diff --git a/snippets/python-mode/.yas-setup.el b/snippets/python-mode/.yas-setup.el
index e9145efd..f7a40c59 100644
--- a/snippets/python-mode/.yas-setup.el
+++ b/snippets/python-mode/.yas-setup.el
@@ -1,21 +1,48 @@
 ;;; -*- lexical-binding: t -*-
+
+; Copyright (C) miscellaneous contributors, see git history
+; Copyright (C) 2024 Daniel Hornung <d.hornung@indiscale.com>
+;
+; This program is free software: you can redistribute it and/or modify
+; it under the terms of the GNU General Public License as
+; published by the Free Software Foundation, either version 3 of the
+; License, or (at your option) any later version.
+;
+; This program is distributed in the hope that it will be useful,
+; but WITHOUT ANY WARRANTY; without even the implied warranty of
+; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+; GNU General Public License for more details.
+;
+; You should have received a copy of the GNU General Public License
+; along with this program. If not, see <https://www.gnu.org/licenses/>.
+
 (require 'yasnippet)
 (defvar yas-text)
 
 (defvar python-split-arg-arg-regex
-"\\([[:alnum:]*]+\\)\\(:[[:blank:]]*[[:alpha:]]*\\)?\\([[:blank:]]*=[[:blank:]]*[[:alnum:]]*\\)?"
+  "\\([[:alnum:]*]+\\)\\(:[[:blank:]]*\\([][:alpha:][]*\\)\\)?\\([[:blank:]]*=[[:blank:]]*\\([[:alnum:]]*\\)\\)?"
 "Regular expression matching an argument of a python function.
-First group should give the argument name.")
+Groups:
+- 1: the argument name
+- 3: the type
+- 5: the default value")
 
 (defvar python-split-arg-separator
 "[[:space:]]*,[[:space:]]*"
 "Regular expression matching the separator in a list of argument.")
 
 (defun python-split-args (arg-string)
-  "Split a python argument string ARG-STRING into a tuple of argument names."
-  (mapcar (lambda (x)
+  "Split python argument string ARG-STRING.
+
+The result is a list ((name, type, default), ...) of argument names, types and
+default values."
+  (mapcar (lambda (x)           ; organize output
             (when (string-match python-split-arg-arg-regex x)
-              (match-string-no-properties 1 x)))
+              (list
+               (match-string-no-properties 1 x) ; name
+               (match-string-no-properties 3 x) ; type
+               (match-string-no-properties 5 x) ; default
+               )))
           (split-string arg-string python-split-arg-separator t)))
 
 (defun python-args-to-docstring ()
@@ -26,7 +53,9 @@ First group should give the argument name.")
          (formatted-args (mapconcat
                           (lambda (x)
                             (concat (nth 0 x) (make-string (- max-len (length (nth 0 x))) ? ) " -- "
-                                    (if (nth 1 x) (concat "\(default " (nth 1 x) "\)"))))
+                                    (if (nth 1 x) (concat (nth 1 x) ": "))
+                                    (if (nth 2 x) (concat "\(default " (nth 2 x) "\)"))
+                                    ))
                           args
                           indent)))
     (unless (string= formatted-args "")
@@ -36,7 +65,11 @@ First group should give the argument name.")
   "return docstring format for the python arguments in yas-text"
   (let* ((args (python-split-args yas-text))
          (format-arg (lambda(arg)
-                       (concat (nth 0 arg) " : " (if (nth 1 arg) ", optional") "\n")))
+                       (concat (nth 0 arg) " : "            ; name
+                               (if (nth 1 arg) (nth 1 arg)) ; type  TODO handle Optional[Foo] correctly
+                               (if (nth 2 arg) (concat (when (nth 1 arg) ", ")
+                                                       "default=" (nth 2 arg))) ; default
+                               "\n")))
          (formatted-params (mapconcat format-arg args "\n"))
          (formatted-ret (mapconcat format-arg (list (list "out")) "\n")))
     (unless (string= formatted-params "")
@@ -44,3 +77,25 @@ First group should give the argument name.")
                  (list "\nParameters\n----------" formatted-params
                        "\nReturns\n-------" formatted-ret)
                  "\n"))))
+
+
+;; Tests
+
+(ert-deftest test-split ()
+  "For starters, only test a single string for expected output."
+  (should (equal
+           (python-split-args "foo=3, bar: int = 2, baz: Optional[MyType], foobar")
+           (list '("foo" nil "3")
+                 '("bar" "int" "2")
+                 '("baz" "Optional[MyType]" nil)
+                 '("foobar" nil nil)))
+  ))
+
+;; For manual testing and development:
+
+;; (setq yas-text "foo=3, bar: int = 2, baz: Optional[MyType], foobar")
+;; (split-string yas-text python-split-arg-separator t)
+;;
+;; (python-split-args yas-text)
+;; (python-args-to-docstring)
+;; (python-args-to-docstring-numpy)