2. Event Basics

When you first learn Python, the script you run might look like this:

Code

message = "I am a chest! "
n_repeat = 4
print(f"print message: '{message}' {n_repeat} times")

repeated_message = message * n_repeat
print(repeated_message)

When you run script, the script runs from the first line to the last line only once.

Output

print message: 'I am a chest! ' 4 times
I am a chest! I am a chest! I am a chest! I am a chest! 

Let the Event Run the Code

But we don’t want the code to run just once. We want the code to run whenever something happens in the game!

This is where the Event comes in.

Step 1: Put the code in a function

def my_click_event():
    message = "I am a chest! "
    n_repeat = 4
    repeated_message = message * n_repeat
    print(repeated_message)

Now you can run the code whenever you want, for as many times as possible.

my_click_event()
print("Call it again!")
my_click_event()
print("Call it again!")
my_click_event()
print("That's enough.")

Output

I am a chest! I am a chest! I am a chest! I am a chest! 
Call it again!
I am a chest! I am a chest! I am a chest! I am a chest!
Call it again!
I am a chest! I am a chest! I am a chest! I am a chest! 
That's enough.

Step 2: Let the game run your functions

You forgo the ablity to call the function by yourself, and let PyScratch run it for you.

We used the when_this_sprite_clicked event in this case.

We just add this line on top of the function @<sprite>.when_this_sprite_clicked and replace <sprite> with your sprite.

Requires PyScratch version 2.1.0 or above.

@chest.when_this_sprite_clicked()
def my_click_event():
    message = "I am a chest! "
    n_repeat = 4
    repeated_message = message * n_repeat
    print(repeated_message)

Now put in chest.py, save it, and run main.py.

The game running your function

Multiple events

When you have multiple events, just out the events one after another. The order of the events does not matter.

chest.py

import pyscratch as pysc
from pyscratch import game

chest = pysc.create_single_costume_sprite("assets/chest-open.png")

@chest.when_this_sprite_clicked()
def click_event1():
    pass

@chest.when_this_sprite_clicked()
def cick_event2():
    pass

@chest.when_game_start()
def game_start_event1():
    pass

Other Events

For now, we focus only on these two events

• @<sprite>.when_this_sprite_clicked
• @<sprite>.when_game_start

The other events take in parameters and will thus be introduced in the future.

Next Step