Changing Python default in 12.04 LTS
Solution 1:
Don't do it
Since many important programs are written in python changing default python may crash your system, so set python for individual apps.
You can locate python3 at /usr/bin/python3
. If you want python3 by default try Ubuntu 12.10
Solution 2:
I would not recommend overwriting the system python binaries.
I mainly use Perl and Perlbrew for testing code and new Perl releases.
You may want to check out something like Pythonbrew that will allow you to maintain your system Python while providing you a sandbox to play in with your newer distribution.