use class factory to set required class variables?

[Alan]

I have a class ``A`` that is intentionally incomplete:
it has methods that refer to class variables that do not exist.
The class ``A`` has several complicated methods, a number
of which reference the "missing" class variables.
Obviously, I do not directly use ``A``.

I have a class factory ``f``` that subclasses ``A`` *only* in
order to define the class variables.

The motivation/problem:
I did this because I need many versions of class ``A``,
which differ only in the class variables, which are not
known until run time.

Q: On the face of it, did I pick a reasonable solution to
my problem?  If so is this a standard pattern?  If not,
can you mention a better approach?

My solution is working for me, but the class ``A``
is bugging me, because of the odd (to me) way in
which it is incomplete.  Obviously, I'm not a
computer science type ...

Thanks,
Alan Isaac