Tkinter and exceptions

[Nick Craig-Wood]

I'm just starting out with Tkinter programming (using Programming
Python as a reference), and I couldn't find the answer to this
anywhere...

How do you catch general exceptions in a Tkinter program. If you run
the below and click the "Exception" or "Callback Exception" buttons
you see a traceback on stderr under unix, and nothing at all under
windows (if run as a pyw).

How so you catch those exceptions so that they can pop up in a dialog?
There doesn't seem to be a hook. I was imagining that there would be a
global error handler I could hook / override?

from Tkinter import *

class AppDemo(Frame):
"""A sample tk app"""

def __init__(self, parent=None):
Frame.__init__(self, parent)
self.pack(expand=YES, fill=BOTH)
self.make_tool_bar()
self.master.title("A Title")
self.bang = 0
self.process()

def process(self):
self.after(1000, self.process)
if self.bang:
self.bang = 0
raise ValueError("Callback Exception")

def make_tool_bar(self):
self.toolbar = Frame(self, cursor='hand2', relief=SUNKEN, bd=2)
self.toolbar.pack(side=BOTTOM, fill=X)
Button(self.toolbar, text='Exception', command=self.make_exception).pack(side=TOP, fill=X)
Button(self.toolbar, text='Callback Exception', command=self.make_callback_exception).pack(side=TOP, fill=X)
Button(self.toolbar, text='Quit', command=self.quit).pack(side=TOP, fill=X)

def make_exception(self):
raise ValueError("Exception")

def make_callback_exception(self):
self.bang = 1

if __name__ == "__main__":
AppDemo().mainloop()

 

[Peter Otten]

I'm just starting out with Tkinter programming (using Programming
Python as a reference), and I couldn't find the answer to this
anywhere...

How do you catch general exceptions in a Tkinter program. If you run
the below and click the "Exception" or "Callback Exception" buttons
you see a traceback on stderr under unix, and nothing at all under
windows (if run as a pyw).

How so you catch those exceptions so that they can pop up in a dialog?
There doesn't seem to be a hook. I was imagining that there would be a
global error handler I could hook / override?

Overriding report_callback_exception() seems to work:

from Tkinter import *

import traceback
import tkMessageBox

class AppDemo(Frame):
"""A sample tk app"""

def __init__(self, parent=None):
Frame.__init__(self, parent)
self.pack(expand=YES, fill=BOTH)
self.make_tool_bar()
self.master.title("A Title")
self.bang = 0

def show_error(*args):
a = traceback.format_exception(*args)
tkMessageBox.showerror(a[-1], "\n".join(a[:-1]))
self._root().report_callback_exception = show_error

self.process()

def process(self):
self.after(1000, self.process)
if self.bang:
self.bang = 0
raise ValueError("Callback Exception")

def make_tool_bar(self):
self.toolbar = Frame(self, cursor='hand2', relief=SUNKEN, bd=2)
self.toolbar.pack(side=BOTTOM, fill=X)
Button(self.toolbar, text='Exception',
command=self.make_exception).pack(side=TOP, fill=X)
Button(self.toolbar, text='Callback Exception',
command=self.make_callback_exception).pack(side=TOP, fill=X)
Button(self.toolbar, text='Quit',
command=self.quit).pack(side=TOP, fill=X)

def make_exception(self):
raise ValueError("Exception")

def make_callback_exception(self):
self.bang = 1

if __name__ == "__main__":
AppDemo().mainloop()

Peter

 

[Nick Craig-Wood]

Overriding report_callback_exception() seems to work:

Thank you. That is exactly what I needed to know!