Regarding Installer Program (for windows).
I think what you are looking for is InstallForge. This is a tool that you can use to build your own installation wizard. This website pythonguis is a tutorial for PyInstaller and InstallForge. You can skip the PyInstaller part and go towards the middle to view the InstallForge tutorial if you are not interested in making your py application executable using PyInstaller, although I recommended it as many have mentioned.
InstallForge has the ability to make your own install wizard which you can program to install your py files or executables in the directory you want and create a shortcut to the application you want your friends to run.
If you don’t have to download the python interpreter version as you stated, if you bundle your py files with Pyinstaller, it will already include the python interpreter version, making it easier to bundle within your InstallForge. Another StackOverflow thread here, explains how you can install python using the command line, assuming you already have the python interpreter installation. To actually download python from the web in an automated way I was not able to find info on a system designed for this, although I’m sure it’s not impossible if you get creative.
After you figured out how you want to bundle, and install your program, you can program your system to auto-update itself with the PyUpdater python module found in pip