diff --git a/002-basic-control-structures/Python Course - 002a - And so we begin.ipynb b/002-basic-control-structures/Python Course - 002a - And so we begin.ipynb
index 42250fb..fe6f91c 100644
--- a/002-basic-control-structures/Python Course - 002a - And so we begin.ipynb	
+++ b/002-basic-control-structures/Python Course - 002a - And so we begin.ipynb	
@@ -209,17 +209,6 @@
     "## Straw Polls"
    ]
   },
-  {
-   "cell_type": "markdown",
-   "metadata": {
-    "slideshow": {
-     "slide_type": "fragment"
-    }
-   },
-   "source": [
-    "* https://www.strawpoll.me/20175488"
-   ]
-  },
   {
    "cell_type": "markdown",
    "metadata": {
@@ -228,7 +217,7 @@
     }
    },
    "source": [
-    " - when you have completed an exercise, vote Yes on this poll"
+    " - when you have completed an exercise, raise a hand"
    ]
   },
   {
@@ -239,18 +228,7 @@
     }
    },
    "source": [
-    "* you can vote again at each exercise"
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "metadata": {
-    "slideshow": {
-     "slide_type": "notes"
-    }
-   },
-   "source": [
-    "* you can vote No, if you reckon I've miscounted"
+    "* we will make sure all hands are down at the start of the exercise"
    ]
   },
   {
@@ -323,7 +301,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.3"
+   "version": "3.7.6"
   },
   "livereveal": {
    "theme": "beige",
diff --git a/019-git/.gitignore b/019-git/.gitignore
index 8675f85..b70fafd 100644
--- a/019-git/.gitignore
+++ b/019-git/.gitignore
@@ -1,4 +1,5 @@
 .ipynb_checkpoints
 /example.py
 /Introduction to git.ipynb
-/.gitignore
\ No newline at end of file
+/.gitignore
+/Introduction to git rebasing.ipynb
\ No newline at end of file
diff --git a/019-git/test/example.py b/019-git/test/example.py
index ebb98a8..d146d91 100644
--- a/019-git/test/example.py
+++ b/019-git/test/example.py
@@ -13,4 +13,4 @@ def reverse(text):
 if __name__ == "__main__":
     print(capitalize("testing"))
     print(capitalize(['a', 'b', ' ', 'c']))
-    print(reverse("Testing"))
\ No newline at end of file
+    print(reverse("Testing"))
diff --git a/021-conical/Alchemy - A Sequel.ipynb b/021-conical/Alchemy - A Sequel.ipynb
index 933372e..c173f6f 100644
--- a/021-conical/Alchemy - A Sequel.ipynb	
+++ b/021-conical/Alchemy - A Sequel.ipynb	
@@ -354,9 +354,9 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "PythonCourse",
+   "display_name": "Python 3",
    "language": "python",
-   "name": "pythoncourse"
+   "name": "python3"
   },
   "language_info": {
    "codemirror_mode": {
@@ -368,7 +368,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.3"
+   "version": "3.7.6"
   }
  },
  "nbformat": 4,
diff --git a/022-burette/A Magnum of Opera.ipynb b/022-burette/A Magnum of Opera.ipynb
index 3523fb0..a9323e3 100644
--- a/022-burette/A Magnum of Opera.ipynb	
+++ b/022-burette/A Magnum of Opera.ipynb	
@@ -68,7 +68,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
+   "execution_count": 52,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -80,38 +80,43 @@
     "    # Called when you call the function\n",
     "    def __call__(self, *args):\n",
     "        original_result = self._f(*args)\n",
-    "        return str(original_result)"
+    "        return float(original_result)"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": 55,
    "metadata": {},
    "outputs": [],
    "source": [
     "@StringifyResult\n",
     "def add_numbers(a, b):\n",
-    "    return a + b"
+    "    return a + b\n",
+    "\n",
+    "@StringifyResult\n",
+    "def double_numbers(a):\n",
+    "    return 2 * a"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 56,
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "'4'"
+       "6.0"
       ]
      },
-     "execution_count": 6,
+     "execution_count": 56,
      "metadata": {},
      "output_type": "execute_result"
     }
    ],
    "source": [
-    "add_numbers(1, 3)"
+    "add_numbers(1, 3)\n",
+    "double_numbers(3)"
    ]
   },
   {
@@ -123,7 +128,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 57,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -139,7 +144,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": 58,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -150,7 +155,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": 59,
    "metadata": {},
    "outputs": [
     {
@@ -159,7 +164,7 @@
        "'4'"
       ]
      },
-     "execution_count": 11,
+     "execution_count": 59,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -215,7 +220,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 12,
+   "execution_count": 60,
    "metadata": {},
    "outputs": [
     {
@@ -224,7 +229,7 @@
        "{'c': 4, 'a': 4, 'b': 8}"
       ]
      },
-     "execution_count": 12,
+     "execution_count": 60,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -249,7 +254,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
+   "execution_count": 62,
    "metadata": {},
    "outputs": [
     {
@@ -258,7 +263,7 @@
        "{'c': 4, 'a': 4, 'b': 8}"
       ]
      },
-     "execution_count": 14,
+     "execution_count": 62,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -281,7 +286,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 29,
+   "execution_count": 63,
    "metadata": {},
    "outputs": [
     {
@@ -297,7 +302,7 @@
        "{'c': 4, 'a': 4, 'b': 8}"
       ]
      },
-     "execution_count": 29,
+     "execution_count": 63,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -400,16 +405,16 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 31,
+   "execution_count": 64,
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "<coroutine object my_asynchronous_function at 0x7f006a7f3200>"
+       "<coroutine object my_asynchronous_function at 0x7f006a7f3b00>"
       ]
      },
-     "execution_count": 31,
+     "execution_count": 64,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -427,7 +432,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 39,
+   "execution_count": 67,
    "metadata": {},
    "outputs": [
     {
@@ -436,7 +441,7 @@
        "3"
       ]
      },
-     "execution_count": 39,
+     "execution_count": 67,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -459,7 +464,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 48,
+   "execution_count": 69,
    "metadata": {},
    "outputs": [
     {
@@ -531,7 +536,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 12,
+   "execution_count": 76,
    "metadata": {
     "hideCode": false,
     "hidePrompt": false
@@ -541,25 +546,27 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "Requirement already satisfied: findspark in /opt/conda/lib/python3.7/site-packages (1.4.2)\n",
-      "Requirement already satisfied: cassandra-driver in /opt/conda/lib/python3.7/site-packages (3.24.0)\n",
-      "Requirement already satisfied: flask-cqlalchemy in /opt/conda/lib/python3.7/site-packages (1.2.0)\n",
+      "Collecting findspark\n",
+      "  Using cached findspark-1.4.2-py2.py3-none-any.whl (4.2 kB)\n",
+      "Collecting cassandra-driver\n",
+      "  Using cached cassandra_driver-3.24.0-cp37-cp37m-manylinux1_x86_64.whl (3.8 MB)\n",
+      "Collecting flask-cqlalchemy\n",
+      "  Using cached Flask_CQLAlchemy-1.2.0-py2.py3-none-any.whl (4.3 kB)\n",
       "Collecting flask\n",
-      "  Downloading Flask-1.1.2-py2.py3-none-any.whl (94 kB)\n",
-      "\u001b[K     |████████████████████████████████| 94 kB 2.7 MB/s eta 0:00:011\n",
-      "\u001b[?25hRequirement already satisfied: geomet<0.3,>=0.1 in /opt/conda/lib/python3.7/site-packages (from cassandra-driver) (0.2.1.post1)\n",
+      "  Using cached Flask-1.1.2-py2.py3-none-any.whl (94 kB)\n",
+      "Collecting geomet<0.3,>=0.1\n",
+      "  Using cached geomet-0.2.1.post1-py3-none-any.whl (18 kB)\n",
       "Requirement already satisfied: six>=1.9 in /opt/conda/lib/python3.7/site-packages (from cassandra-driver) (1.15.0)\n",
-      "Requirement already satisfied: blist in /opt/conda/lib/python3.7/site-packages (from flask-cqlalchemy) (1.3.6)\n",
-      "Collecting itsdangerous>=0.24\n",
-      "  Downloading itsdangerous-1.1.0-py2.py3-none-any.whl (16 kB)\n",
+      "Processing /home/jovyan/.cache/pip/wheels/50/2c/17/ae6047bdc296d26322607ef96f49bc0c93b60def0a6dbd258d/blist-1.3.6-cp37-cp37m-linux_x86_64.whl\n",
       "Requirement already satisfied: Jinja2>=2.10.1 in /opt/conda/lib/python3.7/site-packages (from flask) (2.11.2)\n",
       "Requirement already satisfied: click>=5.1 in /opt/conda/lib/python3.7/site-packages (from flask) (7.1.2)\n",
+      "Collecting itsdangerous>=0.24\n",
+      "  Using cached itsdangerous-1.1.0-py2.py3-none-any.whl (16 kB)\n",
       "Collecting Werkzeug>=0.15\n",
-      "  Downloading Werkzeug-1.0.1-py2.py3-none-any.whl (298 kB)\n",
-      "\u001b[K     |████████████████████████████████| 298 kB 7.3 MB/s eta 0:00:01\n",
-      "\u001b[?25hRequirement already satisfied: MarkupSafe>=0.23 in /opt/conda/lib/python3.7/site-packages (from Jinja2>=2.10.1->flask) (1.1.1)\n",
-      "Installing collected packages: itsdangerous, Werkzeug, flask\n",
-      "Successfully installed Werkzeug-1.0.1 flask-1.1.2 itsdangerous-1.1.0\n"
+      "  Using cached Werkzeug-1.0.1-py2.py3-none-any.whl (298 kB)\n",
+      "Requirement already satisfied: MarkupSafe>=0.23 in /opt/conda/lib/python3.7/site-packages (from Jinja2>=2.10.1->flask) (1.1.1)\n",
+      "Installing collected packages: findspark, geomet, cassandra-driver, blist, flask-cqlalchemy, itsdangerous, Werkzeug, flask\n",
+      "Successfully installed Werkzeug-1.0.1 blist-1.3.6 cassandra-driver-3.24.0 findspark-1.4.2 flask-1.1.2 flask-cqlalchemy-1.2.0 geomet-0.2.1.post1 itsdangerous-1.1.0\n"
      ]
     }
    ],
@@ -569,7 +576,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 77,
    "metadata": {
     "hideCode": false,
     "hidePrompt": false
@@ -582,7 +589,7 @@
       "  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current\n",
       "                                 Dload  Upload   Total   Spent    Left  Speed\n",
       "  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0\n",
-      "100 8340k  100 8340k    0     0  4398k      0  0:00:01  0:00:01 --:--:-- 7385k\n"
+      "100 8340k  100 8340k    0     0  70.2M      0 --:--:-- --:--:-- --:--:-- 70.2M\n"
      ]
     }
    ],
@@ -599,7 +606,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": 80,
    "metadata": {
     "hideCode": false,
     "hidePrompt": false
@@ -739,7 +746,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
+   "execution_count": 81,
    "metadata": {
     "hideCode": false,
     "hidePrompt": false
@@ -751,7 +758,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": 82,
    "metadata": {
     "hideCode": false,
     "hidePrompt": false
@@ -778,7 +785,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 72,
    "metadata": {
     "hideCode": false,
     "hidePrompt": false
@@ -790,7 +797,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 28,
+   "execution_count": 83,
    "metadata": {
     "hideCode": false,
     "hidePrompt": false