Why does pygame stop refreshing?

Question

I have the following code to demonstrate my problem:

import pygame
import random
import time

def randPoint(w,h):
    p = int(random.random()*w),int(random.random()*h)
    return p


width=1000
height=1000
screenColor=(0,0,0)
lineColor=(255,255,255)
pygame.init()
screen=pygame.display.set_mode((width,height))
count = 0
while True:
    screen.fill(screenColor)
    start = randPoint(width,height)
    end = randPoint(width,height)
    pygame.draw.line(screen, (255, 255, 255), start, end)
    pygame.display.flip()
    print(count)
    count += 1
    time.sleep(0.05)

After about 100 frames the pygame window freezes although the console continues to print new frame counts. What am I missing here?

score 0 · Answer 1 · answered Mar 12 '22 at 21:07

You'll need to call the pygame.event.get() method within the while loop:

while True:
    pygame.event.get()
    screen.fill(screenColor)
    start = randPoint(width,height)
    end = randPoint(width,height)
    pygame.draw.line(screen, (255, 255, 255), start, end)
    pygame.display.flip()
    print(count)
    count += 1
    time.sleep(0.05)

The above stops the program from freezing, but if you want the X button to work on the window, allowing it to close upon command, simply add this for loop:

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()

Rabbid76 · Answer 2 · 2022-03-12T21:14:59.950

You have to handle the events in the application loop. See pygame.event.get() respectively pygame.event.pump():

For each frame of your game, you will need to make some sort of call to the event queue. This ensures your program can internally interact with the rest of the operating system.

If you don't handle the events, the application stops responding.

clock = pygame.time.Clock()
running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
    screen.fill(screenColor)
    start = randPoint(width,height)
    end = randPoint(width,height)
    pygame.draw.line(screen, (255, 255, 255), start, end)
    pygame.display.flip()
    print(count)
    count += 1
    clock.tick(20)

The typical PyGame application loop has to:

limit the frames per second to limit CPU usage with pygame.time.Clock.tick
handle the events by calling either pygame.event.pump() or pygame.event.get().
update the game states and positions of objects dependent on the input events and time (respectively frames)
clear the entire display or draw the background
draw the entire scene (blit all the objects)
update the display by calling either pygame.display.update() or pygame.display.flip()

Why does pygame stop refreshing?

2 Answers2