為什么python跳過這些代碼行？

Question

我正在嘗試繪制一些pygame圓圈並顯示它們，並且當用戶按下鍵時，它將更新這些計數器的位置。 當用戶按下按鍵時，它將在屏幕上的新位置繪制一個圓圈，但不會顯示第一個圖像。 因此，它應該顯示一個圓圈，當他們按下一個鍵時，它會更改圓圈的位置。 它沒有畫出啟動圈。

第一個圈子（這些不會出現）：

#Draw counters using pygame draw line function. These are the default counters on the start position. These don't move.
    countY = 750
    count1 = pygame.draw.circle(window, (black),(150, countY), 25, 0)
    count2 = pygame.draw.circle(window, (black),(250, countY), 25, 0)
    count3 = pygame.draw.circle(window, (255, 255, 255),(450, countY), 25, 0)
    count4 = pygame.draw.circle(window, (255, 255, 255),(550, countY), 25, 0)
    print("Should draw start counters")
    pygame.display.update()

輸入密鑰后繪制的圓圈：

while game:
    for event in pygame.event.get():
        pygame.event.get()

        #Counter 1 movement
        if event.type == pygame.KEYDOWN and event.key == pygame.K_a:
            diceRoll = random.randint(1, 4)

            window.fill(grey)
            grid()

            count1 = pygame.draw.circle(window, (black),(150, countY - 72 * diceRoll), 25, 0)

Answer 1

當按下一個鍵時，用灰色填充背景表面：

if event.type == pygame.KEYDOWN and event.key == pygame.K_a:
    diceRoll = random.randint(1, 4)

    window.fill(grey) # <--- fills the entire surface with a solid color!

而且您不會再畫圓了。

一個簡單的解決方法是保留所有圓的列表，並在每一幀繪制它們（有更有效的方法，但為方便起見，讓我們保持簡單）。

circles = []
countY = 750
circles.append((pygame.color.Color('black'), (150, countY), 25, 0))
circles.append((pygame.color.Color('black'), (250, countY), 25, 0))
circles.append((pygame.color.Color('white'), (450, countY), 25, 0))
circles.append((pygame.color.Color('white'), (550, countY), 25, 0))

while game:
    window.fill(grey)
    for event in pygame.event.get():
        # pygame.event.get() don't call pygame.event.get() twice

        if event.type == pygame.KEYDOWN and event.key == pygame.K_a:
            diceRoll = random.randint(1, 4)
            circles.append((pygame.color.Color('black'), (150, countY - 72 * diceRoll), 25, 0))

    for (color, pos, rad, w) in circles:
        pygame.draw.circle(window, color, pos, rad, w)
    pygame.display.flip()