You can add the devel:languages:python:Factory repository or use the 1 Click Install and a Python 3.3.2 version form here (e.g. from the above repo).
(Show other versions->openSUSE 12.2->Show unstable packages->1 Click Install)
To use it with zypper only (no GUI) you can add the repo as follows:
sudo zypper ar http://download.opensuse.org/repositories/devel:/languages:/python:/Factory/openSUSE_12.2/devel:languages:python:Factory.repo
Then, to use packages from that repo you should give the repo a higher priority (in this case higher priority means lower number 0=high, 100=low). To know the repo id use zypper lr
and search for the repo number in the output. Then use the following command to change the priority:
sudo zypper mr -p priority repo_number
You could use e.g. 50 as priority if your other repos have the standard priority of 99.
Then use zypper update python3
to update python.