Why Doesn't My PyGame Program Run Without an Application Loop?

Understanding PyGame Application Loop and Event Handling

When attempting to run a simple PyGame program, you may encounter a situation where nothing happens after initializing PyGame. This is typically due to the absence of an application loop, which is essential for any PyGame program.

The purpose of an application loop is to handle events, update game objects, draw the scene, and limit the frame rate. Without an application loop, your program will initialize, display the initial screen, and then terminate immediately.

To resolve this issue, implement an application loop as follows:

import pygame
from pygame.locals import *

pygame.init()

win = pygame.display.set_mode((400,400))
pygame.display.set_caption("My first game")
clock = pygame.time.Clock()

run = True
while run:

    # Handle events
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False

    # Update game objects
    # [...]

    # Clear display
    win.fill((0, 0, 0))

    # Draw game objects
    # [...]

    # Update display
    pygame.display.flip()

    # Limit frames per second
    clock.tick(60)

pygame.quit()

The application loop follows these steps:

• Handle Events: This is done by calling either pygame.event.pump() or pygame.event.get().
• Update Game Objects: Update the states and positions of objects based on input events and time.
• Clear Display: Clear the display for drawing.
• Draw Game Objects: Draw all the game objects on the display.
• Update Display: This is done by calling either pygame.display.update() or pygame.display.flip().
• Limit Frames Per Second: Limit the CPU usage by restricting the number of times the application loop runs per second using pygame.time.Clock.tick().

By implementing an application loop, your PyGame program will now run smoothly and handle events correctly.

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