Proper class initialization

[Steven Bethard]

Christoph Zwerschke wrote:
> But I wonder whether it is possible to put all this init code into one 
> class initialization method, something like that:
> 
> class A:
> 
>     @classmethod
>     def init_class(self):
>         sum = 0
>         for i in range(10):
>             sum += i
>         self.sum = sum
> 
>     init_class()

I don't run into this often, but when I do, I usually go Jack 
Diederich's route::

     class A(object):
         class __metaclass__(type):
             def __init__(cls, name, bases, classdict):
                 cls.sum = sum(xrange(10))

But you can also go something more akin to your route::

     class A(object):
         def _get_sum():
             return sum(xrange(10))
         sum = _get_sum()

Note that you don't need to declare _get_sum() as a classmethod, because 
it's not actually a classmethod -- it's getting used before the class 
yet exists.  Just write it as a normal function and use it as such -- 
that is, no ``self`` or ``cls`` parameter.

STeVe