Param
Param is a library providing Parameters: Python attributes extended to have features such as type and range checking, dynamically generated values, documentation strings, default values, etc., each of which is inherited from parent classes if not specified in a subclass.
Param contains only two required Python files, with no external dependencies, and is provided freely for both non-commercial and commercial use under a BSD license, so that it can easily be included as part of other projects.
Please see param's website for official releases, installation instructions, documentation, and examples.