tinypy is a minimalist implementation of Python in 64k of code. It includes a parser and bytecode compiler written in python. tinypy runs on its own C-based virtual machine with garbage collection. It supports a fairly decent subset of Python, including classes with single inheritance, functions with variable or keyword arguments, strings, lists, dicts, numbers, modules, list comprehensions, exceptions with full traceback, some builtins, and several modules.
xpython is a bundle that includes the Python interpreter and runtime and a number of libraries. It can be compiled into a single binary, thus simplifying software distributions without proper package management. The binary contains Python, wxWindows, SQLite, and a number of useful modules.
pythonOCC is a 3D CAD/PLM development library for the Python programming language. It provides 3D hybrid modeling, data exchange (support for the STEP/IGES file format), GUI management support (wxPython, PyQt, python-xlib), parametric modeling, and advanced meshing features. pythonOCC is built upon the OpenCASCADE 3D modeling kernel and the salomegeom and salomesmesh packages. Some high level packages (for parametric modeling, topology, data exchange, webservices, etc.) extend the builtin features of those libraries to enable highly dynamic and modular programming of any CAD application.