      "from __future__ import division\n",
      "\n",
      "\n",
      "def quick_sort(data):\n",
      "    if len(data) < 2:\n",
      "        return data\n",
      "    left = []\n",
      "    right = []\n",
      "    pivot_index = len(data) // 2\n",
      "    pivot_value = data[pivot_index]\n",
 
</s> remove   {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Pythonic-Code\n",
    "\n",
    "The following code from [Stack Overflow](http://stackoverflow.com/questions/18262306/quick-sort-with-python) is very concise, although it might be a little difficult to read:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def quick_sort_alt(arr):\n",
    "    if len(arr) <= 1:\n",
    "        return arr\n",
    "    else:\n",
    "        return quick_sort_alt([x for x in arr[1:] if x < arr[0]]) + [arr[0]] + quick_sort_alt([x for x in arr[1:] if x >= arr[0]])"
   ]
  },
 </s> add  </s> remove     "    try:\n",
    "        test.test_quick_sort(quick_sort_alt)\n",
    "    except NameError:\n",
    "        # Alternate solutions are only defined\n",
    "        # in the solutions file\n",
    "        pass\n",
 </s> add  </s> remove     "    try:\n",
    "        test.test_quick_sort(quick_sort_alt)\n",
    "    except NameError:\n",
    "        # Alternate solutions are only defined\n",
    "        # in the solutions file\n",
    "        pass\n",
 </s> add 
    "    if data is None or len(data) < 2:\n",
      "from __future__ import division\n",
      "\n",
      "\n",
      "def quick_sort(data):\n",
    "    if data is None or len(data) < 2:\n",
      "        return data\n",
      "    left = []\n",
      "    right = []\n",
      "    pivot_index = len(data) // 2\n",
      "    pivot_value = data[pivot_index]\n",
keep keep keep keep replace keep keep keep keep keep
 Polish quicksort challenge and solution

Add None input test case.  Remove difficult to read 'Pythonic' solution.  Update space complexity discussion. 
sorting_searching/quick_sort/quick_sort_solution.ipynb