Python 3.5 has just been released, can I get it as a package for Ubuntu 15.4?
Before Ubuntu adds python 3.5 to the official repositories you have two options to install it now :
Check if someone has come with a PPA containing
python 3.5so that you can install/remove it usingapt-getor other package managerInstall from source
As fas as i can see there is no such PPA available till date so your only option is to install from source file.
You have said :
I don't want to do an old-school source install because that can make it harder to uninstall when the official packages come out.
Perhaps you have not heard of checkinstall yet, it creates a package out of the files that are going to be saved on different places in your computer at the last step of compiling a package from source (sudo make install). So you just need to replace sudo make install with sudo checkinstall and then you can remove the package you named using any package manager in the usual manner.
Check man checkinstall to get more idea.
Update:
A PPA is now available. Check this answer.
There is a another answer to a similar question here: How do I install newer Python versions using apt-get?
Basically, it says that (until official repositories have the new python version) here is a source to use with the package manager, for us who prefer to use this simpler method, as that's what package managers are there for:
sudo add-apt-repository ppa:fkrull/deadsnakes
sudo apt-get update
sudo apt-get install python3.5
Kudos to Felix Krull, who runs this PPA!