索引列表错误

Question

我有一个问题，我真的不知道问题是什么，但我的代码，但我已经有第一个问题修复，然后这个发生。请帮我解决这个问题，或者找出问题所在。

import pygame 
import time 
import random 

pygame.init() 

white = (255,255,255) 
black = (0,0,0) 
red = (255,0,0) 
orange = (255,127,0) 
yellow = (255,255,0) 
green = (0,255,0) 
blue = (0,0,255) 
purple = (143,0,255) 
dark_green = (0,155,0) 

display_width = 800 
display_height = 600 

gameDisplay = pygame.display.set_mode((display_width,display_height)) 
pygame.display.set_caption("Slither") 

img = pygame.image.load(r"C:\Users\BJBGaming\Desktop\snakehead.png") 

clock = pygame.time.Clock() 

block_size = 20 
FPS = 15 

font = pygame.font.SysFont(None, 25) 

def snake(block_size, snakelist): 

    print(snakelist) 
    gameDisplay.blit(img,(snakelist[-1][0], snakelist[-1][1])) 

    for XnY in snakelist[:-1]: 
     pygame.draw.rect(gameDisplay, dark_green, [XnY[0],XnY[1],block_size,block_size]) 

def text_objects(text,color): 
    textSurface = font.render(text, True, color) 
    return textSurface, textSurface.get_rect() 


def message_to_screen(msg,color): 
    textSurf, textRect = text_objects(msg,color) 
    #screen_text = font.render(msg, True, color) 
    #gameDisplay.blit(screen_text, [display_width/2, display_height/2]) 
    textRect.center = (display_width/2), (display_height/2) 
    gameDisplay.blit(textSurf, textRect) 


def gameLoop(): 
    gameExit = False 
    gameOver = False 

    lead_x = display_width/2 
    lead_y = display_height/2 

    lead_x_change = 0 
    lead_y_change = 0 

    snakeList = [] 
    snakeLength = 0 

    randAppleX = round(random.randrange(0, display_width-block_size))#/10.0)*10.0 
    randAppleY = round(random.randrange(0, display_height-block_size))#/10.0)*10.0 

    while not gameExit: 

     while gameOver == True: 
      gameDisplay.fill(white) 
      message_to_screen("Game over, press Q to play again ot W to quit", red) 
      pygame.display.update() 

      for event in pygame.event.get(): 
       if event.type == pygame.QUIT: 
        gameExit = True 
        gameOver = False 
       if event.type == pygame.KEYDOWN: 
        if event.key == pygame.K_w: 
         gameExit = True 
         gameOver = False 
        if event.key == pygame.K_q: 
         gameLoop() 

     for event in pygame.event.get(): 
      if event.type == pygame.QUIT: 
       gameExit = True 
      if event.type == pygame.KEYDOWN: 
       if event.key == pygame.K_LEFT: 
        lead_x_change = -block_size 
        lead_y_change = 0 
       elif event.key == pygame.K_RIGHT: 
        lead_x_change = block_size 
        lead_y_change = 0 

       elif event.key == pygame.K_UP: 
        lead_y_change = -block_size 
        lead_x_change = 0 
       elif event.key == pygame.K_DOWN: 
        lead_y_change = block_size 
        lead_x_change = 0 

     if lead_x >= display_width or lead_x < 0 or lead_y >= display_height or lead_y < 0: 
      gameOver = True 



     lead_x += lead_x_change 
     lead_y += lead_y_change 

     gameDisplay.fill(white) 

     AppleThickness = 30 
     pygame.draw.rect(gameDisplay, red, [randAppleX, randAppleY, AppleThickness, AppleThickness]) 


     snakeHead = [] 
     snakeHead.append(lead_x) 
     snakeHead.append(lead_y) 
     snakeList.append(snakeHead) 
     snake(block_size, snakeList) 

     if len (snakeList) > snakeLength: 
      del snakeList [0] 

     for eachSegment in snakeList[:-1]: 
      if eachSegment == snakeHead: 
       gameOver = True 

     snake(block_size, snakeList) 


     pygame.display.update() 

##  if lead_x >= randAppleX and lead_x <= randAppleX + AppleThickness: 
##   if lead_y >= randAppleY and lead_y <= randAppleY + AppleThickness: 
##    randAppleX = round(random.randrange(0, display_width-block_size))#/10.0)*10.0 
##    randAppleY = round(random.randrange(0, display_height-block_size))#/10.0)*10.0 
##    snakeLength += 1 

     if lead_x > randAppleX and lead_x < randAppleX + AppleThickness or lead_x + block_size > randAppleX and lead_x + block_size < randAppleX + AppleThickness: 

      if lead_y > randAppleY and lead_y < randAppleY + AppleThickness or lead_y + block_size > randAppleY and lead_y + block_size < randAppleY + AppleThickness: 
       randAppleX = round(random.randrange(0, display_width-block_size))#/10.0)*10.0 
       randAppleY = round(random.randrange(0, display_height-block_size))#/10.0)*10.0 
       snakeLength += 1 

      elif lead_y + block_size > randAppleY and lead_y + block_size < randAppleY + AppleThickness: 

       randAppleX = round(random.randrange(0, display_width-block_size))#/10.0)*10.0 
       randAppleY = round(random.randrange(0, display_height-block_size))#/10.0)*10.0 
       snakeLength += 1 



     clock.tick(FPS) 

    pygame.quit() 
    quit() 



gameLoop() 

而我得到的索引错误thingy是这段代码。

Traceback (most recent call last): 
    File "C:\Users\BJBGaming\Desktop\FirstGame.py", line 165, in <module> 
    gameLoop() 
    File "C:\Users\BJBGaming\Desktop\FirstGame.py", line 132, in gameLoop 
    snake(block_size, snakeList) 
    File "C:\Users\BJBGaming\Desktop\FirstGame.py", line 35, in snake 
    gameDisplay.blit(img,(snakelist[-1][0], snakelist[-1][1])) 
IndexError: list index out of range 

请帮助我，我不明白如何解决它。谢谢。

Answer 1

肯定的错误是访问snakelist[-1][0], snakelist[-1][1]。请与您的逻辑：

if len (snakeList) > snakeLength: 
    del snakeList [0] 

难道是的情况下snakeLength == 0和len(snakeList) == 1？如果是，那么您将删除唯一元素，导致snakeList为空。