绘制然后擦除正方形

问题描述

我正在尝试使用 python 图形绘制一个正方形，然后在 3 秒后将其擦除。我有以下代码：

import threading as th
import turtle
import random

thread_count = 0

def draw_square():
    turtle.goto(random.randint(-200,200),random.randint(-200,200))
    for i in range(4):
        turtle.forward(100)
        turtle.left(90)

def erase_square(x,y):
    turtle.pencolor('white')
    turtle.fillcolor('white')
    turtle.goto(x,y)
    turtle.begin_fill()
    for i in range(4):
        turtle.forward(target_size)
        turtle.left(90)
    turtle.end_fill()

def square_timer():
    global thread_count
    if thread_count <= 10: 
        print("Thread count",thread_count)
        draw_square()
        T = th.Timer(3,square_timer)
        T.start()

square_update() 函数将绘制 10 个正方形然后停止。我试图让它绘制一个正方形，然后使用擦除正方形（）通过在其上绘制白色来清除它，然后另一个并重复该过程并在达到 10 时停止。我不知道如何使擦除功能转到绘制正方形的随机位置并“擦除”它。我怎样才能让它绘制和擦除正方形？

解决方法

清除绘图最直接的方法是使用 clear() 方法，而不是尝试在图像上绘制白色：

from turtle import Screen,Turtle
from random import randint

def draw_square():
    turtle.goto(randint(-200,200),randint(-200,200))

    turtle.pendown()

    for _ in range(4):
        turtle.forward(100)
        turtle.left(90)

    turtle.penup()

def erase_square():
    turtle.clear()
    screen.ontimer(square_update)  # no time,ASAP

def square_update():
    draw_square()
    screen.ontimer(erase_square,3000)  # 3 seconds in milliseconds

screen = Screen()

turtle = Turtle()
turtle.hideturtle()
turtle.speed('fastest')
turtle.penup()

square_update()

screen.exitonclick()

您可以按照@JonathanDrukker 的建议使用 undo() 方法，但您必须撤消每一步。即使对于像正方形这样简单的形状，这也需要一点思考，但是对于复杂的形状，这很困难。添加到撤消缓冲区的操作数并不总是与您对乌龟的调用相匹配。但是我们可以从海龟本身获得这个计数，只要我们在绘制和擦除之间不做任何其他海龟动作：

def draw_square():
    turtle.goto(randint(-200,200))

    count = turtle.undobufferentries()
    turtle.pendown()

    for _ in range(4):
        turtle.forward(100)
        turtle.left(90)

    turtle.penup()

    return turtle.undobufferentries() - count

def erase_square(undo_count):
    for _ in range(undo_count):
        turtle.undo()

    screen.ontimer(square_update)

def square_update():
    undo_count = draw_square()
    screen.ontimer(lambda: erase_square(undo_count),3000)

但我要做的是让海龟本身成为正方形，然后移动它而不是擦除并（重新）绘制正方形：

from turtle import Screen,Turtle
from random import randint

CURSOR_SIZE = 20

def draw_square():
    turtle.goto(randint(-200,200))

def square_update():
    turtle.hideturtle()
    draw_square()
    turtle.showturtle()

    screen.ontimer(square_update,3000)

screen = Screen()

turtle = Turtle()
turtle.hideturtle()
turtle.shape('square')
turtle.shapesize(100 / CURSOR_SIZE)
turtle.fillcolor('white')
turtle.penup()

square_update()

screen.exitonclick()