |                  Implementation                  |
+===========================+==================================================+
| `list_name[index]++;`     | 
=> ../assets/list_increment.png                  |
|                           | [IMG]
{width="400"}                               |
+---------------------------+--------------------------------------------------+
| `list_name[index]--;`     | 
=> ../assets/list_decrement.png                  |
|                           | [IMG]
{width="400"}                               |
+---------------------------+--------------------------------------------------+
| `list_name[index] += y;`  | 
=> ../assets/list_add.png [IMG]
{width="400"}     |
+---------------------------+--------------------------------------------------+
| `list_name[index] -= y;`  | 
=> ../assets/list_subtract.png                   |
|                           | [IMG]
{width="400"}                               |
+---------------------------+--------------------------------------------------+
| `list_name[index] *= y;`  | 
=> ../assets/list_multiply.png                   |
|                           | [IMG]
{width="400"}                               |
+---------------------------+--------------------------------------------------+
| `list_name[index] /= y;`  | 
=> ../assets/list_divide.png                     |
|                           | [IMG]
{width="400"}                               |
+---------------------------+--------------------------------------------------+
| `list_name[index] //= y;` | 
=> ../assets/list_floor_divide.png               |
|                           | [IMG]
{width="400"}                               |
+---------------------------+--------------------------------------------------+
| `list_name[index] %= y;`  | 
=> ../assets/list_mod.png [IMG]
{width="400"}     |
+---------------------------+--------------------------------------------------+
| `list_name[index] &= y;`  | 
=> ../assets/list_join.png [IMG]
{width="400"}    |
+---------------------------+--------------------------------------------------+

List Data

Initial data for lists can be stored inside the project. This behaves the same way loading text files into lists works in the Scratch editor. In addition to loading text files, you can also load data from various scripts and commands. This is useful for creating look-up tables or loading data from images or videos.

Loading data from text files

Each line in the text file will be added to the list as a separate item.

list list_name = file ```path/to/file.txt```;

Loading data from bash script

The bash script enclosed in triple-backticks will be executed, and the standard output will be stored in the list, one item per line. The working directory will be set to the project directory.

list list_name = ```cat path/to/file.txt```;

Loading data from any other program

The name of the program may be specified before the triple-backticks. This program will be executed with the standard input set to the script enclosed in the triple-backticks. The standard output will be stored in the list, one item per line. The working directory will be set to the project directory.

Any program that accepts input from stdin and outputs to stdout can be used.

For example, to load data from a python script:

list list_name = python ```
import random
for _ in range(5):
    print(random.randint(-5, 5))

!!! tip     If your script takes a long time to run, you can use bash to cache the output of the     script.

Let's say that your script converts a file `DEPENDENCY.txt`. You wish to only

re-run the script if the file `DEPENDENCY.txt` has changed. We can use stat

to get the last modification time of the file.

TIME=$(stat -c %Y DEPENDENCY.txt)
if [ $TIME -eq $(< DEPENDENCY.time)]; then
    cat DEPENDENCY.cached
    exit
fi
echo $TIME > DEPENDENCY.time
python convert_file.py DEPENDENCY.txt | tee DEPENDENCY.cached

### Struct List Data

If the list's type is a struct, each field will be filled with the value of the corresponding line in the data.

Example:

struct vec3d { x, y, z };

list vec3d points = file ```file.txt```;

contents of `file.txt`:

resulting in the following list:

[

vec3d {

x: 10,

y: 20,

z: 30

vec3d {

x: 40,

y: 50,

z: 60

}

]