[Tutor] singleton pattern

[alan.gauld@bt.com]

> How about trying not to fake out the mechanisms and just using Python
> classes?
> 
> class SingletonInstance:
>   instance = None  # class member for the singleton instance
>   def __init__(self, klass):
>     if self.__class__.instance is None:

Hmm, I need to do some digging. I've never played with 
Python's object model at that level...

Alan G.
> Guido once also suggested that replacing __class__ (which is 
> something I believe Alan was attempting to do) 

I wasn't replacing class just returning a pointer to the 
original instance as an attribute of the Exception.

But the magic methods might provide a better solution, 
I'll take a look over the weekend.

Alan G.