Started the python 3.5.2 exe in session 0 using the task scheduler,
2 instances of python are running in task manager and the process gets hanged, killing the process did not create any logs in %temp% folder.

Are you running python.exe without a script or command? That runs the REPL in session 0, which will block reading from stdin. It's harmless to kill this process. The REPL could detect that it's running in session 0 and exit. However, I'm not in favor of such a change because sometimes I intentionally run in session 0 via psexec.exe.

Sorry I did not understand your comment, what is REPL? I am not using any script just scheduling a task to run python using this command 'python-3.5.2-x86.exe' with /quiet option.

Are u telling me to kill the 2nd process that is getting created by the installer and the installation will work fine?

For some reason you're trying to schedule the installer to run in session 0. I thought you were running python.exe in session 0 via the task scheduler, which would hang in the REPL [1].

[1]: https://en.wikipedia.org/wiki/Read%E2%80%93eval%E2%80%93print_loop

Thank you for the link, yes am running in session 0 via the task scheduler.

I tested installing 3.10 in session 0 for the current user, as a user with the batch logon right. The installation succeeded. If you're running as SYSTEM, then installing for the current user doesn't see reasonable to me. I won't test that case. 

I tested installing 3.10 in session 0 as SYSTEM, with the option InstallAllUsers=1. The installation succeeded. There's a caveat (bpo-25166) that the installer registers the uninstall record only for the current user. The SYSTEM account uses the default profile, so the uninstall record is stored under "HKU\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Uninstall". In this case, to uninstall you have to run the installer as SYSTEM with the /uninstall option.