Python Turtle贪吃蛇游戏报错：'float'对象不可下标访问

我使用Python的turtle模块开发贪吃蛇游戏，项目包含main.py、food.py、scoreboard.py和snake.py四个文件。每当蛇吃到食物时，程序就会停止运行并抛出错误，推测问题出在add_segment方法中。

各文件代码 #

main.py #

from turtle import Screen
from snake import Snake
from food import Food
from scoreboard import Scoreboard
import time

screen = Screen()
screen.setup(600,600)
screen.title("Snake Game")
screen.bgcolor("black")
screen.tracer(0) # 关闭动画

snake = Snake()
food = Food()
scoreboard = Scoreboard()

screen.listen()
screen.onkeypress(fun=snake.up,key="Up")
screen.onkeypress(fun=snake.down,key="Down")
screen.onkeypress(fun=snake.left,key="Left")
screen.onkeypress(fun=snake.right,key="Right")
 
is_game_on = True
score = 0
while is_game_on:
    screen.update()
    time.sleep(0.1)
    snake.move()

    # 检测食物碰撞
    if snake.head.distance(food) < 15:
        food.refresh()
        scoreboard.score_update()
        snake.extend()

    # 检测墙壁碰撞
    if snake.head.xcor() > 280 or snake.head.xcor() < -280 or\
          snake.head.ycor() > 280 or snake.head.ycor()<-280:
        scoreboard.game_over()
        is_game_on = False

screen.exitonclick()

food.py #

import random
from turtle import Turtle

class Food(Turtle):
    def __init__(self) -> None:
        super().__init__()
        self.shape("circle")
        self.penup()
        self.shapesize(stretch_len=0.5,stretch_wid=0.5)
        self.color("red")
        self.speed("fastest")
        self.refresh()

    def refresh(self):
        random_coordinates = ( random.randint(-280,280), random.randint(-280,280) )
        self.goto(random_coordinates)

scoreboard.py #

from turtle import Turtle
ALIGNMENT = "center"
FONT_NAME = "Courier"
FONT_SIZE = 17
FONT_TYPE = "normal"

class Scoreboard(Turtle):
    score = 0

    def __init__(self):
        super().__init__()
        self.color("yellow")
        self.hideturtle()
        self.penup()
        self.teleport(0,275)
        self.write(arg="score = 0",move=False,align=ALIGNMENT,font=(FONT_NAME, FONT_SIZE, FONT_TYPE))
    
    def score_update(self,):
        self.score += 1
        self.clear()
        self.write(arg=f"score = {self.score}",move=False,align=ALIGNMENT,font=(FONT_NAME, FONT_SIZE, FONT_TYPE))
    
    def game_over(self):
        self.home()
        self.write(arg=f"GAME OVER",move=False,align=ALIGNMENT,font=(FONT_NAME, FONT_SIZE, FONT_TYPE))

snake.py #

from turtle import Turtle, Screen

MOVE_DISTANCE = 20
UP = 90
DOWN = 270
LEFT = 180
RIGHT = 0

class Snake:
    def __init__(self) -> None:
        self.segments = []
        self.create_snake()
        self.head = self.segments[0]
        
    def create_snake(self):
        self.x_cor = 0
        for i in range(3):
            self.add_segment(self.x_cor)
            self.x_cor -= 20

    def add_segment(self,position):
        segment = Turtle("square")
        segment.color("white")
        segment.penup()
        segment.speed("slowest")
        segment.teleport(x=position,y=0)
        self.segments.append(segment)
        
    def extend(self):
        self.add_segment((self.segments)[-1].pos())

    def move(self):
        for seq_num in range(len(self.segments) -1, 0 ,-1):
            new_x = self.segments[seq_num - 1].xcor()
            new_y = self.segments[seq_num - 1].ycor()
            self.segments[seq_num].goto(new_x, new_y)     
        self.head.forward(MOVE_DISTANCE)

    def up(self):
        if self.head.heading() != DOWN:
            self.head.setheading(UP)

    def down(self):
        if self.head.heading() != UP:
            self.head.setheading(DOWN)

    def left(self):
        if self.head.heading() != RIGHT:
            self.head.setheading(LEFT)

    def right(self):
        if self.head.heading() != LEFT:
            self.head.setheading(RIGHT)

报错信息 #

Traceback (most recent call last):
  File "/home/xenon_54/Snake_Game/main.py", line 29, in <module>
    screen.update()
  File "/usr/lib64/python3.12/turtle.py", line 1296, in update
    t._drawturtle()
  File "/usr/lib64/python3.12/turtle.py", line 3080, in _drawturtle
    shape = self._polytrafo(self._getshapepoly(tshape))
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.12/turtle.py", line 3033, in _polytrafo
    return [(p0+(e1*x+e0*y)/screen.xscale, p1+(-e0*x+e1*y)/screen.yscale)
             ~~^~~~~~~~~~~~~~~~~~~~~~~~~~
  File "/usr/lib64/python3.12/turtle.py", line 248, in __add__
    return Vec2D(self[0]+other[0], self[1]+other[1])
                         ~~~~~^^^
TypeError: 'float' object is not subscriptable

问题原因 #

报错核心是TypeError: 'float' object is not subscriptable，根源在snake.py的方法配合上：

• extend方法调用add_segment时，传入的self.segments[-1].pos()返回的是Vec2D对象（包含x、y坐标的二元组类型）。
• 但add_segment方法直接把这个Vec2D对象传给teleport(x=position,y=0)的x参数，导致turtle内部处理坐标时，误将Vec2D当成单个数值，最终触发类型错误。

解决方案 #

修改snake.py代码，让add_segment正确处理坐标对即可，以下两种方案任选其一：

方案1：统一使用坐标元组传参 #

1. 修改create_snake方法，传入(x,y)坐标元组：

def create_snake(self):
    self.x_cor = 0
    for i in range(3):
        self.add_segment((self.x_cor, 0))
        self.x_cor -= 20

2. 修改add_segment方法，直接用goto接收坐标：

def add_segment(self, position):
    segment = Turtle("square")
    segment.color("white")
    segment.penup()
    segment.speed("slowest")
    segment.goto(position)
    self.segments.append(segment)

方案2：兼容两种参数类型 #

如果想保留初始的单个x值传参方式，可让方法自动判断参数类型：

def add_segment(self, position):
    segment = Turtle("square")
    segment.color("white")
    segment.penup()
    segment.speed("slowest")
    if isinstance(position, (int, float)):
        segment.teleport(x=position, y=0)
    else:
        segment.goto(position)
    self.segments.append(segment)

修改后蛇吃到食物时就能正常延长，不会再触发报错。

内容的提问来源于stack exchange，提问作者Ayush Dey