{
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   "source": [
    "# Connecting to an existing IPython kernel using the Qt Console"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## The Frontend/Kernel Model"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The traditional IPython (`ipython`) consists of a single process that combines a terminal based UI with the process that runs the users code.\n",
    "\n",
    "While this traditional application still exists, the modern IPython consists of two processes:\n",
    "\n",
    "* Kernel: this is the process that runs the users code.\n",
    "* Frontend: this is the process that provides the user interface where the user types code and sees results.\n",
    "\n",
    "IPython currently has 3 frontends:\n",
    "\n",
    "* Terminal Console (`ipython console`)\n",
    "* Qt Console (`ipython qtconsole`)\n",
    "* Notebook (`ipython notebook`)\n",
    "\n",
    "The Kernel and Frontend communicate over a ZeroMQ/JSON based messaging protocol, which allows multiple Frontends (even of different types) to communicate with a single Kernel. This opens the door for all sorts of interesting things, such as connecting a Console or Qt Console to a Notebook's Kernel.  For example, you may want to connect a Qt console to your Notebook's Kernel and use it as a help\n",
    "browser, calling `??` on objects in the Qt console (whose pager is more flexible than the\n",
    "one in the notebook).  \n",
    "\n",
    "This Notebook describes how you would connect another Frontend to a Kernel that is associated with a Notebook."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Manual connection"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "To connect another Frontend to a Kernel manually, you first need to find out the connection information for the Kernel using the `%connect_info` magic:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{\n",
      "  \"stdin_port\": 52858, \n",
      "  \"ip\": \"127.0.0.1\", \n",
      "  \"hb_port\": 52859, \n",
      "  \"key\": \"7efd45ca-d8a2-41b0-9cea-d9116d0fb883\", \n",
      "  \"shell_port\": 52856, \n",
      "  \"iopub_port\": 52857\n",
      "}\n",
      "\n",
      "Paste the above JSON into a file, and connect with:\n",
      "    $> ipython <app> --existing <file>\n",
      "or, if you are local, you can connect with just:\n",
      "    $> ipython <app> --existing kernel-b3bac7c1-8b2c-4536-8082-8d1df24f99ac.json \n",
      "or even just:\n",
      "    $> ipython <app> --existing \n",
      "if this is the most recent IPython session you have started.\n"
     ]
    }
   ],
   "source": [
    "%connect_info"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "You can see that this magic displays everything you need to connect to this Notebook's Kernel."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Automatic connection using a new Qt Console"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "You can also start a new Qt Console connected to your current Kernel by using the `%qtconsole` magic. This will detect the necessary connection\n",
    "information and start the Qt Console for you automatically."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "a = 10"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "%qtconsole"
   ]
  }
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