You could strictly seperate design(python part) and code(c++ part) like this:
Write a complete c++ programm that works in the terminal/console and then make the python-application call these c++-terminal programm via os.Popen.
So if your programm is a calculator it does this:
(python gui) 5 + 5 -> my_c_programm.exe "5 + 5" -> (returns) 10 -> (python gui) display
that way you can use your programm with and without gui.
Its easier and faster than embedding Python in your c++ programm or extending Python with C++.
I basically do the same thing on my current project, but like this:
php: my webinterface
python: for structure and logic and easy operation
c++: for heavy calculations and where I need speed
so php -> python -> c++
and it works very well for me :)