python - 使用 turtle 图形以奇数顺序执行代码

Question

我目前正在尝试使用 turtle 图形在Python中制作一个类似蛇的游戏，并且当您使用a和d键转动 turtle (如果您与之前的任何回合一致)时，遇到了一个破坏游戏的错误。它似乎正在无序执行代码，但我不知道发生了什么。

完整代码如下

import turtle
import random
import math

x = 400
y = 400
global speed
global points
points = 0
speed = 2
posList = ['']

# turns your character left
def left():
    global speed
    global posList
    key = True
    char.fd(speed)
    char.left(90)
    char.fd(speed)

# turns your character left
def right():
    global speed
    global posList
    key = True
    char.fd(speed)
    char.right(90)
    char.fd(speed)

# adds one box to the point counter
def point():
    global points
    points += 1
    wall.speed(0)
    wall.pendown()
    wall.forward(50)
    wall.seth(90)
    wall.forward(10)
    wall.seth(180)
    wall.forward(50)
    wall.seth(270)
    wall.forward(10)
    wall.penup()
    wall.seth(90)
    wall.forward(12)
    wall.seth(0)
    dot.setx(random.randint(-200,200))
    dot.sety(random.randint(-200,200))
    print(points)

# checks if curren posisition is anywhere you have ever been
def checkBracktrack(pos, poslist):
    found = False
    for thing in posList:
        if thing == pos:
            found=True
    return found

# creates the box that the game occurs in   
turtle.colormode(255)
screen = turtle.Screen()
dot = turtle.Turtle()
dot.penup()
dot.speed(0)
dot.shape('turtle')
dot.setx(random.randint(-200,200))
dot.sety(random.randint(-200,200))
wall = turtle.Turtle()
wall.speed(0)
wall.penup()
wall.goto(x/2,y/2)
wall.pendown()
wall.seth(180)
wall.forward(400)
wall.seth(270)
wall.forward(400)
wall.seth(0)
wall.forward(400)
wall.seth(90)
wall.forward(400)
wall.seth(270)
wall.forward(400)
wall.seth(0)
wall.penup()
wall.forward(100)
char = turtle.Turtle()
x = 0
y = 0

# updates the position of the player turtle
while True:
    screen.onkey(left,"a")
    screen.onkey(right,"d")
    char.hideturtle()
    char.forward(speed)
    char.speed(0)
    turtle.listen(xdummy=None, ydummy=None)
    print(char.pos())
    print(posList[(len(posList)-1)])

    # checks if current position is the same as any position it has ever been in !this is the bit that is having problems!
    if checkBracktrack(char.pos(),posList):
        speed = 0
        break

    # checks if it is close enough to a point marker to 
    if char.ycor() in range(dot.ycor()-10,dot.ycor()+10) and char.xcor() in range(dot.xcor()-10,dot.xcor()+10):
        point()

    # checks if in the box
    if char.ycor() not in range(-200,200) or char.xcor() not in range(-200,200):
        speed = 0

    # adds current location to the list
    posList.append(char.pos())
    char.fd(speed)


print('you travelled',len(posList),'pixels')
print('collided with yourself')
print(char.pos())
print(posList)
name = input('quit')
screen.mainloop()

Answer 1

您的代码存在许多小问题:您需要重新阅读何时使用global；您的 checkBracktrack() 函数将 poslist 作为参数，但对全局 posList 进行操作(大小写错误)；由于额外的 fd() 调用和大于 1 的 speed，您的像素行进距离计算不正确；使用turtle的.distance()方法可以大大简化你的接近测试；您在游戏板上显示点数的代码根本不起作用；当您只需要为每个键调用一次时，您会在循环中一遍又一遍地调用 onkey() ；您的 checkBracktrack() 函数有一个不必要的循环。

我在代码中遇到的最大问题是 while True: 这不应该在基于事件的代码中发生。我重写并简化了下面的代码，解决了上述问题以及其他问题:

from turtle import Turtle, Screen
from random import randint

FONT = ('Arial', 24, 'normal')
WIDTH, HEIGHT = 400, 400
SPEED = 1

def left():
    """ turns your character left """
    char.left(90)

def right():
    """ turns your character right """
    char.right(90)

def point():
    """ adds one box to the point counter """
    global points

    points += 1

    wall.undo()
    wall.write(points, font=FONT)

    dot.setpos(randint(-WIDTH/2, WIDTH/2), randint(-HEIGHT/2, HEIGHT/2))

def checkBracktrack(pos, poslist):
    """ checks if current posiition is anywhere you have ever been """

    return pos in poslist

def move_char():
    """ updates the position of the player turtle """

    over = False
    char.forward(SPEED)

    # checks if current position is the same as any position it has ever been at
    if checkBracktrack(char.pos(), posList):
        over = True

    # checks if in the box
    elif not (-200 <= char.ycor() <= 200 and -200 <= char.xcor() <= 200):
        over = True

    if over:
        print('you travelled', len(posList), 'pixels')
        return

    # adds current location to the list
    posList.append(char.pos())

    # checks if it is close enough to a point marker
    if char.distance(dot) < 20:
        point()

    screen.ontimer(move_char, 10)

points = 0
posList = []

# creates the box in which the game occurs
screen = Screen()
screen.onkey(left, "a")
screen.onkey(right, "d")
screen.listen()

dot = Turtle('turtle')
dot.speed('fastest')
dot.penup()
dot.setpos(randint(-WIDTH/2, WIDTH/2), randint(-HEIGHT/2, HEIGHT/2))

wall = Turtle(visible=False)
wall.speed('fastest')
wall.penup()
wall.goto(WIDTH/2, HEIGHT/2)
wall.pendown()

for _ in range(4):
    wall.right(90)
    wall.forward(400)

wall.penup()
wall.forward(100)
wall.write("0", font=FONT)

char = Turtle(visible=False)
char.speed('fastest')

move_char()

screen.mainloop()

我相信，引发您最初问题的问题在重新编写代码的过程中得到了解决。