I don’t understand your aversion to the recursion solution.  Recursion will enumerate all the combinations.

Well, regardless, if you wish to use another approach that’s okay.  In order to install a Python package where Chimera will find it, you need to install it with Chimera’s Python interpreter.  How you do so is covered in the Programmer’s FAQ: https://www.cgl.ucsf.edu/chimera/docs/ProgrammersGuide/faq.html (actually tomorrow’s FAQ, since it needed a little tweak).  So namely:

3b) Installing Python packages into Chimera.

To use a package from Chimera, you would need to install it with Chimera's Python. Chimera's Python has the Python version number appended to it, so it will be named python2.x (python2.7 when this was written; also on Windows add ".exe"). On non-Mac, it will be found in <your Chimera installation>/bin. On Mac it's in Chimera.app/Contents/Resources/bin — don't use the one in Chimera.app/Contents/MacOS!

The best way to install packages is with pip, using (Chimera's) python2.x -m pip install package. If the pip module is not found, you'll need to install it first with (Chimera's) python2.x -m ensurepip. Then -m pip install will work. For packages not supported by pip, you will have to follow the installation instructions that come with the package.