replacing built-in exception types

[Nishkar Grover]

I'm trying to replace the built-in base exception class with a subclass 
of itself in python 2.5 because we can no longer add attributes to that...

% python2.4 -c 'import exceptions; exceptions.Exception.bar = 1234'

% python2.5 -c 'import exceptions; exceptions.Exception.bar = 1234'
Traceback (most recent call last):
   File "<string>", line 1, in <module>
TypeError: can't set attributes of built-in/extension type 
'exceptions.Exception'

% python2.5 -c 'import exceptions; exceptions.BaseException.bar = 1234'
Traceback (most recent call last):
   File "<string>", line 1, in <module>
TypeError: can't set attributes of built-in/extension type 
'exceptions.BaseException'

I already have a way to programatically construct the hierarchy of 
subclasses, so for example, my subclass of OSError is a subclass of the 
built-in OSError and a subclass of my subclass of EnvironmentError. The 
only thing left to do is find a way to replace the built-in exception 
types with my custom ones.

- Nishkar


Calvin Spealman wrote:
> 
> Why would you do this? How to do it, if its even possible, is far less
> important than if you should even attempt it in the first place.
> 
> 
> On Dec 11, 2007, at 3:51 PM, Nishkar Grover wrote:
>>
>> I'm trying to replace a built-in exception type and here's a simplified
>> example of what I was hoping to do...
>>
>> >>>
>> >>> import exceptions, __builtin__
>> >>>
>> >>> zeroDivisionError = exceptions.ZeroDivisionError
>> >>>
>> >>> class Foo(zeroDivisionError):
>> ...     bar = 'bar'
>> ...
>> >>>
>> >>> exceptions.ZeroDivisionError = Foo
>> >>> ZeroDivisionError = Foo
>> >>> __builtin__.ZeroDivisionError = Foo
>> >>>
>> >>> try:
>> ...     raise ZeroDivisionError
>> ... except ZeroDivisionError, e:
>> ...     print e.bar
>> ...
>> bar
>> >>>
>> >>> try:
>> ...     1/0
>> ... except ZeroDivisionError, e:
>> ...     print e.bar
>> ...
>> Traceback (most recent call last):
>>    File "<stdin>", line 2, in ?
>> ZeroDivisionError: integer division or modulo by zero
>> >>>
>>
>> Notice that I get my customized exception type when I explicitly raise
>> ZeroDivisionError but not when that is implicitly raised by 1/0. It
>> seems like I have to replace that exception type at some lower level,
>> but I'm not sure how/where. Does anyone know of a way to do this?
>>
>> - Nishkar
>>
>> --http://mail.python.org/mailman/listinfo/python-list
>