How to add Custom Events in Pygame? (original) (raw)

Last Updated : 23 Jul, 2025

In this article, we will see how to add custom events in PyGame.

Installation

PyGame library can be installed using the below command:

pip install pygame

Although PyGame comes with a set of events (Eg: KEYDOWN and KEYUP), it allows us to create our own additional custom eventsaccording to the requirements of our game. Custom events increase the control and flexibility we have over our game. A custom event is the same as creating a User-defined event.

Syntax:

<event_name> = pygame.USEREVENT + 1

Example:

# Here ADDITION and SUBTRACTION is the event name

ADDITION = pygame.USEREVENT + 1

SUBTRACTION = pygame.USEREVENT + 2

Now, how do we publish our custom events once they are created? This can be done in two ways:

• Using pygame.event.post() method.
• Using pygame.time.set_timer() method.

Using pygame.event.post() method

We can directly post our events using pygame.event.post() method. This method adds our event to the end of the events on the queue. In order to execute this, we need to convert our event to Pygame's event type inorder to match the attributes of the post method and avoid errors.

Syntax:

# Step 1 - Convert event into event datatype of pygame

ADD_event = pygame.event.Event(event)

# Step 2 - Post the event

pygame.event.post(ADD_event) # event_name as parameter

Using pygame.time.set_timer() method

Broadcasting the event periodically by using PyGame timers. Here, we'll be using another method to publish the event by using set_timer() function, which takes two parameters, a user event name and time interval in milliseconds.

Syntax:

# event_name, time in ms

pygame.time.set_timer(event, duration)

Note: In this, we don't need to convert the user-defined event into PyGame event datatype.

Now to create a plot with custom events firstly the attributes for the screen should be set as per requirement. Then create an event and convert it to PyGame event datatype. Now add code for your operations that will generate a custom event.

In the given implementation both of the approaches have been handled.

Program :

Python3 `

Python program to add Custom Events

import pygame

pygame.init()

Setting up the screen and timer

screen = pygame.display.set_mode((500, 500)) timer = pygame.time.Clock()

set title

pygame.display.set_caption('Custom Events')

defining colours

WHITE = (255, 255, 255) RED = (255, 0, 0) GREEN = (0, 255, 0) BLUE = (0, 0, 255)

Keep a track of active variable

bg_active_color = WHITE screen.fill(WHITE)

custom user event to change color

CHANGE_COLOR = pygame.USEREVENT + 1

custom user event to inflate defalte

box

ON_BOX = pygame.USEREVENT + 2

creating Rectangle

box = pygame.Rect((225, 225, 50, 50)) grow = True

posting a event to switch color after

every 500ms

pygame.time.set_timer(CHANGE_COLOR, 500)

running = True while running:

# checks which all events are posted
# and based on that perform required
# operations
for event in pygame.event.get():
  
    # switching colours after every
    # 500ms
    if event.type == CHANGE_COLOR:
        if bg_active_color == GREEN:
            screen.fill(GREEN)
            bg_active_color = WHITE
        elif bg_active_color == WHITE:
            screen.fill(WHITE)
            bg_active_color = GREEN

    if event.type == ON_BOX:
      
        # to inflate and deflate box
        if grow:
            box.inflate_ip(3, 3)
            grow = box.width < 75
        else:
            box.inflate_ip(-3, -3)
            grow = box.width < 50

    if event.type == pygame.QUIT:
      
        # for quitting the program
        running = False

# Posting event when the cursor is on top 
# of the box
if box.collidepoint(pygame.mouse.get_pos()):
    pygame.event.post(pygame.event.Event(ON_BOX))

# Drawing rectangle on the screen
pygame.draw.rect(screen, RED, box)

# Updating Screen
pygame.display.update()

# Setting Frames per Second
timer.tick(30)

pygame.quit()

`

Output :

In the above implementation, we have used the .post() method to inflate/deflate the box when the cursor is on the top of the box and .set_timer() method to switch background color after every 500ms.