Re: [PyOpenGL-Users] Exception on Exit

[Mike C. F. <mcf...@vr...>]

Ian Mallett wrote:
> Hi,
>
> I have code that creates an exception on exit.  I can't imagine why. 
>
> Exception exceptions.TypeError: "'NoneType' object is not callable" in 
> <bound method glLibLight.__del__ of <glLib.glLibLight.glLibLight 
> instance at 0x034B3F80>> ignored
>
> This error only happens on exit.  Ideas?
I'm gathering "glLib.glLibLight" is your code.  You'll have a __del__ 
method on one of those objects that tries to call e.g. an OpenGL 
function.  During interpreter shutdown the global namespaces of modules 
are cleared out so that every name is set to None.  Your __del__ method 
is trying to call a function by name and the result is an attempt to 
call the None object.  If you need to have access to a function in a 
__del__ method you need to arrange to be sure that function is available 
(e.g. by binding as an argument) or check that it is non-null before 
calling it, or catch the error in the __del__.

Incidentally, it is generally better to use weakrefs rather than __del__ 
methods, as __del__ methods prevent garbage collection from operating if 
there is a loop in your object references.  See the vbo module for an 
example of usage, though as I read it I realize that it's not properly 
handling cases where the namespace is cleared out before it's called 
either.  (Should catch the errors to make it safe).

HTH,
Mike

-- 
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  Mike C. Fletcher
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