This assumes a recent (Ubuntu >= 8.04) version.
Requirements:
sudo apt-get build-essential
sudo apt-get install python-dev
sudo apt-get install python-numpy python-numpy-dev python-scipy
Options:
sudo apt-get install ipython
sudo apt-get install python-matplotlib
For getting the code via version control:
sudo apt-get install bzr
Then follow the instructions at Checking out the latest version