The screen goes black when I try to run the program

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i am a new coder using python and i am reading a book called hello world 3rd edition and i am try to run listing 16.14 but all i get is a black screen, what the program is suppose to do is make a imported image of a beach ball move across the screen horizontally and when reaching the edge bounce back forever intill the window is closed

What I have tried:

Python

import pygame, sys
pygame.init()
screen = pygame.display.set_mode([640, 480])
screen.fill([255,255,255])
my_ball=pygame.image.load("beach_ball.png")
x = 50
y = 50
x_speed = 10
running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
            pygame.time.delay(20)
            pygame.draw.rect(screen,[255,255,255],[x,y,90,90],0)
            x = x + x_speed
if x > screen.get_width()-90 or x <0:
      x_speed = -x_speed
      screen.blit(my_ball,[x, y])
      pygame.display.flip()
pygame.quit()

Posted 10-Jul-23 15:49pm

Kao Enyeartdecarlo

Updated 10-Jul-23 18:27pm

OriginalGriff

v2

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OriginalGriff · Accepted Answer · 2023-07-10T18:27:00

In Python, indentation controls what code is part of what block: all the contiguous code at a particular indentation level is part of a block, and any lesser indentation ends that.
As a result, your if statement

Python

if x > screen.get_width()-90 or x <0:

terminates the while loop above it meaning that the loop consists only of this code:

Python

while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
            pygame.time.delay(20)
            pygame.draw.rect(screen,[255,255,255],[x,y,90,90],0)
            x = x + x_speed

Since running does not change inside the loop unless the user exits, and the loop does nothing else at all until that does happen, the screen remains blank.