1 files changed, 49 insertions, 38 deletions

diff --git a/notebooks/python/python_oo.ipynb b/notebooks/python/python_oo.ipynb
index ff48ca0..b56aa26 100644
--- a/notebooks/python/python_oo.ipynb
+++ b/notebooks/python/python_oo.ipynb
@@ -36,11 +36,11 @@
    "id": "be3062ad-9437-4ba2-9975-c2837b0af9dc",
    "metadata": {},
    "source": [
-    "# The big picture - the course so far\n",
+    "# The course so far\n",
     "\n",
     "- Basics: About the language, the Python eco-system, types, modules, functions, scopes, decorators, string formatting\n",
     "\n",
-    "- **Object-oriented programming in Python: How Python \"really works\"**\n",
+    "- **Object-oriented programming in Python - How Python \"really works\": classes and objects, building / extending custom types (classes), inheritance, iterators**\n",
     "\n",
     "- Control flow: if / for / while / try, use of iterators, \"tactical programming\" tips\n",
     "\n",
@@ -78,13 +78,20 @@
     "\n",
     "The following four concepts / principles are presented in most object-oriented programming books:\n",
     "\n",
-    "- separate and hide \"private\" details from the outside world and / or child (inheriting) functionality (*encapsulation*) - supports *separation of concerns*\n",
-    "\n",
     "- separate the interface from its implementation (*abstraction*)\n",
     "\n",
+    "- separate and hide \"private\" details from the outside world and / or child (inheriting) functionality (*encapsulation*) - supports *separation of concerns*\n",
+    "\n",
     "- inherit and extend / adapt existing functionality, through \"is-a\" relationship hierarchy (*inheritance*)\n",
     "\n",
-    "- execute different code / functionality based on the object's place in the hierarchy (polymorphism)"
+    "- execute different code / functionality based on the object's place in the hierarchy (polymorphism)\n",
+    "\n",
+    "\n",
+    "## Difference between *abstraction* and *encapsulation*\n",
+    "\n",
+    "*Abstraction* hides complexity by giving you a more abstract picture, while *encapsulation* hides internal work so that you can change it later.\n",
+    "\n",
+    "*Abstraction* solves problems at the design level while *encapsulation* solves problems at the implementation level."
    ]
   },
   {
@@ -210,7 +217,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 40,
+   "execution_count": 1,
    "id": "a9c30a5d-aa86-45ab-b897-f051df80f1d8",
    "metadata": {},
    "outputs": [
@@ -218,17 +225,17 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "car1.get_obj_info_str() = \"I am <__main__.Car object at 0x7fdda86a51d0> with id 140589990040016 from <class '__main__.Car'> with id 93981278397392\"\n",
-      "car2.get_obj_info_str() = \"I am <__main__.Car object at 0x7fdda86c4d90> with id 140589990170000 from <class '__main__.Car'> with id 93981278397392\"\n",
-      "id(Car.cls_extras) = 140589990168000, id(Car.__init__) = 140589989979424\n",
-      "car1.model = 'BMW', car1.reg_nr = 'EC76183', car1.extras = ['GPSnav', 'Sound system'], id(car1.cls_extras) = 140589990168000, id(car1.__init__) = 140589990039168\n",
-      "car2.model = 'Scoda', car2.reg_nr = 'BD77655', car2.extras = ['GPSnav'], id(car2.cls_extras) = 140589990168000, id(car2.__init__) = 140589990039808\n",
-      "car1.cls_extras = ['GPSnav', 'Sound system'], id(car1.cls_extras) = 140589990168000\n",
-      "car2.cls_extras = ['GPSnav', 'Sound system'], id(car2.cls_extras) = 140589990168000\n",
+      "car1.get_obj_info_str() = \"I am <__main__.Car object at 0x7f5630542810> with id 140008154736656 from <class '__main__.Car'> with id 94904583728688\"\n",
+      "car2.get_obj_info_str() = \"I am <__main__.Car object at 0x7f5633ec8190> with id 140008215052688 from <class '__main__.Car'> with id 94904583728688\"\n",
+      "car1.model = 'BMW', car1.reg_nr = 'EC76183', car1.extras = ['GPSnav', 'Sound system'], id(car1.cls_extras) = 140008154734272, id(car1.__init__) = 140008154735680\n",
+      "car2.model = 'Scoda', car2.reg_nr = 'BD77655', car2.extras = ['GPSnav'], id(car2.cls_extras) = 140008154734272, id(car2.__init__) = 140008154736768\n",
+      "id(Car.cls_extras) = 140008154734272, id(Car.__init__) = 140008154484864\n",
+      "car1.cls_extras = ['GPSnav', 'Sound system'], id(car1.cls_extras) = 140008154734272\n",
+      "car2.cls_extras = ['GPSnav', 'Sound system'], id(car2.cls_extras) = 140008154734272\n",
       "True\n",
       "hasattr(car1, 'import_tax_paid') = True\n",
       "hasattr(car2, 'import_tax_paid') = False\n",
-      "id(car1.__class__) = 93981278397392, id(car2.__class__) = 93981278397392, id(Car) = 93981278397392\n"
+      "id(car1.__class__) = 94904583728688, id(car2.__class__) = 94904583728688, id(Car) = 94904583728688\n"
      ]
     }
    ],
@@ -270,9 +277,9 @@
     "#     - checks if 'attr' is a class attribute\n",
     "#     - raises AttributeError\n",
     "# setter: (re)defines an instance attribute\n",
-    "print(f\"{id(Car.cls_extras) = }, {id(Car.__init__) = }\")\n",
     "print(f\"{car1.model = }, {car1.reg_nr = }, {car1.extras = }, {id(car1.cls_extras) = }, {id(car1.__init__) = }\")\n",
     "print(f\"{car2.model = }, {car2.reg_nr = }, {car2.extras = }, {id(car2.cls_extras) = }, {id(car2.__init__) = }\")\n",
+    "print(f\"{id(Car.cls_extras) = }, {id(Car.__init__) = }\")\n",
     "car1.cls_extras.extend(car1.extras)\n",
     "# car1.cls_extras = car1.extras  # N.B. This will create a *NEW instance attribute* called 'cls_extras'\n",
     "print(f\"{car1.cls_extras = }, {id(car1.cls_extras) = }\")\n",
@@ -298,7 +305,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 41,
+   "execution_count": 2,
    "id": "391e816e-c53b-454b-9e9f-3587234f1fea",
    "metadata": {},
    "outputs": [
@@ -388,7 +395,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 42,
+   "execution_count": 3,
    "id": "e82feefb-025d-4cbb-a8ac-ddc3cc01269c",
    "metadata": {},
    "outputs": [
@@ -470,7 +477,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 43,
+   "execution_count": 4,
    "id": "71a90ec6-3cc0-441e-a866-c2c2b9984559",
    "metadata": {},
    "outputs": [
@@ -478,9 +485,9 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "my_first_vector = Vector(start=<Point(x=0, y=0)>, end=<Point(x=9, y=12)>)\n",
-      "my_first_vector = Vector(start=<Point(x=0, y=0)>, end=<Point(x=12, y=12)>)\n",
-      "other_vector = Vector(start=<Point(x=0, y=0)>, end=<Point(x=12, y=12)>)\n",
+      "my_first_vector = Vector(start=Point(x=0, y=0), end=Point(x=9, y=12))\n",
+      "my_first_vector = Vector(start=Point(x=0, y=0), end=Point(x=12, y=12))\n",
+      "other_vector = Vector(start=Point(x=0, y=0), end=Point(x=12, y=12))\n",
       "other_vector.length = Decimal('16.97056274847714058562026469')\n",
       "True\n",
       "True\n",
@@ -502,7 +509,7 @@
     "        self._x = x\n",
     "        self._y = y\n",
     "\n",
-    "    def __bool__(self):\n",
+    "    def __bool__(self) -> bool:\n",
     "        \"\"\"\n",
     "        Called to implement truth value testing and the built-in operation\n",
     "        bool(); should return False or True. When this method is not defined,\n",
@@ -529,7 +536,7 @@
     "\n",
     "    # \"fix\" self.__y -> self._y\n",
     "    def __repr__(self) -> str:\n",
-    "        return f\"<Point(x={self._x!r}, y={self._y!r})>\"\n",
+    "        return f\"Point(x={self._x!r}, y={self._y!r})\"\n",
     "\n",
     "    def __str__(self) -> str:\n",
     "        return f\"{self._x}:{self._y}\"\n",
@@ -588,7 +595,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 44,
+   "execution_count": 5,
    "id": "a4d2735d-d167-4f43-ad55-cb3d13ece2dc",
    "metadata": {},
    "outputs": [
@@ -596,7 +603,7 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "list(vector) = [<Point(x=1, y=1)>, <Point(x=4, y=6)>]\n",
+      "list(vector) = [Point(x=1, y=1), Point(x=4, y=6)]\n",
       "1:1\n",
       "4:6\n",
       "Exhausted\n"
@@ -631,7 +638,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 45,
+   "execution_count": 6,
    "id": "a6ead5e6-e987-4bda-bf48-30f91877278d",
    "metadata": {},
    "outputs": [
@@ -662,7 +669,7 @@
     "        protocol via __getitem__(), see this section in the language\n",
     "        reference.\n",
     "        \"\"\"\n",
-    "        # ont of the following two strategies may be employed:\n",
+    "        # one of the following two strategies may be employed:\n",
     "        # return point is self._start or point is self._end\n",
     "        # return point == self._start or point == self._end\n",
     "        return point == self._start or point == self._end\n",
@@ -690,7 +697,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 46,
+   "execution_count": 7,
    "id": "11f6a3fb-64d7-40a9-a130-27548ec4b802",
    "metadata": {},
    "outputs": [
@@ -699,9 +706,9 @@
      "output_type": "stream",
      "text": [
       "__mul__ called\n",
-      "vector * 3 = Vector(start=<Point(x=2, y=2)>, end=<Point(x=12, y=18)>)\n",
+      "vector * 3 = Vector(start=Point(x=2, y=2), end=Point(x=12, y=18))\n",
       "__rmul__ called\n",
-      "3 * vector = Vector(start=<Point(x=2, y=2)>, end=<Point(x=12, y=18)>)\n"
+      "3 * vector = Vector(start=Point(x=2, y=2), end=Point(x=12, y=18))\n"
      ]
     }
    ],
@@ -727,6 +734,8 @@
     "            return self._start\n",
     "        if key in (\"end\", 1):\n",
     "            return self._end\n",
+    "        if isinstance(key, int):\n",
+    "            raise IndexError\n",
     "        raise KeyError\n",
     "\n",
     "    def __mul__(self, other):\n",
@@ -757,7 +766,7 @@
     "        returns NotImplemented.\n",
     "        \"\"\"\n",
     "        print(\"__rmul__ called\")\n",
-    "        return Vector(self._start, Point(self._end.x * other, self._end.y * other))\n",
+    "        return Vector(self._start, Point(self._end.x * other, self._end.y * other))  # self.__class__ may be used instead of Vector???\n",
     "\n",
     "    # __rmul__ = __mul__\n",
     "\n",
@@ -768,7 +777,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 47,
+   "execution_count": 8,
    "id": "c345a69f-02da-40e7-bb37-c0511b6af096",
    "metadata": {},
    "outputs": [
@@ -777,7 +786,7 @@
      "output_type": "stream",
      "text": [
       "9\n",
-      "Vector.from_str('1:1:5:6') = Vector(start=<Point(x=1, y=1)>, end=<Point(x=5, y=6)>)\n"
+      "Vector.from_str('1:1:5:6') = Vector(start=Point(x=1, y=1), end=Point(x=5, y=6))\n"
      ]
     }
    ],
@@ -789,6 +798,8 @@
     "    @staticmethod\n",
     "    def get_manhattan_distance(point1: Point, point2: Point) -> int:\n",
     "        \"\"\"Returns the Manhattan distance of two points\"\"\"\n",
+    "        # usually this will be a regular method of type:\n",
+    "        # def get_manhattan_distance(self, other: Point) -> int:\n",
     "        return abs(point1.x - point2.x) + abs(point1.y - point2.y)\n",
     "\n",
     "\n",
@@ -859,7 +870,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 48,
+   "execution_count": 9,
    "id": "44d47e1c-1a06-4577-8db6-6ec78ce5cef8",
    "metadata": {},
    "outputs": [
@@ -1033,7 +1044,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 49,
+   "execution_count": 10,
    "id": "e6076925-75f0-456c-aed5-7db0a24a67a1",
    "metadata": {},
    "outputs": [
@@ -1144,7 +1155,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 50,
+   "execution_count": 11,
    "id": "cf79617a-95d2-48f2-be66-fa1fa34e4e04",
    "metadata": {},
    "outputs": [
@@ -1223,7 +1234,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 51,
+   "execution_count": 12,
    "id": "95a1d0cc-0006-4ddc-b08d-d0b8b02acfba",
    "metadata": {},
    "outputs": [
@@ -1289,7 +1300,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 52,
+   "execution_count": 13,
    "id": "38066107-0190-4383-ba14-a4e9cd454a9c",
    "metadata": {},
    "outputs": [