Hey Fredrik, thanks for responding. :) Your posts are always helpful and informative!
On Wed, 2006-03-08 at 15:41 +0100, Fredrik Lundh wrote: > Jeremy L. Moles wrote: > > >I have an object (written as part C extension, part pure Python) called > > foo that I've been using without much fuss for a few months now. > > However, in my latest project (a rather large one involving > > multi-threading, pygtk, etc.), I'm seeing some really strange behavior > > with a particular instance of my foo object. > > > > About midway through my program, any attempt to use the instance fails; > > however, if I add print statements before trying to invoke methods on > > it, the foo object instance works fine. > > fails in what way? Unfortunately, very silently. There aren't any exceptions thrown or anything. The be more specific, the C part of the object is a wrapper around some socket Send/Recv functions (that interface w/ wpa_supplicant). The problem I'm getting is that unless I add that print statement, wpaobject.Recv() returns "", whereas with the print statement it returns what it should (a large string representing the response from wpa_supplicant). More strange is that this is the first time I've had to do this. Up until this point, every unittest and app has succeeded without such trickery. > if you get a spurious exception, it's very likely that your C extension sets > the > exception state (either directly or because some API function it uses fails), > but > forgets to report this back to Python. > > e.g. if you have a C function that does something like > > PyErr_SetString(PyExc_AttributeError, "blah blah"): > > Py_INCREF(Py_None); > return Py_None; > > instead of > > PyErr_SetString(PyExc_AttributeError, "blah blah"): > > return NULL; > > the interpreter won't raise the exception immediately (since it expected you > to > return NULL if something went wrong), but the exception may still be raised at > a later time, if you run interpreter code that does something like > > do something > if (PyErr_Occurred()) > ... /* this will catch your error even if "something" succeeds */ ... > > *or* it may be masked, by code that does > > PyErr_Clear(); > do something > > the actual exception might give you additional clues (e.g. if you get a > KeyError, > look for unchecked dictionary accesses in your code, etc). > > hope this helps! > > </F> > > -- http://mail.python.org/mailman/listinfo/python-list
