Self Referencing Class Definition in python

Try this:

class Plan(SiloBase):
    cost = DataField(int)
    start = DataField(System.DateTime)
    name = DataField(str)
    items = DataCollection(int)

Plan.subPlan = ReferenceField(Plan)

OR use __new__ like this:

class Plan(SiloBase):

    def __new__(cls, *args, **kwargs):
        cls.cost = DataField(int)
        cls.start = DataField(System.DateTime)
        cls.name = DataField(str)
        cls.items = DataCollection(int)
        cls.subPlan = ReferenceField(cls)
        return object.__new__(cls, *args, **kwargs)

i've got a metaclass that reads this information and does some setup

Most frameworks that use metaclasses provide a way to resolve this. For instance, Django:

subplan = ForeignKey('self')

Google App Engine:

subplan = SelfReferenceProperty()

The problem with solutions like tacking an additional property on later or using __new__ is that most ORM metaclasses expect the class properties to exist at the time when the class is created.

I understand what is happening, the name of the class isn't in scope inside the class.

Not exactly. The name of the class is not yet defined when defining it's contents (e.g. scope).