Intercept methods/raise exception

[Gordon McMillan]

Remco Gerlich wrote:

>Thomas Weholt wrote in comp.lang.python:
>> I tried using __getattr__, like
>> 
>> def __getattr__(self, attrname):
>>    print 'Trace:', attrname
>>    return getattr(self, attrname)
>> 
>> But it crashed terribly. The object in question is accessed lots of
>> times. When I ran it, it printed :
>> Trace: __coerce__
>> Some hundred, thousands times, then collapsed with a bang.
>
>This is simple infinite recursion. 

You got that right!

> The getattr() call calls __getattr__,
>etc.
>
>Try returning self.__dict__[attrname].

And that wrong! If the object exists, __getattr__ never gets called. You 
can trap all assigments to attributes through __setattr__, but only by 
using a proxy can you trap all accesses.

- Gordon