2019-01-03-Loop-de-loop.ipynb

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   "source": [
    "from tornado.ioloop import IOLoop, PeriodicCallback\n",
    "from tornado.httpclient import AsyncHTTPClient\n",
    "from tornado import gen\n",
    "from tornado.platform.asyncio import to_tornado_future\n",
    "from asyncio import sleep\n",
    "import time\n",
    "from ipywidgets import FloatSlider, Checkbox, HBox"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "IOLoop has all the goodies."
   ]
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  {
   "cell_type": "code",
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   "metadata": {},
   "outputs": [],
   "source": [
    "loop = IOLoop.instance()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "If you name your functions, and then call them indirectly, you can hack on them while it's running."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [],
   "source": [
    "def increment(*args, **kwargs):\n",
    "    if running.value:\n",
    "        x.value += 3\n",
    "        loop.call_later(0.5, increment)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "`stdout` doesn't work so great, but widgets are fine."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "application/vnd.jupyter.widget-view+json": {
       "model_id": "0f8537501199496895791ac4f02f7db6",
       "version_major": 2,
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      },
      "text/plain": [
       "HBox(children=(Checkbox(value=False, description='running'), FloatSlider(value=0.0)))"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "running = Checkbox(description=\"running\")\n",
    "x = FloatSlider()\n",
    "running.observe(lambda _: running.value and loop.add_callback(lambda: increment()), \"value\")\n",
    "\n",
    "HBox([running, x])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "You can also set up a more regular clock with `PeriodicCallbac`"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [],
   "source": [
    "def tick():\n",
    "    if running.value:\n",
    "        x.value -= 0.5"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [],
   "source": [
    "cb = PeriodicCallback(lambda: tick(), 1000)\n",
    "cb.start()"
   ]
  }
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