      {
       "name": "stdout",
       "output_type": "stream",
       "text": [
        "Empty input\n",
        "One element\n",
        "Two or more elements\n",
        "Success: test_quick_sort\n",
        "\n",
        "Empty input\n",
        "One element\n",
        "Two or more elements\n",
        "Success: test_quick_sort\n",
        "\n"
 
</s> remove     "    if len(data) < 2:\n",
 </s> add     "    if data is None or len(data) < 2:\n", </s> remove    "execution_count": 3,
 </s> add    "execution_count": 2, </s> remove    "execution_count": 4,
 </s> add    "execution_count": 3,
      "None input\n",
      {
       "name": "stdout",
       "output_type": "stream",
       "text": [
      "None input\n",
      "None input\n",
      "None input\n",
      "None input\n",
      "None input\n",
        "Empty input\n",
        "One element\n",
        "Two or more elements\n",
        "Success: test_quick_sort\n",
        "\n"
keep keep keep keep replace replace replace replace 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