Question

此代码应利用鼠标运动事件在当前鼠标位置绘制一个点：

import turtle

def motion(event):
    x, y = event.x, event.y
    turtle.goto(x-300, 300-y)
    turtle.dot(5, "red")

turtle.pu()
turtle.setup(600, 600)
turtle.hideturtle()
canvas = turtle.getcanvas()
canvas.bind("<Motion>", motion)

如果鼠标移动非常缓慢，该代码将按预期工作几秒钟或更长时间。然后抛出：

>>> 
====================== RESTART: C:/code/turtle_move.py 
======================
>>> Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Users\...\AppData\Local\Programs\Python\Python36-32\lib\tkinter\__init__.py", line 1698, in __call__
    args = self.subst(*args)
  File "C:\Users\...\AppData\Local\Programs\Python\Python36-32\lib\tkinter\__init__.py", line 1428, in _substitute
    e.type = EventType(T)
RecursionError: maximum recursion depth exceeded

=============================== RESTART: Shell 
===============================
>>>

非常感谢您的帮助。

Answer 1

问题在于，当事件处理程序仍在处理前一个事件时，会出现一个新事件，因此该事件处理程序是从事件处理程序内部调用的，看起来像是递归！解决方法是在事件处理程序内部禁用事件绑定：

from turtle import Screen, Turtle

def motion(event):
    canvas.unbind("<Motion>")
    turtle.goto(event.x - 300, 300 - event.y)
    turtle.dot(5, "red")
    canvas.bind("<Motion>", motion)

screen = Screen()
screen.setup(600, 600)

turtle = Turtle(visible=False)
turtle.speed('fastest')
turtle.penup()

canvas = screen.getcanvas()
canvas.bind("<Motion>", motion)
screen.mainloop()

使用Python乌龟鼠标移动获取“超出最大递归深度”

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