Python - 在'elif'語句中持續報告語法錯誤

Question

我是一名初學者，目前正在學習Python。在構建經典遊戲「Pong！」時，我遇到了這個問題，在這個問題中，Python一直告訴我在elif語句中有一個語法錯誤。不過，我只是不能找出我的問題是...這裏是我的一些代碼：

def draw(canvas): 
    global score1, score2, pad1_pos, pad2_pos, ball_vel, RIGHT, c 
     # update ball 
    '''reflections on the left wall''' 
    if (ball_pos[0] == BALL_RADIUS + PAD_WIDTH) and (ball_pos in [range(pad1_pos, pad1_pos + PAD_HEIGHT)]): 
     print ball_pos 
     ball_vel[0] = - ball_vel[1] 
     ball_vel[1] = ball_vel[1] 
     c += 10 

    '''scoring of paddle1''' 
    elif (ball_pos[0] == BALL_RADIUS + PAD_WIDTH) and not (ball_pos in [range(pad1_pos, pad1_pos + PAD_HEIGHT)]): 
     score2 += 1 
     spawn_ball() 
     RIGHT = False 

    '''reflections on the right wall''' 
    elif ball_pos[0] == (WIDTH - 1) - BALL_RADIUS - PAD_WIDTH and (ball_pos in [range(pad2_pos, pad2_pos + PAD_HEIGHT)]): 
     '''remember how Python counts the values starting from 0''' 
     '''the first pixel of a 600p wall is 0 and the last one is 599''' 
     ball_vel[0] = - ball_vel[1] 
     ball_vel[1] = ball_vel [1] 
     c += 10 

    '''scoring of paddle2''' 
    elif ball_pos[0] == (WIDTH - 1) - BALL_RADIUS - PAD_WIDTH and not (ball_pos in [range(pad2_pos, pad2_pos + PAD_HEIGHT)]): 
     score1 += 1 
     spawn_ball() 
     RIGHT = True 

    '''reflections on the upper wall''' 
    elif ball_pos[1] == BALL_RADIUS: 
     ball_vel[0] = ball_vel[0] 
     ball_vel[1] = - ball_vel[1] 

    '''reflections on the bottom wall''' 
    elif ball_pos[1] == (HEIGHT - 1) - BALL_RADIUS: 
     ball_vel[0] = ball_vel[0] 
     ball_vel[1] = - ball_vel[1] 

我沒貼我的完整繪製函數，但這個問題在我的第一個elif的語句右邊出現說：「行85：SyntaxError：壞輸入（'elif'）」。我不知道我的語法錯誤在哪裏，奇怪的是我的if語句結果很好。我想知道如果我的elif聲明的內容是有效的，因爲它是一個相當長的一個，作爲一個初學者，我傾向於弄亂長代碼...

順便說一下，我在這裏要做的是基本上可以確定球何時應該反射，以及反射到何處。因此，我使用'in'和'range'語句來設置我的槳的範圍，以便球只會反射在槳上（範圍內）。我不確定這是否是正確的做法，請讓我知道是否在這裏搞亂了任何東西。這是我第一個發佈在堆棧上的第一個問題，我只是在徹底檢查了我的代碼之後才做出來的。對不起，這個問題結果超長，但我真的很感激，如果有人能幫助我。

Answer 1

我同意，你應該考慮改變你的單行註釋使用英鎊的象徵。我運行了你的代碼，當我縮進多行註釋時，語法錯誤消失了。正如其他答案中提到的那樣，編譯器在if statement之後，預計要麼是一次縮進代碼，要麼是elif statement或與您的if具有相同縮進級別的新代碼。

def draw(canvas): 
    global score1, score2, pad1_pos, pad2_pos, ball_vel, RIGHT, c 
     # update ball 
    ''' 
    reflections on the left wall 
    ''' 
    if (ball_pos[0] == BALL_RADIUS + PAD_WIDTH) and (ball_pos in [range(pad1_pos, pad1_pos + PAD_HEIGHT)]): 
     print ball_pos 
     ball_vel[0] = - ball_vel[1] 
     ball_vel[1] = ball_vel[1] 
     c += 10 

    elif (ball_pos[0] == BALL_RADIUS + PAD_WIDTH) and (ball_pos in [range(pad1_pos, pad1_pos + PAD_HEIGHT)]): 
     print ball_pos 
     ball_vel[0] = - ball_vel[1] 
     ball_vel[1] = ball_vel[1] 
     c += 10 

    elif ball_pos[0] == (WIDTH - 1) - BALL_RADIUS - PAD_WIDTH and (ball_pos in range(pad2_pos, pad2_pos + PAD_HEIGHT)): 
     '''remember how Python counts the values starting from 0''' 
     '''the first pixel of a 600p wall is 0 and the last one is 599''' 
     ball_vel[0] = - ball_vel[1] 
     ball_vel[1] = ball_vel [1] 
     c += 10 

     '''scoring of paddle2''' 
    elif ball_pos[0] == (WIDTH - 1) - BALL_RADIUS - PAD_WIDTH and not (ball_pos in range(pad2_pos, pad2_pos + PAD_HEIGHT)): 
     score1 += 1 
     spawn_ball() 
     RIGHT = True 

     '''reflections on the upper wall''' 
    elif ball_pos[1] == BALL_RADIUS: 
     ball_vel[0] = ball_vel[0] 
     ball_vel[1] = - ball_vel[1] 

     '''reflections on the bottom wall''' 
    elif ball_pos[1] == (HEIGHT - 1) - BALL_RADIUS: 
     ball_vel[0] = ball_vel[0] 
     ball_vel[1] = - ball_vel[1] 

Answer 2

an elif只能緊跟在if塊或elif塊之後。在if和elif之間有一個字符串常量'''scoring of paddle1'''，所以嚴格來說，一個不會立即跟隨另一個。

考慮更改您的評論使用英鎊符號：#scoring of paddle1