customizing metaclass constructed classes

[Robin Becker]

I have a set of classes for database access which are constructed using a 
special metaclass and base class.

so in the base module

#base.py
class M(type):
    def __init__(cls, name, bases, dict):
       super(M, cls).__init__(name, bases, dict)
       for f in dict['_fieldDefs']:
           #create special property based on the field def
           ....

class A(object):
    __metaclass__ = M
    _fieldDefs = []

    #base methods
    ......

in the database module we use the above
eg

#database.py
class C(A):
   _fieldDefs =[
     IntColumn('id',primaryKey=1,allowNull=0),
     TextColumn('name',allowNull=0,size=50),
     TextColumn('description',allowNull=1,size=50),
     ]

Now to my question: can I change the definition of the client class C at run 
time? I want to do something like add another element to C's _fieldDefs and then 
get it to go through the construction phase provided by M. It's clearly 
pointless for me to try something like

from database import C
C._fieldDefs.append(....)

as C is constructed by the import.
I either have to delay C's construction or reconstruct it.

Would something like this do?

def reconstruct():
     import database
     class C(database.C):
       _fieldDefs = database.C._fieldDefs+[......]
     database.C = C

Is there a better way to do this which preserves more of C's original identity? 
I suppose I want to call the metaclass initialization again, but can't see a way 
to do that.
-- 
Robin Becker