Hello,
pythonOCC is a set of Python bindings to the free OpenCascade library (http://www.opencascade.org). Latest release of pythonOCC provides a full wxPython based 3D viewer. A sample, named CADViewer, can import and display any STEP, IGES or STL files with less than 200 lines of Python code. At last, pythonOCC is released under the term of the CeCILL free license.
You can have more info on http://www.pythonocc.org. Any comment or suggestion is welcome.
Best regards,
Thomas Paviot