Python乌龟不能把乌龟限制在一个bord内

Question

我试着让一只乌龟停下来，直到它改变了方向。在

from turtle import *
import turtle
import time

user_speed = 46
border_pen = Turtle()
shouldMove = True
#alreadyStoppedDown = False
#alreadyStoppedUp = False
prev_heading = heading()

#Set up border
def setup(turt):
    turt.ht()
    turt.pu()
    turt.speed(0)
    turt.goto(-250,250)
    turt.pd()
    turt.begin_fill()
    for x in range(4):
        turt.fd(500)
        turt.rt(90)
    turt.color('black')
    turt.end_fill()

#Set up user
def user():
    pu()
    shape('square')
    shapesize(2)
    color('orange')
    speed(0)
    goto(-230,230)
    speed(1)

#Keybind functions
def down():
    global prev_heading
    prev_heading = heading()
    speed(0)
    setheading(-90)
    speed(1)
def up():
    global prev_heading
    prev_heading = heading()
    speed(0)
    setheading(90)
    speed(1)
def left():
    global prev_heading
    prev_heading = heading()
    speed(0)
    setheading(180)
    speed(1)
def right():
    global prev_heading
    prev_heading = heading()
    speed(0)
    setheading(0)
    speed(1)

#Border restriction
def restrict():
    global shouldMove
    if ycor() <= -230:
        shouldMove = False
        global prev_heading
        prev_heading = heading()

def main():
    global shouldMove
    while True:
        #Debugging
        print(shouldMove)
        print(heading(),prev_heading,ycor())

        if shouldMove:
            fd(user_speed)
            restrict()
        else:
            if heading() != prev_heading:
                shouldMove = True
            else:
                continue

setup(border_pen)
user()

onkey(up,'w')
onkey(down,'s')
onkey(left,'a')
onkey(right,'d')
listen()

main()

我只设置了边界底部的限制。在

我能让乌龟停止移动，但当它停止移动时，它不会改变它的方向。我试着按wasd来改变它的方向，但它一直呆在那里直到窗口崩溃。我试着想出多种解决办法，但我做不到。这里的主要问题是当海龟的ycor（）小于或等于-230时，它会停止，但不会改变它的航向。在

当我更改main（）使其在ycor（）小于或等于-230时，它将向右移动一次，因为ycor（）仍然是-230，它将停止移动。在

^{pr2}$

我这样做是为了好玩，我看了一个使用处理的蛇游戏的编码训练，我试图用Python中的turtle模块重新创建它。是的，我是初学者。我想尝试使用turtle模块重新制作snake游戏，尽管我可以使用其他模块，如PyGame，因为我不熟悉PyGame。这个问题有什么解决办法吗？或者我不能用海龟模块来做这个吗？在

Answer 1

我在代码中看到的主要问题是while True:，它在事件驱动的世界中没有一席之地。（因为它可以阻止事件！）我们将改用ontimer()事件。下一个问题是控制结构太复杂了。我们将放弃它的大部分，只保留布尔值shouldMove作为控制。最后，将函数接口与turtle的面向对象接口混合在一起。我们将把import改为只允许面向对象的接口：

from turtle import Turtle, Screen

USER_SPEED = 20

WIDTH = 500
CURSOR_SIZE = 20
CURSOR_MULTIPLIER = 2
MINIMUM = ((CURSOR_SIZE * CURSOR_MULTIPLIER) / 2) - WIDTH / 2
MAXIMUM = WIDTH / 2 - ((CURSOR_SIZE * CURSOR_MULTIPLIER) / 2)

# Set up border
def setup(turtle):
    turtle.penup()
    turtle.speed('fastest')
    turtle.goto(-WIDTH / 2, WIDTH / 2)
    turtle.pendown()

    turtle.begin_fill()
    for _ in range(4):
        turtle.forward(WIDTH)
        turtle.right(90)
    turtle.end_fill()

# Set up user
def user(turtle):
    turtle.penup()
    turtle.shapesize(CURSOR_MULTIPLIER)
    turtle.color('orange')
    turtle.speed('fastest')

# Keybind functions
def down():
    global shouldMove

    if user_pen.heading() != 270:
        user_pen.setheading(270)
        shouldMove = True

def up():
    global shouldMove

    if user_pen.heading() != 90:
        user_pen.setheading(90)
        shouldMove = True

def left():
    global shouldMove

    if user_pen.heading() != 180:
        user_pen.setheading(180)
        shouldMove = True

def right():
    global shouldMove

    if user_pen.heading() != 0:
        user_pen.setheading(0)
        shouldMove = True

# Border restriction

def move():
    global shouldMove

    if shouldMove:
        user_pen.forward(USER_SPEED)

        if not(MINIMUM <= user_pen.ycor() <= MAXIMUM and MINIMUM <= user_pen.xcor() <= MAXIMUM):
            user_pen.undo()
            shouldMove = False

    screen.ontimer(move, 25)

screen = Screen()

border_pen = Turtle(visible=False)
user_pen = Turtle('square')

setup(border_pen)
user(user_pen)

screen.onkey(up, 'w')
screen.onkey(down, 's')
screen.onkey(left, 'a')
screen.onkey(right, 'd')
screen.listen()

shouldMove = True

move()

screen.mainloop()

这应该像你描述的那样。乌龟会一直沿着直线移动，直到你按下方向键或者它停在边界处。在