Rework debouncer

Author: davidbrochart

docs/source/examples/Widget Events.ipynb

@@ -391,14 +391,14 @@
     "        execution until after `wait` seconds\n",
     "        have elapsed since the last time it was invoked. \"\"\"\n",
     "    def decorator(fn):\n",
+    "        timer = None\n",
     "        def debounced(*args, **kwargs):\n",
+    "            nonlocal timer\n",
     "            def call_it():\n",
     "                fn(*args, **kwargs)\n",
-    "            try:\n",
-    "                debounced.t.cancel()\n",
-    "            except(AttributeError):\n",
-    "                pass\n",
-    "            debounced.t = Timer(wait, call_it)\n",
+    "            if timer is not None:\n",
+    "                timer.cancel()\n",
+    "            timer = Timer(wait, call_it)\n",
     "        return debounced\n",
     "    return decorator"
    ]