IndexError：列表索引超出范围，蛇游戏

Question

'''
Created on 13.3.2016
worm game
@author: Hai
'''
import pygame
import random
from pygame import * ##

class Worm:
    def __init__(self, surface):
        self.surface = surface
        self.x = surface.get_width() / 2
        self.y = surface.get_height() / 2
        self.length = 1
        self.grow_to = 50
        self.vx = 0
        self.vy = -1
        self.body = []
        self.crashed = False
        self.color = 255, 255, 0

    def key_event(self, event):
        """ Handle keyboard events that affect the worm. """
        if event.key == pygame.K_UP and self.vy != 1:
            self.vx = 0
            self.vy = -1
        elif event.key == pygame.K_RIGHT and self.vx != -1:
            self.vx = 1
            self.vy = 0
        elif event.key == pygame.K_DOWN and self.vy != -1:
            self.vx = 0
            self.vy = 1
        elif event.key == pygame.K_LEFT and self.vx != 1:
            self.vx = -1
            self.vy = 0

    def move(self):
        """ Moving worm """
        self.x += self.vx # add vx to x
        self.y += self.vy

        if (self.x, self.y) in self.body:
            self.crashed = True

        self.body.insert(0, (self.x, self.y))

        # Changes worm to right size so it is grow_to
        if self.grow_to > self.length: 
            self.length += 1

        # If body is longer than length then pop
        if len(self.body) > self.length:
            self.body.pop()
    """            
    def draw(self):

        self.surface.set_at((int(self.x), int(self.y)), (255, 255, 255))
        self.surface.set_at((int(self.last[0]),int(self.last[1])), (0,0,0))
    """
    def position(self):
        return self.x, self.y

    def eat(self):
        self.grow_to += 25

    def draw(self):

        x, y = self.body[0]
        self.surface.set_at((int(x), int(y)), self.color)
        x, y = self.body[-1]
        self.surface.set_at((int(x), int(y)), (0, 0, 0))

    #    for x, y in self.body:
    #        self.surface.set_at((int(x), int(y)), self.color)
    #        pygame.draw.rect(self.surface, self.color, (self.x, self.y, 6, 6), 0)
    # worm's head


class Food:
    def __init__(self, surface):
            self.surface = surface
            self.x = random.randint(0, surface.get_width())
            self.y = random.randint(0, surface.get_height())
            self.color = 255,255,255

    def draw(self):
        self.surface.set_at((int(self.x),int(self.y)), self.color)
        pygame.draw.rect(self.surface, self.color, (self.x, self.y, 6, 6), 0)

    def position(self):
        return self.x, self.y

    """ Check if worm have eaten this food """
    def check(self, x, y):
        if x < self.x or x > self.x + 6:
            return False
        elif y < self.y or y > self.y + 6:
            return False
        else:
            return True

    def erase(self):
        pygame.draw.rect(self.surface, (0,0,0), (int(self.x), int(self.y), 6, 6), 0)        



w = h = 500

screen = pygame.display.set_mode((w, h))
clock = pygame.time.Clock()

pygame.mixer.init()
chomp = pygame.mixer.Sound("bow.wav")

score = 0
worm = Worm(screen) ###
food = Food(screen)
running = True

while running:
    # screen.fill((0, 0, 0)) optimized in worm draw()
    worm.draw()
    food.draw()
    worm.move()


    if worm.crashed or worm.x <= 0 or worm.x >= w-1 or worm.y <= 0 or worm.y >= h-1:
        print("U lose")
        running = False
    elif food.check(worm.x, worm.y):
        worm.eat()
        food.erase()
        chomp.play()
        score += 1
        print("Score is: %d" % score)
        food = Food(screen)


    for event in pygame.event.get():
        if event.type == pygame.QUIT: # Pressed X
            running = False
        elif event.type == pygame.KEYDOWN: # When pressing keyboard
            worm.key_event(event)

    pygame.display.flip()
    clock.tick(100)

你好我收到错误 x, y = self.body[0] IndexError：列表索引超出范围 我正在做这个教程： https://lorenzod8n.wordpress.com/2008/03/01/pygame-tutorial-9-first-improvements-to-the-game/

我对python很陌生，请帮助我

Answer 1

问题是在你的类的__init__ 函数中，你定义了self.body = []。这意味着列表包含 0 个项目。

稍后在您的代码中，您引用self.body[0] 和self.body[1]，它们是列表中的第一项和第二项。由于这些不存在，因此会引发错误。要解决此问题，您需要使用两个项目初始化 self.body。

Answer 2

根据您正在执行的操作的顺序，您的body 列表实际上仍然是空的。按照你的代码逻辑，你会看到。

您首先在此处实例化您的蠕虫：

worm = Worm(screen) ###

因此，如果您查看Worm 的__init__，您将self.body 设置为一个空列表[]。

如果您遵循从那时起直到您实际调用的所有代码：

worm.draw()

您实际上从未在body 列表中插入任何内容。因此，当您尝试在 draw 方法中访问您的正文列表时：

error x, y = self.body[0]

您肯定会遇到索引超出范围错误，因为没有可访问的内容。

要纠正这个问题，您需要提供一个默认值，例如：

# arbitrary data
self.body = [0, 0]

或者，在您的绘图方法中确定如何使用以下条件处理空列表：

if self.body:
    # do things

Answer 3

在你的 Worm 的 __init__ 函数中，你可以将 self.body[] 设置为 self.body[(0, 0)]，这样可以。引发错误是因为您在开始时定义了一个空列表，后来您尝试通过传递索引 (self.body[0]) 从列表中获取项目。但由于列表为空，Python 无法获取请求的值。

希望这会有所帮助！