Python Mode (python-mode.el) is a major editing mode for the EmacsEditor. It is part of the source distribution of Python (as the file Misc/python-mode.el).
Emacs 22 now comes with its own updated python.el mode. See EmacsEditor for more details.
The EmacsWiki page for PythonMode has information on how to install, configure and add shortcuts keys to python-mode.
The [http://www.python.org/emacs/python-mode/python-mode.el current release] is version 4.6 (~123KB). The list of changes since the last released version [http://www.python.org/emacs/python-mode/changes-406.html are given in detail], as well as some [http://www.python.org/emacs/python-mode/installation.html installation notes.] If you're having problems with font-lock in python-mode, read the [http://www.python.org/emacs/python-mode/faq.html FAQ.]