diff --git a/.vscode/settings.json b/.vscode/settings.json
index 91ceb037c..b37fe572a 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -17,7 +17,6 @@
   "files.autoSave": "afterDelay",
   "screencastMode.onlyKeyboardShortcuts": true,
   "terminal.integrated.fontSize": 18,
-  "workbench.activityBar.visible": true,
   "workbench.colorTheme": "Visual Studio Dark",
   "workbench.fontAliasing": "antialiased",
   "workbench.statusBar.visible": true
diff --git a/ch00-introduction/00_04_codespace.ipynb b/ch00-introduction/00_04_codespace.ipynb
index cb0c19d79..d65fbe8a5 100644
--- a/ch00-introduction/00_04_codespace.ipynb
+++ b/ch00-introduction/00_04_codespace.ipynb
@@ -47,7 +47,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3 (ipykernel)",
+   "display_name": ".venv",
    "language": "python",
    "name": "python3"
   },
@@ -61,7 +61,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.11.8"
+   "version": "3.12.1"
   }
  },
  "nbformat": 4,
diff --git a/ch01-datastructures/01_01_loops.ipynb b/ch01-datastructures/01_01_loops.ipynb
index 221f58679..44d37764f 100644
--- a/ch01-datastructures/01_01_loops.ipynb
+++ b/ch01-datastructures/01_01_loops.ipynb
@@ -9,7 +9,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 1,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -28,9 +28,26 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 2,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "0\n",
+      "1\n",
+      "2\n",
+      "3\n",
+      "4\n",
+      "5\n",
+      "6\n",
+      "7\n",
+      "8\n",
+      "9\n"
+     ]
+    }
+   ],
    "source": [
     "for i in range(0, 10):\n",
     "    print(i)"
@@ -38,9 +55,21 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 3,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "0\n",
+      "1\n",
+      "2\n",
+      "3\n",
+      "4\n"
+     ]
+    }
+   ],
    "source": [
     "for i in range(5):\n",
     "    print(i)"
@@ -48,9 +77,21 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 4,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "0\n",
+      "2\n",
+      "4\n",
+      "6\n",
+      "8\n"
+     ]
+    }
+   ],
    "source": [
     "for i in range(0, 10, 2):\n",
     "    print(i)"
@@ -58,7 +99,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 5,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -73,7 +114,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 6,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -91,27 +132,353 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 7,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "[[0, 0, 0, 0, 0, 100],\n",
+       " [0, 0, 0, 0, 1, 95],\n",
+       " [0, 0, 0, 0, 2, 90],\n",
+       " [0, 0, 0, 0, 3, 85],\n",
+       " [0, 0, 0, 0, 4, 80],\n",
+       " [0, 0, 0, 0, 5, 75],\n",
+       " [0, 0, 0, 0, 6, 70],\n",
+       " [0, 0, 0, 0, 7, 65],\n",
+       " [0, 0, 0, 0, 8, 60],\n",
+       " [0, 0, 0, 0, 9, 55],\n",
+       " [0, 0, 0, 0, 10, 50],\n",
+       " [0, 0, 0, 0, 11, 45],\n",
+       " [0, 0, 0, 0, 12, 40],\n",
+       " [0, 0, 0, 0, 13, 35],\n",
+       " [0, 0, 0, 0, 14, 30],\n",
+       " [0, 0, 0, 0, 15, 25],\n",
+       " [0, 0, 0, 0, 16, 20],\n",
+       " [0, 0, 0, 0, 17, 15],\n",
+       " [0, 0, 0, 0, 18, 10],\n",
+       " [0, 0, 0, 0, 19, 5],\n",
+       " [0, 0, 0, 0, 20, 0],\n",
+       " [0, 0, 0, 1, 0, 90],\n",
+       " [0, 0, 0, 1, 1, 85],\n",
+       " [0, 0, 0, 1, 2, 80],\n",
+       " [0, 0, 0, 1, 3, 75],\n",
+       " [0, 0, 0, 1, 4, 70],\n",
+       " [0, 0, 0, 1, 5, 65],\n",
+       " [0, 0, 0, 1, 6, 60],\n",
+       " [0, 0, 0, 1, 7, 55],\n",
+       " [0, 0, 0, 1, 8, 50],\n",
+       " [0, 0, 0, 1, 9, 45],\n",
+       " [0, 0, 0, 1, 10, 40],\n",
+       " [0, 0, 0, 1, 11, 35],\n",
+       " [0, 0, 0, 1, 12, 30],\n",
+       " [0, 0, 0, 1, 13, 25],\n",
+       " [0, 0, 0, 1, 14, 20],\n",
+       " [0, 0, 0, 1, 15, 15],\n",
+       " [0, 0, 0, 1, 16, 10],\n",
+       " [0, 0, 0, 1, 17, 5],\n",
+       " [0, 0, 0, 1, 18, 0],\n",
+       " [0, 0, 0, 2, 0, 80],\n",
+       " [0, 0, 0, 2, 1, 75],\n",
+       " [0, 0, 0, 2, 2, 70],\n",
+       " [0, 0, 0, 2, 3, 65],\n",
+       " [0, 0, 0, 2, 4, 60],\n",
+       " [0, 0, 0, 2, 5, 55],\n",
+       " [0, 0, 0, 2, 6, 50],\n",
+       " [0, 0, 0, 2, 7, 45],\n",
+       " [0, 0, 0, 2, 8, 40],\n",
+       " [0, 0, 0, 2, 9, 35],\n",
+       " [0, 0, 0, 2, 10, 30],\n",
+       " [0, 0, 0, 2, 11, 25],\n",
+       " [0, 0, 0, 2, 12, 20],\n",
+       " [0, 0, 0, 2, 13, 15],\n",
+       " [0, 0, 0, 2, 14, 10],\n",
+       " [0, 0, 0, 2, 15, 5],\n",
+       " [0, 0, 0, 2, 16, 0],\n",
+       " [0, 0, 0, 3, 0, 70],\n",
+       " [0, 0, 0, 3, 1, 65],\n",
+       " [0, 0, 0, 3, 2, 60],\n",
+       " [0, 0, 0, 3, 3, 55],\n",
+       " [0, 0, 0, 3, 4, 50],\n",
+       " [0, 0, 0, 3, 5, 45],\n",
+       " [0, 0, 0, 3, 6, 40],\n",
+       " [0, 0, 0, 3, 7, 35],\n",
+       " [0, 0, 0, 3, 8, 30],\n",
+       " [0, 0, 0, 3, 9, 25],\n",
+       " [0, 0, 0, 3, 10, 20],\n",
+       " [0, 0, 0, 3, 11, 15],\n",
+       " [0, 0, 0, 3, 12, 10],\n",
+       " [0, 0, 0, 3, 13, 5],\n",
+       " [0, 0, 0, 3, 14, 0],\n",
+       " [0, 0, 0, 4, 0, 60],\n",
+       " [0, 0, 0, 4, 1, 55],\n",
+       " [0, 0, 0, 4, 2, 50],\n",
+       " [0, 0, 0, 4, 3, 45],\n",
+       " [0, 0, 0, 4, 4, 40],\n",
+       " [0, 0, 0, 4, 5, 35],\n",
+       " [0, 0, 0, 4, 6, 30],\n",
+       " [0, 0, 0, 4, 7, 25],\n",
+       " [0, 0, 0, 4, 8, 20],\n",
+       " [0, 0, 0, 4, 9, 15],\n",
+       " [0, 0, 0, 4, 10, 10],\n",
+       " [0, 0, 0, 4, 11, 5],\n",
+       " [0, 0, 0, 4, 12, 0],\n",
+       " [0, 0, 0, 5, 0, 50],\n",
+       " [0, 0, 0, 5, 1, 45],\n",
+       " [0, 0, 0, 5, 2, 40],\n",
+       " [0, 0, 0, 5, 3, 35],\n",
+       " [0, 0, 0, 5, 4, 30],\n",
+       " [0, 0, 0, 5, 5, 25],\n",
+       " [0, 0, 0, 5, 6, 20],\n",
+       " [0, 0, 0, 5, 7, 15],\n",
+       " [0, 0, 0, 5, 8, 10],\n",
+       " [0, 0, 0, 5, 9, 5],\n",
+       " [0, 0, 0, 5, 10, 0],\n",
+       " [0, 0, 0, 6, 0, 40],\n",
+       " [0, 0, 0, 6, 1, 35],\n",
+       " [0, 0, 0, 6, 2, 30],\n",
+       " [0, 0, 0, 6, 3, 25],\n",
+       " [0, 0, 0, 6, 4, 20],\n",
+       " [0, 0, 0, 6, 5, 15],\n",
+       " [0, 0, 0, 6, 6, 10],\n",
+       " [0, 0, 0, 6, 7, 5],\n",
+       " [0, 0, 0, 6, 8, 0],\n",
+       " [0, 0, 0, 7, 0, 30],\n",
+       " [0, 0, 0, 7, 1, 25],\n",
+       " [0, 0, 0, 7, 2, 20],\n",
+       " [0, 0, 0, 7, 3, 15],\n",
+       " [0, 0, 0, 7, 4, 10],\n",
+       " [0, 0, 0, 7, 5, 5],\n",
+       " [0, 0, 0, 7, 6, 0],\n",
+       " [0, 0, 0, 8, 0, 20],\n",
+       " [0, 0, 0, 8, 1, 15],\n",
+       " [0, 0, 0, 8, 2, 10],\n",
+       " [0, 0, 0, 8, 3, 5],\n",
+       " [0, 0, 0, 8, 4, 0],\n",
+       " [0, 0, 0, 9, 0, 10],\n",
+       " [0, 0, 0, 9, 1, 5],\n",
+       " [0, 0, 0, 9, 2, 0],\n",
+       " [0, 0, 0, 10, 0, 0],\n",
+       " [0, 0, 1, 0, 0, 75],\n",
+       " [0, 0, 1, 0, 1, 70],\n",
+       " [0, 0, 1, 0, 2, 65],\n",
+       " [0, 0, 1, 0, 3, 60],\n",
+       " [0, 0, 1, 0, 4, 55],\n",
+       " [0, 0, 1, 0, 5, 50],\n",
+       " [0, 0, 1, 0, 6, 45],\n",
+       " [0, 0, 1, 0, 7, 40],\n",
+       " [0, 0, 1, 0, 8, 35],\n",
+       " [0, 0, 1, 0, 9, 30],\n",
+       " [0, 0, 1, 0, 10, 25],\n",
+       " [0, 0, 1, 0, 11, 20],\n",
+       " [0, 0, 1, 0, 12, 15],\n",
+       " [0, 0, 1, 0, 13, 10],\n",
+       " [0, 0, 1, 0, 14, 5],\n",
+       " [0, 0, 1, 0, 15, 0],\n",
+       " [0, 0, 1, 1, 0, 65],\n",
+       " [0, 0, 1, 1, 1, 60],\n",
+       " [0, 0, 1, 1, 2, 55],\n",
+       " [0, 0, 1, 1, 3, 50],\n",
+       " [0, 0, 1, 1, 4, 45],\n",
+       " [0, 0, 1, 1, 5, 40],\n",
+       " [0, 0, 1, 1, 6, 35],\n",
+       " [0, 0, 1, 1, 7, 30],\n",
+       " [0, 0, 1, 1, 8, 25],\n",
+       " [0, 0, 1, 1, 9, 20],\n",
+       " [0, 0, 1, 1, 10, 15],\n",
+       " [0, 0, 1, 1, 11, 10],\n",
+       " [0, 0, 1, 1, 12, 5],\n",
+       " [0, 0, 1, 1, 13, 0],\n",
+       " [0, 0, 1, 2, 0, 55],\n",
+       " [0, 0, 1, 2, 1, 50],\n",
+       " [0, 0, 1, 2, 2, 45],\n",
+       " [0, 0, 1, 2, 3, 40],\n",
+       " [0, 0, 1, 2, 4, 35],\n",
+       " [0, 0, 1, 2, 5, 30],\n",
+       " [0, 0, 1, 2, 6, 25],\n",
+       " [0, 0, 1, 2, 7, 20],\n",
+       " [0, 0, 1, 2, 8, 15],\n",
+       " [0, 0, 1, 2, 9, 10],\n",
+       " [0, 0, 1, 2, 10, 5],\n",
+       " [0, 0, 1, 2, 11, 0],\n",
+       " [0, 0, 1, 3, 0, 45],\n",
+       " [0, 0, 1, 3, 1, 40],\n",
+       " [0, 0, 1, 3, 2, 35],\n",
+       " [0, 0, 1, 3, 3, 30],\n",
+       " [0, 0, 1, 3, 4, 25],\n",
+       " [0, 0, 1, 3, 5, 20],\n",
+       " [0, 0, 1, 3, 6, 15],\n",
+       " [0, 0, 1, 3, 7, 10],\n",
+       " [0, 0, 1, 3, 8, 5],\n",
+       " [0, 0, 1, 3, 9, 0],\n",
+       " [0, 0, 1, 4, 0, 35],\n",
+       " [0, 0, 1, 4, 1, 30],\n",
+       " [0, 0, 1, 4, 2, 25],\n",
+       " [0, 0, 1, 4, 3, 20],\n",
+       " [0, 0, 1, 4, 4, 15],\n",
+       " [0, 0, 1, 4, 5, 10],\n",
+       " [0, 0, 1, 4, 6, 5],\n",
+       " [0, 0, 1, 4, 7, 0],\n",
+       " [0, 0, 1, 5, 0, 25],\n",
+       " [0, 0, 1, 5, 1, 20],\n",
+       " [0, 0, 1, 5, 2, 15],\n",
+       " [0, 0, 1, 5, 3, 10],\n",
+       " [0, 0, 1, 5, 4, 5],\n",
+       " [0, 0, 1, 5, 5, 0],\n",
+       " [0, 0, 1, 6, 0, 15],\n",
+       " [0, 0, 1, 6, 1, 10],\n",
+       " [0, 0, 1, 6, 2, 5],\n",
+       " [0, 0, 1, 6, 3, 0],\n",
+       " [0, 0, 1, 7, 0, 5],\n",
+       " [0, 0, 1, 7, 1, 0],\n",
+       " [0, 0, 2, 0, 0, 50],\n",
+       " [0, 0, 2, 0, 1, 45],\n",
+       " [0, 0, 2, 0, 2, 40],\n",
+       " [0, 0, 2, 0, 3, 35],\n",
+       " [0, 0, 2, 0, 4, 30],\n",
+       " [0, 0, 2, 0, 5, 25],\n",
+       " [0, 0, 2, 0, 6, 20],\n",
+       " [0, 0, 2, 0, 7, 15],\n",
+       " [0, 0, 2, 0, 8, 10],\n",
+       " [0, 0, 2, 0, 9, 5],\n",
+       " [0, 0, 2, 0, 10, 0],\n",
+       " [0, 0, 2, 1, 0, 40],\n",
+       " [0, 0, 2, 1, 1, 35],\n",
+       " [0, 0, 2, 1, 2, 30],\n",
+       " [0, 0, 2, 1, 3, 25],\n",
+       " [0, 0, 2, 1, 4, 20],\n",
+       " [0, 0, 2, 1, 5, 15],\n",
+       " [0, 0, 2, 1, 6, 10],\n",
+       " [0, 0, 2, 1, 7, 5],\n",
+       " [0, 0, 2, 1, 8, 0],\n",
+       " [0, 0, 2, 2, 0, 30],\n",
+       " [0, 0, 2, 2, 1, 25],\n",
+       " [0, 0, 2, 2, 2, 20],\n",
+       " [0, 0, 2, 2, 3, 15],\n",
+       " [0, 0, 2, 2, 4, 10],\n",
+       " [0, 0, 2, 2, 5, 5],\n",
+       " [0, 0, 2, 2, 6, 0],\n",
+       " [0, 0, 2, 3, 0, 20],\n",
+       " [0, 0, 2, 3, 1, 15],\n",
+       " [0, 0, 2, 3, 2, 10],\n",
+       " [0, 0, 2, 3, 3, 5],\n",
+       " [0, 0, 2, 3, 4, 0],\n",
+       " [0, 0, 2, 4, 0, 10],\n",
+       " [0, 0, 2, 4, 1, 5],\n",
+       " [0, 0, 2, 4, 2, 0],\n",
+       " [0, 0, 2, 5, 0, 0],\n",
+       " [0, 0, 3, 0, 0, 25],\n",
+       " [0, 0, 3, 0, 1, 20],\n",
+       " [0, 0, 3, 0, 2, 15],\n",
+       " [0, 0, 3, 0, 3, 10],\n",
+       " [0, 0, 3, 0, 4, 5],\n",
+       " [0, 0, 3, 0, 5, 0],\n",
+       " [0, 0, 3, 1, 0, 15],\n",
+       " [0, 0, 3, 1, 1, 10],\n",
+       " [0, 0, 3, 1, 2, 5],\n",
+       " [0, 0, 3, 1, 3, 0],\n",
+       " [0, 0, 3, 2, 0, 5],\n",
+       " [0, 0, 3, 2, 1, 0],\n",
+       " [0, 0, 4, 0, 0, 0],\n",
+       " [0, 1, 0, 0, 0, 50],\n",
+       " [0, 1, 0, 0, 1, 45],\n",
+       " [0, 1, 0, 0, 2, 40],\n",
+       " [0, 1, 0, 0, 3, 35],\n",
+       " [0, 1, 0, 0, 4, 30],\n",
+       " [0, 1, 0, 0, 5, 25],\n",
+       " [0, 1, 0, 0, 6, 20],\n",
+       " [0, 1, 0, 0, 7, 15],\n",
+       " [0, 1, 0, 0, 8, 10],\n",
+       " [0, 1, 0, 0, 9, 5],\n",
+       " [0, 1, 0, 0, 10, 0],\n",
+       " [0, 1, 0, 1, 0, 40],\n",
+       " [0, 1, 0, 1, 1, 35],\n",
+       " [0, 1, 0, 1, 2, 30],\n",
+       " [0, 1, 0, 1, 3, 25],\n",
+       " [0, 1, 0, 1, 4, 20],\n",
+       " [0, 1, 0, 1, 5, 15],\n",
+       " [0, 1, 0, 1, 6, 10],\n",
+       " [0, 1, 0, 1, 7, 5],\n",
+       " [0, 1, 0, 1, 8, 0],\n",
+       " [0, 1, 0, 2, 0, 30],\n",
+       " [0, 1, 0, 2, 1, 25],\n",
+       " [0, 1, 0, 2, 2, 20],\n",
+       " [0, 1, 0, 2, 3, 15],\n",
+       " [0, 1, 0, 2, 4, 10],\n",
+       " [0, 1, 0, 2, 5, 5],\n",
+       " [0, 1, 0, 2, 6, 0],\n",
+       " [0, 1, 0, 3, 0, 20],\n",
+       " [0, 1, 0, 3, 1, 15],\n",
+       " [0, 1, 0, 3, 2, 10],\n",
+       " [0, 1, 0, 3, 3, 5],\n",
+       " [0, 1, 0, 3, 4, 0],\n",
+       " [0, 1, 0, 4, 0, 10],\n",
+       " [0, 1, 0, 4, 1, 5],\n",
+       " [0, 1, 0, 4, 2, 0],\n",
+       " [0, 1, 0, 5, 0, 0],\n",
+       " [0, 1, 1, 0, 0, 25],\n",
+       " [0, 1, 1, 0, 1, 20],\n",
+       " [0, 1, 1, 0, 2, 15],\n",
+       " [0, 1, 1, 0, 3, 10],\n",
+       " [0, 1, 1, 0, 4, 5],\n",
+       " [0, 1, 1, 0, 5, 0],\n",
+       " [0, 1, 1, 1, 0, 15],\n",
+       " [0, 1, 1, 1, 1, 10],\n",
+       " [0, 1, 1, 1, 2, 5],\n",
+       " [0, 1, 1, 1, 3, 0],\n",
+       " [0, 1, 1, 2, 0, 5],\n",
+       " [0, 1, 1, 2, 1, 0],\n",
+       " [0, 1, 2, 0, 0, 0],\n",
+       " [0, 2, 0, 0, 0, 0],\n",
+       " [1, 0, 0, 0, 0, 0]]"
+      ]
+     },
+     "execution_count": 7,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "combinations"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 8,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "293"
+      ]
+     },
+     "execution_count": 8,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "len(combinations)"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 9,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "0\n",
+      "1\n",
+      "2\n",
+      "3\n",
+      "4\n"
+     ]
+    }
+   ],
    "source": [
     "for count_25 in range(4+1):\n",
     "    print(count_25)"
@@ -119,9 +486,21 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 10,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "0\n",
+      "25\n",
+      "50\n",
+      "75\n",
+      "100\n"
+     ]
+    }
+   ],
    "source": [
     "for amount_25 in range(0, 100+1, 25):\n",
     "    print(amount_25)"
@@ -129,7 +508,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 11,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -149,9 +528,312 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 12,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
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+       " [0, 0, 0, 50, 50, 0],\n",
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+       " [0, 0, 0, 60, 5, 35],\n",
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+       " [0, 0, 0, 60, 35, 5],\n",
+       " [0, 0, 0, 60, 40, 0],\n",
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+       " [0, 0, 0, 70, 5, 25],\n",
+       " [0, 0, 0, 70, 10, 20],\n",
+       " [0, 0, 0, 70, 15, 15],\n",
+       " [0, 0, 0, 70, 20, 10],\n",
+       " [0, 0, 0, 70, 25, 5],\n",
+       " [0, 0, 0, 70, 30, 0],\n",
+       " [0, 0, 0, 80, 0, 20],\n",
+       " [0, 0, 0, 80, 5, 15],\n",
+       " [0, 0, 0, 80, 10, 10],\n",
+       " [0, 0, 0, 80, 15, 5],\n",
+       " [0, 0, 0, 80, 20, 0],\n",
+       " [0, 0, 0, 90, 0, 10],\n",
+       " [0, 0, 0, 90, 5, 5],\n",
+       " [0, 0, 0, 90, 10, 0],\n",
+       " [0, 0, 0, 100, 0, 0],\n",
+       " [0, 0, 25, 0, 0, 75],\n",
+       " [0, 0, 25, 0, 5, 70],\n",
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+       " [0, 0, 25, 0, 35, 40],\n",
+       " [0, 0, 25, 0, 40, 35],\n",
+       " [0, 0, 25, 0, 45, 30],\n",
+       " [0, 0, 25, 0, 50, 25],\n",
+       " [0, 0, 25, 0, 55, 20],\n",
+       " [0, 0, 25, 0, 60, 15],\n",
+       " [0, 0, 25, 0, 65, 10],\n",
+       " [0, 0, 25, 0, 70, 5],\n",
+       " [0, 0, 25, 0, 75, 0],\n",
+       " [0, 0, 25, 10, 0, 65],\n",
+       " [0, 0, 25, 10, 5, 60],\n",
+       " [0, 0, 25, 10, 10, 55],\n",
+       " [0, 0, 25, 10, 15, 50],\n",
+       " [0, 0, 25, 10, 20, 45],\n",
+       " [0, 0, 25, 10, 25, 40],\n",
+       " [0, 0, 25, 10, 30, 35],\n",
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+       " [0, 0, 25, 10, 40, 25],\n",
+       " [0, 0, 25, 10, 45, 20],\n",
+       " [0, 0, 25, 10, 50, 15],\n",
+       " [0, 0, 25, 10, 55, 10],\n",
+       " [0, 0, 25, 10, 60, 5],\n",
+       " [0, 0, 25, 10, 65, 0],\n",
+       " [0, 0, 25, 20, 0, 55],\n",
+       " [0, 0, 25, 20, 5, 50],\n",
+       " [0, 0, 25, 20, 10, 45],\n",
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+       " [0, 0, 25, 20, 20, 35],\n",
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+       " [0, 0, 25, 30, 45, 0],\n",
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+       " [0, 0, 25, 50, 15, 10],\n",
+       " [0, 0, 25, 50, 20, 5],\n",
+       " [0, 0, 25, 50, 25, 0],\n",
+       " [0, 0, 25, 60, 0, 15],\n",
+       " [0, 0, 25, 60, 5, 10],\n",
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+       " [0, 0, 25, 60, 15, 0],\n",
+       " [0, 0, 25, 70, 0, 5],\n",
+       " [0, 0, 25, 70, 5, 0],\n",
+       " [0, 0, 50, 0, 0, 50],\n",
+       " [0, 0, 50, 0, 5, 45],\n",
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+       " [0, 0, 50, 0, 15, 35],\n",
+       " [0, 0, 50, 0, 20, 30],\n",
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+       " [0, 0, 50, 0, 45, 5],\n",
+       " [0, 0, 50, 0, 50, 0],\n",
+       " [0, 0, 50, 10, 0, 40],\n",
+       " [0, 0, 50, 10, 5, 35],\n",
+       " [0, 0, 50, 10, 10, 30],\n",
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+       " [0, 0, 50, 10, 20, 20],\n",
+       " [0, 0, 50, 10, 25, 15],\n",
+       " [0, 0, 50, 10, 30, 10],\n",
+       " [0, 0, 50, 10, 35, 5],\n",
+       " [0, 0, 50, 10, 40, 0],\n",
+       " [0, 0, 50, 20, 0, 30],\n",
+       " [0, 0, 50, 20, 5, 25],\n",
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+       " [0, 0, 50, 30, 0, 20],\n",
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+       " [0, 0, 50, 30, 10, 10],\n",
+       " [0, 0, 50, 30, 15, 5],\n",
+       " [0, 0, 50, 30, 20, 0],\n",
+       " [0, 0, 50, 40, 0, 10],\n",
+       " [0, 0, 50, 40, 5, 5],\n",
+       " [0, 0, 50, 40, 10, 0],\n",
+       " [0, 0, 50, 50, 0, 0],\n",
+       " [0, 0, 75, 0, 0, 25],\n",
+       " [0, 0, 75, 0, 5, 20],\n",
+       " [0, 0, 75, 0, 10, 15],\n",
+       " [0, 0, 75, 0, 15, 10],\n",
+       " [0, 0, 75, 0, 20, 5],\n",
+       " [0, 0, 75, 0, 25, 0],\n",
+       " [0, 0, 75, 10, 0, 15],\n",
+       " [0, 0, 75, 10, 5, 10],\n",
+       " [0, 0, 75, 10, 10, 5],\n",
+       " [0, 0, 75, 10, 15, 0],\n",
+       " [0, 0, 75, 20, 0, 5],\n",
+       " [0, 0, 75, 20, 5, 0],\n",
+       " [0, 0, 100, 0, 0, 0],\n",
+       " [0, 50, 0, 0, 0, 50],\n",
+       " [0, 50, 0, 0, 5, 45],\n",
+       " [0, 50, 0, 0, 10, 40],\n",
+       " [0, 50, 0, 0, 15, 35],\n",
+       " [0, 50, 0, 0, 20, 30],\n",
+       " [0, 50, 0, 0, 25, 25],\n",
+       " [0, 50, 0, 0, 30, 20],\n",
+       " [0, 50, 0, 0, 35, 15],\n",
+       " [0, 50, 0, 0, 40, 10],\n",
+       " [0, 50, 0, 0, 45, 5],\n",
+       " [0, 50, 0, 0, 50, 0],\n",
+       " [0, 50, 0, 10, 0, 40],\n",
+       " [0, 50, 0, 10, 5, 35],\n",
+       " [0, 50, 0, 10, 10, 30],\n",
+       " [0, 50, 0, 10, 15, 25],\n",
+       " [0, 50, 0, 10, 20, 20],\n",
+       " [0, 50, 0, 10, 25, 15],\n",
+       " [0, 50, 0, 10, 30, 10],\n",
+       " [0, 50, 0, 10, 35, 5],\n",
+       " [0, 50, 0, 10, 40, 0],\n",
+       " [0, 50, 0, 20, 0, 30],\n",
+       " [0, 50, 0, 20, 5, 25],\n",
+       " [0, 50, 0, 20, 10, 20],\n",
+       " [0, 50, 0, 20, 15, 15],\n",
+       " [0, 50, 0, 20, 20, 10],\n",
+       " [0, 50, 0, 20, 25, 5],\n",
+       " [0, 50, 0, 20, 30, 0],\n",
+       " [0, 50, 0, 30, 0, 20],\n",
+       " [0, 50, 0, 30, 5, 15],\n",
+       " [0, 50, 0, 30, 10, 10],\n",
+       " [0, 50, 0, 30, 15, 5],\n",
+       " [0, 50, 0, 30, 20, 0],\n",
+       " [0, 50, 0, 40, 0, 10],\n",
+       " [0, 50, 0, 40, 5, 5],\n",
+       " [0, 50, 0, 40, 10, 0],\n",
+       " [0, 50, 0, 50, 0, 0],\n",
+       " [0, 50, 25, 0, 0, 25],\n",
+       " [0, 50, 25, 0, 5, 20],\n",
+       " [0, 50, 25, 0, 10, 15],\n",
+       " [0, 50, 25, 0, 15, 10],\n",
+       " [0, 50, 25, 0, 20, 5],\n",
+       " [0, 50, 25, 0, 25, 0],\n",
+       " [0, 50, 25, 10, 0, 15],\n",
+       " [0, 50, 25, 10, 5, 10],\n",
+       " [0, 50, 25, 10, 10, 5],\n",
+       " [0, 50, 25, 10, 15, 0],\n",
+       " [0, 50, 25, 20, 0, 5],\n",
+       " [0, 50, 25, 20, 5, 0],\n",
+       " [0, 50, 50, 0, 0, 0],\n",
+       " [0, 100, 0, 0, 0, 0],\n",
+       " [100, 0, 0, 0, 0, 0]]"
+      ]
+     },
+     "execution_count": 12,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "combinations_amounts"
    ]
@@ -230,7 +912,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3 (ipykernel)",
+   "display_name": ".venv",
    "language": "python",
    "name": "python3"
   },
@@ -244,7 +926,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.11.8"
+   "version": "3.12.1"
   }
  },
  "nbformat": 4,
diff --git a/ch01-datastructures/01_02_list_tuples.ipynb b/ch01-datastructures/01_02_list_tuples.ipynb
index 605aed80b..bf592b2fd 100644
--- a/ch01-datastructures/01_02_list_tuples.ipynb
+++ b/ch01-datastructures/01_02_list_tuples.ipynb
@@ -34,72 +34,161 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 3,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "['Huey', 'Dewey', 'Louie']"
+      ]
+     },
+     "execution_count": 3,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "nephews"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 4,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "3"
+      ]
+     },
+     "execution_count": 4,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "len(nephews)"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 5,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "0"
+      ]
+     },
+     "execution_count": 5,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "len([])"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 6,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'Huey'"
+      ]
+     },
+     "execution_count": 6,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "nephews[0]"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 7,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'Louie'"
+      ]
+     },
+     "execution_count": 7,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "nephews[2]"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 8,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "ename": "IndexError",
+     "evalue": "list index out of range",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[31m---------------------------------------------------------------------------\u001b[39m",
+      "\u001b[31mIndexError\u001b[39m                                Traceback (most recent call last)",
+      "\u001b[36mCell\u001b[39m\u001b[36m \u001b[39m\u001b[32mIn[8]\u001b[39m\u001b[32m, line 1\u001b[39m\n\u001b[32m----> \u001b[39m\u001b[32m1\u001b[39m \u001b[43mnephews\u001b[49m\u001b[43m[\u001b[49m\u001b[32;43m3\u001b[39;49m\u001b[43m]\u001b[49m\n",
+      "\u001b[31mIndexError\u001b[39m: list index out of range"
+     ]
+    }
+   ],
    "source": [
     "nephews[3]"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 9,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'Louie'"
+      ]
+     },
+     "execution_count": 9,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "nephews[-1]"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 10,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'Dewey'"
+      ]
+     },
+     "execution_count": 10,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "nephews[-2]"
    ]
@@ -116,9 +205,20 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 12,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "['Huey Duck', 'Dewey Duck', 'Louie Duck']"
+      ]
+     },
+     "execution_count": 12,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "nephews"
    ]
@@ -134,45 +234,95 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 14,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "[1, [2, 3], 'alpha']"
+      ]
+     },
+     "execution_count": 14,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "mix_it_up"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 15,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "False"
+      ]
+     },
+     "execution_count": 15,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "'Huey' in nephews"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 16,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "True"
+      ]
+     },
+     "execution_count": 16,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "'Huey Duck' in nephews"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 17,
+   "execution_count": 20,
    "metadata": {},
    "outputs": [],
    "source": [
-    "nephews.append('April Duck')"
+    "nephews.append(['May Duck', 'June Duck'])"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 21,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "['Huey Duck',\n",
+       " 'Dewey Duck',\n",
+       " 'Louie Duck',\n",
+       " 'April Duck',\n",
+       " 'May Duck',\n",
+       " 'June Duck',\n",
+       " ['May Duck', 'June Duck']]"
+      ]
+     },
+     "execution_count": 21,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "nephews"
    ]
@@ -197,7 +347,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 21,
+   "execution_count": 22,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -206,16 +356,35 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 23,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "['Huey Duck',\n",
+       " 'Dewey Duck',\n",
+       " 'Louie Duck',\n",
+       " 'April Duck',\n",
+       " 'May Duck',\n",
+       " 'June Duck',\n",
+       " ['May Duck', 'June Duck'],\n",
+       " 'Donald Duck',\n",
+       " 'Daisy Duck']"
+      ]
+     },
+     "execution_count": 23,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "ducks"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 23,
+   "execution_count": 24,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -224,16 +393,36 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 25,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "['Scrooge McDuck',\n",
+       " 'Huey Duck',\n",
+       " 'Dewey Duck',\n",
+       " 'Louie Duck',\n",
+       " 'April Duck',\n",
+       " 'May Duck',\n",
+       " 'June Duck',\n",
+       " ['May Duck', 'June Duck'],\n",
+       " 'Donald Duck',\n",
+       " 'Daisy Duck']"
+      ]
+     },
+     "execution_count": 25,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "ducks"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 25,
+   "execution_count": 26,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -242,16 +431,35 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 27,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "['Huey Duck',\n",
+       " 'Dewey Duck',\n",
+       " 'Louie Duck',\n",
+       " 'April Duck',\n",
+       " 'May Duck',\n",
+       " 'June Duck',\n",
+       " ['May Duck', 'June Duck'],\n",
+       " 'Donald Duck',\n",
+       " 'Daisy Duck']"
+      ]
+     },
+     "execution_count": 27,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "ducks"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 27,
+   "execution_count": 28,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -532,11 +740,71 @@
    "source": [
     "any_args(1,2,3)"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Understanding del vs remove"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 29,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Original: ['apple', 'banana', 'cherry', 'banana']\n",
+      "After del fruits[1]: ['apple', 'cherry', 'banana']\n"
+     ]
+    }
+   ],
+   "source": [
+    "# del - deletes by INDEX\n",
+    "fruits = ['apple', 'banana', 'cherry', 'banana']\n",
+    "print(\"Original:\", fruits)\n",
+    "\n",
+    "del fruits[1]  # Delete the item at index 1 (banana)\n",
+    "print(\"After del fruits[1]:\", fruits)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 30,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Original: ['apple', 'banana', 'cherry', 'banana']\n",
+      "After remove('banana'): ['apple', 'cherry', 'banana']\n"
+     ]
+    }
+   ],
+   "source": [
+    "# remove() - removes by VALUE (first occurrence only!)\n",
+    "fruits = ['apple', 'banana', 'cherry', 'banana']\n",
+    "print(\"Original:\", fruits)\n",
+    "\n",
+    "fruits.remove('banana')  # Removes the FIRST 'banana' it finds\n",
+    "print(\"After remove('banana'):\", fruits)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
   }
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3 (ipykernel)",
+   "display_name": ".venv",
    "language": "python",
    "name": "python3"
   },
@@ -550,7 +818,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.11.8"
+   "version": "3.12.1"
   }
  },
  "nbformat": 4,
diff --git a/ch01-datastructures/01_03_dicts_sets.ipynb b/ch01-datastructures/01_03_dicts_sets.ipynb
index a8e0ade0b..140e9e5c0 100644
--- a/ch01-datastructures/01_03_dicts_sets.ipynb
+++ b/ch01-datastructures/01_03_dicts_sets.ipynb
@@ -9,7 +9,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 1,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -25,7 +25,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 2,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -34,34 +34,67 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 3,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "{'United States': 'Washington, DC', 'France': 'Paris', 'Italy': 'Rome'}"
+      ]
+     },
+     "execution_count": 3,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "capitals"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 4,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "(3, 0)"
+      ]
+     },
+     "execution_count": 4,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "len(capitals), len({})"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 5,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'Rome'"
+      ]
+     },
+     "execution_count": 5,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "capitals['Italy']"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 6,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -70,34 +103,70 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 7,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "{'United States': 'Washington, DC',\n",
+       " 'France': 'Paris',\n",
+       " 'Italy': 'Rome',\n",
+       " 'Spain': 'Madrid'}"
+      ]
+     },
+     "execution_count": 7,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "capitals"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 9,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'KeyError'"
+      ]
+     },
+     "execution_count": 9,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
-    "capitals['Germany']"
+    "capitals['Germany'] if 'Germany' in capitals else 'KeyError'"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 10,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "(False, True)"
+      ]
+     },
+     "execution_count": 10,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "'Germany' in capitals, 'Italy' in capitals"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 11,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -106,16 +175,32 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 12,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "{'United States': 'Washington, DC',\n",
+       " 'France': 'Paris',\n",
+       " 'Italy': 'Rome',\n",
+       " 'Spain': 'Madrid',\n",
+       " 'Germany': 'Berlin',\n",
+       " 'United Kingdom': 'London'}"
+      ]
+     },
+     "execution_count": 12,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "{**capitals, **morecapitals}"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 13,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -124,16 +209,32 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 14,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "{'United States': 'Washington, DC',\n",
+       " 'France': 'Paris',\n",
+       " 'Italy': 'Rome',\n",
+       " 'Spain': 'Madrid',\n",
+       " 'Germany': 'Berlin',\n",
+       " 'United Kingdom': 'London'}"
+      ]
+     },
+     "execution_count": 14,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "capitals"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 15,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -142,16 +243,31 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 16,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "{'United States': 'Washington, DC',\n",
+       " 'France': 'Paris',\n",
+       " 'Italy': 'Rome',\n",
+       " 'Spain': 'Madrid',\n",
+       " 'Germany': 'Berlin'}"
+      ]
+     },
+     "execution_count": 16,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "capitals"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 17,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -160,9 +276,40 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 19,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "{(7, 15): 'Michele', (3, 14): 'Albert'}"
+      ]
+     },
+     "execution_count": 19,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "birthdays"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 18,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "'Michele'"
+      ]
+     },
+     "execution_count": 18,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "birthdays[(7,15)]"
    ]
@@ -333,11 +480,321 @@
     "for c in continents:\n",
     "    print(c)"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "**Example: dictionaries with various hashable key types**\n",
+    "\n",
+    "Below is a compact example that uses many kinds of hashable objects as dictionary keys and demonstrates retrieval and iteration. Mutable objects like `list` are not hashable and cannot be used as keys."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Dictionary with mixed hashable keys:\n",
+      " {42: 'an int key', 3.14: 'a float key', 'name': 'a str key', (1, 2): 'a tuple key', frozenset({1, 2}): 'a frozenset key', True: 'a bool key', b'bytes': 'a bytes key', datetime.date(2025, 12, 11): 'a date key', Point(x=1, y=2): 'a frozen dataclass instance key'}\n",
+      "Access some values:\n",
+      " a tuple key a date key a frozen dataclass instance key\n",
+      "\n",
+      "Types of keys:\n",
+      "<class 'int'> -> 42\n",
+      "<class 'float'> -> 3.14\n",
+      "<class 'str'> -> name\n",
+      "<class 'tuple'> -> (1, 2)\n",
+      "<class 'frozenset'> -> frozenset({1, 2})\n",
+      "<class 'bool'> -> True\n",
+      "<class 'bytes'> -> b'bytes'\n",
+      "<class 'datetime.date'> -> 2025-12-11\n",
+      "<class '__main__.Point'> -> Point(x=1, y=2)\n",
+      "  This key is a Point with coordinates: 1 2\n",
+      "\n",
+      "Collision example (1 and True): {1: 'true'}\n"
+     ]
+    }
+   ],
+   "source": [
+    "from dataclasses import dataclass\n",
+    "import datetime\n",
+    "\n",
+    "@dataclass(frozen=True)\n",
+    "class Point:\n",
+    "    x: int\n",
+    "    y: int\n",
+    "\n",
+    "p = Point(1, 2)\n",
+    "\n",
+    "d = {\n",
+    "    42: \"an int key\",\n",
+    "    3.14: \"a float key\",\n",
+    "    \"name\": \"a str key\",\n",
+    "    (1, 2): \"a tuple key\",\n",
+    "    frozenset({1, 2}): \"a frozenset key\",\n",
+    "    True: \"a bool key\",\n",
+    "    b'bytes': \"a bytes key\",\n",
+    "    datetime.date(2025, 12, 11): \"a date key\",\n",
+    "    p: \"a frozen dataclass instance key\",\n",
+    "}\n",
+    "\n",
+    "print(\"Dictionary with mixed hashable keys:\\n\", d)\n",
+    "print(\"Access some values:\\n\", d[(1, 2)], d[datetime.date(2025, 12, 11)], d[p])\n",
+    "\n",
+    "print('\\nTypes of keys:')\n",
+    "for k in d:\n",
+    "    print(type(k), '->', k)\n",
+    "    if isinstance(k, Point):\n",
+    "        print('  This key is a Point with coordinates:', k.x, k.y)\n",
+    "\n",
+    "# Note: the following would raise TypeError (unhashable):\n",
+    "# d[[1,2]] = 'list as key'  # TypeError: unhashable type: 'list'\n",
+    "\n",
+    "# Special note: bool is a subclass of int, so True and 1 collide as keys:\n",
+    "d2 = {1: 'one', True: 'true'}\n",
+    "print('\\nCollision example (1 and True):', d2)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "**Frozenset examples**\n",
+    "\n",
+    "A `frozenset` is an immutable `set`. It supports non-mutating set operations and is hashable, so it can be used as a dictionary key or stored inside a `set`."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "fs: frozenset({1, 2, 3})\n",
+      "fs.add -> AttributeError 'frozenset' object has no attribute 'add'\n",
+      "union with {3,4}: frozenset({1, 2, 3, 4})\n",
+      "intersection with [2,3]: frozenset({2, 3})\n",
+      "fs == set([1,2,3]): True\n",
+      "dict access by frozenset key: value for frozenset key\n",
+      "set containing frozensets: {frozenset({1}), frozenset({2, 3})}\n",
+      "fs after union (original unchanged): frozenset({1, 2, 3}) -> new: frozenset({1, 2, 3, 4})\n"
+     ]
+    }
+   ],
+   "source": [
+    "# frozenset demo\n",
+    "fs = frozenset([1, 2, 3])\n",
+    "print('fs:', fs)\n",
+    "\n",
+    "# immutability: mutating methods don't exist (this will raise AttributeError)\n",
+    "try:\n",
+    "    fs.add(4)\n",
+    "except Exception as e:\n",
+    "    print('fs.add ->', type(e).__name__, e)\n",
+    "\n",
+    "# non-mutating operations return new frozensets\n",
+    "print('union with {3,4}:', fs.union({3, 4}))\n",
+    "print('intersection with [2,3]:', fs.intersection([2, 3]))\n",
+    "\n",
+    "# equality with set compares by membership\n",
+    "print('fs == set([1,2,3]):', fs == set([1, 2, 3]))\n",
+    "\n",
+    "# frozenset can be used as a dict key or as an element of a set\n",
+    "d = {fs: 'value for frozenset key'}\n",
+    "print('dict access by frozenset key:', d[fs])\n",
+    "\n",
+    "s = {frozenset([1]), frozenset([2, 3])}\n",
+    "print('set containing frozensets:', s)\n",
+    "\n",
+    "# unhashable example (would raise TypeError):\n",
+    "# d[set([1,2])] = 'bad'  # TypeError: unhashable type: 'set' (not hashable)\n",
+    "\n",
+    "# note: frozenset methods do not modify in-place; they return new frozensets\n",
+    "fs2 = fs.union([4])\n",
+    "print('fs after union (original unchanged):', fs, '-> new:', fs2)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "**Making classes immutable/hashable: dataclass vs manual dunder methods**\n",
+    "\n",
+    "There are two main approaches:\n",
+    "1. **`@dataclass(frozen=True)`** — Simple, automatic immutability and hashability  \n",
+    "2. **Manual `__hash__` & `__eq__` overrides** — More control, but requires you to handle immutability separately\n",
+    "\n",
+    "For finality (preventing subclassing), use `@final` from `typing` module.\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 11,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Dataclass approach:\n",
+      "  p1: PointDataclass(x=1, y=2)\n",
+      "  hash(p1): -3550055125485641917\n",
+      "  Can use as dict key: {PointDataclass(x=1, y=2): 'success'}\n",
+      "  p1.x = 5 -> FrozenInstanceError: cannot assign to field 'x'\n",
+      "\n",
+      "Manual approach:\n",
+      "  p2: PointManual(1, 2)\n",
+      "  hash(p2): -3550055125485641917\n",
+      "  Can use as dict key: {PointManual(1, 2): 'success'}\n",
+      "  Equality works: True\n",
+      "  p2.x = 5 -> AttributeError (property read-only)\n",
+      "\n",
+      "Final class (with @final decorator):\n",
+      "  FinalPoint(3, 4): FinalPoint(x=3, y=4)\n"
+     ]
+    }
+   ],
+   "source": [
+    "# Approach 1: dataclass with frozen=True (simple, automatic)\n",
+    "from dataclasses import dataclass\n",
+    "from typing import final\n",
+    "\n",
+    "@dataclass(frozen=True)\n",
+    "class PointDataclass:\n",
+    "    x: int\n",
+    "    y: int\n",
+    "\n",
+    "p1 = PointDataclass(1, 2)\n",
+    "print(\"Dataclass approach:\")\n",
+    "print(\"  p1:\", p1)\n",
+    "print(\"  hash(p1):\", hash(p1))\n",
+    "print(\"  Can use as dict key:\", {p1: \"success\"})\n",
+    "\n",
+    "# Try to mutate (will raise FrozenInstanceError)\n",
+    "try:\n",
+    "    p1.x = 5\n",
+    "except Exception as e:\n",
+    "    print(f\"  p1.x = 5 -> {type(e).__name__}: {e}\")\n",
+    "\n",
+    "print()\n",
+    "\n",
+    "# Approach 2: Manual __hash__ and __eq__ (more control, but more code)\n",
+    "class PointManual:\n",
+    "    def __init__(self, x: int, y: int):\n",
+    "        # Store in private attributes to prevent direct mutation\n",
+    "        self._x = x\n",
+    "        self._y = y\n",
+    "    \n",
+    "    @property\n",
+    "    def x(self):\n",
+    "        return self._x\n",
+    "    \n",
+    "    @property\n",
+    "    def y(self):\n",
+    "        return self._y\n",
+    "    \n",
+    "    def __eq__(self, other):\n",
+    "        if not isinstance(other, PointManual):\n",
+    "            return False\n",
+    "        return self._x == other._x and self._y == other._y\n",
+    "    \n",
+    "    def __hash__(self):\n",
+    "        return hash((self._x, self._y))\n",
+    "    \n",
+    "    def __repr__(self):\n",
+    "        return f\"PointManual({self._x}, {self._y})\"\n",
+    "\n",
+    "p2 = PointManual(1, 2)\n",
+    "print(\"Manual approach:\")\n",
+    "print(\"  p2:\", p2)\n",
+    "print(\"  hash(p2):\", hash(p2))\n",
+    "print(\"  Can use as dict key:\", {p2: \"success\"})\n",
+    "print(\"  Equality works:\", PointManual(1, 2) == p2)\n",
+    "\n",
+    "# Attempting direct mutation is harder (properties prevent it)\n",
+    "try:\n",
+    "    p2.x = 5\n",
+    "except AttributeError as e:\n",
+    "    print(f\"  p2.x = 5 -> AttributeError (property read-only)\")\n",
+    "\n",
+    "print()\n",
+    "\n",
+    "# Approach 3: Using @final to prevent subclassing\n",
+    "@final\n",
+    "@dataclass(frozen=True)\n",
+    "class FinalPoint:\n",
+    "    x: int\n",
+    "    y: int\n",
+    "\n",
+    "print(\"Final class (with @final decorator):\")\n",
+    "print(\"  FinalPoint(3, 4):\", FinalPoint(3, 4))\n",
+    "# Trying to subclass FinalPoint would raise TypeError at class definition time\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 9,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Trying to subclass TrulyFinalPoint:\n",
+      "  ✓ Correctly raised: Cannot subclass subTrulyFinalPoint; it is final\n",
+      "\n",
+      "@final (from typing) is only for static type checkers:\n",
+      "  - Mypy will flag violations\n",
+      "  - But Python allows subclassing at runtime\n",
+      "  - Use __init_subclass__ to enforce at runtime\n"
+     ]
+    }
+   ],
+   "source": [
+    "# IMPORTANT: @final only works at type-checking time, NOT at runtime!\n",
+    "# This means Mypy will complain, but Python won't prevent it.\n",
+    "\n",
+    "# To actually enforce immutability at runtime, use __init_subclass__:\n",
+    "@dataclass(frozen=True)\n",
+    "class TrulyFinalPoint:\n",
+    "    x: int\n",
+    "    y: int\n",
+    "    \n",
+    "    def __init_subclass__(cls, **kwargs):\n",
+    "        raise TypeError(f\"Cannot subclass {cls.__name__}; it is final\")\n",
+    "\n",
+    "print(\"Trying to subclass TrulyFinalPoint:\")\n",
+    "try:\n",
+    "    class subTrulyFinalPoint(TrulyFinalPoint):\n",
+    "        pass\n",
+    "except TypeError as e:\n",
+    "    print(f\"  ✓ Correctly raised: {e}\")\n",
+    "\n",
+    "print(\"\\n@final (from typing) is only for static type checkers:\")\n",
+    "print(\"  - Mypy will flag violations\")\n",
+    "print(\"  - But Python allows subclassing at runtime\")\n",
+    "print(\"  - Use __init_subclass__ to enforce at runtime\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
   }
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3 (ipykernel)",
+   "display_name": ".venv",
    "language": "python",
    "name": "python3"
   },
@@ -351,7 +808,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.11.8"
+   "version": "3.12.1"
   }
  },
  "nbformat": 4,