Changing user preferences

I need to change the user preferences -> file -> Relative Paths. By deault, it’s checked marked which is True, yet the api docs here suggests it should be false. Changing the value in the python console like this

bpy.types.UserPreferencesFilePaths.use_relative_paths = False

has no effect either way, setting it True or False, there’s no change in the user preferences.

What I am looking for is absolute file paths, not the default relative file paths. I have a StringProperty that is set for DIR_PATH and it returns relative file paths. If I change the user pref to not using relative paths, it returns the absolute file path. So I am looking for a way to get the absolute file path. If I can’t change user prefs via the above code, how can I find the absolute file path?