Some C-API functions clear the error indicator?

Duncan Booth duncan.booth at invalid.invalid
Fri Jan 29 15:58:42 CET 2010

Austin Bingham <austin.bingham at> wrote:

> The functions that do this don't seem to indicate in their
> documentation that this will happen. So first, does anyone know why
> this is happening? Is it because of the context in which I'm making
> the calls? Is there any pattern or reason behind which functions will
> do this? Or am I just doing something wrong?
(Just guessing here)
I would expect that any function that executes Python code will clear the 

I think that has to happen otherwise the Python code will throw an 
exception whenever it gets round to checking for errors. In the past I've 
found that if you fail to check for an error in C code before returning to 
the interpreter you get the exception thrown a few instructions later, so 
something similar would probably happen if you call other Python code from 

If it is anything that executes Python then that would include any function 
that creates or destroys an object with Python constructor or destructor 
code. or that compares or otherwise operates on instances defined in 
Python. In particular it might mean that any function that doesn't appear 
to clear the error could do so in a slightly different situation.

Duncan Booth

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