Cyclic class definations

[John Henry]

Hi list,

I am trying to understand better Python packaging.  This might be a
messed up class hierachy but how would I break this cyclic relatioship?

In file A:

from B import B_Class

Class_A_Main():
   def ....
   def SomeMethod(self):
      res=B_Class(self)

Class_A_SubClass(Class_A_Main):
   def ...


In file B:

Class B_Class():
   def __init__(self,parent):
      ...
   def SomeMethod(self):
      res=C_Class(self)


In file C:

from file A import Class_A_SubClass

Class C_Class(Class_A_SubClass):
   def __init__(self, parent):
      ...


As you can see, the cyclic relationship exists because C_Class is a
sub-class of SubClass which is in turn a sub-class of Class_A_Main and
in one of the methods of Class_A, it has a need to create a C_Class
object.

I tried to merge the files A and C (by placing C_Class behind A_Class)
and have the method in A_Class create C_Class directly but that doesn't
work because Python says C_Class is not defined when it's processing
the A_Class method.   May be somebody can tell me how to "forward
declare" a class?

Regards,