Ubuntu 12.04 ships with python 2.7.3. You should be able to download https://www.python.org/ftp/python/2.7.6/Python-2.7.6.tgz and follow the README file. The steps should be simple enough.

./configure

make

make install

Note that you don't have to remove python-2.7.3 from your system to install an other version. You can switch between different versions using

sudo update-alternatives --config python

Also, did you check this out?

https://stackoverflow.com/questions/20445565/ubuntu-12-04-lts-update-python-2-7-3-to-2-7-6-without-breaking-dependencies