[vtk-developers] patch for turning (almost) all VTK errors into Python exceptions, IMPROVED
dgobbi at atamai.com
Tue Aug 8 10:12:10 EDT 2006
Charl P. Botha wrote:
> Dear all,
> On 8/5/06, Prabhu Ramachandran <prabhu_r at users.sf.net> wrote:
>> >>>>> "Charl" == Charl P Botha <cpbotha at cpbotha.net> writes:
>> Charl> Hi there (Python)-gang, I've made a patch for VTK 5.0 which
>> Charl> will turn almost all VTK errors into Python exceptions. It
>> Charl> works around the exception non-safety of VTK. Have a look
>> Charl> here:
>> Charl> What do VTK/Python people think? This definitely fills a
>> Charl> niche, and it could be conditionally included in VTK. The
>> Charl> only drawback is the extra PyErr_Occurred() call after
>> Charl> every VTK method call, and of course the extra line or two
>> Charl> of Python code to set up the new vtkEventOutputWindow).
>> This is nice, thanks. However, does this work for errors generated by
>> VTK objects that were not instantiated in Python? Do exceptions
>> "leak" in this case? From what I can tell of the patch, the answer is
>> yes. If so is this a problem, and how big is it?
> I've made a new and improved solution, see here:
> This is much simpler than the previous attempt, but works better. I
> made a vtkPythonOutputWindow that turns Errors and Warnings into
> RuntimeError and RuntimeWarning Python exceptions, and outputs Text
> and DebugText using the Python print command. vtkPythonUtil sets this
> OutputWindow as the singleton instance.
> The wrapping code still has the check for PyErr_Occurred(), as this is
> necessary as the final step of turning the error into an exception.
> With this new solution, when VTK is being used from Python, ALL VTK
> objects, directly created in Python or not, will generate Python
> exceptions when they make use of any of the VTK error or warning
> macros. In addition, one can revert to the old behaviour with a
> Python one-liner.
> This one is definitely commitable to VTK HEAD.
> Any comments?
I took a look at the patch, I would say that this is definitely the best
My only question is whether raising a python exception is going to cause
a vtkInteractor-based application to halt when you really only want it to
print the error and continue. Let me expand on this a bit:
If you've ever written an application with Tkinter, PyQt or wxPython you've
noticed that when a python exception occurs, the exception is printed
the app returns to its main loop and continues.
I just want to make sure that an app that uses VTK's built-in main loop
doesn't use a separate GUI toolkit) will also return to the main loop
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