How to customize emacs in python mode to highlight operators?

Question

I'm setting up emacs to be my python IDE, and I've found plenty of material online that explain auto-completion, among a variety of other features. What I can't figure out, though, is how to get the syntax highlighter to do its highlighting magic on operators.

How can I customize my emacs in python mode to make + - different colors? I'd also like it to make integers, floats, and parentheses different colors as well.

Answer 1

i actually have something like this setup for my programming modes. this defines 2 separate faces, one for operators and one for the "end statement" symbol (not so useful in python, obviously). you can modify the "\\([][|!.+=&/%*,<>(){}:^~-]+\\)" regex to match the operators you are interested in and customize the faces to be the color you want.

(defvar font-lock-operator-face 'font-lock-operator-face)

(defface font-lock-operator-face
  '((((type tty) (class color)) nil)
    (((class color) (background light))
     (:foreground "dark red"))
    (t nil))
  "Used for operators."
  :group 'font-lock-faces)

(defvar font-lock-end-statement-face 'font-lock-end-statement-face)

(defface font-lock-end-statement-face
  '((((type tty) (class color)) nil)
    (((class color) (background light))
     (:foreground "DarkSlateBlue"))
    (t nil))
  "Used for end statement symbols."
  :group 'font-lock-faces)

(defvar font-lock-operator-keywords
  '(("\\([][|!.+=&/%*,<>(){}:^~-]+\\)" 1 font-lock-operator-face)
    (";" 0 font-lock-end-statement-face)))

then, you just enable this by adding a hook to the relevant modes (this example assumes you are using "python-mode"):

(add-hook 'python-mode-hook
                  '(lambda ()
                     (font-lock-add-keywords nil font-lock-operator-keywords t))
                  t t)

Answer 2

Put the following in your ~/.emacs file:

;
; Python operator and integer highlighting
; Integers are given font lock's "constant" face since that's unused in python
; Operators, brackets are given "widget-inactive-face" for convenience to end-user 
;

(font-lock-add-keywords 'python-mode
    '(("\\<\\(object\\|str\\|else\\|except\\|finally\\|try\\|\\)\\>" 0 py-builtins-face)  ; adds object and str and fixes it so that keywords that often appear with : are assigned as builtin-face
    ("\\<[\\+-]?[0-9]+\\(.[0-9]+\\)?\\>" 0 'font-lock-constant-face) ; FIXME: negative or positive prefixes do not highlight to this regexp but does to one below
    ("\\([][{}()~^<>:=,.\\+*/%-]\\)" 0 'widget-inactive-face)))