This program compiles to a DLL and allows you to execute python code upon injection if the python interpreter is persistent.
After you have compiled it, you can now use an injector like this to embed the DLL into the pyinstaller executable.
As in the directory of where the script file your injecting to lies, the DLL will try to find injection.txt containing plain python code which is then executed in a seperate thread, but with the python interpreter inside the proc you injected to.