python.el is a decent python mode for emacs developed by Dave Love that had been part of GNU emacs for quite a few years. It provides tight integration with standard elisp packages such as comint.el, compile.el, info-look.el and gud.el. Many people have been using it for authoring python. They provide feedback and bug fixes to ensure it works reliably in all major platforms.

As of this writing (2012/08/01), upstream has replaced python.el with another implementation that provides more or less the same feature set. Being a happy user of Dave's python.el, I extracted python.el from emacs trunk keeping the revision history and placed it here for the convenience of people so that they don't have to fix something that ain't broken.

File emacs.py, emacs2.py and emacs3.py should be placed in PYTHONPATH or data-directory.

If you place these files in a different directory, you need something like this (remember to replace MY_EMACSPY_DIR with the real path):

(defadvice run-python (around python-emacspy-directory activate)
  (let ((process-environment (cons (concat "PYTHONPATH=" "MY_EMACSPY_DIR")
                                   process-environment)))
    ad-do-it))