diff --git a/11.exceptions.ipynb b/11.exceptions.ipynb
index 60101e9..f5e8d9a 100644
--- a/11.exceptions.ipynb
+++ b/11.exceptions.ipynb
@@ -235,18 +235,21 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": 5,
    "id": "5022b7c8-a19f-45cb-9d40-58abc48de961",
    "metadata": {
     "tags": []
    },
    "outputs": [
     {
-     "ename": "SyntaxError",
-     "evalue": "expected 'except' or 'finally' block (572013031.py, line 6)",
+     "ename": "NameError",
+     "evalue": "name 'd' is not defined",
      "output_type": "error",
      "traceback": [
-      "\u001b[0;36m  Cell \u001b[0;32mIn[10], line 6\u001b[0;36m\u001b[0m\n\u001b[0;31m    print(\"hello\")\u001b[0m\n\u001b[0m    ^\u001b[0m\n\u001b[0;31mSyntaxError\u001b[0m\u001b[0;31m:\u001b[0m expected 'except' or 'finally' block\n"
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mNameError\u001b[0m                                 Traceback (most recent call last)",
+      "Cell \u001b[0;32mIn[5], line 5\u001b[0m\n\u001b[1;32m      3\u001b[0m     b \u001b[38;5;241m=\u001b[39m \u001b[38;5;241m0\u001b[39m\n\u001b[1;32m      4\u001b[0m     \u001b[38;5;66;03m#c = a / b\u001b[39;00m\n\u001b[0;32m----> 5\u001b[0m     \u001b[38;5;28mprint\u001b[39m(\u001b[43md\u001b[49m)\n\u001b[1;32m      6\u001b[0m     \u001b[38;5;28mprint\u001b[39m(\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mlast line of try\u001b[39m\u001b[38;5;124m\"\u001b[39m)\n\u001b[1;32m      7\u001b[0m \u001b[38;5;28;01mexcept\u001b[39;00m \u001b[38;5;167;01mZeroDivisionError\u001b[39;00m:\n",
+      "\u001b[0;31mNameError\u001b[0m: name 'd' is not defined"
      ]
     }
    ],
@@ -254,11 +257,14 @@
     "try:\n",
     "    a = 3\n",
     "    b = 0\n",
-    "    c = a / b\n",
+    "    #c = a / b\n",
+    "    print(d)\n",
     "    print(\"last line of try\")\n",
     "except ZeroDivisionError:\n",
     "    c = 0\n",
     "    print(f\"can't divide by zero, set c = {c}\")\n",
+    "#except NameError:\n",
+    "#    print(\"used unknown name\")\n",
     "print(\"and then this happens\")"
    ]
   },
@@ -274,7 +280,7 @@
     "```python\n",
     "# multiple except blocks for different behaviors\n",
     "try:\n",
-    "    something():\n",
+    "    something()\n",
     "except ValueError:\n",
     "    ...\n",
     "except IndexError:\n",
@@ -284,7 +290,7 @@
     "```python\n",
     "# one block w/ multiple types in a tuple\n",
     "try:\n",
-    "    something()\n",
+    "    somthing()\n",
     "except (ValueError, IndexError, KeyError):  # tuple of return values\n",
     "    ...\n",
     "```\n",
@@ -293,9 +299,10 @@
     "# base exception type, use sparingly\n",
     "try:\n",
     "    something()\n",
+    "except ArithmeticError:   # catches all errors derived from ArithmeticError\n",
+    "    ...\n",
     "except Exception:   # catches all runtime exceptions\n",
     "    ...\n",
-    "except ArithmeticError:   # catches all errors derived from ArithmeticError\n",
     "```\n",
     "\n",
     "\n",
@@ -328,7 +335,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 12,
+   "execution_count": 7,
    "id": "fd6d0e12-eae2-466e-8536-db5d246091f0",
    "metadata": {},
    "outputs": [],
@@ -341,7 +348,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": 20,
    "id": "58c691a9-14ed-4fe1-9b0d-eb9b52a4d44d",
    "metadata": {},
    "outputs": [
@@ -351,7 +358,7 @@
        "9"
       ]
      },
-     "execution_count": 10,
+     "execution_count": 20,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -362,25 +369,42 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": 27,
    "id": "5fd8e7ee-53c6-4cd1-8748-cd66f06da9ac",
    "metadata": {},
    "outputs": [
     {
-     "ename": "ValueError",
-     "evalue": "f requires a positive argument",
-     "output_type": "error",
-     "traceback": [
-      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
-      "\u001b[0;31mValueError\u001b[0m                                Traceback (most recent call last)",
-      "Cell \u001b[0;32mIn[11], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43mf\u001b[49m\u001b[43m(\u001b[49m\u001b[38;5;241;43m-\u001b[39;49m\u001b[38;5;241;43m1\u001b[39;49m\u001b[43m)\u001b[49m\n",
-      "Cell \u001b[0;32mIn[9], line 3\u001b[0m, in \u001b[0;36mf\u001b[0;34m(positive)\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[38;5;28;01mdef\u001b[39;00m \u001b[38;5;21mf\u001b[39m(positive):\n\u001b[1;32m      2\u001b[0m     \u001b[38;5;28;01mif\u001b[39;00m positive \u001b[38;5;241m<\u001b[39m \u001b[38;5;241m0\u001b[39m:\n\u001b[0;32m----> 3\u001b[0m         \u001b[38;5;28;01mraise\u001b[39;00m \u001b[38;5;167;01mValueError\u001b[39;00m(\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mf requires a positive argument\u001b[39m\u001b[38;5;124m\"\u001b[39m)\n\u001b[1;32m      4\u001b[0m     \u001b[38;5;28;01mreturn\u001b[39;00m positive \u001b[38;5;241m*\u001b[39m positive\n",
-      "\u001b[0;31mValueError\u001b[0m: f requires a positive argument"
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "got an error:  f requires a positive argument\n"
      ]
     }
    ],
    "source": [
-    "f(-1)"
+    "try:\n",
+    "    y = f(-1)\n",
+    "except ValueError as exc:\n",
+    "    y = 0\n",
+    "    print(\"got an error: \", exc)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 26,
+   "id": "769fb253-ae47-4e47-a6fd-9a37e1ef3d5e",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "0\n"
+     ]
+    }
+   ],
+   "source": [
+    "print(y)"
    ]
   },
   {
@@ -404,6 +428,7 @@
    "source": [
     "class InvalidColor(Exception):\n",
     "    \"\"\" This exception is raised when an invalid color is passed. \"\"\"\n",
+    "    pass\n",
     "\n",
     "VALID_COLORS = (...)\n",
     "\n",
@@ -448,7 +473,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
+   "execution_count": 30,
    "id": "320d3309-099a-4f2e-9096-983101bfc157",
    "metadata": {},
    "outputs": [
@@ -456,21 +481,22 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "got a value error error message\n",
+      "else executed\n",
       "always prints at the end\n"
      ]
     }
    ],
    "source": [
     "try:\n",
-    "    #pass\n",
-    "    raise ValueError(\"error message\")\n",
+    "   1 / 2\n",
     "except ValueError as e:\n",
-    "    print(\"got a value error\", e)\n",
+    "    print(\"got a value error:\", e)\n",
+    "except Exception as e:\n",
+    "    print(\"got some other error:\", type(e), e)\n",
     "else:\n",
-    "    print(\"no exception raised\")\n",
+    "    print(\"else executed\")\n",
     "finally:\n",
-    "    print(\"always prints at the end\")"
+    "    print(\"always prints at the end\")\n"
    ]
   },
   {
diff --git a/12.inheritance.ipynb b/12.inheritance.ipynb
index 968aafd..ccdbd21 100644
--- a/12.inheritance.ipynb
+++ b/12.inheritance.ipynb
@@ -14,7 +14,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
+   "execution_count": 1,
    "id": "feaa69a2",
    "metadata": {
     "tags": []
@@ -38,6 +38,7 @@
     "        self.year = 1\n",
     "        self.major = \"Undeclared\"\n",
     "        self.course_grades = {}\n",
+    "        self.extracurriculars = []\n",
     "        \n",
     "    def add_grade(self, course_name, grade):\n",
     "        self.course_grades[course_name] = grade\n",
@@ -55,7 +56,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": 45,
    "id": "c410fb1d",
    "metadata": {
     "tags": []
@@ -70,7 +71,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": 46,
    "id": "f9deab26",
    "metadata": {
     "tags": []
@@ -80,8 +81,8 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "Student(name=Adam, id=1, gpa=0)\n",
-      "Student(name=Beth, id=2, gpa=3.65)\n"
+      "Student(name=Adam, id=8, gpa=0)\n",
+      "Student(name=Beth, id=9, gpa=3.65)\n"
      ]
     }
    ],
@@ -168,7 +169,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 12,
+   "execution_count": 49,
    "id": "47f7dfc9",
    "metadata": {
     "tags": []
@@ -187,7 +188,8 @@
     "    \n",
     "    # overrides parent's add_grade\n",
     "    def add_grade(self, course_name, grade):\n",
-    "        print(\"Sorry, you cannot add grades to Alums\")\n",
+    "        raise NotImplementedError(\"cannot add grades to Alum\")\n",
+    "        #print(\"Sorry, you cannot add grades to Alums\")\n",
     "        # we choose not call super().add_grade here\n",
     "    \n",
     "    # overrides parent's __repr__\n",
@@ -200,7 +202,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": 51,
    "id": "4811b0fd",
    "metadata": {
     "tags": []
@@ -210,9 +212,8 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "Student(name=Charlie, id=3, gpa=0) is an alum\n",
-      "6 years since graduation\n",
-      "Sorry, you cannot add grades to Alums\n"
+      "Student(name=Charlie, id=13, gpa=0) is an alum\n",
+      "6 years since graduation\n"
      ]
     },
     {
@@ -221,7 +222,7 @@
        "0"
       ]
      },
-     "execution_count": 13,
+     "execution_count": 51,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -230,13 +231,13 @@
     "alum1 = Alum(\"Charlie\", 2016)\n",
     "print(alum1)\n",
     "print(alum1.years_since_graduation(2022), \"years since graduation\")\n",
-    "alum1.add_grade(\"Python\", \"B\")\n",
+    "#alum1.add_grade(\"Python\", \"B\")\n",
     "alum1.gpa"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 16,
+   "execution_count": 54,
    "id": "18a75666-9986-4e2b-9d55-ec0e0b9e930d",
    "metadata": {
     "tags": []
@@ -248,13 +249,27 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 56,
    "id": "b6719a36-b827-4373-87e0-23714438b83f",
    "metadata": {
     "tags": []
    },
-   "outputs": [],
-   "source": []
+   "outputs": [
+    {
+     "ename": "TypeError",
+     "evalue": "unsupported operand type(s) for +: 'Alum' and 'Alum'",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
+      "Cell \u001b[0;32mIn[56], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43malum1\u001b[49m\u001b[43m \u001b[49m\u001b[38;5;241;43m+\u001b[39;49m\u001b[43m \u001b[49m\u001b[43malum2\u001b[49m\n",
+      "\u001b[0;31mTypeError\u001b[0m: unsupported operand type(s) for +: 'Alum' and 'Alum'"
+     ]
+    }
+   ],
+   "source": [
+    "alum1 + alum2"
+   ]
   },
   {
    "cell_type": "markdown",
@@ -278,7 +293,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": 8,
    "id": "a46d5b02",
    "metadata": {
     "tags": []
@@ -290,7 +305,7 @@
        "True"
       ]
      },
-     "execution_count": 13,
+     "execution_count": 8,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -301,12 +316,23 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 9,
    "id": "d3596a45-2c00-4541-910d-08251d3f9c5f",
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "True"
+      ]
+     },
+     "execution_count": 9,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "# same as?\n",
     "type(7) == int"
@@ -314,7 +340,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 10,
    "id": "eaa8b6db-e7df-4137-b4c8-67dfa0be06d5",
    "metadata": {},
    "outputs": [
@@ -324,7 +350,7 @@
        "False"
       ]
      },
-     "execution_count": 6,
+     "execution_count": 10,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -335,7 +361,28 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 57,
+   "id": "9cfc8480-ecca-4f80-9dfe-70a655bc5b3c",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "True"
+      ]
+     },
+     "execution_count": 57,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "isinstance(7,  object)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 62,
    "id": "0e50f7bc-541e-4fec-9cd6-ad708f312831",
    "metadata": {},
    "outputs": [
@@ -345,32 +392,75 @@
        "True"
       ]
      },
-     "execution_count": 7,
+     "execution_count": 62,
      "metadata": {},
      "output_type": "execute_result"
     }
    ],
    "source": [
     "# isinstance checks the inheritance hierarchy \n",
-    "isinstance(7, object)"
+    "isinstance(alum2, object)"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 64,
+   "id": "34e491d5-ac5c-4dc9-b059-491e0f0f73b0",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "False"
+      ]
+     },
+     "execution_count": 64,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "type(alum2) == Student"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 65,
    "id": "cd55fd8d",
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "True"
+      ]
+     },
+     "execution_count": 65,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "isinstance([1, 2, 3], list)"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 17,
    "id": "feb9f2ac",
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "True"
+      ]
+     },
+     "execution_count": 17,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "s1 = Student(\"Sarah\")\n",
     "isinstance(s1, Student)"
@@ -378,10 +468,21 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 18,
    "id": "e6a2f3b1",
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "True"
+      ]
+     },
+     "execution_count": 18,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "# child classes are instances of parent types\n",
     "alum1 = Alum(\"Charlie\", 2016)\n",
@@ -390,10 +491,21 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 19,
    "id": "8f759efb",
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "False"
+      ]
+     },
+     "execution_count": 19,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "# but not vice-versa\n",
     "isinstance(s1, Alum)"
@@ -401,7 +513,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 15,
+   "execution_count": 20,
    "id": "1d52b927",
    "metadata": {
     "tags": []
@@ -414,7 +526,7 @@
      "traceback": [
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
       "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
-      "Cell \u001b[0;32mIn[15], line 2\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[38;5;66;03m# takes class names\u001b[39;00m\n\u001b[0;32m----> 2\u001b[0m \u001b[38;5;28;43missubclass\u001b[39;49m\u001b[43m(\u001b[49m\u001b[43malum1\u001b[49m\u001b[43m,\u001b[49m\u001b[43m \u001b[49m\u001b[43mStudent\u001b[49m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn[20], line 2\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[38;5;66;03m# takes class names\u001b[39;00m\n\u001b[0;32m----> 2\u001b[0m \u001b[38;5;28;43missubclass\u001b[39;49m\u001b[43m(\u001b[49m\u001b[43malum1\u001b[49m\u001b[43m,\u001b[49m\u001b[43m \u001b[49m\u001b[43mStudent\u001b[49m\u001b[43m)\u001b[49m\n",
       "\u001b[0;31mTypeError\u001b[0m: issubclass() arg 1 must be a class"
      ]
     }
@@ -426,7 +538,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 16,
+   "execution_count": 22,
    "id": "a71ee1cb",
    "metadata": {
     "tags": []
@@ -435,16 +547,16 @@
     {
      "data": {
       "text/plain": [
-       "False"
+       "True"
       ]
      },
-     "execution_count": 16,
+     "execution_count": 22,
      "metadata": {},
      "output_type": "execute_result"
     }
    ],
    "source": [
-    "issubclass(Student, Alum)"
+    "issubclass(Alum, Student)"
    ]
   },
   {
@@ -478,7 +590,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
+   "execution_count": 66,
    "id": "1d4e00ca",
    "metadata": {
     "tags": []
@@ -488,7 +600,7 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "Help on Alum in module __main__ object:\n",
+      "Help on class Alum in module __main__:\n",
       "\n",
       "class Alum(Student)\n",
       " |  Alum(name, grad_year)\n",
@@ -529,13 +641,100 @@
       " |  ----------------------------------------------------------------------\n",
       " |  Data and other attributes inherited from Student:\n",
       " |  \n",
-      " |  next_id_counter = 5\n",
+      " |  next_id_counter = 16\n",
       "\n"
      ]
     }
    ],
    "source": [
-    "help(alum1)"
+    "help(Alum)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 67,
+   "id": "45f732f0-2036-416e-a44c-70b99b18a960",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "(__main__.Alum, __main__.Student, object)"
+      ]
+     },
+     "execution_count": 67,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "Alum.__mro__"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 23,
+   "id": "592f6930-cf36-4ec1-a4f3-ea1947fa7173",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Help on class super in module builtins:\n",
+      "\n",
+      "class super(object)\n",
+      " |  super() -> same as super(__class__, <first argument>)\n",
+      " |  super(type) -> unbound super object\n",
+      " |  super(type, obj) -> bound super object; requires isinstance(obj, type)\n",
+      " |  super(type, type2) -> bound super object; requires issubclass(type2, type)\n",
+      " |  Typical use to call a cooperative superclass method:\n",
+      " |  class C(B):\n",
+      " |      def meth(self, arg):\n",
+      " |          super().meth(arg)\n",
+      " |  This works for class methods too:\n",
+      " |  class C(B):\n",
+      " |      @classmethod\n",
+      " |      def cmeth(cls, arg):\n",
+      " |          super().cmeth(arg)\n",
+      " |  \n",
+      " |  Methods defined here:\n",
+      " |  \n",
+      " |  __get__(self, instance, owner=None, /)\n",
+      " |      Return an attribute of instance, which is of type owner.\n",
+      " |  \n",
+      " |  __getattribute__(self, name, /)\n",
+      " |      Return getattr(self, name).\n",
+      " |  \n",
+      " |  __init__(self, /, *args, **kwargs)\n",
+      " |      Initialize self.  See help(type(self)) for accurate signature.\n",
+      " |  \n",
+      " |  __repr__(self, /)\n",
+      " |      Return repr(self).\n",
+      " |  \n",
+      " |  ----------------------------------------------------------------------\n",
+      " |  Static methods defined here:\n",
+      " |  \n",
+      " |  __new__(*args, **kwargs) from builtins.type\n",
+      " |      Create and return a new object.  See help(type) for accurate signature.\n",
+      " |  \n",
+      " |  ----------------------------------------------------------------------\n",
+      " |  Data descriptors defined here:\n",
+      " |  \n",
+      " |  __self__\n",
+      " |      the instance invoking super(); may be None\n",
+      " |  \n",
+      " |  __self_class__\n",
+      " |      the type of the instance invoking super(); may be None\n",
+      " |  \n",
+      " |  __thisclass__\n",
+      " |      the class invoking super()\n",
+      "\n"
+     ]
+    }
+   ],
+   "source": [
+    "help(super)"
    ]
   },
   {
@@ -584,12 +783,18 @@
     "    def __init__(self,x,y):\n",
     "        self.x = x\n",
     "        self.y = y  \n",
+    "\n",
+    "    def dot_product(self, other):\n",
+    "        ...\n",
     "        \n",
     "class Vec3:\n",
     "    def __init__(self,x,y,z):\n",
     "        self.x = x\n",
     "        self.y = y  \n",
-    "        self.z = z "
+    "        self.z = z \n",
+    "\n",
+    "     def dot(self, other):\n",
+    "        ..."
    ]
   },
   {
@@ -606,7 +811,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 43,
+   "execution_count": 72,
    "id": "a2cddb6d",
    "metadata": {
     "tags": []
@@ -615,7 +820,10 @@
    "source": [
     "from abc import ABC, abstractmethod\n",
     "\n",
-    "class Vector(ABC):    \n",
+    "class Vector(ABC):  \n",
+    "    def print_x(self):\n",
+    "        print(self.x)\n",
+    "    \n",
     "    @abstractmethod\n",
     "    def dot_product(self, other):\n",
     "        pass"
@@ -623,7 +831,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 44,
+   "execution_count": 71,
    "id": "a32d26a8",
    "metadata": {
     "tags": []
@@ -631,13 +839,13 @@
    "outputs": [
     {
      "ename": "TypeError",
-     "evalue": "Can't instantiate abstract class Vector with abstract method dot_product",
+     "evalue": "Can't instantiate abstract class Vector with abstract methods __repr__, dot_product",
      "output_type": "error",
      "traceback": [
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
       "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
-      "Cell \u001b[0;32mIn[44], line 2\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[38;5;66;03m# we can't instantiate abstract classes\u001b[39;00m\n\u001b[0;32m----> 2\u001b[0m v \u001b[38;5;241m=\u001b[39m \u001b[43mVector\u001b[49m\u001b[43m(\u001b[49m\u001b[43m)\u001b[49m\n",
-      "\u001b[0;31mTypeError\u001b[0m: Can't instantiate abstract class Vector with abstract method dot_product"
+      "Cell \u001b[0;32mIn[71], line 2\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[38;5;66;03m# we can't instantiate abstract classes\u001b[39;00m\n\u001b[0;32m----> 2\u001b[0m v \u001b[38;5;241m=\u001b[39m \u001b[43mVector\u001b[49m\u001b[43m(\u001b[49m\u001b[43m)\u001b[49m\n",
+      "\u001b[0;31mTypeError\u001b[0m: Can't instantiate abstract class Vector with abstract methods __repr__, dot_product"
      ]
     }
    ],
@@ -648,7 +856,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 45,
+   "execution_count": 75,
    "id": "5a9ae047",
    "metadata": {
     "tags": []
@@ -675,7 +883,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 46,
+   "execution_count": 76,
    "id": "e25536d1",
    "metadata": {
     "tags": []
@@ -710,6 +918,24 @@
     "print(isinstance(v3a, Vector))"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": 78,
+   "id": "69ac4241-b251-4485-9ba9-3b0348d82c34",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "1\n"
+     ]
+    }
+   ],
+   "source": [
+    "v2a.print_x()"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": 47,
@@ -762,7 +988,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 53,
+   "execution_count": 79,
    "id": "4f98cf62-52da-4072-bf5a-da7de3ad9a98",
    "metadata": {
     "tags": []
@@ -793,7 +1019,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 54,
+   "execution_count": 43,
    "id": "8faf9c31-33e4-42f1-a8e8-8b72a7f1f96f",
    "metadata": {
     "tags": []
@@ -803,7 +1029,29 @@
     "wrench = InventoryItem(\"Wrench\", 12.95, 10)\n",
     "hammer = InventoryItem(\"Hammer\", 16, 8)\n",
     "nails = InventoryItem(\"Nails\", 0.03, 1000)\n",
-    "saw = InventoryItem(\"Saw\", 99)"
+    "saw = InventoryItem(\"Saw\", 99)\n",
+    "saw2 = InventoryItem(\"Saw\", 99)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 44,
+   "id": "94f14911-335c-4097-8658-b9a30a70d53b",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "True"
+      ]
+     },
+     "execution_count": 44,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "saw == saw2"
    ]
   },
   {
@@ -884,7 +1132,9 @@
    "id": "73195ac4-c0cc-4f8b-8852-2b63168e1713",
    "metadata": {},
    "outputs": [],
-   "source": []
+   "source": [
+    "functools."
+   ]
   }
  ],
  "metadata": {
diff --git a/13.python-data-model.ipynb b/13.python-data-model.ipynb
index 23a9b8e..0e84298 100644
--- a/13.python-data-model.ipynb
+++ b/13.python-data-model.ipynb
@@ -35,7 +35,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": 61,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -54,14 +54,14 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 62,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "<__main__.StaticArray object at 0x107899060>\n"
+      "<__main__.StaticArray object at 0x1079a50f0>\n"
      ]
     }
    ],
@@ -72,7 +72,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
+   "execution_count": 63,
    "metadata": {
     "tags": []
    },
@@ -81,7 +81,7 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "<__main__.StaticArray object at 0x107899b70>\n"
+      "<__main__.StaticArray object at 0x107b550f0>\n"
      ]
     }
    ],
@@ -92,7 +92,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 4,
+   "execution_count": 64,
    "metadata": {},
    "outputs": [
     {
@@ -126,7 +126,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": 65,
    "metadata": {
     "tags": []
    },
@@ -173,7 +173,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 67,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -214,7 +214,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 68,
    "metadata": {},
    "outputs": [
     {
@@ -223,7 +223,7 @@
        "4"
       ]
      },
-     "execution_count": 7,
+     "execution_count": 68,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -235,7 +235,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": 70,
    "metadata": {},
    "outputs": [
     {
@@ -244,7 +244,7 @@
        "True"
       ]
      },
-     "execution_count": 8,
+     "execution_count": 70,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -256,27 +256,27 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
+   "execution_count": 72,
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "1"
+       "True"
       ]
      },
-     "execution_count": 9,
+     "execution_count": 72,
      "metadata": {},
      "output_type": "execute_result"
     }
    ],
    "source": [
-    "sa[0]"
+    "sa[3]"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": 73,
    "metadata": {},
    "outputs": [
     {
@@ -286,8 +286,8 @@
      "traceback": [
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
       "\u001b[0;31mIndexError\u001b[0m                                Traceback (most recent call last)",
-      "Cell \u001b[0;32mIn[10], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43msa\u001b[49m\u001b[43m[\u001b[49m\u001b[38;5;241;43m42\u001b[39;49m\u001b[43m]\u001b[49m \u001b[38;5;241m=\u001b[39m \u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mhello\u001b[39m\u001b[38;5;124m\"\u001b[39m\n",
-      "Cell \u001b[0;32mIn[6], line 29\u001b[0m, in \u001b[0;36mStaticArray.__setitem__\u001b[0;34m(self, index, val)\u001b[0m\n\u001b[1;32m     27\u001b[0m \u001b[38;5;28;01mdef\u001b[39;00m \u001b[38;5;21m__setitem__\u001b[39m(\u001b[38;5;28mself\u001b[39m, index, val):\n\u001b[1;32m     28\u001b[0m     \u001b[38;5;28;01mif\u001b[39;00m index \u001b[38;5;241m>\u001b[39m\u001b[38;5;241m=\u001b[39m \u001b[38;5;28mself\u001b[39m\u001b[38;5;241m.\u001b[39mcapacity \u001b[38;5;129;01mor\u001b[39;00m index \u001b[38;5;241m<\u001b[39m \u001b[38;5;241m-\u001b[39m\u001b[38;5;28mself\u001b[39m\u001b[38;5;241m.\u001b[39mcapacity:\n\u001b[0;32m---> 29\u001b[0m         \u001b[38;5;28;01mraise\u001b[39;00m \u001b[38;5;167;01mIndexError\u001b[39;00m(\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mIndex out of range\u001b[39m\u001b[38;5;124m\"\u001b[39m)\n\u001b[1;32m     30\u001b[0m     \u001b[38;5;28mself\u001b[39m\u001b[38;5;241m.\u001b[39mitems[index] \u001b[38;5;241m=\u001b[39m val\n",
+      "Cell \u001b[0;32mIn[73], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43msa\u001b[49m\u001b[43m[\u001b[49m\u001b[38;5;241;43m42\u001b[39;49m\u001b[43m]\u001b[49m \u001b[38;5;241m=\u001b[39m \u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mhello\u001b[39m\u001b[38;5;124m\"\u001b[39m\n",
+      "Cell \u001b[0;32mIn[67], line 29\u001b[0m, in \u001b[0;36mStaticArray.__setitem__\u001b[0;34m(self, index, val)\u001b[0m\n\u001b[1;32m     27\u001b[0m \u001b[38;5;28;01mdef\u001b[39;00m \u001b[38;5;21m__setitem__\u001b[39m(\u001b[38;5;28mself\u001b[39m, index, val):\n\u001b[1;32m     28\u001b[0m     \u001b[38;5;28;01mif\u001b[39;00m index \u001b[38;5;241m>\u001b[39m\u001b[38;5;241m=\u001b[39m \u001b[38;5;28mself\u001b[39m\u001b[38;5;241m.\u001b[39mcapacity \u001b[38;5;129;01mor\u001b[39;00m index \u001b[38;5;241m<\u001b[39m \u001b[38;5;241m-\u001b[39m\u001b[38;5;28mself\u001b[39m\u001b[38;5;241m.\u001b[39mcapacity:\n\u001b[0;32m---> 29\u001b[0m         \u001b[38;5;28;01mraise\u001b[39;00m \u001b[38;5;167;01mIndexError\u001b[39;00m(\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mIndex out of range\u001b[39m\u001b[38;5;124m\"\u001b[39m)\n\u001b[1;32m     30\u001b[0m     \u001b[38;5;28mself\u001b[39m\u001b[38;5;241m.\u001b[39mitems[index] \u001b[38;5;241m=\u001b[39m val\n",
       "\u001b[0;31mIndexError\u001b[0m: Index out of range"
      ]
     }
@@ -395,7 +395,21 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 12,
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "for i in iterable:\n",
+    "    print(i)\n",
+    "\n",
+    "iterator = iter(iterable)\n",
+    "while True:\n",
+    "    print(next(iterator))"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 56,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -408,6 +422,7 @@
     "        return self\n",
     "\n",
     "    def __next__(self):\n",
+    "        print(f\"next was called, moving {self.current} to {self.current+1}\")\n",
     "        if self.current >= self.n:\n",
     "            raise StopIteration\n",
     "        else:\n",
@@ -420,43 +435,35 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": 59,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "0\n",
-      "1\n",
-      "2\n",
-      "3\n",
-      "4\n"
-     ]
-    },
-    {
-     "ename": "StopIteration",
-     "evalue": "",
-     "output_type": "error",
-     "traceback": [
-      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
-      "\u001b[0;31mStopIteration\u001b[0m                             Traceback (most recent call last)",
-      "Cell \u001b[0;32mIn[13], line 4\u001b[0m\n\u001b[1;32m      2\u001b[0m \u001b[38;5;28;01mfor\u001b[39;00m i \u001b[38;5;129;01min\u001b[39;00m sr:\n\u001b[1;32m      3\u001b[0m     \u001b[38;5;28mprint\u001b[39m(i)\n\u001b[0;32m----> 4\u001b[0m \u001b[38;5;28;43mnext\u001b[39;49m\u001b[43m(\u001b[49m\u001b[43msr\u001b[49m\u001b[43m)\u001b[49m\n",
-      "Cell \u001b[0;32mIn[12], line 11\u001b[0m, in \u001b[0;36mSimpleRange.__next__\u001b[0;34m(self)\u001b[0m\n\u001b[1;32m      9\u001b[0m \u001b[38;5;28;01mdef\u001b[39;00m \u001b[38;5;21m__next__\u001b[39m(\u001b[38;5;28mself\u001b[39m):\n\u001b[1;32m     10\u001b[0m     \u001b[38;5;28;01mif\u001b[39;00m \u001b[38;5;28mself\u001b[39m\u001b[38;5;241m.\u001b[39mcurrent \u001b[38;5;241m>\u001b[39m\u001b[38;5;241m=\u001b[39m \u001b[38;5;28mself\u001b[39m\u001b[38;5;241m.\u001b[39mn:\n\u001b[0;32m---> 11\u001b[0m         \u001b[38;5;28;01mraise\u001b[39;00m \u001b[38;5;167;01mStopIteration\u001b[39;00m\n\u001b[1;32m     12\u001b[0m     \u001b[38;5;28;01melse\u001b[39;00m:\n\u001b[1;32m     13\u001b[0m         \u001b[38;5;28mself\u001b[39m\u001b[38;5;241m.\u001b[39mcurrent \u001b[38;5;241m+\u001b[39m\u001b[38;5;241m=\u001b[39m \u001b[38;5;241m1\u001b[39m\n",
-      "\u001b[0;31mStopIteration\u001b[0m: "
+      "0 0\n",
+      "0 1\n",
+      "0 2\n",
+      "1 0\n",
+      "1 1\n",
+      "1 2\n",
+      "2 0\n",
+      "2 1\n",
+      "2 2\n"
      ]
     }
    ],
    "source": [
-    "sr = SimpleRange(5)\n",
+    "sr = range(3)\n",
     "for i in sr:\n",
-    "    print(i)\n",
-    "next(sr)"
+    "    for j in sr:\n",
+    "        print(i, j)"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
+   "execution_count": 57,
    "metadata": {
     "tags": []
    },
@@ -537,7 +544,7 @@
    "outputs": [],
    "source": [
     "# Adding __iter__ to StaticArray\n",
-    "class StaticArrayIterator:\n",
+    "eclass StaticArrayIterator:\n",
     "    def __init__(self, values):\n",
     "        self.values = values\n",
     "        self.position = 0\n",