Postpone creation of attributes until needed

[Marc 'BlackJack' Rintsch]

In <1181559496.911368.219210 at p77g2000hsh.googlegroups.com>, Frank Millman
wrote:

> On Jun 11, 12:21 pm, Steven D'Aprano
> <s... at REMOVE.THIS.cybersource.com.au> wrote:
>> > I use __slots__ to catch any invalid attributes, otherwise I would get
>> > a 'maximum recursion depth exceeded' error.
>>
>> That's the wrong solution to that problem. To avoid that problem,
>> __getattr__ should write directly to self.__dict__.
>>
> 
> Are you saying that instead of
> 
>     self.z = self.x * self.y
>     return getattr(self.name)
> 
> I should have
> 
>     self.__dict__['z'] = self.x * self.y
>     return self.__dict__[name]
> 
> I tried that, but I get AttributeError: 'A' object has no attribute
> '__dict__'.

That's because you used `__slots__`.  One of the drawbacks of `__slots__`.

Ciao,
	Marc 'BlackJack' Rintsch