当我尝试退出应用程序窗口时，Python 返回错误答案

【问题标题】：Python returns an error when i try to quit the application window当我尝试退出应用程序窗口时，Python 返回错误
【发布时间】：2019-12-20 16:58:32
【问题描述】：

我正在关注这个小项目的视频，但遇到了这个错误

Traceback (most recent call last):
File "C:/Users/Dell/Desktop/Pygame/games/pong.py", line 92, in <module>
ball.setx(ball.xcor()+ball.dx)
File "C:\Users\Dell\AppData\Local\Programs\Python\Python37-32\lib\turtle.py", line 1808, in setx
self._goto(Vec2D(x, self._position[1]))
File "C:\Users\Dell\AppData\Local\Programs\Python\Python37-32\lib\turtle.py", line 3158, in _goto
screen._pointlist(self.currentLineItem),
File "C:\Users\Dell\AppData\Local\Programs\Python\Python37-32\lib\turtle.py", line 755, in _pointlist
cl = self.cv.coords(item)
File "<string>", line 1, in coords
File "C:\Users\Dell\AppData\Local\Programs\Python\Python37-32\lib\tkinter\__init__.py", line 2469, in coords
self.tk.call((self._w, 'coords') + args))]
_tkinter.TclError: invalid command name ".!canvas"

当我按下退出按钮关闭窗口时会发生这种情况。如何解决？

代码如下：

import turtle

wn = turtle.Screen()
wn.title("Pong")
wn.bgcolor('black')
wn.setup(width=800, height=600)
wn.tracer(0)
#Score
score_a = 0
score_b = 0


#paddle A
paddle_a = turtle.Turtle()
paddle_a.speed(0)
paddle_a.shape("square")
paddle_a.color("white")
paddle_a.shapesize(stretch_wid=5, stretch_len = 1)
paddle_a.penup()
paddle_a.goto(-350,0)
#paddle B
paddle_b = turtle.Turtle()
paddle_b.speed(0)
paddle_b.shape("square")
paddle_b.color("white")
paddle_b.shapesize(stretch_wid=5, stretch_len = 1)
paddle_b.penup()
paddle_b.goto(350,0)


#Ball

ball = turtle.Turtle()
ball.speed(0)
ball.shape("circle")
ball.color("white")
ball.penup()
ball.goto(0,0)
ball.dx = 0.5
ball.dy = 0.5

#pen

pen = turtle.Turtle()
pen.speed(0)
pen.color("white")
pen.penup()
pen.hideturtle()
pen.goto(0,260)
pen.write("Player A: 0 Player B: 0", align="center", font=('Courier', 24, "normal"))

#Function
def paddle_a_up():
    y = paddle_a.ycor()
    y+=20
    paddle_a.sety(y)

def paddle_a_down():
    y = paddle_a.ycor()
    y-=20
    paddle_a.sety(y)

def paddle_b_up():
    y = paddle_b.ycor()
    y+=20
    paddle_b.sety(y)


def paddle_b_down():
    y = paddle_b.ycor()
    y-=20
    paddle_b.sety(y)
#Keyboard binding
wn.listen()
wn.onkeypress(paddle_a_up, "w")
wn.onkeypress(paddle_a_down, "s")
wn.onkeypress(paddle_b_up, "Up")
wn.onkeypress(paddle_b_down, "Down")

running = True
#main game loop
while running:
    wn.update()

    #move the ball
    ball.setx(ball.xcor()+ball.dx)
    ball.sety(ball.ycor()+ball.dy)

    #border
    if ball.ycor() > 280:
        ball.sety(280)
        ball.dy*=-1

    if ball.ycor() < -280:
        ball.sety(-280)
        ball.dy*=-1

    if ball.xcor() > 380:
        ball.goto(0,0)
        ball.dx*=-1
        score_a+=1
        pen.clear()
        pen.write(f"Player A: {score_a} Player B: {score_b}", align="center", font=('Courier', 24, "normal"))

    if ball.xcor() < -380:
        ball.goto(0,0)
        ball.dx*=-1
        score_b += 1
        pen.clear()
        pen.write(f"Player A: {score_a} Player B: {score_b}", align="center", font=('Courier', 24, "normal"))

    #colliosion
    if (ball.xcor() > 330 and ball.xcor() < 340) and (ball.ycor() < paddle_b.ycor() + 50 and ball.ycor() > paddle_b.ycor() -50):
        ball.setx(330)
        ball.dx*=-1
    if (ball.xcor() < -330 and ball.xcor() > -340) and (ball.ycor() < paddle_a.ycor() + 50 and ball.ycor() > paddle_a.ycor() -50):
        ball.setx(-330)
        ball.dx*=-1

我阅读了有关放置 .mainloop() 方法的信息，但我不知道该放在哪里。我非常了解while循环永远运行并且没有条件在这里停止所以我如何使循环停止？按下退出按钮后如何告诉python停止循环并退出窗口？

【问题讨论】：

标签： python python-3.x turtle-graphics

【解决方案1】：

看起来turtle 使用tkinter。在 Tk 中，有一个名为 protocol 的方法，您可以使用它来控制某些事件发生时会发生什么，其中一个事件正在点击红色的“X”。

为了调用它，我们需要获取根级窗口。

放置

canvas = wn.getcanvas()
root = canvas.winfo_toplevel()

将 root 设置为您的根窗口。

您可以从这里使用root.protocol("WM_DELETE_WINDOW", on_close) 调用名为on_close 的函数或任何您想命名的函数。

您的函数可能看起来像这样。

def on_close():
    global running
    running = False

这会让你跳出循环并关闭你的程序。

完整代码。

import turtle

wn = turtle.Screen()

canvas = wn.getcanvas()
root = canvas.winfo_toplevel()

wn.title("Pong")
wn.bgcolor('black')
wn.setup(width=800, height=600)
wn.tracer(0)
#Score
score_a = 0
score_b = 0


#paddle A
paddle_a = turtle.Turtle()
paddle_a.speed(0)
paddle_a.shape("square")
paddle_a.color("white")
paddle_a.shapesize(stretch_wid=5, stretch_len = 1)
paddle_a.penup()
paddle_a.goto(-350,0)
#paddle B
paddle_b = turtle.Turtle()
paddle_b.speed(0)
paddle_b.shape("square")
paddle_b.color("white")
paddle_b.shapesize(stretch_wid=5, stretch_len = 1)
paddle_b.penup()
paddle_b.goto(350,0)


#Ball

ball = turtle.Turtle()
ball.speed(0)
ball.shape("circle")
ball.color("white")
ball.penup()
ball.goto(0,0)
ball.dx = 0.5
ball.dy = 0.5

#pen

pen = turtle.Turtle()
pen.speed(0)
pen.color("white")
pen.penup()
pen.hideturtle()
pen.goto(0,260)
pen.write("Player A: 0 Player B: 0", align="center", font=('Courier', 24, "normal"))

#Function
def paddle_a_up():
    y = paddle_a.ycor()
    y+=20
    paddle_a.sety(y)

def paddle_a_down():
    y = paddle_a.ycor()
    y-=20
    paddle_a.sety(y)

def paddle_b_up():
    y = paddle_b.ycor()
    y+=20
    paddle_b.sety(y)


def paddle_b_down():
    y = paddle_b.ycor()
    y-=20
    paddle_b.sety(y)
#Keyboard binding
wn.listen()
wn.onkeypress(paddle_a_up, "w")
wn.onkeypress(paddle_a_down, "s")
wn.onkeypress(paddle_b_up, "Up")
wn.onkeypress(paddle_b_down, "Down")

def on_close():
    global running
    running = False

root.protocol("WM_DELETE_WINDOW", on_close)

running = True
#main game loop
while running:
    wn.update()



    #move the ball
    ball.setx(ball.xcor()+ball.dx)
    ball.sety(ball.ycor()+ball.dy)

    #border
    if ball.ycor() > 280:
        ball.sety(280)
        ball.dy*=-1

    if ball.ycor() < -280:
        ball.sety(-280)
        ball.dy*=-1

    if ball.xcor() > 380:
        ball.goto(0,0)
        ball.dx*=-1
        score_a+=1
        pen.clear()
        pen.write(f"Player A: {score_a} Player B: {score_b}", align="center", font=('Courier', 24, "normal"))

    if ball.xcor() < -380:
        ball.goto(0,0)
        ball.dx*=-1
        score_b += 1
        pen.clear()
        pen.write(f"Player A: {score_a} Player B: {score_b}", align="center", font=('Courier', 24, "normal"))

    #colliosion
    if (ball.xcor() > 330 and ball.xcor() < 340) and (ball.ycor() < paddle_b.ycor() + 50 and ball.ycor() > paddle_b.ycor() -50):
        ball.setx(330)
        ball.dx*=-1
    if (ball.xcor() < -330 and ball.xcor() > -340) and (ball.ycor() < paddle_a.ycor() + 50 and ball.ycor() > paddle_a.ycor() -50):
        ball.setx(-330)
        ball.dx*=-1

【讨论】：

【解决方案2】：

我们可以从turtle 内部解决这个问题，无需下降到tkinter 基础。一般来说，你需要遵守规则。具体来说，没有while running: aka while True:。 Turtle 是一个基于事件的环境，您不会让事件得到正确处理，从而导致错误消息。

我们需要一个ontimer() 事件，而不是while 循环：

from turtle import Screen, Turtle

FONT = ('Courier', 24, 'normal')

# Score
score_a = 0
score_b = 0

# Function
def paddle_a_up():
    paddle_a.sety(paddle_a.ycor() + 20)

def paddle_a_down():
    paddle_a.sety(paddle_a.ycor() - 20)

def paddle_b_up():
    paddle_b.sety(paddle_b.ycor() + 20)

def paddle_b_down():
    paddle_b.sety(paddle_b.ycor() - 20)

def single_step():
    global score_a, score_b

    # move the ball
    ball.setposition(ball.xcor() + ball.dx, ball.ycor() + ball.dy)

    # border
    if ball.ycor() > 280:
        ball.sety(280)
        ball.dy *= -1
    elif ball.ycor() < -280:
        ball.sety(-280)
        ball.dy *= -1

    if ball.xcor() > 380:
        ball.goto(0, 0)
        ball.dx *= -1
        score_a += 1
        pen.clear()
        pen.write(f"Player A: {score_a} Player B: {score_b}", align='center', font=FONT)

    if ball.xcor() < -380:
        ball.goto(0, 0)
        ball.dx *= -1
        score_b += 1
        pen.clear()
        pen.write(f"Player A: {score_a} Player B: {score_b}", align='center', font=FONT)

    # collision
    if 330 < ball.xcor() < 340 and paddle_b.ycor() - 50 < ball.ycor() < paddle_b.ycor() + 50:
        ball.setx(330)
        ball.dx *= -1
    elif -340 < ball.xcor() < -330 and paddle_a.ycor() - 50 < ball.ycor() < paddle_a.ycor() + 50:
        ball.setx(-330)
        ball.dx *= -1

    screen.update()

    screen.ontimer(single_step)

screen = Screen()
screen.title('Pong')
screen.bgcolor('black')
screen.setup(width=800, height=600)
screen.tracer(0)

# paddle A
paddle_a = Turtle()
paddle_a.shape('square')
paddle_a.color('white')
paddle_a.shapesize(stretch_wid=5, stretch_len=1)
paddle_a.penup()
paddle_a.setx(-350)

# paddle B
paddle_b = Turtle()
paddle_b.shape('square')
paddle_b.color('white')
paddle_b.shapesize(stretch_wid=5, stretch_len=1)
paddle_b.penup()
paddle_b.setx(350)

# Ball
ball = Turtle()
ball.shape('circle')
ball.color('white')
ball.penup()

ball.dx = 1
ball.dy = 1

# pen
pen = Turtle()
pen.hideturtle()
pen.color('white')
pen.penup()

pen.sety(260)
pen.write("Player A: 0 Player B: 0", align='center', font=FONT)

# Keyboard binding
screen.onkeypress(paddle_a_up, 'w')
screen.onkeypress(paddle_a_down, 's')
screen.onkeypress(paddle_b_up, 'Up')
screen.onkeypress(paddle_b_down, 'Down')
screen.listen()

single_step()

screen.mainloop()

现在，当您关闭窗口时，该事件将由运行游戏的同一 mainloop 事件处理程序处理。

【讨论】：