关闭我的 tkinter 串行应用程序，给了我一个例外

Posted 2023-02-23

【中文标题】关闭我的 tkinter 串行应用程序，给了我一个例外

【英文标题】：Closing my tkinter serial app, gives me an exception

【发布时间】：2021-02-26 23:15:42

【问题描述】：

我有这个程序可以从串行中获取数据并将它们显示在 tkinter 帧上。

这是代码：

import tkinter as tk
import tkinter.ttk as ttk
import serial.tools.list_ports
from tkinter import scrolledtext 
#new stuff from vid
import time
import serial
import threading
import continuous_threading


#to be used on our canvas
HEIGHT = 700
WIDTH = 800

#hardcoded baud rate
baudRate = 9600



ser = serial.Serial('COM16', baudRate)
val1 = 0
index = []
def readSerial():
    global val1
    ser_bytes = ser.readline()
    ser_bytes = ser_bytes.decode("utf-8")
    val1 = ser_bytes
    scrollbar.insert("end", val1)
    
t1 = continuous_threading.PeriodicThread(0.1, readSerial)
#----------------------------------------------------------------------

# --- functions ---

#the following two functtions are for the seria port selection, on frame 1
def serial_ports():    
    return serial.tools.list_ports.comports()

def on_select(event=None):

    global COMPort
    COMPort = cb.get()
    print(COMPort)



# --- functions ---


#--------------------------------------------------------------------------------------------------------------
# --- main ---
root = tk.Tk() #here we create our tkinter window
root.title("Sensor Interface")

#we use canvas as a placeholder, to get our initial screen size (we have defined HEIGHT and WIDTH)
canvas = tk.Canvas(root, height=HEIGHT, width=WIDTH)
canvas.pack()

#we use frames to organize all the widgets in the screen
# --- frame 1 ---
frame1 = tk.Frame(root)
frame1.place(relx=0, rely=0.05, relheight=0.03, relwidth=1, anchor='nw') #we use relheight and relwidth to fill whatever the parent is - in this case- root

label0 = tk.Label(frame1, text="Select the COM port that the device is plugged in: ")
label0.config(font=("TkDefaultFont", 8))
label0.place(relx = 0.1, rely=0.3, relwidth=0.3, relheight=0.5)


cb = ttk.Combobox(frame1, values=serial_ports())
cb.place(relx=0.5, rely=0.5, anchor='center')
# assign function to cmbobox
cb.bind('<<ComboboxSelected>>', on_select)
# --- frame 1 ---




# --- frame 2 ---
frame2 = tk.Frame(root, bg='#80c1ff') #remove color later
frame2.place(relx=0, rely=0.1, relheight=1, relwidth=1, anchor='nw')

# make a scrollbar
scrollbar = scrolledtext.ScrolledText(frame2)
scrollbar.place(relx=0, rely=0, relheight=1, relwidth=1, anchor='nw')
# --- frame 2 ---
#--------------------------------------------------------------------------------------------------------
t1.start() 

root.mainloop() #here we run our app

当我终止生成的 GUI 时，我在终端上得到这个异常：

Exception in thread Thread-1:
Fatal Python error: could not acquire lock for <_io.BufferedWriter name='<stderr
>'> at interpreter shutdown, possibly due to daemon threads
Python runtime state: finalizing (tstate=005C8F38)

Thread 0x00001a30 (most recent call first):
  File "C:\Users\User1\AppData\Local\Programs\Python\Python38-32\lib\threading.p
y", line 1202 in invoke_excepthook
  File "C:\Users\User1\AppData\Local\Programs\Python\Python38-32\lib\threading.p
y", line 934 in _bootstrap_inner
  File "C:\Users\User1\AppData\Local\Programs\Python\Python38-32\lib\threading.p
y", line 890 in _bootstrap

Current thread 0x00001918 (most recent call first):
<no Python frame>

当我用 control+C 从终端终止它时，我得到：

Traceback (most recent call last):
  File "mySerial.py", line 110, in <module>
    root.mainloop() #here we run our app
  File "C:\Users\User1\AppData\Local\Programs\Python\Python38-32\lib\tkinter\__i
nit__.py", line 1420, in mainloop
    self.tk.mainloop(n)
KeyboardInterrupt
Exception in thread Thread-1:
Fatal Python error: could not acquire lock for <_io.BufferedWriter name='<stderr
>'> at interpreter shutdown, possibly due to daemon threads
Python runtime state: finalizing (tstate=00578F38)

Thread 0x00001ad0 (most recent call first):
  File "C:\Users\User1\AppData\Local\Programs\Python\Python38-32\lib\threading.p
y", line 1202 in invoke_excepthook
  File "C:\Users\User1\AppData\Local\Programs\Python\Python38-32\lib\threading.p
y", line 934 in _bootstrap_inner
  File "C:\Users\User1\AppData\Local\Programs\Python\Python38-32\lib\threading.p
y", line 890 in _bootstrap

Current thread 0x000013d8 (most recent call first):
<no Python frame>

为什么会这样？

编辑：这是我的代码和错误消息，尝试 AST 的建议：

import tkinter as tk
import tkinter.ttk as ttk
import serial.tools.list_ports
from tkinter import scrolledtext 
import time
import serial
import threading
import continuous_threading


#to be used on our canvas
HEIGHT = 700
WIDTH = 800

#hardcoded baud rate
baudRate = 9600

# flag to be notified when application is terminated
stop=False


ser = serial.Serial('COM16', baudRate)
val1 = 0

def readSerial():
    global val1, stop
    if not stop:
       ser_bytes = ser.readline()
       ser_bytes = ser_bytes.decode("utf-8")
       val1 = ser_bytes
       scrollbar.insert("end", val1)
    else:
        return

t1 = continuous_threading.PeriodicThread(0.1, readSerial)
#----------------------------------------------------------------------

# --- functions ---

#the following two functions are for the seria port selection, on frame 1
def serial_ports():    
    return serial.tools.list_ports.comports()

def on_select(event=None):

    global COMPort
    COMPort = cb.get()
    print(COMPort)

def on_close():
    global stop
    stop=True
    root.destroy()



# --- functions ---


#--------------------------------------------------------------------------------
# --- main ---
root = tk.Tk() #here we create our tkinter window
root.title("Sensor Interface")
root.protocol('WM_DELETE_WINDOW', on_close)

#we use canvas as a placeholder, to get our initial screen size (we have defined HEIGHT and WIDTH)
canvas = tk.Canvas(root, height=HEIGHT, width=WIDTH)
canvas.pack()

#we use frames to organize all the widgets in the screen
# --- frame 1 ---
frame1 = tk.Frame(root)
frame1.place(relx=0, rely=0.05, relheight=0.03, relwidth=1, anchor='nw') #we use relheight and relwidth to fill whatever the parent is - in this case- root

label0 = tk.Label(frame1, text="Select the COM port that the device is plugged in: ")
label0.config(font=("TkDefaultFont", 8))
label0.place(relx = 0.1, rely=0.3, relwidth=0.3, relheight=0.5)


cb = ttk.Combobox(frame1, values=serial_ports())
cb.place(relx=0.5, rely=0.5, anchor='center')
# assign function to cmbobox
cb.bind('<<ComboboxSelected>>', on_select)
# --- frame 1 ---




# --- frame 2 ---
frame2 = tk.Frame(root, bg='#80c1ff') #remove color later
frame2.place(relx=0, rely=0.1, relheight=1, relwidth=1, anchor='nw')

# make a scrollbar
scrollbar = scrolledtext.ScrolledText(frame2)
scrollbar.place(relx=0, rely=0, relheight=1, relwidth=1, anchor='nw')
# --- frame 2 ---
#--------------------------------------------------------------------------------
t1.start() 
root.mainloop() #here we run our app

我得到的错误是我列为代码的第一个错误。

编辑 2： 当我做 AST 的第二种方法时：

如果我关闭 GUI（按 X），它会在没有任何错误的情况下关闭，但提示卡在终端上 - 我无法输入任何内容，甚至键盘退出 (Control+C) 也不起作用。

如果程序运行并且我在终端中使用键盘退出 (Control+C) 退出，我会收到键盘中断错误（我已列为代码的第二个错误）

【问题讨论】：

即使在 GUI 被破坏并产生错误后，周期性线程仍会继续运行，因为它不再存在。您可以尝试使用标志来避免这种情况。

嗯，谢谢，但我不确定我是否理解如何在这里使用标志。

【参考方案1】：

据我说，这是因为可能有一个计划线程在应用程序被销毁后执行，因此无法找到它必须更新的 GUI 元素。

我没有尝试运行您的代码，但我认为这可能会有所帮助

将窗口删除与更新标志的函数相关联 (stop)

def on_close():
    global stop
    stop=True
    root.destroy()

root.protocol('WM_DELETE_WINDOW', on_close)
stop=False

并修改readSerial 函数以检查是否相同

def readSerial():
    global val1,stop
    if not stop:
        ser_bytes = ser.readline()
        ser_bytes = ser_bytes.decode("utf-8")
        val1 = ser_bytes
        scrollbar.insert("end", val1)
    else:
        return

编辑

这是threading.py 中引发异常的函数。

def _bootstrap(self):
    # Wrapper around the real bootstrap code that ignores
    # exceptions during interpreter cleanup.  Those typically
    # happen when a daemon thread wakes up at an unfortunate
    # moment, finds the world around it destroyed, and raises some
    # random exception *** while trying to report the exception in
    # _bootstrap_inner() below ***.  Those random exceptions
    # don't help anybody, and they confuse users, so we suppress
    # them.  We suppress them only when it appears that the world
    # indeed has already been destroyed, so that exceptions in
    # _bootstrap_inner() during normal business hours are properly
    # reported.  Also, we only suppress them for daemonic threads;
    # if a non-daemonic encounters this, something else is wrong.
    try:
        self._bootstrap_inner()
    except:
        if self._daemonic and _sys is None:
            return
        raise

因为在这种情况下，当所有的non-daemonic线程都被杀死时，杀死线程是可以的，您可以尝试将线程设置为daemonic，以便自动处理异常。我认为这种方法不需要标志。

t1.daemon=True
t1.start()

【讨论】：

谢谢。尝试了相信它会工作的代码，但问题仍然存在。使用完整代码（以及您的建议）和错误消息编辑了问题。

@user1584421 我目前无法完全重现该错误，但我已经用另一种可能的方法更新了答案，如果可行，请告诉我。另外，您能否尝试将您的代码减少到 minimal, reproducible example 以便更容易使用。

对不起，escessive代码。它仍然不起作用。当我关闭 GUI（按 X）时，它会在没有任何错误的情况下关闭，但提示卡在终端上 - 我无法输入任何内容，甚至键盘退出 (Control+C) 也不起作用。当程序运行并且我使用终端中的键盘退出 (Control+C) 退出时，我得到 Doesnt fit in a comment 所以请参阅问题中的 EDIT2

@user1584421 到目前为止所有的错误都是一模一样的，请不要一遍又一遍地填写问题，将其剥离以包含一次，这样其他人会更容易阅读。我现在确实注意到了这个问题，但我无法得到继续发生的错误。我只是好奇是否有使用线程的特定需要？你看过after方法吗？

我很抱歉...我没有注意到它完全一样...我会清理我的问题。我的应用程序所做的只是从串行（从 arduino 传入）中获取数据并将它们显示到 tkinter scrollText 框架。本质上，它取代了 arduino IDE，因为我只想接收串行。由于我是 Tkinter 的新手（几乎是 python 的新手），我看到了一些有关如何完成此操作的 youtube 教程。我做到了，但它没有刷新，教程提到我必须创建线程，因为串行阻塞。这就是我这样做的原因。你知道其他方法吗？