Merge pull request jupyter-widgets#3060 from davidbrochart/fix_doc

Fix debouncing and throttling code

docs/source/examples/Widget Events.ipynb

@@ -379,12 +379,14 @@
     "    def __init__(self, timeout, callback):\n",
     "        self._timeout = timeout\n",
     "        self._callback = callback\n",
-    "        self._task = asyncio.ensure_future(self._job())\n",
     "\n",
     "    async def _job(self):\n",
     "        await asyncio.sleep(self._timeout)\n",
     "        self._callback()\n",
     "\n",
+    "    def start(self):\n",
+    "        self._task = asyncio.ensure_future(self._job())\n",
+    "\n",
     "    def cancel(self):\n",
     "        self._task.cancel()\n",
     "\n",
@@ -401,6 +403,7 @@
     "            if timer is not None:\n",
     "                timer.cancel()\n",
     "            timer = Timer(wait, call_it)\n",
+    "            timer.start()\n",
     "        return debounced\n",
     "    return decorator"
    ]
@@ -454,22 +457,22 @@
     "        more than once every wait period. \"\"\"\n",
     "    def decorator(fn):\n",
     "        time_of_last_call = 0\n",
-    "        scheduled = False\n",
+    "        scheduled, timer = False, None\n",
     "        new_args, new_kwargs = None, None\n",
     "        def throttled(*args, **kwargs):\n",
-    "            nonlocal new_args, new_kwargs, time_of_last_call, scheduled\n",
+    "            nonlocal new_args, new_kwargs, time_of_last_call, scheduled, timer\n",
     "            def call_it():\n",
-    "                nonlocal new_args, new_kwargs, time_of_last_call, scheduled\n",
+    "                nonlocal new_args, new_kwargs, time_of_last_call, scheduled, timer\n",
     "                time_of_last_call = time()\n",
     "                fn(*new_args, **new_kwargs)\n",
     "                scheduled = False\n",
     "            time_since_last_call = time() - time_of_last_call\n",
-    "            new_args = args\n",
-    "            new_kwargs = kwargs\n",
+    "            new_args, new_kwargs = args, kwargs\n",
     "            if not scheduled:\n",
-    "                new_wait = max(0, wait - time_since_last_call)\n",
-    "                Timer(new_wait, call_it)\n",
     "                scheduled = True\n",
+    "                new_wait = max(0, wait - time_since_last_call)\n",
+    "                timer = Timer(new_wait, call_it)\n",
+    "                timer.start()\n",
     "        return throttled\n",
     "    return decorator"
    ]