How can a compiled .exe be stuffed into another .exe?

Question

Python

How can a compiled .exe be stuffed into another .exe? What would be all in one .exe beautifully equipped. The executable is compiled using pyinstaller and the sources use subprocess.

Answer 1

To a similar question, only more generalized, I gave it here:
How to make pyinstaller take everything with it ...
I think you can do the same with exe files.
You need the --add-binary switch for binaries.

Answer 2

UPX ?