Python dynamic attribute creation

[Neil Hodgson]

WANG Cong:

> 4) Also, this will _somewhat_ violate the OOP princples, in OOP,
> this is and should be implemented by inherence.

   Most object oriented programming languages starting with Smalltalk
have allowed adding attributes (addInstVarName) to classes at runtime.
Low level OOPLs like C++ and Delphi did not implement this for
efficiency reasons.

   Neil