Use MMM for SageTeX in emacs

mmm-sagetex.el

;; add this to your .emacs / init.el to use mmm (multiple major modes) with SageTeX. This works with AUCTeX and
;; emacs 23.4. The fontification gets a little wonky, though; quotes inside a SageTeX environment throw
;; off the highlighting for the LaTeX bits that follow. But the modes correctly get switched.

;; if you don't have sage-mode installed, you can either (1) do "sage -i sage-mode" and follow the instructions to
;; enable it, or (2) replace sage-mode below with python-mode, which is good enough for regular editing of Sage code

(require 'mmm-auto)
(setq mmm-global-mode 'maybe)

(mmm-add-classes
 '((sagetex
    :submode sage-mode
    :delimiter-mode nil
    :front "\\\\begin{sage\\(block\\|silent\\|verbatim\\|example\\|commandline\\)}"
    :back "\\\\end{sage~1}"
    :save-matches 1)))

(mmm-add-mode-ext-class nil "\\.tex\\'" 'sagetex)