4 files changed, 451 insertions, 83 deletions

diff --git a/notebooks/python/cryptographic_primitives.ipynb b/notebooks/python/cryptographic_primitives.ipynb
new file mode 100644
index 0000000..4d96549
--- /dev/null
+++ b/notebooks/python/cryptographic_primitives.ipynb
@@ -0,0 +1,261 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": 12,
+   "id": "fedd7d1a-36a9-4255-8305-a720dfb7b500",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "b\"{\\x8ea\\xf8wu!\\xeb\\xc4\\xc9\\xcb|\\\\\\xf1K\\xd5t\\x80i\\xbcD\\xb6!\\xfc\\xee\\x06lQ'V0\\xc6\"\n",
+      "7b8e61f8777521ebc4c9cb7c5cf14bd5748069bc44b621fcee066c51275630c6\n",
+      "b'e45h+Hd1IevEyct8XPFL1XSAabxEtiH87gZsUSdWMMY='\n"
+     ]
+    }
+   ],
+   "source": [
+    "# hashes\n",
+    "\n",
+    "import base64\n",
+    "import hashlib\n",
+    "\n",
+    "hashed_result = hashlib.sha256(b\"This is a tesu\")\n",
+    "print(hashed_result.digest())\n",
+    "print(hashed_result.hexdigest())\n",
+    "print(base64.b64encode(hashed_result.digest()))\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 13,
+   "id": "9082c388-1c30-46dc-8897-15bf5db255c8",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "password_hash1 = 'pbkdf2_sha256$100000$j2jYEb1TvX/wh5JEAYGag6h+hRNTGe3rjyv5pegVBu4=$7cV7MljnJJYuGndge3jozwFP28aP8Gfj+QFGvv5bpfo='\n",
+      "password_hash2 = 'pbkdf2_sha256$100000$8+PsThJmJXNAbQ/zaR5AgRA/CuNv8L1uPUXRNuWHc9k=$Kf07CSCVQOTQrvWX5l/ZBdA7zsaEFH247QjUaewpxaU='\n"
+     ]
+    }
+   ],
+   "source": [
+    "# PBKDF2\n",
+    "\n",
+    "import base64\n",
+    "import hashlib\n",
+    "import os\n",
+    "\n",
+    "\n",
+    "def get_password_hash(plaintext_password: str) -> str:\n",
+    "    \"\"\"\n",
+    "    Returns a complete password hash based on `plaintext_password`\n",
+    "\n",
+    "    :return: The hashed version of `plaintext_password`\n",
+    "    :rtype: str\n",
+    "    \"\"\"\n",
+    "    # parameters typycally sent as arguments or fetched from config\n",
+    "    hash_algo = \"sha256\"  # the hash algorithm to use for HMAC\n",
+    "    iterations = 100000  # amount of iterations\n",
+    "\n",
+    "    salt = os.urandom(32)  # 32 bytes of random data\n",
+    "\n",
+    "    key = hashlib.pbkdf2_hmac(hash_algo, plaintext_password.encode(), salt, iterations)\n",
+    "\n",
+    "    return (\n",
+    "        f\"pbkdf2_{hash_algo}${iterations}$\"\n",
+    "        f\"{base64.b64encode(salt).decode(\"ascii\")}$\"\n",
+    "        f\"{base64.b64encode(key).decode(\"ascii\")}\"\n",
+    "    )\n",
+    "\n",
+    "\n",
+    "def password_matches(plaintext_password: str, password_hash: str) -> bool:\n",
+    "    \"\"\"Returns True if `plaintext_password` matches `password_hash`, False otherwise\"\"\"\n",
+    "    hash_tokens = password_hash.split(\"$\")\n",
+    "    hash_algo = hash_tokens[0].split(\"_\")[1]\n",
+    "    iterations = int(hash_tokens[1])\n",
+    "    salt = base64.b64decode(hash_tokens[2])\n",
+    "    key = hashlib.pbkdf2_hmac(hash_algo, plaintext_password.encode(), salt, iterations)\n",
+    "    return key == base64.b64decode(hash_tokens[3])\n",
+    "\n",
+    "\n",
+    "password_hash1 = get_password_hash(\"didn't expect a Spanish Inquisition!\")\n",
+    "password_hash2 = get_password_hash(\"didn't expect a Spanish Inquisition!\")\n",
+    "print(f\"{password_hash1 = }\")\n",
+    "print(f\"{password_hash2 = }\")\n",
+    "\n",
+    "# print(password_matches(\"didn't expect a Spanish Inquisition!\", 'pbkdf2_sha256$100000$JfwrS72mFimypbwhJ/NCyds2dkXtknvfWM5AM3+Z5GQ=$k8YA8csSJZhuYW0um7utq3+lSX5pTAQPd9dukObWrPo='))"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 14,
+   "id": "1274325e-f670-4af8-a0bc-2ff7f668f769",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "('gxk9W0XFgbzbjRWB7zCPjbWs3', '00000bf5db2c3c6484904bf5e8314aeb123f5594af1f283fb62e14c7d196e84c')\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Proof of work\n",
+    "\n",
+    "import hashlib\n",
+    "import random\n",
+    "import string\n",
+    "\n",
+    "VALID_CHARS = string.ascii_letters + string.digits  # valid characters for response\n",
+    "\n",
+    "\n",
+    "def pow_solve_rnd(challenge: str, starting_chars: str = \"00000\", answer_size: int = 25) -> tuple:\n",
+    "    \"\"\"\n",
+    "    Solves a POW challenge for SHA-256 using `random.choice`\n",
+    "\n",
+    "    :return: (response, SHA-256 digest) tuple that solves the challenge\n",
+    "    :rtype: tuple\n",
+    "    \"\"\"\n",
+    "    while True:\n",
+    "        attempt = ''.join(\n",
+    "            [random.choice(VALID_CHARS) for x in range(answer_size)])\n",
+    "        dig = hashlib.sha256(('{0}:{1}'.format(challenge, attempt)).encode()).hexdigest()\n",
+    "        if dig.startswith(starting_chars):\n",
+    "            return attempt, dig\n",
+    "\n",
+    "print(f\"{pow_solve_rnd('2024-08-07')}\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 25,
+   "id": "6752c055-7e49-46c4-858b-599d069a7e77",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "enc-val$2$6ppVDmiJi0P9BnHuzwFUPA+vV/Gsb4INe2O9E/Ma2uI=$6879D8rw8645nbQ/NQtY3Q+AwKTWpd1P6Q==\n",
+      "Invalid tag when decrypting enc-val$2$tmuH3MTDQ9vMbxJ1pZUb0rQlF43Lgr/AYfkA+vSOZs0=$5CVt3VrxhuuOOVt1vCXeGpbhNh/20IcFNg==\n",
+      "None\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Encryption / decryption using AES-256-GCM\n",
+    "\n",
+    "import hashlib\n",
+    "import os\n",
+    "\n",
+    "from cryptography.exceptions import InvalidTag\n",
+    "from cryptography.hazmat.primitives.ciphers.aead import AESGCM\n",
+    "\n",
+    "\n",
+    "def encrypt(password: str, data: str) -> str:\n",
+    "    \"\"\"\n",
+    "    Encrypts `data` using `password` and AES-256-GCM.\n",
+    "\n",
+    "    The output string is in the following format:\n",
+    "    enc-val$`version-num`$`bas64-salt`$`base64-encrypted_data`\n",
+    "\n",
+    "    :param password: The password to generate the key with\n",
+    "    :type password: str\n",
+    "\n",
+    "    :param data: The data to be encrypted\n",
+    "    :type data: str\n",
+    "\n",
+    "    :return: The output string\n",
+    "    :rtype: str\n",
+    "    \"\"\"\n",
+    "    data_bytes = data.encode()\n",
+    "    salt = os.urandom(32)\n",
+    "    aesgcm = AESGCM(\n",
+    "        hashlib.scrypt(\n",
+    "            password.encode(), salt=salt, n=2**14, r=8, p=1, dklen=32\n",
+    "        )\n",
+    "    )\n",
+    "    nonce = salt[:12]\n",
+    "    # padding_length_bytes = b\"-1\"  # no padding used 2 bytes \"sign\"\n",
+    "    edata = aesgcm.encrypt(\n",
+    "        nonce, data_bytes, salt\n",
+    "    )\n",
+    "    return (\n",
+    "        f\"enc-val$2${base64.b64encode(salt).decode()}${base64.b64encode(edata).decode()}\"\n",
+    "    )\n",
+    "\n",
+    "\n",
+    "def decrypt(password: str, edata: str) -> str:\n",
+    "    \"\"\"\n",
+    "    Decrypts `edata` using `password`.\n",
+    "\n",
+    "    `edata` is in the following format:\n",
+    "    enc-val$`version-num`$`bas64-salt`$`base64-encrypted_data`\n",
+    "\n",
+    "    :param password: The password to generate the key with\n",
+    "    :type password: str\n",
+    "\n",
+    "    :param edata: The data to be decrypted\n",
+    "    :type edata: str\n",
+    "\n",
+    "    :return: The output string / decrypted data\n",
+    "    :rtype: str\n",
+    "    \"\"\"\n",
+    "    # check for supported versions first...\n",
+    "\n",
+    "    try:\n",
+    "        salt, data = (base64.b64decode(t) for t in edata[10:].split('$'))\n",
+    "        nonce = salt[:12]\n",
+    "        aesgcm = AESGCM(\n",
+    "            hashlib.scrypt(\n",
+    "                password.encode(), salt=salt, n=2**14, r=8, p=1, dklen=32\n",
+    "            )\n",
+    "        )\n",
+    "\n",
+    "        # decrypt\n",
+    "        data = aesgcm.decrypt(nonce, data, salt)\n",
+    "        return data.decode()\n",
+    "    except InvalidTag:\n",
+    "        print(f\"Invalid tag when decrypting {edata}\")\n",
+    "\n",
+    "print(f\"{encrypt('my passphrase', 'my secret')}\")\n",
+    "print(f\"{decrypt('my passphrase', 'enc-val$2$tmuH3MTDQ9vMbxJ1pZUb0rQlF43Lgr/AYfkA+vSOZs0=$5CVt3VrxhuuOOVt1vCXeGpbhNh/20IcFNg==')}\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "8ccfb453-d3fd-4383-a01d-f81b19f2cb82",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3 (ipykernel)",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.13.9"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}
diff --git a/notebooks/python/python_3_8_to_3_11.ipynb b/notebooks/python/python_3_8_to_3_11.ipynb
index b8724e8..016c108 100644
--- a/notebooks/python/python_3_8_to_3_11.ipynb
+++ b/notebooks/python/python_3_8_to_3_11.ipynb
@@ -834,7 +834,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.11.7"
+   "version": "3.12.3"
   }
  },
  "nbformat": 4,
diff --git a/notebooks/python/python_intro.ipynb b/notebooks/python/python_intro.ipynb
index f129ffe..f101400 100644
--- a/notebooks/python/python_intro.ipynb
+++ b/notebooks/python/python_intro.ipynb
@@ -50,6 +50,19 @@
   },
   {
    "cell_type": "markdown",
+   "id": "779bac39-4646-4b80-9970-343a3daef1e7",
+   "metadata": {},
+   "source": [
+    "## Important PEPs\n",
+    "\n",
+    "- [PEP0](https://peps.python.org/) - Index of Python Enhancement Proposals\n",
+    "- [PEP8](https://peps.python.org/pep-0008/) - Style Guide for Python Code\n",
+    "- [PEP257](https://peps.python.org/pep-0257/) - Docstring Conventions\n",
+    "- [PEP484](https://peps.python.org/pep-0484/) - Type Hints"
+   ]
+  },
+  {
+   "cell_type": "markdown",
    "id": "6d1edcfc-b001-4393-9c24-72adc9b5fccf",
    "metadata": {},
    "source": [
@@ -72,7 +85,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "4f144f73-51c1-419d-b71e-ee513f68f41c",
+   "id": "81573ed5-b76e-4726-9f44-7dc017fd0896",
    "metadata": {},
    "source": [
     "## Built-in functions\n",
@@ -81,8 +94,6 @@
     "\n",
     "[https://docs.python.org/3/library/functions.html](https://docs.python.org/3/library/functions.html)\n",
     "\n",
-    "- `dir([obj])` - returns a list of valid attributes for that object\n",
-    "\n",
     "- `id(obj)` - returns the \"identity\" of an object - an integer which is guaranteed to be unique\n",
     "\n",
     "- `print(...)` - prints objects to a text stream\n",
@@ -94,6 +105,12 @@
   },
   {
    "cell_type": "markdown",
+   "id": "bc180243-fe11-405c-beb9-83db4f793a05",
+   "metadata": {},
+   "source": []
+  },
+  {
+   "cell_type": "markdown",
    "id": "a0c57535-e285-47af-80f9-1d4a16de5f25",
    "metadata": {},
    "source": [
@@ -116,26 +133,28 @@
    "source": [
     "# Common built-in types:\n",
     "\n",
-    "s = 'foo'  # this is a string / str, same as str('foo'), may be encoded, immutable (s[0] = 'r' is NOT possible)\n",
+    "my_string = 'foo'  # a string / str, same as str('foo'), may be encoded\n",
+    "                   # immutable (s[0] = 'r' is NOT possible)\n",
     "\n",
-    "b = b'foo'  # bytes, same as bytes('foo', 'utf-8'), may be decoded, immutable\n",
+    "my_bytes = b'foo'  # bytes, same as bytes('foo', 'utf-8'), may be decoded, immutable\n",
     "\n",
-    "i = 6  # int, same as int('6'), immutable\n",
+    "my_int = 6  # int, same as int('6'), immutable\n",
     "\n",
-    "f = 0.1  # float, same as float('0.1'), immutable, Note!!: Floats have a fixed size,\n",
-    "# hence they don't necessarily behave they way we expect from math class.\n",
+    "my_float = 0.1  # float, same as float('0.1'), immutable, Note!!: Floats have a fixed size,\n",
+    "                # hence they don't necessarily behave they way we expect from math class.\n",
+    "# 24732847234232342892343428.3 == 24732847234232342892343428.1  # True\n",
     "\n",
-    "b = False  # bool, same as bool(0), bool(''), bool(None)... immutable / constant\n",
+    "my_bool = False  # bool, same as bool(0), bool(''), bool(None)... immutable / constant\n",
     "\n",
-    "n = None  # NoneType, similar to 'null' in other languages, immutable / constant\n",
+    "my_none = None  # NoneType, similar to 'null' in other languages, immutable / constant\n",
     "\n",
-    "l = [1, False, 'foo']  # list, same as list((1, False, 'foo'))\n",
+    "my_list = [1, False, 'foo']  # list, same as list((1, False, 'foo'))\n",
     "\n",
-    "t = (1, False, 'foo')  # tuple, same as tuple([1, False, 'foo']), immutable\n",
+    "my_tuple = (1, False, 'foo')  # tuple, same as tuple([1, False, 'foo']), immutable\n",
     "\n",
-    "d = {'foo': 1, 'bar': 8}  # dict, same as dict(foo=1, bar=8), similar to hash in other languages\n",
+    "my_dict = {'foo': 1, 'bar': 8}  # dict, same as dict(foo=1, bar=8), similar to hash in other languages\n",
     "\n",
-    "s = {'foo', 'bar', 1, 1, 4}  # set, same as set(['foo', 'bar', 1, 1, 4]), removes duplicates"
+    "my_set = {'foo', 'bar', 1, 1, 4}  # set, same as set(['foo', 'bar', 1, 1, 4]), removes duplicates"
    ]
   },
   {
@@ -203,7 +222,7 @@
     "s3[0]  # Out: S\n",
     "s3[-1]  # Out: t\n",
     "s3[1:]  # Out: tatnett\n",
-    "s3[1:-1]  # Out: tatnett\n",
+    "s3[1:-1]  # Out: tatnet\n",
     "s3[-3:]  # Out: ett\n",
     "s3[1:-1:2]  # Out: tte\n",
     "\n",
@@ -223,6 +242,29 @@
   },
   {
    "cell_type": "markdown",
+   "id": "25d0f9dc-d783-4a23-a3ee-c0b6cee3d4ab",
+   "metadata": {},
+   "source": [
+    "## Lists vs. tuples\n",
+    "\n",
+    "Tuples are not sumply \"read-only\" lists.\n",
+    "\n",
+    "\"Though tuples may seem similar to lists, they are often used in different situations and for different purposes.\n",
+    "Tuples are immutable, and usually contain a heterogeneous sequence of elements that are accessed via unpacking ... or indexing.\n",
+    "Lists are mutable, and their elements are usually homogeneous and are accessed by iterating over the list.\n",
+    "\n",
+    "```python\n",
+    "my_tuple = (1,2)\n",
+    "my_list = [1,2] \n",
+    "\n",
+    "# tuples are immutable and hashable, hence they can be used as keys in mapping objects as dicts\n",
+    "d = {my_tuple: 1}  # OK\n",
+    "d = {my_list: 1}  # Error\n",
+    "```"
+   ]
+  },
+  {
+   "cell_type": "markdown",
    "id": "6b2bc8fa-a5dc-4a58-92b2-abfb19bfe2ed",
    "metadata": {},
    "source": [
@@ -302,7 +344,7 @@
    "id": "40db50e4-fb7a-4a77-a074-bc4413f27212",
    "metadata": {},
    "source": [
-    "## Creating and maintaining a Python environment (cont...)\n",
+    "## Creating and maintaining a Python environment - goals\n",
     "\n",
     "Desired qualities for a flexible Python environment:\n",
     "\n",
@@ -324,10 +366,11 @@
    "id": "c661bf56-add0-402c-a629-a857f81d0758",
    "metadata": {},
    "source": [
-    "## Creating and maintaining a Python environment (cont...)\n",
+    "## Creating and maintaining a Python environment - using devbox / WSL / UNIX systems directly\n",
     "\n",
     "Exploting the operating system can be done by:\n",
     "\n",
+    "- using the official Python packages that are maintained by the OS (Ubuntu packages in the case of WSL @ Statnett or a Red Hat enterprise VM @ Statnett) is often good enough\n",
     "- (re)defining `PYTHONPATH`\n",
     "- using symlinks to point at packages placed at different locations"
    ]
@@ -337,7 +380,7 @@
    "id": "db8952aa-0944-4644-9626-7460786fd72a",
    "metadata": {},
    "source": [
-    "## Creating and maintaining a Python environment (cont...)\n",
+    "## Creating and maintaining a Python environment - using the Python virtual environment - *venv*\n",
     "\n",
     "Using venv can be done by directly invoking python:\n",
     "\n",
@@ -365,10 +408,13 @@
    "id": "299641e6-3d87-4a86-a124-eb49edb75b4b",
    "metadata": {},
    "source": [
-    "## Creating and maintaining a Python environment (cont...)\n",
+    "## Creating and maintaining a Python environment - using Poetry\n",
     "\n",
     "Poetry [https://python-poetry.org](https://python-poetry.org) is the prefered environment and dependency management tool at Statnett.\n",
     "\n",
+    "Although Poetry creates and uses vierual environment(s) behind the scenes,\n",
+    "it is centered around the concept of \"projects\" and not the virtual environment itself\n",
+    "\n",
     "```bash\n",
     "# create project and a virtual environment from scratch\n",
     "poetry new my-project\n",
@@ -411,7 +457,7 @@
     {
      "data": {
       "text/plain": [
-       "-42990858669078524"
+       "-3158428850515418558"
       ]
      },
      "execution_count": 15,
@@ -435,8 +481,8 @@
     "hash(t)  # returns f.i. -6333845781340707986\n",
     "# hash(l)  # TypeError: unhashable type: 'list'\n",
     "\n",
-    "s = 'the long and winding road'\n",
-    "s2 = 'the long and winding road'\n",
+    "s = \"the long and winding road\"\n",
+    "s2 = \"the long and winding road\"\n",
     "\n",
     "# check if s and s2 are the same object:\n",
     "id(s)  # Out: 139858905258704\n",
@@ -816,7 +862,7 @@
     "# the function will behave differently depending on what parameters were\n",
     "# used when calling its enclosing function (factory function)\n",
     "\n",
-    "def get_multiplier_of(base: int) -> str:\n",
+    "def get_multiplier_of(base: int):\n",
     "    \"\"\"the function enclosing its nested functions\"\"\"\n",
     "    # this function is the enclosing function of the function `multiplier_function`\n",
     "\n",
@@ -958,19 +1004,7 @@
    "execution_count": 22,
    "id": "4346260d-76af-437e-9c10-1c1d0c478695",
    "metadata": {},
-   "outputs": [
-    {
-     "ename": "NameError",
-     "evalue": "name 'is_admin' is not defined",
-     "output_type": "error",
-     "traceback": [
-      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
-      "\u001b[0;31mNameError\u001b[0m                                 Traceback (most recent call last)",
-      "Cell \u001b[0;32mIn[22], line 25\u001b[0m\n\u001b[1;32m     19\u001b[0m         \u001b[38;5;28;01mreturn\u001b[39;00m decorated\n\u001b[1;32m     21\u001b[0m     \u001b[38;5;28;01mreturn\u001b[39;00m api_access_decorator\n\u001b[1;32m     24\u001b[0m \u001b[38;5;129m@requires_access\u001b[39m(access_secret\u001b[38;5;241m=\u001b[39m\u001b[38;5;124m'\u001b[39m\u001b[38;5;124mb28cfeaa65b73cf\u001b[39m\u001b[38;5;124m'\u001b[39m)\n\u001b[0;32m---> 25\u001b[0m \u001b[38;5;129m@is_admin\u001b[39m\n\u001b[1;32m     26\u001b[0m \u001b[38;5;28;01mdef\u001b[39;00m \u001b[38;5;21msensitive_function\u001b[39m(data, \u001b[38;5;241m*\u001b[39m\u001b[38;5;241m*\u001b[39mkwargs):\n\u001b[1;32m     27\u001b[0m \u001b[38;5;250m    \u001b[39m\u001b[38;5;124;03m\"\"\"very sensitive function\"\"\"\u001b[39;00m\n\u001b[1;32m     28\u001b[0m     db\u001b[38;5;241m.\u001b[39msave(data)\n",
-      "\u001b[0;31mNameError\u001b[0m: name 'is_admin' is not defined"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "# Decorators (cont ...) - a complete example\n",
     "\n",
@@ -996,7 +1030,7 @@
     "\n",
     "\n",
     "@requires_access(access_secret='b28cfeaa65b73cf')\n",
-    "@is_admin\n",
+    "# @is_admin - decorators can be \"chained\"\n",
     "def sensitive_function(data, **kwargs):\n",
     "    \"\"\"very sensitive function\"\"\"\n",
     "    db.save(data)"
@@ -1030,11 +1064,19 @@
     "\n",
     "\n",
     "# modern Python >= 3.6 f-strings\n",
-    "f'{s} - {i} - {f:5.2f}'  # Out: 'another string - 27 -  6.58'\n",
+    "f\"{s} - {i} - {f:5.2f}\"  # Out: 'another string - 27 -  6.58'\n",
     "```       \n",
     "\n",
     "See https://docs.python.org/3/library/string.html#formatspec for the complete format specification"
    ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "23972592-e838-4fa7-81f1-ca3ca129e757",
+   "metadata": {},
+   "outputs": [],
+   "source": []
   }
  ],
  "metadata": {
@@ -1053,7 +1095,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.11.7"
+   "version": "3.13.9"
   }
  },
  "nbformat": 4,
diff --git a/notebooks/python/python_oo.ipynb b/notebooks/python/python_oo.ipynb
index e38d7f3..1ef2a72 100644
--- a/notebooks/python/python_oo.ipynb
+++ b/notebooks/python/python_oo.ipynb
@@ -66,7 +66,55 @@
     "\n",
     "- improving modularity\n",
     "\n",
-    "- providing foundation for a more intuitive design"
+    "- providing foundation for a more intuitive design\n",
+    "\n",
+    "A pseudo code example:\n",
+    "\n",
+    "```c\n",
+    "/* crating and drawing a (pseudo) widget in C */\n",
+    "my_widget = mylibrary_widget_init(); /* a struct of the type widget */\n",
+    "mylibrary_widget_draw(my_widget);\n",
+    "```\n",
+    "\n",
+    "```python\n",
+    "# creating and drawing a (pseudo) widget in Python\n",
+    "import mylibrary\n",
+    "\n",
+    "my_widget = mylibrary.Widget()\n",
+    "my_widget.draw()\n",
+    "```"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "878cb805-a2d7-46a3-a34a-0507495420f7",
+   "metadata": {},
+   "source": [
+    "# Do I need to know / understand OOP when I am programming in Python?\n",
+    "\n",
+    "Most definitely - **yes**.\n",
+    "\n",
+    "While using programming language that is not object-oriented (like *C* and / or *Rust*) is always possible,\n",
+    "when using Python there are no *sane* alternatives that have ever been demonstrated:\n",
+    "\n",
+    "- Understanding OO behaviour and syntax is a must in order to understand Python code in general\n",
+    "- OOP is at the core of Python's design - everything in Python is an object\n",
+    "- Good programming and design is not only about solving a particular task. It is about reusing code and making your code reusable in turn\n",
+    "- Following the priciples described above is more challenging when not using OO in general."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "b83dc815-ed51-4e5a-a30e-fa0252217194",
+   "metadata": {},
+   "source": [
+    "# I am doing only simple things with Python. Do I still need to learn OOP?\n",
+    "\n",
+    "Most definitely - **yes**.\n",
+    "\n",
+    "- A simple task provides a great opportunity to learn and practice OOP\n",
+    "- Using OOP **does not mean overcomplicating** your code. When applied correctly - it means the opposite\n",
+    "- Doing \"simple things\" exclusively is not very ambitious approach to programming and learning in general"
    ]
   },
   {
@@ -109,13 +157,20 @@
     "\n",
     "- object - an instance of a class that may contain its own attributes as well as references to its class' attributes\n",
     "\n",
-    "- attribute - variable, property, function defined in the class and present in its instances\n",
+    "- attribute - variable, property, function defined in the class and present in its instances - in Python: any name following a dot. Attributes may be *read-only* or *writable*. In the latter case, assignment to attributes is possible.\n",
     "\n",
     "- class variable - attribute of which a single copy exists, regardless of how many instances of the class exist\n",
     "\n",
     "- object / instance variable, object / instance attribute - attribute for which each instantiated object of the class has a separate copy, or instance\n",
     "\n",
-    "- method - member function - function that is an attribute"
+    "- method - member function - function that is an attribute\n",
+    "\n",
+    "```python\n",
+    "# my_str_obj is an object (instance) of the class str\n",
+    "my_str_object = str(\"Test\")  # or my_str_object = \"Test\"\n",
+    "my_str_object.lower  # attribute that is a function -> method\n",
+    "my_str_object.lower()  # calling the method \"lower\"\n",
+    "```"
    ]
   },
   {
@@ -218,7 +273,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": 41,
    "id": "a9c30a5d-aa86-45ab-b897-f051df80f1d8",
    "metadata": {},
    "outputs": [
@@ -226,17 +281,17 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "car1.get_obj_info_str() = \"I am <__main__.Car object at 0x7f70e643d590> with id 140122876269968 from <class '__main__.Car'> with id 93964809433504\"\n",
-      "car2.get_obj_info_str() = \"I am <__main__.Car object at 0x7f70e63ddf10> with id 140122875879184 from <class '__main__.Car'> with id 93964809433504\"\n",
-      "car1.model = 'BMW', car1.reg_nr = 'EC76183', car1.extras = ['GPSnav', 'Sound system'], id(car1.cls_extras) = 140122875882432, id(car1.get_obj_info_str) = 140122875878080\n",
-      "car2.model = 'Scoda', car2.reg_nr = 'BD77655', car2.extras = ['GPSnav'], id(car2.cls_extras) = 140122875882432, id(car2.get_obj_info_str) = 140122875880192\n",
-      "id(Car.cls_extras) = 140122875882432, id(Car.get_obj_info_str) = 140122875964416\n",
-      "car1.cls_extras = ['GPSnav', 'Sound system'], id(car1.cls_extras) = 140122875882432\n",
-      "car2.cls_extras = ['GPSnav', 'Sound system'], id(car2.cls_extras) = 140122875882432\n",
+      "car1.get_obj_info_str() = \"I am <__main__.Car object at 0x7fd00029ff80> with id 140531332677504 from <class '__main__.Car'> with id 93887620597168\"\n",
+      "car2.get_obj_info_str() = \"I am <__main__.Car object at 0x7fd00029ea50> with id 140531332672080 from <class '__main__.Car'> with id 93887620597168\"\n",
+      "car1.model = 'BMW', car1.reg_nr = 'EC76183', car1.extras = ['GPSnav', 'Sound system'], id(car1.cls_extras) = 140531337557440, id(car1.get_obj_info_str) = 140531251735488\n",
+      "car2.model = 'Scoda', car2.reg_nr = 'BD77655', car2.extras = ['GPSnav'], id(car2.cls_extras) = 140531337557440, id(car2.get_obj_info_str) = 140531251728064\n",
+      "id(Car.cls_extras) = 140531337557440, id(Car.get_obj_info_str) = 140531252010400\n",
+      "car1.cls_extras = ['GPSnav', 'Sound system'], id(car1.cls_extras) = 140531337557440\n",
+      "car2.cls_extras = ['GPSnav', 'Sound system'], id(car2.cls_extras) = 140531337557440\n",
       "True\n",
       "hasattr(car1, 'import_tax_paid') = True\n",
       "hasattr(car2, 'import_tax_paid') = False\n",
-      "id(car1.__class__) = 93964809433504, id(car2.__class__) = 93964809433504, id(Car) = 93964809433504\n"
+      "id(car1.__class__) = 93887620597168, id(car2.__class__) = 93887620597168, id(Car) = 93887620597168\n"
      ]
     }
    ],
@@ -288,7 +343,7 @@
     "#     - checks if 'attr' is an instance attribute\n",
     "#     - checks if 'attr' is a class attribute (through the method resolution order - MRO)\n",
     "#     - raises AttributeError\n",
-    "# setter:\n",
+    "# setter (making the attribute writable):\n",
     "#     - (re)defines an instance attribute\n",
     "\n",
     "# Details not covered in this course:\n",
@@ -323,7 +378,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 42,
    "id": "391e816e-c53b-454b-9e9f-3587234f1fea",
    "metadata": {},
    "outputs": [
@@ -413,7 +468,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
+   "execution_count": 43,
    "id": "e82feefb-025d-4cbb-a8ac-ddc3cc01269c",
    "metadata": {},
    "outputs": [
@@ -495,7 +550,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 4,
+   "execution_count": 44,
    "id": "71a90ec6-3cc0-441e-a866-c2c2b9984559",
    "metadata": {},
    "outputs": [
@@ -613,7 +668,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": 45,
    "id": "a4d2735d-d167-4f43-ad55-cb3d13ece2dc",
    "metadata": {},
    "outputs": [
@@ -656,7 +711,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 46,
    "id": "a6ead5e6-e987-4bda-bf48-30f91877278d",
    "metadata": {},
    "outputs": [
@@ -715,7 +770,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 47,
    "id": "11f6a3fb-64d7-40a9-a130-27548ec4b802",
    "metadata": {},
    "outputs": [
@@ -797,7 +852,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": 48,
    "id": "c345a69f-02da-40e7-bb37-c0511b6af096",
    "metadata": {},
    "outputs": [
@@ -806,6 +861,9 @@
      "output_type": "stream",
      "text": [
       "9\n",
+      "9\n",
+      "140531251904896\n",
+      "140531251904896\n",
       "Vector.from_str('1:1:5:6') = Vector(start=Point(x=1, y=1), end=Point(x=5, y=6))\n"
      ]
     }
@@ -837,7 +895,14 @@
     "            Point(coordinates[2], coordinates[3]),\n",
     "        )\n",
     "\n",
-    "print(Point.get_manhattan_distance(Point(1, 1), Point(5, 6)))\n",
+    "point1 = Point(1, 1)\n",
+    "point2 = Point(5, 6)\n",
+    "print(f\"{point1.get_manhattan_distance(point1, point2)}\")  # works, but should not be used in that way\n",
+    "print(f\"{Point.get_manhattan_distance(point1, point2)}\")\n",
+    "print(f\"{id(point1.get_manhattan_distance)}\")\n",
+    "print(f\"{id(point2.get_manhattan_distance)}\")\n",
+    "# print(f\"{id(point1.from_str)}\") <-- not available as an instance attribute\n",
+    "\n",
     "print(f\"{Vector.from_str('1:1:5:6') = }\")"
    ]
   },
@@ -890,7 +955,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
+   "execution_count": 49,
    "id": "44d47e1c-1a06-4577-8db6-6ec78ce5cef8",
    "metadata": {},
    "outputs": [
@@ -903,32 +968,32 @@
       "\n",
       "class TigerShark(Fish)\n",
       " |  TigerShark(weight: int, alive: bool = True, **kwargs)\n",
-      " |  \n",
+      " |\n",
       " |  Base class for all tiger sharks\n",
-      " |  \n",
+      " |\n",
       " |  Method resolution order:\n",
       " |      TigerShark\n",
       " |      Fish\n",
       " |      Animal\n",
       " |      builtins.object\n",
-      " |  \n",
+      " |\n",
       " |  Methods defined here:\n",
-      " |  \n",
+      " |\n",
       " |  __init__(self, weight: int, alive: bool = True, **kwargs)\n",
       " |      Initialize self.  See help(type(self)) for accurate signature.\n",
-      " |  \n",
+      " |\n",
       " |  ----------------------------------------------------------------------\n",
       " |  Data descriptors inherited from Animal:\n",
-      " |  \n",
+      " |\n",
       " |  __dict__\n",
-      " |      dictionary for instance variables (if defined)\n",
-      " |  \n",
+      " |      dictionary for instance variables\n",
+      " |\n",
       " |  __weakref__\n",
-      " |      list of weak references to the object (if defined)\n",
-      " |  \n",
+      " |      list of weak references to the object\n",
+      " |\n",
       " |  alive\n",
       " |      getter property alive\n",
-      " |  \n",
+      " |\n",
       " |  weight\n",
       " |      getter property weight\n",
       "\n",
@@ -1064,7 +1129,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": 50,
    "id": "e6076925-75f0-456c-aed5-7db0a24a67a1",
    "metadata": {},
    "outputs": [
@@ -1169,7 +1234,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": 51,
    "id": "cf79617a-95d2-48f2-be66-fa1fa34e4e04",
    "metadata": {},
    "outputs": [
@@ -1192,14 +1257,14 @@
       " |      Adam\n",
       " |      Eve\n",
       " |      builtins.object\n",
-      " |  \n",
+      " |\n",
       " |  Data descriptors inherited from Adam:\n",
-      " |  \n",
+      " |\n",
       " |  __dict__\n",
-      " |      dictionary for instance variables (if defined)\n",
-      " |  \n",
+      " |      dictionary for instance variables\n",
+      " |\n",
       " |  __weakref__\n",
-      " |      list of weak references to the object (if defined)\n",
+      " |      list of weak references to the object\n",
       "\n"
      ]
     }
@@ -1256,7 +1321,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 12,
+   "execution_count": 52,
    "id": "95a1d0cc-0006-4ddc-b08d-d0b8b02acfba",
    "metadata": {},
    "outputs": [
@@ -1324,7 +1389,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": 53,
    "id": "38066107-0190-4383-ba14-a4e9cd454a9c",
    "metadata": {},
    "outputs": [
@@ -1418,7 +1483,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.11.7"
+   "version": "3.13.9"
   }
  },
  "nbformat": 4,