python 2.3.2 hangs when returning an int

[omission9]

Any advice on the following would be much appreciated. I have thrown
everything I have at it and am completely stumped. I apologize for the
length, I have tried to be as succint as possible.

I have a pythoncard/wxPython application. The application works well
except that users were reporting occasional crashes. The application
would simply stop and just hang. I was able to reproduce the bug
faithfully and ran the application in the python debugger pdb.py.
The trace is below and I simply cannot understand why it is hanging
where it is. The application gets stuck executing

return len(self.data[0])

which is in this function

def GetNumberCols(self):
if len(self.data) <= 0:
return 0
else:
return len(self.data[0])

This works many many times during the applications execution, indeed
several successful runs of this line are visible immediatley above the
hang. I have also printed out the value of self.data. This is a list
containing 12 inner lists each of length 3 at the point of the hang and
is never larger than that.
What on earth could cause this to stop the interpreter cold in its
tracks without an exception being thrown? CPU usage on the machine is
high throughout the application's execution and stays as such after the
"hang" begins. I eventually kill the app although I have let it run for
a long time and it never leaves this line.
For what its worth, I am using python 2.3.2 on windows2k.

Anyone have idea what could be happening?

c:\python23\lib\site-packages\wxpython\grid.py(664)_setOORInfo()->None
-> return val
(Pdb) s
--Return--
c:\python23\lib\site-packages\wxpython\grid.py(850)__init__()->None
-> self._setOORInfo(self)
(Pdb) s


c:\cygwin\home\ar881\development\bt_analysis\console\ndbbtable.py(17)__init

__()
-> self.data = data
(Pdb) s


c:\cygwin\home\ar881\development\bt_analysis\console\ndbbtable.py(18)__init

__()
-> self.colLabels = headings
(Pdb) s

 

[Thomas Heller]

Any advice on the following would be much appreciated. I have thrown
everything I have at it and am completely stumped. I apologize for the
length, I have tried to be as succint as possible.

I have a pythoncard/wxPython application. The application works well
except that users were reporting occasional crashes. The application
would simply stop and just hang. I was able to reproduce the bug
faithfully and ran the application in the python debugger pdb.py.
The trace is below and I simply cannot understand why it is hanging
where it is. The application gets stuck executing

return len(self.data[0])

Does pythoncard or wxPython (or your program) use weak references?
There have been serious bugs fixed with weakrefs in Python 2.3.3.

Thomas

 

[Ziaran]

I guess it is a thread synchronization progblem
In that case some other thread modifies self.data leaving it empty in the
time between the if statement expression is evalutaed and the time the
return statement is executed.

Can this be the case?

 

[omission9]

Thanks to all who responded. This took me forever to replicate and is
not that easy to demonstrate outside of my fairly complex application.
Basically, I feel that this is the fault of the Python garbage
collector. What was happening was that in one function I locally defined
a class which extended wxGrid. In another function, which was called by
the first one mentioned, I instantiated another instance, local to the
function, of that class. It seems that even though the wxGrid class
used in the calling function was only used after the function call
some stray references or something to the other instance were still
drifting around in the interpreter which were causing some bizarro
problems like the one in my original post. By eliminating the instance
in the function that was being called I eliminated the problem.
BIZARRE!! What made this so awful was that it took many many iterations
of these functions to generate the error. I have no idea why it didn't
blow the first, say, hundred times through.
Maybe if I ever get the motivation I'll attach a C debugger to the whole
thing and look deeper into the guts.

Any advice on the following would be much appreciated. I have thrown
everything I have at it and am completely stumped. I apologize for the
length, I have tried to be as succint as possible.

I have a pythoncard/wxPython application. The application works well
except that users were reporting occasional crashes. The application
would simply stop and just hang. I was able to reproduce the bug
faithfully and ran the application in the python debugger pdb.py.
The trace is below and I simply cannot understand why it is hanging
where it is. The application gets stuck executing

return len(self.data[0])

which is in this function

def GetNumberCols(self):
if len(self.data) <= 0:
return 0
else:
return len(self.data[0])

This works many many times during the applications execution, indeed
several successful runs of this line are visible immediatley above the
hang. I have also printed out the value of self.data. This is a list
containing 12 inner lists each of length 3 at the point of the hang and
is never larger than that.
What on earth could cause this to stop the interpreter cold in its
tracks without an exception being thrown? CPU usage on the machine is
high throughout the application's execution and stays as such after the
"hang" begins. I eventually kill the app although I have let it run for
a long time and it never leaves this line.
For what its worth, I am using python 2.3.2 on windows2k.

Anyone have idea what could be happening?

c:\python23\lib\site-packages\wxpython\grid.py(664)_setOORInfo()->None
-> return val
(Pdb) s
--Return--
c:\python23\lib\site-packages\wxpython\grid.py(850)__init__()->None
-> self._setOORInfo(self)
(Pdb) s


c:\cygwin\home\ar881\development\bt_analysis\console\ndbbtable.py(17)__init

__()
-> self.data = data
(Pdb) s


c:\cygwin\home\ar881\development\bt_analysis\console\ndbbtable.py(18)__init

__()
-> self.colLabels = headings
(Pdb) s