如何修复turtle，python库中的“主线程不在主循环”错误？答案

【问题标题】：How to fix 'main thread is not in main loop' error in turtle, python library?如何修复turtle，python库中的“主线程不在主循环”错误？
【发布时间】：2019-08-07 20:18:31
【问题描述】：

我正在尝试使用 Pynput 和 Turtle 库在我的笔记本触控板上模拟数字化平板电脑，但我一直收到同样的错误：

RuntimeError: 主线程不在主循环中

这是完整的代码：

from pynput import mouse
import turtle as tt
import time

tt.speed(0)

class MyException(Exception): pass

def on_move(x,y):
    print('Pointer: {0}'.format((x,y)))
    pos = (x,y)
    tt.setpos(pos)

def on_click(x, y, button, pressed):
    if button == mouse.Button.left:
        raise MyException(button)

with mouse.Listener(
        on_click=on_click,
        on_move=on_move) as listener:
    try:
        listener.join()
    except MyException as e:
        print('{0} was clicked'.format(e.args[0]))

【问题讨论】：

标签： python emulation turtle-graphics pynput

【解决方案1】：

from pynput.mouse import Listener

def on_move(x, y):
    print('Pointer moved to {0}'.format(
        (x, y)))

def on_click(x, y, button, pressed):
    print('{0} at {1}'.format(
        'Pressed' if pressed else 'Released',
        (x, y)))
    if not pressed:
        # Stop listener
        return False

def on_scroll(x, y, dx, dy):
    print('Scrolled {0}'.format(
        (x, y)))

# Collect events until released
with Listener(
        on_move=on_move,
        on_click=on_click,
        on_scroll=on_scroll) as listener:
    listener.join()

来自https://pythonhosted.org/pynput/mouse.html

【讨论】：

Pynput 部分（获取触控板输入并使用监听器）我没问题。当我尝试与 Turtle 集成时，问题就来了。
你必须为此使用多线程。一线程听二动乌龟
是的，明白了。但我在实施时遇到了一些麻烦。有什么想法吗？

【解决方案2】：

我猜您只是导入 pynput，因为海龟屏幕对象缺少其 tkinter 基础的 'Motion' 事件。如果是这样，我们可以将缺失的事件安装到 turtle 中来实现您的数字化器：

from turtle import Turtle, Screen, Vec2D
from functools import partial

class MyException(Exception):
    pass

def onscreenmove(self, fun, add=None):

    ''' Event method missing from turtle '''

    if fun is None:
        self.cv.unbind('<Motion>')
    else:
        def eventfun(event):
            fun(self.cv.canvasx(event.x) / self.xscale, -self.cv.canvasy(event.y) / self.yscale)

        self.cv.bind('<Motion>', eventfun, add)

def on_left_click(x, y):
    raise MyException(Vec2D(x, y))

def on_move(x, y):
    screen.onmove(None)  # disable events inside handler

    print('Pointer: {0}'.format(Vec2D(x, y)))

    turtle.setheading(turtle.towards(x, y))
    turtle.goto(x, y)

    screen.onmove(on_move)  # reenable handler

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

screen = Screen()
screen.onmove = partial(onscreenmove, screen)  # install missing method

screen.onmove(on_move)
screen.onclick(on_left_click, btn=1)  # btn=1 is the default

screen.mainloop()

屏幕

控制台

> python3 test.py
Pointer: (336.00,-73.00)
Pointer: (289.00,-56.00)
Pointer: (256.00,-43.00)
Pointer: (233.00,-35.00)
Pointer: (220.00,-31.00)
Pointer: (216.00,-30.00)
...
Pointer: (139.00,-37.00)
Pointer: (131.00,-35.00)
Pointer: (117.00,-25.00)
Pointer: (165.00,-24.00)
Pointer: (275.00,-28.00)
Pointer: (337.00,-29.00)
Exception in Tkinter callback
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/tkinter/__init__.py", line 1705, in __call__
    return self.func(*args)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/turtle.py", line 675, in eventfun
    fun(x, y)
  File "test.py", line 20, in on_left_click
    raise MyException(Vec2D(x, y))
MyException: (151.00,334.00)
Pointer: (150.00,334.00)
Pointer: (147.00,334.00)
Pointer: (143.00,334.00)
...
Pointer: (20.00,273.00)
Pointer: (-46.00,306.00)
Pointer: (-141.00,360.00)
>

【讨论】：