1，首先在ship

class Ship():

    def __init__(self, ai_settings, screen):
        """初始化飛船並設定其初始位置"""
        --snip--

        # 空格和發射標誌
        self.space = False
        self.bullets_fire = True

2，首先重構程式碼，判斷空格鍵按下和放開狀態

def check_events(ship):
    """響應按鍵和滑鼠事件"""
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()

        elif event.type == pygame.KEYDOWN:
            check_keydown_events(event, ship)

        elif event.type == pygame.KEYUP:
            check_keyup_events(event, ship)

def check_keydown_events(event, ship):
    """響應按鍵"""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = True
    elif event.key == pygame.K_LEFT:
        ship.moving_left = True
    elif event.key == pygame.K_SPACE:
        ship.space = True   # 增加判斷空格鍵響應

def check_keyup_events(event, ship):
    """響應鬆開"""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = False
    elif event.key == pygame.K_LEFT:
        ship.moving_left = False
    elif event.key == pygame.K_SPACE:
        ship.space = False  # 增加判斷空格鍵響應

3，重構fire_bullet增加開關判斷，增加子彈位置判斷（由於沒找到其他好的方法，只能通過子彈畫素位置判斷）

def fire_bullet(ai_settings, screen, ship, bullets):
    if len(bullets) < ai_settings.bullets_allowed and ship.space and ship.bullets_fire: # 這裡加了開火開關
        new_bullet = Bullet(ai_settings, screen, ship)
        bullets.add(new_bullet)

def update_bullets(ai_settings, screen, ship, bullets, fire_speed):
    bullets.update()
    fire = 0  # 設定標誌
    fire_bullet(ai_settings, screen, ship, bullets)
    for bullet in bullets.copy():
        if bullet.rect.bottom >= fire_speed:
            fire += 1 # 這裡的fire_speed值是700，如果有子彈y值大於700，則修改fire值+1
    if fire > 0:  # 判斷fire值，相當於開關
        ship.bullets_fire = False
    else:
        ship.bullets_fire = True  # True則開火
    for bullet in bullets.copy():
        if bullet.rect.bottom <= 0:
            bullets.remove(bullet)

4，如果update_bullets不傳形參fire_speed的話，直接在if中輸入數值

# 開始遊戲的主迴圈
while True:
    # 開始遊戲主迴圈
    gf.check_events(ship)
    ship.update()
    gf.update_bullets(ai_settings, screen, ship, bullets, ai_settings.bullet_fire_speed)
    gf.update_screen(ai_settings, screen, ship, bullets)

這是比較笨的方法，新手勿噴。

另外求教 bullets.copy怎麼能獲取到最近發射的bullet 屬性？這個不是列表，嘗試了會有報錯。