[Tutor] inheritance/classmethods/metaclasses

[Kent Johnson]

On Thu, Jun 19, 2008 at 9:50 AM, Eric Abrahamsen
<eric at ericabrahamsen.net> wrote:

> I'm making a few classes for a very simple ORM, where the classes reflect
> objects that I'm persisting via pickle. I'd like to add and delete instances
> via add() and delete() classmethods, so that the classes can keep track of
> the comings and goings of their instances.

What you have almost works. Try this:

class Model(object):
    @classmethod
    def add(cls, *args):
       inst = cls(*args)
       cls.instances.append(inst)

class File(Model):
   instances = []
   def __init__(self, *args):
       self.filename = args[0]
       self.keyword = args[1]


File.add('somefilename','keywordforthisfile')

print File.instances


You have to define instances in each class; a metaclass could do that
for you. Anyway I hope this gets you a little farther.

Kent