Python 中的 screen.fill() 命令不起作用

Question

我有一个问题，我希望今天有人能帮助我，如果你能的话，请按照我被困住的方式去做，这里的文章告诉我，我被告知的错误应该有效。我正在使用 IntelliJ 的 PyCharm 和最新版本的 python - 3.8.5 所以我的目标是让我的 PyGame 窗口变成白色，因为在启动时它是黑色的，所以当我输入以下代码时会出现这个错误：

import pygame

# Initialise the pygame functions#

pygame.init()

# Create the screen for the user#

root = pygame.display.set_mode((800, 600))

pygame.display.set_caption("Space Invaders")

icon = pygame.image.load("space.png")

pygame.display.set_icon(icon)

# Makes the pygame window appear for longer than a few milliseconds#

runtime = True

while runtime:

    for event in pygame.event.get():

        if event.type == pygame.QUIT:

            runtime = False

    screen.fill(255, 255, 255) #The error appears here and I cant find out why because I have looked at articles and they say this should work#

    pygame.display.update()

PyCharm 的响应是：

pygame 1.9.6

Hello from the pygame community. https://www.pygame.org/contribute.html

Traceback (most recent call last):

  File "C:/Users/doesnotcompute10/OneDrive/Main Doccuments/Personal/Code/Code.PythonPycharm/PyGame/Learning/Space Invaders.py", line 25, in <module>

    screen.fill(255, 255, 255)

NameError: name 'screen' is not defined

Process finished with exit code 1

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