[Tkinter-discuss] Okay, this one really has me baffled -- KeyboardInterrupt signal not working!

[Jared Cohen]

Thanks a bunch for everybody's help with the syntax highlighting 
problem, but I finally got fed up with trying, so now I'm looking for a 
good XML parser to do the work for me ;-)

Anyway, now there's a new problem. Part of my application executes a 
system command, captures the standard input/output/error pipes using 
"(stdin, stdout_err) = os.popen4(...)", and displays them to a Pmw 
TextDialog.

Now then, this system command may take a long time to execute, so I want 
the user to be able to abort the process if they decide it's taking too 
long or if they realize they made a mistake. In essence, the output 
dialog should function like a shell window, which means the user can 
press Ctrl-C to send an interrupt signal. I *THOUGHT* I could do that by 
adding an Abort button, which raises a KeyboardException. Here's the 
full code snippet:

########################################################################################

    def SetupOutputDialog(self):
        self.outputDialog = Pmw.TextDialog(self.root,
                                           title="Output",
                                           text_state='disabled',
                                           buttons=('OK', 'Abort'),
                                           command=self.OutputButtonPress)
        ......

    def OutputButtonPress(self, button):
        if button == 'OK':
            self.outputDialog.withdraw()
        elif button == 'Abort':
            raise KeyboardInterrupt

    .....

    (stdin, stdout_err) = os.popen4(compileString + " &")
    s = stdout_err.readline()
    while s != "":
        self.outputDialog.appendtext(s)
        self.outputDialog.update()
        s = stdout_err.readline()

########################################################################################


Seems perfectly sound, right? But for some reason, the Abort button 
doesn't seem to work right. When I press it, I get the following exception:

KeyboardInterrupt Exception in Tk callback
  Function: <function <lambda> at 0x40ac9bc4> (type: <type 'function'>)
  Args: ()
Traceback (innermost last):
  File "/usr/lib/python2.3/site-packages/Pmw/Pmw_1_2/lib/PmwBase.py", 
line 1747, in __call__
    return apply(self.func, args)
  File "/usr/lib/python2.3/site-packages/Pmw/Pmw_1_2/lib/PmwDialog.py", 
line 153, in <lambda>
    command=lambda self=self, name=name: self._doCommand(name))
  File "/usr/lib/python2.3/site-packages/Pmw/Pmw_1_2/lib/PmwDialog.py", 
line 132, in _doCommand
    return command(name)
  File "/home/jmc/projects/tkfre/src/freMainGui.py", line 361, in 
OutputButtonPress
    raise KeyboardInterrupt
KeyboardInterrupt:

That seems like the exception I was supposed to get.......but the 
process didn't stop!!! It detected the interrupt signal, but it didn't 
interrupt anything!

The wierd thing is, if I Alt-Tab back into the shell from which I 
started this application, and actually type Ctrl-C there, THEN it works. 
But I don't understand why raising the KeyboardInterrupt signal doesn't 
seem to do anything! Can anyone help please?