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+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "id": "0",
+   "metadata": {},
+   "source": [
+    "# Python Insights 🤓"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "1",
+   "metadata": {
+    "jp-MarkdownHeadingCollapsed": true
+   },
+   "source": [
+    "## Why intervals are open-ended in Python?"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "2",
+   "metadata": {
+    "jp-MarkdownHeadingCollapsed": true
+   },
+   "source": [
+    "Half-open intervals `[start:end)` with 0-based indexing"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "3",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "lst = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i']\n",
+    "lst"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "4",
+   "metadata": {},
+   "source": [
+    "### 1. Length is just end - start"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "5",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "lst[1:4]  # ['b', 'c', 'd'] — length is 4-1 = 3"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "6",
+   "metadata": {},
+   "source": [
+    "### 2. Consecutive slices don't overlap"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "7",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "lst[0:3]  # ['a', 'b', 'c']"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "8",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "lst[3:6]  # ['d', 'e', 'f']"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "9",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "lst[6:9]  # ['g', 'h', 'i']"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "10",
+   "metadata": {},
+   "source": [
+    "### 3. First n elements is clean"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "11",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "n = 5\n",
+    "lst[:n]  # ['a', 'b', 'c', 'd', 'e'] — exactly n elements"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "12",
+   "metadata": {},
+   "source": [
+    "### 4. Empty slices make sense"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "13",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "lst[3:3]  # [] — naturally empty"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "14",
+   "metadata": {
+    "jp-MarkdownHeadingCollapsed": true
+   },
+   "source": [
+    "## What happens inside a `for` and `while` loops?"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "15",
+   "metadata": {},
+   "source": [
+    "**Remember:** in Python, `for item in container` allows you to assign the `item` variable to **every single element** that `container` holds.\n",
+    "One at a time.\n",
+    "\n",
+    "We call these container objects **iterables**."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "16",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "fruits = [\"apple\", \"banana\", \"cherry\"]  # a list, a tuple, a string, a dictionary, a set... are all iterables\n",
+    "count = 0\n",
+    "\n",
+    "for fruit in fruits:\n",
+    "    count += 1\n",
+    "    print(f\"Item {count}: {fruit}\")\n",
+    "\n",
+    "print(f\"Total fruits: {count}\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "17",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "for index, fruit = enumerate(fruits):\n",
+    "    print(index, fruit)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "18",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "a, b, c = 1, 2, 3"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "19",
+   "metadata": {},
+   "source": [
+    "Let's try to \"visualize\" what happens with the [Python Tutor](https://pythontutor.com/render.html#code=fruits%20%3D%20%5B%22apple%22,%20%22banana%22,%20%22cherry%22%5D%0Acount%20%3D%200%0A%0Afor%20fruit%20in%20fruits%3A%0A%20%20%20%20count%20%2B%3D%201%0A%20%20%20%20print%28f%22Item%20%7Bcount%7D%3A%20%7Bfruit%7D%22%29%0A%0Aprint%28f%22Total%20fruits%3A%20%7Bcount%7D%22%29&cumulative=false&curInstr=0&heapPrimitives=nevernest&mode=display&origin=opt-frontend.js&py=311&rawInputLstJSON=%5B%5D&textReferences=false)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "20",
+   "metadata": {},
+   "source": [
+    "The same idea with a `while` loop"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "21",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "fruits = [\"apple\", \"banana\", \"cherry\"]\n",
+    "i = 0\n",
+    "\n",
+    "while i < len(fruits):\n",
+    "    fruit = fruits[i]\n",
+    "    print(f\"Item {i+1}: {fruit}\")\n",
+    "    i += 1\n",
+    "\n",
+    "print(\"Done!\")"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "22",
+   "metadata": {},
+   "source": [
+    "With the [Python Tutor](https://pythontutor.com/render.html#code=fruits%20%3D%20%5B%22apple%22,%20%22banana%22,%20%22cherry%22%5D%0Ai%20%3D%200%0A%0Awhile%20i%20%3C%20len%28fruits%29%3A%0A%20%20%20%20fruit%20%3D%20fruits%5Bi%5D%0A%20%20%20%20print%28f%22Item%20%7Bi%2B1%7D%3A%20%7Bfruit%7D%22%29%0A%20%20%20%20i%20%2B%3D%201%0A%0Aprint%28%22Done!%22%29&cumulative=false&curInstr=0&heapPrimitives=nevernest&mode=display&origin=opt-frontend.js&py=311&rawInputLstJSON=%5B%5D&textReferences=false)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "23",
+   "metadata": {},
+   "source": [
+    "### One example"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "24",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "numbers = [1, 2, 3]\n",
+    "result = []\n",
+    "\n",
+    "for num in numbers:\n",
+    "    result.append(num * 2)\n",
+    "    print(f\"Num is: {num}\")\n",
+    "\n",
+    "print(f\"Numbers (list): {numbers}\")  # What do you think are the values of numbers?\n",
+    "print(result)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "25",
+   "metadata": {},
+   "source": [
+    "## Some live coding together"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "26",
+   "metadata": {},
+   "source": [
+    "### Remove vowels"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "27",
+   "metadata": {},
+   "source": [
+    "<a href=\"https://leetle.app/?date=2025-07-02\" target=\"_blank\">From Leetle, 2 July 2025</a>\n",
+    "\n",
+    "Write a function that takes a string and returns a new string with all vowels (a, e, i, o, u) removed.\n",
+    "Both uppercase and lowercase vowels should be removed.\n",
+    "\n",
+    "Examples:\n",
+    "- Input: `\"hello, world!\"`\n",
+    "- Output: `\"hll, wrld!\"`"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "28",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def solve(message: str) -> str:\n",
+    "    vowels = \"aeiouAEIOU\"\n",
+    "    result = \"\"\n",
+    "    for char in message:\n",
+    "        if char not in vowels:\n",
+    "            result += char\n",
+    "    return result"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "29",
+   "metadata": {},
+   "source": [
+    "### Old phones keyboards"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "30",
+   "metadata": {},
+   "source": [
+    "<a href=\"https://leetle.app/?date=2025-08-04\" target=\"_blank\">From Leetle, 8 August 2025</a>\n",
+    "\n",
+    "Write a function that decodes old phone keypad text input.\n",
+    "Each number represents letters: `2=ABC`, `3=DEF`, `4=GHI`, `5=JKL`, `6=MNO`, `7=PQRS`, `8=TUV`, `9=WXYZ`.\n",
+    "Multiple presses select the letter (`22=B`, `777=R`).\n",
+    "Space separates different letters on same key."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "31",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def solve(string: str) -> str:\n",
+    "    keypad = {\n",
+    "        \"2\": \"ABC\", \"3\": \"DEF\", \"4\": \"GHI\", \"5\": \"JKL\",\n",
+    "        \"6\": \"MNO\", \"7\": \"PQRS\", \"8\": \"TUV\", \"9\": \"WXYZ\",\n",
+    "    }\n",
+    "    result = \"\"\n",
+    "    for word in string.split():\n",
+    "        press = len(word) - 1\n",
+    "        number = keypad[word[0]]\n",
+    "        result += keypad[number][press]\n",
+    "    return result"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "32",
+   "metadata": {},
+   "source": [
+    "### Sum until a single digit"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "33",
+   "metadata": {},
+   "source": [
+    "<a href=\"https://leetle.app/?date=2025-05-03\">From Leetle, 3 May 2025</a>\n",
+    "\n",
+    "Write a function that repeatedly sums the digits of a number until a single digit is obtained.\n",
+    "\n",
+    "Examples:\n",
+    "\n",
+    "| Input | Output | Steps |\n",
+    "| --- | --- | --- |\n",
+    "| 16 | 7 | 6+1 = 7 |\n",
+    "| 546 | 6 | 5+4+6 = 15 then 1+5 = 6 |"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "34",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def solve(number: int) -> int:\n",
+    "    ..."
+   ]
+  }
+ ],
+ "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": "3.13.7"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}