examples/Interactive Widgets/Nonblocking Console.ipynb

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    "# Console related imports.\n",
    "from subprocess import Popen, PIPE\n",
    "import os\n",
    "from IPython.utils.py3compat import bytes_to_str, string_types\n",
    "\n",
    "# Widget related imports.\n",
    "from IPython.html import  widgets\n",
    "from IPython.display import display"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Define function to run a process without blocking the input."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
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    "def read_process(process, append_output):\n",
    "    \"\"\" Try to read the stdout and stderr of a process and render it using \n",
    "    the append_output method provided\n",
    "    \n",
    "    Parameters\n",
    "    ----------\n",
    "    process: Popen handle\n",
    "    append_output: method handle\n",
    "        Callback to render output.  Signature of\n",
    "        append_output(output, [prefix=])\"\"\"\n",
    "    \n",
    "    try:\n",
    "        stdout = process.stdout.read()\n",
    "        if stdout is not None and len(stdout) > 0:\n",
    "            append_output(stdout, prefix='    ')\n",
    "    except:\n",
    "        pass\n",
    "        \n",
    "    try:\n",
    "        stderr = process.stderr.read()\n",
    "        if stderr is not None and len(stderr) > 0:\n",
    "            append_output(stderr, prefix='ERR ')\n",
    "    except:\n",
    "        pass\n",
    "\n",
    "\n",
    "def set_pipe_nonblocking(pipe):\n",
    "    \"\"\"Set a pipe as non-blocking\"\"\"\n",
    "    try:\n",
    "        import fcntl\n",
    "        fl = fcntl.fcntl(pipe, fcntl.F_GETFL)\n",
    "        fcntl.fcntl(pipe, fcntl.F_SETFL, fl | os.O_NONBLOCK)\n",
    "    except:\n",
    "        pass\n",
    "\n",
    "kernel = get_ipython().kernel\n",
    "def run_command(command, append_output, has_user_exited=None):\n",
    "    \"\"\"Run a command asyncronously\n",
    "    \n",
    "    Parameters\n",
    "    ----------\n",
    "    command: str\n",
    "        Shell command to launch a process with.\n",
    "    append_output: method handle\n",
    "        Callback to render output.  Signature of\n",
    "        append_output(output, [prefix=])\n",
    "    has_user_exited: method handle\n",
    "        Check to see if the user wants to stop the command.\n",
    "        Must return a boolean.\"\"\"\n",
    "    \n",
    "    # Echo input.\n",
    "    append_output(command, prefix='>>> ')\n",
    "    \n",
    "    # Create the process.  Make sure the pipes are set as non-blocking.\n",
    "    process = Popen(command, shell=True, stdout=PIPE, stderr=PIPE)\n",
    "    set_pipe_nonblocking(process.stdout)\n",
    "    set_pipe_nonblocking(process.stderr)\n",
    "    \n",
    "    # Only continue to read from the command \n",
    "    while (has_user_exited is None or not has_user_exited()) and process.poll() is None:\n",
    "        read_process(process, append_output)\n",
    "        kernel.do_one_iteration() # Run IPython iteration.  This is the code that\n",
    "                                  # makes this operation non-blocking.  This will\n",
    "                                  # allow widget messages and callbacks to be \n",
    "                                  # processed.\n",
    "        \n",
    "    # If the process is still running, the user must have exited.\n",
    "    if process.poll() is None:\n",
    "        process.kill()\n",
    "    else:\n",
    "        read_process(process, append_output) # Read remainer\n",
    "        \n",
    "    \n",
    "        \n",
    "        "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Create the console widgets without displaying them."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "console_container = widgets.VBox(visible=False)\n",
    "console_container.padding = '10px'\n",
    "\n",
    "output_box = widgets.Textarea()\n",
    "output_box.height = '400px'\n",
    "output_box.font_family = 'monospace'\n",
    "output_box.color = '#AAAAAA'\n",
    "output_box.background_color = 'black'\n",
    "output_box.width = '800px'\n",
    "\n",
    "input_box = widgets.Text()\n",
    "input_box.font_family = 'monospace'\n",
    "input_box.color = '#AAAAAA'\n",
    "input_box.background_color = 'black'\n",
    "input_box.width = '800px'\n",
    "\n",
    "console_container.children = [output_box, input_box]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Hook the process execution methods up to our console widgets."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
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   "outputs": [],
   "source": [
    "\n",
    "def append_output(output, prefix):\n",
    "    if isinstance(output, string_types):\n",
    "        output_str = output\n",
    "    else:\n",
    "        output_str = bytes_to_str(output)\n",
    "    output_lines = output_str.split('\\n')\n",
    "    formatted_output = '\\n'.join([prefix + line for line in output_lines if len(line) > 0]) + '\\n'\n",
    "    output_box.value += formatted_output\n",
    "    output_box.scroll_to_bottom()\n",
    "    \n",
    "def has_user_exited():\n",
    "    return not console_container.visible\n",
    "\n",
    "def handle_input(sender):\n",
    "    sender.disabled = True\n",
    "    try:\n",
    "        command = sender.value\n",
    "        sender.value = ''\n",
    "        run_command(command, append_output=append_output, has_user_exited=has_user_exited)\n",
    "    finally:\n",
    "        sender.disabled = False\n",
    "        \n",
    "input_box.on_submit(handle_input)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Create the button that will be used to display and hide the console.  Display both the console container and the new button used to toggle it."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "toggle_button = widgets.Button(description=\"Start Console\")\n",
    "def toggle_console(sender):\n",
    "    console_container.visible = not console_container.visible\n",
    "    if console_container.visible:\n",
    "        toggle_button.description=\"Stop Console\"\n",
    "        input_box.disabled = False\n",
    "    else:\n",
    "        toggle_button.description=\"Start Console\"\n",
    "toggle_button.on_click(toggle_console)\n",
    "\n",
    "display(toggle_button)\n",
    "display(console_container)"
   ]
  }
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