Align numeric sequences in Python programs

align-numbers.el

(defun align-numbers (start end)
  (interactive "r")
  (let* ((reg (buffer-substring-no-properties start end))
         (parts (mapcar #'y:string-strip (split-string reg ",")))
         (widest (apply #'max (mapcar #'length parts)))
         (full (mapcar (lambda (s)
                         (concat (make-string (- widest (length s)) ? ) s))
                       parts))
         (line (mapconcat #'identity full ", ")))
    (delete-region start end)
    (insert-string line)))