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 "metadata": {
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 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "heading",
     "level": 1,
     "metadata": {},
     "source": [
      "Running Code in the IPython Notebook"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "First and foremost, the IPython Notebook is an interactive environment for writing and running code. IPython is capable of running code in a wide range of languages. However, in IPython 2.0, the default kernel runs Python code."
     ]
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Code cells allow you to enter and run Python code"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Run a code cell using `Shift-Enter` or pressing the <button><i class=\"icon-play fa fa-play\"></i></button> button in the toolbar above:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "a = 10"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 1
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "print(a)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "10\n"
       ]
      }
     ],
     "prompt_number": 2
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "There are two other keyboard shortcuts for running code:\n",
      "\n",
      "* `Alt-Enter` runs the current cell and inserts a new one below.\n",
      "* `Ctrl-Enter` run the current cell and enters command mode."
     ]
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Managing the IPython Kernel"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Code is run in a separate process called the IPython Kernel.  The Kernel can be interrupted or restarted.  Try running the following cell and then hit the <button><i class='icon-stop fa fa-stop'></i></button> button in the toolbar above."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "import time\n",
      "time.sleep(10)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "If the Kernel dies you will be prompted to restart it. Here we call the low-level system libc.time routine with the wrong argument via\n",
      "ctypes to segfault the Python interpreter:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "import sys\n",
      "from ctypes import CDLL\n",
      "# This will crash a Linux or Mac system\n",
      "# equivalent calls can be made on Windows\n",
      "dll = 'dylib' if sys.platform == 'darwin' else 'so.6'\n",
      "libc = CDLL(\"libc.%s\" % dll) \n",
      "libc.time(-1)  # BOOM!!"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Cell menu"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "The \"Cell\" menu has a number of menu items for running code in different ways. These includes:\n",
      "\n",
      "* Run and Select Below\n",
      "* Run and Insert Below\n",
      "* Run All\n",
      "* Run All Above\n",
      "* Run All Below"
     ]
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Restarting the kernels"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "The kernel maintains the state of a notebook's computations. You can reset this state by restarting the kernel. This is done by clicking on the <button><i class='icon-repeat'></i></button> in the toolbar above."
     ]
    }
   ],
   "metadata": {}
  }
 ]
}