This tutorial shows how to install older & newer versions of python in Ubuntu. Felix Krull has created a PPA that contains multiple python versions:

• python 2.4.6 for Ubuntu 10.04, Ubuntu 12.04, Ubuntu 12.10, Ubuntu 13.04, Ubuntu 11.10, Ubuntu 11.04
• python 2.5.6 for Ubuntu 10.04, Ubuntu 12.04, Ubuntu 12.10, Ubuntu 13.04, Ubuntu 11.10, Ubuntu 11.04
• python 2.6.8 for Ubuntu 13.04, Ubuntu 12.04, Ubuntu 12.10
• python 2.7 for Ubuntu 10.04, Ubuntu 10.10
• python 3.1 for Ubuntu 13.04, Ubuntu 12.10, Ubuntu 12.04, Ubuntu 11.10
• python 3.2 for Ubuntu 13.04, Ubuntu 10.04
• python 3.3 for Ubuntu 12.04, Ubuntu 11.10, Ubuntu 10.04

To add the ppa, run below command in terminal:

sudo add-apt-repository ppa:fkrull/deadsnakes

Then update package lists:

sudo apt-get update

To install python 2.4 in Ubuntu 12.04, etc. run below command:

sudo apt-get install python2.4

To install python 2.5 in Ubuntu 12.04, etc. run:

sudo apt-get install python2.5

To install python 2.6 in Ubuntu 12.10, Ubuntu 12.04, run:

sudo apt-get install python2.6

To install python 2.7 in Ubuntu 10.04, Ubuntu 10.10

sudo apt-get install python2.7

To install Python 3.2 in Ubuntu 12.04:

sudo apt-get install python3.2

To install Python 3.3 in Ubuntu 12.04:

sudo apt-get install python3.3