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    "#range()\n",
    "\n",
    "In this short lecture we will be discussing the range function. We haven't developed a very deep level of knowledge of functions yet, but we can understand the basics of this simple (but extremely useful!) function.\n",
    "\n",
    "range() allows us to create a list of numbers ranging from a starting point *up to* an ending point. We can also specify step size. Lets walk through a few examples:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]"
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "range(0,10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "list"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "x =range(0,10)\n",
    "type(x)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": true
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   "source": [
    "start = 0 #Default\n",
    "stop = 20 \n",
    "x = range(start,stop)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
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   "source": [
    "x"
   ]
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  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Great! Notice how it went *up to* 20, but doesn't actually produce 20. Just like in indexing. What about step size? We can specify that as a third argument:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[0, 2, 4, 6, 8, 10, 12, 14, 16, 18]"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "x = range(start,stop,2)\n",
    "#Show\n",
    "x"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Awesome! Well thats it...or is it?"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### <font color='red'>Python 3 Alert!</font>\n",
    "\n",
    "You might have been wondering, what happens if I want to use a huge range of numbers? Can my computer store that all in memory?\n",
    "\n",
    "Great thinking! This is a dilemma that can be solve with the use of a generator. For a simplified explanation: A generator allows the generation of generated objects that are provided at that instance but does not store every instance generated into memory.\n",
    "\n",
    "This means a generator would not create a list to generate like range() does, but instead provide a one time generation of the numbers in that range. Python 2 has a built-in range generator called xrange(). It is recommended to use xrange() for **for** loops in Python 2. \n",
    "\n",
    "The good news is in Python 3, range() behaves as a generator and you don't need to worry about it. Let's see a quick example with xrange()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {
    "collapsed": false
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   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0\n",
      "1\n",
      "2\n",
      "3\n",
      "4\n",
      "5\n",
      "6\n",
      "7\n",
      "8\n",
      "9\n"
     ]
    }
   ],
   "source": [
    "for num in range(10):\n",
    "    print num"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0\n",
      "1\n",
      "2\n",
      "3\n",
      "4\n",
      "5\n",
      "6\n",
      "7\n",
      "8\n",
      "9\n"
     ]
    }
   ],
   "source": [
    "for num in xrange(10):\n",
    "    print num"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "collapsed": true
   },
   "source": [
    "So the main takeaway here is for Python 2, if you are using range() in a way that you don't need to save the results in a list, use xrange() instead. For Python 3, use range() in any instance.\n",
    "\n",
    "You should now have a good understanding of how to use range() in either version of Python."
   ]
  }
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