Implementing ExecuteTime in ein.

If you want to try this in your installation of ein then place a call
to (require 'ein-timestamp) in your init file after loading ein.

lisp/ein-timestamp.el

@@ -0,0 +1,61 @@
+;;; ein-timestamp.el --- Elisp implementation of the ExecuteTime nbextension
+
+;; Copyright (C) 2018- John M. Miller
+
+;; Author: John M. Miller <millejoh at mac.com>
+
+;; This file is NOT part of GNU Emacs.
+
+;; ein-timestamp.el 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.
+
+;; ein-timestamp.el 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 ein-kernel.el.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; A rough approximation of the ExecuteTime (https://jupyter-contrib-nbextensions.readthedocs.io/en/latest/nbextensions/execute_time/readme.html) nbextension
+
+;;; Code:
+
+(require 'ein-kernel)
+(require 'ein-cell)
+
+(defun ein:timestamp--shell-reply-hook (msg-type header content metadata)
+  (when (string-equal msg-type "execute_reply")
+    (let ((start-time (plist-get metadata :started))
+          (end-time (plist-get header :date)))
+      (plist-put metadata :execute-time (cons start-time end-time)))))
+
+(defun ein:timestamp--execute-reply-hook (cell content metadata)
+  (if-let ((etime (plist-get metadata :execute-time)))
+      (if (ein:cell-metadata cell)
+          (plist-put (ein:cell-metadata cell)
+                     :execute-time
+                     etime)
+        (setf (ein:cell-metadata cell) (list :execute-time etime))))
+  (ein:cell-running-set cell nil)
+  (ewoc-invalidate (ein:basecell--ewoc cell) (ein:cell-element-get cell :footer)))
+
+(defmethod ein:cell-insert-footer :after ((cell ein:codecell))
+  (if (slot-value cell 'running)
+      (ein:insert-read-only "Execution pending\n\n")
+    (if-let ((etime (plist-get (ein:cell-metadata cell) :execute-time)))
+        (let ((start-time (date-to-time (car etime)))
+              (end-time (date-to-time (cdr etime))))
+          (ein:insert-read-only (format "Last executed %s in %ss\n\n"
+                                        (current-time-string start-time)
+                                        (float-time (time-subtract end-time start-time))))))))
+
+(add-hook 'ein:on-shell-reply-functions 'ein:timestamp--shell-reply-hook)
+(add-hook 'ein:on-execute-reply-functions 'ein:timestamp--execute-reply-hook)
+
+(provide 'ein-timestamp)
+