How can I make silent exceptions louder in tkinter?

Question

If I run the following code from a terminal, I get a helpful error message in the terminal:

import Tkinter as tk

master = tk.Tk()

def callback():
    raise         


        

Answer 1

I found this thread while looking to solve the same problem. I had to make some modifications based on current tkinter version methodologies. I also added a customized error message handler since I figured my user wouldn't know what the Tk error message meant.

In the __init__ of your class include:

parent.report_callback_exception = self.report_callback_exception

then in your Tk class:

    def report_callback_exception(self, exc, val, tb):
        #Handles tkinter exceptions
        err_msg = {'Index 0 out of range': 'None found'}
        try:
            err = err_msg[str(val)]
        except KeyError:
            err = 'Oops, try again'
        messagebox.showerror('Error Found', err)

You could expand the err_msg dictionary to include whatever else you wanted. In my case I am building a searchable database off an Entry object, so if the user has typed in a string that doesn't exist in the database, it is giving the user a plain language error.

Answer 2

First a followup: Just today, a patch on the CPython tracker for the tkinter.Tk.report_callback_exception docstring made it clear that Jochen's solution is intended. The patch also (and primarily) stopped tk from crashing on callback exceptions when run under pythonw on Windows.

Second: here is a bare-bones beginning of a solution to making stderr function with no console (this should really be a separate SO question).

import sys, tkinter

root = tkinter.Tk()

class Stderr(tkinter.Toplevel):
    def __init__(self):
        self.txt = tkinter.Text(root)
        self.txt.pack()
    def write(self, s):
        self.txt.insert('insert', s)

sys.stderr = Stderr()

1/0 # traceback appears in window

More is needed to keep the popup window hidden until needed and then make it visible.

Answer 3

There is report_callback_exception to do this:

import traceback
import tkMessageBox

# You would normally put that on the App class
def show_error(self, *args):
    err = traceback.format_exception(*args)
    tkMessageBox.showerror('Exception',err)
# but this works too
tk.Tk.report_callback_exception = show_error

If you didn't import 'Tkinter as tk', then do

Tkinter.Tk.report_callback_exception = show_error