I am normally a vim user but am looking at emacs again. One of the features that emacs has that I love is how it does interactive debugging.
First thing to do is to have the python debugger in your path and called 'pdb'. On my Ubuntu system that would be:
cd ~/bin ln -s /usr/lib/python2.4/pdb.py pdb
Now edit your favorite python script with emacs and start the debugger: