Pygame程序运行黑屏，仅关闭窗口可见预期画面求助

我已自行排查Pygame程序的黑屏问题但未获进展，确认未过度调用.display命令，程序运行无报错但窗口始终呈黑屏状态，仅在关闭窗口时能短暂看到预期显示内容。以下是程序代码，恳请帮忙分析问题原因：

import math
import random

import pygame
from pygame import mixer

# Initialize the pygame
pygame.init()

# create the screen
screen = pygame.display.set_mode((800, 600))

# Background
background = pygame.image.load('space background.png')

# Background Sound
# come back to this from bg music   'mixer.music.load('insert file name')'
# mixer.music.play(-1)

# Title and Icon
pygame.display.set_caption("Space Invaders")
icon = pygame.image.load('ufo.png')
pygame.display.set_icon(icon)

# Player
playerImg = pygame.image.load('ship.png')
playerX = 370
playerY = 480
playerX_change = 0

# Enemy
enemyImg = []
enemyX = []
enemyY = []
enemyX_change = []
enemyY_change = []
num_of_enemies = 6

for i in range(num_of_enemies):
    enemyImg.append(pygame.image.load('enemy.png'))
    enemyX.append(random.randint(0, 735))
    enemyY.append(random.randint(50, 150))
    enemyX_change.append(0.3)
    enemyY_change.append(40)

# Bullet

# Ready -  you cat see the bullet on the screen
# Fire - The bullet is currently moving

bulletImg = pygame.image.load('bullet.png')
bulletX = 0
bulletY = 480
bulletX_change = 0
bulletY_change = 1  # Bullet speed
bullet_state = "ready"

# Score

score_value = 0
font = pygame.font.Font('Minecraft.ttf', 24)
textX = 10
testY = 10  # might have to change back to 'text'

# Game Over text
over_font = pygame.font.Font('Minecraft.ttf', 64)


def show_score(x, y):
    score = font.render("Score : " + str(score_value), True, (225, 225, 255))
    screen.blit(score, (x, y))


def game_over_text(x, y):
    over_text = over_font.render("GAME OVER", True, (225, 225, 255))
    screen.blit(over_text, (200, 250))


def player(x, y):
    screen.blit(playerImg, (x, y))


def enemy(x, y, i):
    screen.blit(enemyImg[i], (x, y))


def fire_bullet(x, y):
    global bullet_state
    bullet_state = "fire"
    screen.blit(bulletImg, (x + 16, y + 10))


def iscollision(enemyX, enemyY, bulletX, bulletY):
    distance = math.sqrt(math.pow(enemyX - bulletX, 2)) + (math.pow(enemyY - bulletY, 2))
    if distance < 27:
        return True
    else:
        return False


# Game Loop
running = True
while running:

    # RGB
    screen.fill((0, 0, 0))
    # background image
    screen.blit(background, (0, 0))
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

        # if keystroke is pressed check whether its right or left
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_LEFT:
                playerX_change = -0.7  # player speed
            if event.key == pygame.K_RIGHT:
                playerX_change = 0.7
            if event.key == pygame.K_SPACE:
                if bullet_state == "ready":
                    bullet_Sound = mixer.Sound('laser.wav')
                    bullet_Sound.play()
                    # Get the current X corrdinate of te spaceship
                    bulletX = playerX
                    fire_bullet(playerX, bulletY)

        if event.type == pygame.KEYUP:
            if event.key == pygame.K_LEFT or event.key == pygame.K_RIGHT:
                playerX_change = 0

    # 5 = 5 + -0.1 -> 5 = 5 - 0.1
    # 5 = 5 + 0.1

    # Checking for boundries of spaceship
    playerX += playerX_change
    if playerX <= 0:
        playerX = 0
    elif playerX >= 736:
        playerX = 736

    # Enemy Movement
    for i in range(num_of_enemies):

        # Game over
        if enemyY[i] > 440:
            for j in range(num_of_enemies):
                enemyY[j] = 2000
                game_over_text()
                break

        enemyX[i] += enemyX_change[i]
        if enemyX[i] <= 0:
            enemyX_change[i] = 0.3  # enemy speed
            enemyY[i] += enemyY_change[i]
        elif enemyX[i] >= 736:
            enemyX_change[i] = -0.3
            enemyY[i] += enemyY_change[i]

        # Collision
        collision = iscollision(enemyX[i], enemyY[i], bulletX, bulletY)
        if collision:
            explosion_Sound = mixer.Sound('explosion.wav')
            explosion_Sound.play()
            bulletY = 480
            bullet_state = "ready"
            score_value += 100
            enemyX[i] = random.randint(0, 736)
            enemyY[i] = random.randint(50, 150)

        enemy(enemyX[i], enemyY[i], i)

# Bullet Movement
if bulletY <= 0:
    bulletY = 480
    bullet_state = "ready"

if bullet_state == "fire":
    fire_bullet(bulletX, bulletY)
    bulletY -= bulletY_change

player(playerX, playerY)
show_score(textX, testY)
pygame.display.update()

问题原因及修复方案 #

核心问题 #

所有绘制、子弹逻辑和显示更新的代码都写在了游戏主循环while running的外面，这些代码只会在循环终止（窗口关闭）时执行一次，这就是窗口全程黑屏、关闭时才短暂看到内容的根本原因。

其他次要问题 #

1. 函数调用参数错误：game_over_text定义时需要接收x,y参数，但调用时未传参，会触发报错
2. 碰撞检测公式错误：iscollision里的距离计算把加号放在了math.sqrt()外面，正确公式应为math.sqrt(math.pow(enemyX - bulletX, 2) + math.pow(enemyY - bulletY, 2))
3. 变量名笔误：分数显示的Y坐标变量testY应为textY，否则会用错坐标位置

修复后的完整代码 #

import math
import random

import pygame
from pygame import mixer

# Initialize the pygame
pygame.init()

# create the screen
screen = pygame.display.set_mode((800, 600))

# Background
background = pygame.image.load('space background.png')

# Background Sound
# come back to this from bg music   'mixer.music.load('insert file name')'
# mixer.music.play(-1)

# Title and Icon
pygame.display.set_caption("Space Invaders")
icon = pygame.image.load('ufo.png')
pygame.display.set_icon(icon)

# Player
playerImg = pygame.image.load('ship.png')
playerX = 370
playerY = 480
playerX_change = 0

# Enemy
enemyImg = []
enemyX = []
enemyY = []
enemyX_change = []
enemyY_change = []
num_of_enemies = 6

for i in range(num_of_enemies):
    enemyImg.append(pygame.image.load('enemy.png'))
    enemyX.append(random.randint(0, 735))
    enemyY.append(random.randint(50, 150))
    enemyX_change.append(0.3)
    enemyY_change.append(40)

# Bullet

# Ready -  you can't see the bullet on the screen
# Fire - The bullet is currently moving

bulletImg = pygame.image.load('bullet.png')
bulletX = 0
bulletY = 480
bulletX_change = 0
bulletY_change = 1  # Bullet speed
bullet_state = "ready"

# Score

score_value = 0
font = pygame.font.Font('Minecraft.ttf', 24)
textX = 10
textY = 10

# Game Over text
over_font = pygame.font.Font('Minecraft.ttf', 64)


def show_score(x, y):
    score = font.render("Score : " + str(score_value), True, (225, 225, 255))
    screen.blit(score, (x, y))


def game_over_text():
    over_text = over_font.render("GAME OVER", True, (225, 225, 255))
    screen.blit(over_text, (200, 250))


def player(x, y):
    screen.blit(playerImg, (x, y))


def enemy(x, y, i):
    screen.blit(enemyImg[i], (x, y))


def fire_bullet(x, y):
    global bullet_state
    bullet_state = "fire"
    screen.blit(bulletImg, (x + 16, y + 10))


def iscollision(enemyX, enemyY, bulletX, bulletY):
    distance = math.sqrt(math.pow(enemyX - bulletX, 2) + math.pow(enemyY - bulletY, 2))
    if distance < 27:
        return True
    else:
        return False


# Game Loop
running = True
while running:

    # RGB
    screen.fill((0, 0, 0))
    # background image
    screen.blit(background, (0, 0))
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

        # if keystroke is pressed check whether its right or left
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_LEFT:
                playerX_change = -0.7  # player speed
            if event.key == pygame.K_RIGHT:
                playerX_change = 0.7
            if event.key == pygame.K_SPACE:
                if bullet_state == "ready":
                    bullet_Sound = mixer.Sound('laser.wav')
                    bullet_Sound.play()
                    # Get the current X corrdinate of te spaceship
                    bulletX = playerX
                    fire_bullet(playerX, bulletY)

        if event.type == pygame.KEYUP:
            if event.key == pygame.K_LEFT or event.key == pygame.K_RIGHT:
                playerX_change = 0

    # Checking for boundries of spaceship
    playerX += playerX_change
    if playerX <= 0:
        playerX = 0
    elif playerX >= 736:
        playerX = 736

    # Enemy Movement
    game_over = False
    for i in range(num_of_enemies):

        # Game over
        if enemyY[i] > 440:
            game_over = True
            break

        enemyX[i] += enemyX_change[i]
        if enemyX[i] <= 0:
            enemyX_change[i] = 0.3  # enemy speed
            enemyY[i] += enemyY_change[i]
        elif enemyX[i] >= 736:
            enemyX_change[i] = -0.3
            enemyY[i] += enemyY_change[i]

        # Collision
        collision = iscollision(enemyX[i], enemyY[i], bulletX, bulletY)
        if collision:
            explosion_Sound = mixer.Sound('explosion.wav')
            explosion_Sound.play()
            bulletY = 480
            bullet_state = "ready"
            score_value += 100
            enemyX[i] = random.randint(0, 736)
            enemyY[i] = random.randint(50, 150)

        enemy(enemyX[i], enemyY[i], i)
    
    if game_over:
        for j in range(num_of_enemies):
            enemyY[j] = 2000
        game_over_text()

    # Bullet Movement
    if bulletY <= 0:
        bulletY = 480
        bullet_state = "ready"

    if bullet_state == "fire":
        fire_bullet(bulletX, bulletY)
        bulletY -= bulletY_change

    player(playerX, playerY)
    show_score(textX, textY)
    pygame.display.update()

内容的提问来源于stack exchange，提问作者GOOD kid m.A.A.d city