Is this an Intended behaviour of __getattr__?

[Jeff Shannon]

Grace wrote:

> I'm a bit confused with this:
>
> class Node:
>     def __init__(self):
>         self._next=None
>     def __getattr__(self,attr):
>         if attr=='next':
>             if self._next is not None:
>                 return self._next
>             else:
>                 self._next=Node()
>                 return self._next
>         print attr,"was called..."
>         error=3/0  #supposed to raise exception
>         raise AttributeError
>
> if __name__=='__main__':
>     f=Node()
>     links=[f.next,f.next,f.next.next,f.next.next]
>     for each in links:
>         print each
>     print f.errorPlz
>
> And this yields exactly,
>

[snipping output]

>
> Why did it suck up all ZeroDivisionErrors while outputting the "was
> called..." messages? Special case with magic methods? Is this an intended
> behaviour? Then what is the exact process/mechanism?
>
> Thanks in advance.

IIRC, when searching for attributes, __getattr__() is only called when the
attribute is not found in any of the usual places.  It's a last-ditch save,
rather than a total redefine, in this sense.  Since the interpreter is able
to find attributes for __str__(), et al, it uses those and does not pass
through __getattr__().

Of  course, I could be totally wrong.  :)

Jeff Shannon
Technician/Programmer
Credit International