one-time initialization of class members

Steven Bethard steven.bethard at gmail.com
Thu Jun 14 00:54:01 CEST 2007


James Turk wrote:
> Hi,
> 
> I have a situation where I have some class members that should only be
> done once.  Essentially my problem looks like this:
> 
> class Base(object):
>     dataset = None
> 
>     def __init__(self, param):
>         if type(self).dataset is None:
>             # code to load dataset based on param, expensive
> 
> class ChildClass1(Base):
>     def __init__(self):
>         Base.__init__(self, data_params)
> 
> class AnotherChildClass(Base):
>     def __init__(self):
>         Base.__init__(self, other_data_params)
> 
> 
> This seems to work, initialization is only done at the first creation
> of either class.  I was just wondering if this is the 'pythonic' way
> to do this as my solution does feel a bit hackish.

What should happen with code like::

     ChildClass1('foo')
     ChildClass1('bar')

The 'param' is different, but 'dataset' should only get set the first time?

STeVe



More information about the Python-list mailing list