From 8de993b2f71742e87b09d823ab83b994ec462120 Mon Sep 17 00:00:00 2001
From: Lopes <fabio.lopes@empa.ch>
Date: Mon, 3 Nov 2025 18:08:26 +0100
Subject: [PATCH 01/11] Resolving part of the issue #272

---
 03_functions.ipynb                   |  10 +-
 04_input_output.ipynb                | 559 ++++++++++++++++++++++-----
 05_object_oriented_programming.ipynb |   2 +-
 tutorial/quiz/input_output.py        |   8 +-
 tutorial/tests/data/example1.csv     |  11 +
 tutorial/tests/data/me.txt           |   1 +
 tutorial/tests/data/numbers.txt      |  10 +
 tutorial/tests/data/output.txt       | Bin 0 -> 10 bytes
 tutorial/tests/data/output1.txt      | Bin 0 -> 2048 bytes
 tutorial/tests/test_03_functions.py  |  28 +-
 10 files changed, 512 insertions(+), 117 deletions(-)
 create mode 100644 tutorial/tests/data/example1.csv
 create mode 100644 tutorial/tests/data/me.txt
 create mode 100644 tutorial/tests/data/numbers.txt
 create mode 100644 tutorial/tests/data/output.txt
 create mode 100644 tutorial/tests/data/output1.txt

diff --git a/03_functions.ipynb b/03_functions.ipynb
index ef3f619f..a549e075 100644
--- a/03_functions.ipynb
+++ b/03_functions.ipynb
@@ -489,7 +489,7 @@
     "\n",
     "*Hint:* you can use the [built-in function](https://docs.python.org/3/library/functions.html#round) `round(number, ndigits)` function to round the floating point `number` to a given number expressed by `ndigits`.\n",
     "\n",
-    "Example: `length=2`, `width=3` should return `\"6.00 cm^2\"`\n",
+    "Example: `length=1.5`, `width=2.57` should return `\"3.85 cm^2\"`\n",
     "\n",
     "<div class=\"alert alert-block alert-warning\">\n",
     "    <h4><b>Note</b></h4>\n",
@@ -515,7 +515,7 @@
     "\n",
     "    Returns:\n",
     "        - A string representing the area with 2 decimal places,\n",
-    "          followed by \"cm^2\" (e.g., \"6.00 cm^2\")\n",
+    "          followed by \"cm^2\" (e.g., \"3.85 cm^2\")\n",
     "    \"\"\"\n",
     "    return"
    ]
@@ -528,12 +528,14 @@
     "### Part 2\n",
     "\n",
     "Extend the previous function, now called `solution_calculate_metric_area`, by adding a `unit` parameter that can be either \"cm\" or \"m\".\n",
+    "The default `length` and `width` unit is centimeters (\"cm\").\n",
+    "\n",
     "If the unit is \"m\", convert the measurements to centimeters before calculating the area.\n",
     "The result should still be in cm^2.\n",
     "\n",
     "*Hint:* remember the [built-in function](https://docs.python.org/3/library/functions.html#round) `round(number, ndigits)`.\n",
     "\n",
-    "Example: `length=2`, `width=3`, `unit=\"m\"` should return `\"60000.00 cm^2\"` (because 2m × 3m = 6m² = 60000cm²)\n",
+    "Example: `length=2.0`, `width=3.0`, `unit=\"m\"` should return `\"60000.0 cm^2\"` (because 2m × 3m = 6m² = 60000cm²)\n",
     "\n",
     "<div class=\"alert alert-block alert-warning\">\n",
     "    <h4><b>Note</b></h4>\n",
@@ -573,7 +575,7 @@
     "### Part 3\n",
     "\n",
     "Extend the previous function, now called `solution_calculate_area`, to support the following units: cm, m, mm, yd, and ft.\n",
-    "The calculated area should always be in centimeters, so you need to take care of the appropriate conversions (when needed).\n",
+    "The calculated area should always be in cm^2, so you need to take care of the appropriate conversions (when needed).\n",
     "Keep the same string format for the result.\n",
     "\n",
     "Use the following conversion factors:\n",
diff --git a/04_input_output.ipynb b/04_input_output.ipynb
index 7a4c3153..4ce37f05 100644
--- a/04_input_output.ipynb
+++ b/04_input_output.ipynb
@@ -40,11 +40,11 @@
     "      - [Reading/Writing CSV files](#Reading/Writing-CSV-files)\n",
     "        - [Quiz on CSV](#Quiz-on-CSV)\n",
     "    - [Exercises](#Exercises)\n",
-    "      - [Exercise 1: CSV to dictionary 🌶️](#Exercise-1:-CSV-to-dictionary-🌶️)\n",
-    "      - [Exercise 2: Counting words 🌶️](#Exercise-2:-Counting-words-🌶️)\n",
-    "      - [Exercise 3: Letter statistics 🌶️🌶️](#Exercise-3:-Letter-statistics-🌶️🌶️)\n",
-    "      - [Exercise 4: Translating words 🌶️🌶️](#Exercise-4:-Translating-words-🌶️🌶️)\n",
-    "      - [Exercise 5: Binary format 🌶️🌶️🌶️](#Exercise-5:-Binary-format-🌶️🌶️🌶️)"
+    "      - [Exercise 1: CSV to dictionary (easy)](#Exercise-1:-CSV-to-dictionary-(easy))\n",
+    "      - [Exercise 2: Counting words (easy)](#Exercise-2:-Counting-words-(easy))\n",
+    "      - [Exercise 3: Letter statistics (medium)](#Exercise-3:-Letter-statistics-(medium))\n",
+    "      - [Exercise 4: Translating words (medium)](#Exercise-4:-Translating-words-(medium))\n",
+    "      - [Exercise 5: Binary format (hard)](#Exercise-5:-Binary-format-(hard))"
    ]
   },
   {
@@ -75,13 +75,7 @@
     "- connecting to databases or other network services\n",
     "\n",
     "\n",
-    "The majority of these operations are covered by the Python standard library. We are going to see how to use them in this chapter.\n",
-    "\n",
-    "<div class=\"alert alert-block alert-info\">\n",
-    "    <h4><b>Note</b></h4>\n",
-    "In reference to the chapter on functional programming, it is interesting to note that these functions perform <b>side-effects</b>. Therefore, any code containing these operations is no longer <b>pure</b> and is not referentially transparent. The same function can return different values for the same argument if called multiple times, and the function can have <b>long-distance</b> effects. That means they can modify the program state elsewhere, leading to unexpected results.<br><br>\n",
-    "Therefore, we suggest separating input and output from the other computations in your program. For example, if you have a complex calculation requiring several user inputs at several stages of the process, consider writing a function that only performs the calculation given all inputs and then requires all inputs separately, for example, through a single file. This makes your code easier to debug, test and understand.\n",
-    "</div>"
+    "The majority of these operations are covered by the Python standard library. We are going to see how to use them in this chapter."
    ]
   },
   {
@@ -108,8 +102,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "It is also possible to print any other python object using `print`. \n",
-    "In that case, the `__str__` **magic method** on that object's class is [called](https://docs.python.org/3/reference/datamodel.html#object.__str__)."
+    "It is also possible to print any other python object using `print`."
    ]
   },
   {
@@ -154,7 +147,9 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "metadata": {},
+   "metadata": {
+    "scrolled": true
+   },
    "outputs": [],
    "source": [
     "import tutorial.quiz.input_output as op\n",
@@ -245,7 +240,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "%%ipytest debug\n",
+    "%%ipytest\n",
     "\n",
     "def solution_print_odd(n: int) -> None: \n",
     "    \"\"\"Prints all odd numbers from 1 to n\n",
@@ -255,8 +250,7 @@
     "\n",
     "    Returns:\n",
     "        - None (prints to console)\n",
-    "    \"\"\"\n",
-    "    pass"
+    "    \"\"\""
    ]
   },
   {
@@ -287,7 +281,6 @@
     "    Returns:\n",
     "        - None (prints to console)\n",
     "    \"\"\"\n",
-    "    pass\n",
     "\n",
     "solution_print_salutation()"
    ]
@@ -495,9 +488,25 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "b5d9190bff57413c8c14c640aa74557a",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "Paths(children=(Question(children=(HTML(value='<strong>Q1:</strong> What does the operator <code>/</code> do w…"
+      ]
+     },
+     "execution_count": 1,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "import tutorial.quiz.input_output as op\n",
     "op.Paths()"
@@ -513,9 +522,34 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "<div style='background-color: #ffebee; border-radius: 5px; padding: 10px;'>🚫 <strong style='color: red;'>OpenAI API key is not provided.</strong><br>API key is missing.</div>"
+      ],
+      "text/plain": [
+       "<IPython.core.display.HTML object>"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    },
+    {
+     "data": {
+      "text/html": [
+       "<div style='background-color: #fffde7; border-radius: 5px; padding: 10px;'>🔄 <strong>IPytest extension (re)loaded.</strong></div>"
+      ],
+      "text/plain": [
+       "<IPython.core.display.HTML object>"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%reload_ext tutorial.tests.testsuite"
    ]
@@ -535,9 +569,24 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 3,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "5a82cdcf4ce1468d8718502eafc1c89a",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -565,9 +614,24 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 9,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "2f2eb3ad53e4430b836b3fbcaa5f0f66",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -597,9 +661,24 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 10,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "5acc98c538244a7487e51251a8ce1b71",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -613,8 +692,7 @@
     "\n",
     "    Returns:\n",
     "        - The number of directories in the directory\n",
-    "    \"\"\"\n",
-    "    pass\n"
+    "    \"\"\""
    ]
   },
   {
@@ -637,11 +715,19 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 11,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "['Hello, I am a file with some text.\\n']\n"
+     ]
+    }
+   ],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -662,11 +748,20 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 12,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "['Hello, I am a file with some text.\\n']\n",
+      "[]\n"
+     ]
+    }
+   ],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -689,11 +784,34 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 13,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "this\n",
+      "\n",
+      "file\n",
+      "\n",
+      "has multiple\n",
+      "\n",
+      "lines\n",
+      "\n",
+      "how many\n",
+      "\n",
+      "lines\n",
+      "\n",
+      "does this file\n",
+      "\n",
+      "have?\n",
+      "\n"
+     ]
+    }
+   ],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -721,9 +839,25 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 14,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "ad907828193c4bbaa30116d5342f87dd",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "ReadFiles(children=(Question(children=(HTML(value='<strong>Q1:</strong> Can you read from a file before callin…"
+      ]
+     },
+     "execution_count": 14,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "import tutorial.quiz.input_output as op\n",
     "op.ReadFiles()"
@@ -739,9 +873,34 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 15,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "<div style='background-color: #ffebee; border-radius: 5px; padding: 10px;'>🚫 <strong style='color: red;'>OpenAI API key is not provided.</strong><br>API key is missing.</div>"
+      ],
+      "text/plain": [
+       "<IPython.core.display.HTML object>"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    },
+    {
+     "data": {
+      "text/html": [
+       "<div style='background-color: #fffde7; border-radius: 5px; padding: 10px;'>🔄 <strong>IPytest extension (re)loaded.</strong></div>"
+      ],
+      "text/plain": [
+       "<IPython.core.display.HTML object>"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%reload_ext tutorial.tests.testsuite"
    ]
@@ -756,9 +915,24 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 18,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "658982e189394032bd022f74294fd393",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -773,7 +947,7 @@
     "    Returns:\n",
     "        - A list of strings, each representing a line in the file\n",
     "    \"\"\"\n",
-    "    pass"
+    "    return"
    ]
   },
   {
@@ -792,7 +966,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 19,
    "metadata": {
     "tags": []
    },
@@ -818,7 +992,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 20,
    "metadata": {
     "tags": []
    },
@@ -849,9 +1023,25 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 21,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "cb48e1322fe843a2ae8628f24d467a16",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "WriteFiles(children=(Question(children=(HTML(value='<strong>Q1:</strong> What does <code>w</code> in the secon…"
+      ]
+     },
+     "execution_count": 21,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "import tutorial.quiz.input_output as op\n",
     "op.WriteFiles()"
@@ -867,9 +1057,34 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 22,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "<div style='background-color: #ffebee; border-radius: 5px; padding: 10px;'>🚫 <strong style='color: red;'>OpenAI API key is not provided.</strong><br>API key is missing.</div>"
+      ],
+      "text/plain": [
+       "<IPython.core.display.HTML object>"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    },
+    {
+     "data": {
+      "text/html": [
+       "<div style='background-color: #fffde7; border-radius: 5px; padding: 10px;'>🔄 <strong>IPytest extension (re)loaded.</strong></div>"
+      ],
+      "text/plain": [
+       "<IPython.core.display.HTML object>"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%reload_ext tutorial.tests.testsuite"
    ]
@@ -884,9 +1099,24 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 23,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "044f8550f1914cb49ee4d639a7d553c6",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -902,8 +1132,7 @@
     "\n",
     "    Returns:\n",
     "        - None (writes to file)\n",
-    "    \"\"\"\n",
-    "    pass"
+    "    \"\"\""
    ]
   },
   {
@@ -911,24 +1140,45 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "2. Modify the function `solution_read_write_file` to read the lines from the file `input_file` and write them in the form `line, length`, to the file `output_file`. Here `line` is the line of text in `input_file` **without the line ending**, `length` is **number of characters** in that line **without the line separator**.\n",
-    "If `input_file` contains these lines:\n",
+    "2. Modify the function `solution_read_write_file` to read the lines from the file `input_file` and write them in the form `line, length`, to the file `output_file`. Here `line` is the line of text in `input_file` **without the line ending (\\r\\n)**, `length` is **number of characters** in that line. The characters are added automatically by the operating system when reading a file. Windows uses **\\r\\n** whereas Linux and MacOS use only **\\n**. To remove the line ending characters, use ```strip(\"\\r\\n\")```, e.g.: ```line.strip(\"\\r\\n\")```.\n",
+    "\n",
+    "    If `input_file` contains these lines:\n",
+    "    \n",
     "    ```\n",
     "    first\n",
     "    second\n",
     "    ```\n",
+    "    \n",
     "    we expect the output file to contain these lines:\n",
+    "    \n",
     "    ```\n",
     "    first, 5\n",
     "    second, 6\n",
-    "    ```"
+    "    ```\n",
+    "    \n",
+    "    Do not forget to add a **\\n** when writing lines in the file."
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 31,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "5ec927991895480bbfc1d720c592a674",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -945,8 +1195,7 @@
     "\n",
     "    Returns:\n",
     "        - None (writes to file)\n",
-    "    \"\"\"\n",
-    "    pass"
+    "    \"\"\""
    ]
   },
   {
@@ -974,11 +1223,19 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 32,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "['Hello, I am a file with some text.\\n']\n"
+     ]
+    }
+   ],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -1013,9 +1270,25 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 33,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "4a284a916de749929f85bee97e286c61",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "ContextManagers(children=(Question(children=(HTML(value='<strong>Q1:</strong> Do you need to call <code>close<…"
+      ]
+     },
+     "execution_count": 33,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "import tutorial.quiz.input_output as op\n",
     "op.ContextManagers()"
@@ -1040,11 +1313,19 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 34,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "b'\\x00\\x01\\x02\\x03\\x04\\x05\\x06\\x07\\x08\\t'\n"
+     ]
+    }
+   ],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -1067,11 +1348,19 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 35,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]\n"
+     ]
+    }
+   ],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -1096,7 +1385,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 36,
    "metadata": {
     "tags": []
    },
@@ -1125,11 +1414,19 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 37,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276, 277, 278, 279, 280, 281, 282, 283, 284, 285, 286, 287, 288, 289, 290, 291, 292, 293, 294, 295, 296, 297, 298, 299, 300, 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 311, 312, 313, 314, 315, 316, 317, 318, 319, 320, 321, 322, 323, 324, 325, 326, 327, 328, 329, 330, 331, 332, 333, 334, 335, 336, 337, 338, 339, 340, 341, 342, 343, 344, 345, 346, 347, 348, 349, 350, 351, 352, 353, 354, 355, 356, 357, 358, 359, 360, 361, 362, 363, 364, 365, 366, 367, 368, 369, 370, 371, 372, 373, 374, 375, 376, 377, 378, 379, 380, 381, 382, 383, 384, 385, 386, 387, 388, 389, 390, 391, 392, 393, 394, 395, 396, 397, 398, 399, 400, 401, 402, 403, 404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414, 415, 416, 417, 418, 419, 420, 421, 422, 423, 424, 425, 426, 427, 428, 429, 430, 431, 432, 433, 434, 435, 436, 437, 438, 439, 440, 441, 442, 443, 444, 445, 446, 447, 448, 449, 450, 451, 452, 453, 454, 455, 456, 457, 458, 459, 460, 461, 462, 463, 464, 465, 466, 467, 468, 469, 470, 471, 472, 473, 474, 475, 476, 477, 478, 479, 480, 481, 482, 483, 484, 485, 486, 487, 488, 489, 490, 491, 492, 493, 494, 495, 496, 497, 498, 499, 500, 501, 502, 503, 504, 505, 506, 507, 508, 509, 510, 511, 512, 513, 514, 515, 516, 517, 518, 519, 520, 521, 522, 523, 524, 525, 526, 527, 528, 529, 530, 531, 532, 533, 534, 535, 536, 537, 538, 539, 540, 541, 542, 543, 544, 545, 546, 547, 548, 549, 550, 551, 552, 553, 554, 555, 556, 557, 558, 559, 560, 561, 562, 563, 564, 565, 566, 567, 568, 569, 570, 571, 572, 573, 574, 575, 576, 577, 578, 579, 580, 581, 582, 583, 584, 585, 586, 587, 588, 589, 590, 591, 592, 593, 594, 595, 596, 597, 598, 599, 600, 601, 602, 603, 604, 605, 606, 607, 608, 609, 610, 611, 612, 613, 614, 615, 616, 617, 618, 619, 620, 621, 622, 623, 624, 625, 626, 627, 628, 629, 630, 631, 632, 633, 634, 635, 636, 637, 638, 639, 640, 641, 642, 643, 644, 645, 646, 647, 648, 649, 650, 651, 652, 653, 654, 655, 656, 657, 658, 659, 660, 661, 662, 663, 664, 665, 666, 667, 668, 669, 670, 671, 672, 673, 674, 675, 676, 677, 678, 679, 680, 681, 682, 683, 684, 685, 686, 687, 688, 689, 690, 691, 692, 693, 694, 695, 696, 697, 698, 699, 700, 701, 702, 703, 704, 705, 706, 707, 708, 709, 710, 711, 712, 713, 714, 715, 716, 717, 718, 719, 720, 721, 722, 723, 724, 725, 726, 727, 728, 729, 730, 731, 732, 733, 734, 735, 736, 737, 738, 739, 740, 741, 742, 743, 744, 745, 746, 747, 748, 749, 750, 751, 752, 753, 754, 755, 756, 757, 758, 759, 760, 761, 762, 763, 764, 765, 766, 767, 768, 769, 770, 771, 772, 773, 774, 775, 776, 777, 778, 779, 780, 781, 782, 783, 784, 785, 786, 787, 788, 789, 790, 791, 792, 793, 794, 795, 796, 797, 798, 799, 800, 801, 802, 803, 804, 805, 806, 807, 808, 809, 810, 811, 812, 813, 814, 815, 816, 817, 818, 819, 820, 821, 822, 823, 824, 825, 826, 827, 828, 829, 830, 831, 832, 833, 834, 835, 836, 837, 838, 839, 840, 841, 842, 843, 844, 845, 846, 847, 848, 849, 850, 851, 852, 853, 854, 855, 856, 857, 858, 859, 860, 861, 862, 863, 864, 865, 866, 867, 868, 869, 870, 871, 872, 873, 874, 875, 876, 877, 878, 879, 880, 881, 882, 883, 884, 885, 886, 887, 888, 889, 890, 891, 892, 893, 894, 895, 896, 897, 898, 899, 900, 901, 902, 903, 904, 905, 906, 907, 908, 909, 910, 911, 912, 913, 914, 915, 916, 917, 918, 919, 920, 921, 922, 923, 924, 925, 926, 927, 928, 929, 930, 931, 932, 933, 934, 935, 936, 937, 938, 939, 940, 941, 942, 943, 944, 945, 946, 947, 948, 949, 950, 951, 952, 953, 954, 955, 956, 957, 958, 959, 960, 961, 962, 963, 964, 965, 966, 967, 968, 969, 970, 971, 972, 973, 974, 975, 976, 977, 978, 979, 980, 981, 982, 983, 984, 985, 986, 987, 988, 989, 990, 991, 992, 993, 994, 995, 996, 997, 998, 999, 1000, 1001, 1002, 1003, 1004, 1005, 1006, 1007, 1008, 1009, 1010, 1011, 1012, 1013, 1014, 1015, 1016, 1017, 1018, 1019, 1020, 1021, 1022, 1023]\n"
+     ]
+    }
+   ],
    "source": [
     "import pathlib as pl\n",
     "import struct\n",
@@ -1156,11 +1453,41 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 38,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "bytes: ['0x0', '0x0', '0x0', '0x0'], integer: 0, string: \u0000\n",
+      "bytes: ['0x1', '0x0', '0x0', '0x0'], integer: 1, string: \u0001\n",
+      "bytes: ['0x2', '0x0', '0x0', '0x0'], integer: 2, string: \u0002\n",
+      "bytes: ['0x3', '0x0', '0x0', '0x0'], integer: 3, string: \u0003\n",
+      "bytes: ['0x4', '0x0', '0x0', '0x0'], integer: 4, string: \u0004\n",
+      "bytes: ['0x5', '0x0', '0x0', '0x0'], integer: 5, string: \u0005\n",
+      "bytes: ['0x3c', '0x0', '0x0', '0x0'], integer: 60, string: <\n",
+      "bytes: ['0x3d', '0x0', '0x0', '0x0'], integer: 61, string: =\n",
+      "bytes: ['0x3e', '0x0', '0x0', '0x0'], integer: 62, string: >\n",
+      "bytes: ['0x3f', '0x0', '0x0', '0x0'], integer: 63, string: ?\n",
+      "bytes: ['0x40', '0x0', '0x0', '0x0'], integer: 64, string: @\n",
+      "bytes: ['0x41', '0x0', '0x0', '0x0'], integer: 65, string: A\n",
+      "bytes: ['0x42', '0x0', '0x0', '0x0'], integer: 66, string: B\n",
+      "bytes: ['0x43', '0x0', '0x0', '0x0'], integer: 67, string: C\n",
+      "bytes: ['0x44', '0x0', '0x0', '0x0'], integer: 68, string: D\n",
+      "bytes: ['0x45', '0x0', '0x0', '0x0'], integer: 69, string: E\n",
+      "bytes: ['0x46', '0x0', '0x0', '0x0'], integer: 70, string: F\n",
+      "bytes: ['0x47', '0x0', '0x0', '0x0'], integer: 71, string: G\n",
+      "bytes: ['0x48', '0x0', '0x0', '0x0'], integer: 72, string: H\n",
+      "bytes: ['0x49', '0x0', '0x0', '0x0'], integer: 73, string: I\n",
+      "bytes: ['0x0', '0x2', '0x0', '0x0'], integer: 512, string: Ȁ\n",
+      "bytes: ['0x1', '0x2', '0x0', '0x0'], integer: 513, string: ȁ\n",
+      "bytes: ['0x2', '0x2', '0x0', '0x0'], integer: 514, string: Ȃ\n"
+     ]
+    }
+   ],
    "source": [
     "for i in range(0, 6):\n",
     "    bt = i.to_bytes(4, 'little')\n",
@@ -1193,15 +1520,28 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 46,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "The `uft8` codepoint  is = 67, the bytes representation = b'C\\x00\\x00\\x00', the representation is C\n",
+      "The `uft8` codepoint  is = 105, the bytes representation = b'i\\x00\\x00\\x00', the representation is i\n",
+      "The `uft8` codepoint  is = 97, the bytes representation = b'a\\x00\\x00\\x00', the representation is a\n",
+      "The `uft8` codepoint  is = 111, the bytes representation = b'o\\x00\\x00\\x00', the representation is o\n"
+     ]
+    }
+   ],
    "source": [
     "message = \"Ciao\"\n",
     "message_secret = bytes(message, \"utf-8\")\n",
-    "[print(f\"The `uft8` codepoint  is = {enc}, the bytes representation = {enc.to_bytes(4, 'little')}, the representation is {chr(enc)}\") for plain, enc in zip(message, message_secret)]"
+    "print_messages = [f\"The `uft8` codepoint  is = {enc}, the bytes representation = {enc.to_bytes(4, 'little')}, the representation is {chr(enc)}\" for plain, enc in zip(message, message_secret)]\n",
+    "for msg in print_messages:\n",
+    "    print(msg)"
    ]
   },
   {
@@ -1230,11 +1570,21 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 47,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "['1', '2', 'some']\n",
+      "['3', '4', 'numbers']\n",
+      "['5', '6', 'here']\n"
+     ]
+    }
+   ],
    "source": [
     "import csv\n",
     "import pathlib as pl\n",
@@ -1330,7 +1680,7 @@
     "tags": []
    },
    "source": [
-    "### Exercise 1: CSV to dictionary 🌶️"
+    "### Exercise 1: CSV to dictionary (easy)"
    ]
   },
   {
@@ -1404,7 +1754,7 @@
     "    Returns:\n",
     "        - A dictionary with each row represented as a key, value pair\n",
     "    \"\"\"\n",
-    "    pass"
+    "    return"
    ]
   },
   {
@@ -1414,7 +1764,7 @@
     "tags": []
    },
    "source": [
-    "### Exercise 2: Counting words 🌶️"
+    "### Exercise 2: Counting words (easy)"
    ]
   },
   {
@@ -1472,7 +1822,7 @@
     "    Returns:\n",
     "        - The number of words in the file\n",
     "    \"\"\"\n",
-    "    pass"
+    "    return"
    ]
   },
   {
@@ -1482,7 +1832,7 @@
     "tags": []
    },
    "source": [
-    "### Exercise 3: Letter statistics 🌶️🌶️"
+    "### Exercise 3: Letter statistics (medium)"
    ]
   },
   {
@@ -1538,7 +1888,7 @@
     "    Returns:\n",
     "        - A dictionary with a count of each letter\n",
     "    \"\"\"\n",
-    "    pass"
+    "    return"
    ]
   },
   {
@@ -1548,7 +1898,7 @@
     "tags": []
    },
    "source": [
-    "### Exercise 4: Translating words 🌶️🌶️"
+    "### Exercise 4: Translating words (medium)"
    ]
   },
   {
@@ -1615,8 +1965,7 @@
     "    Returns:\n",
     "        - A list of tuples with the english / italian words\n",
     "    \"\"\"\n",
-    "\n",
-    "    pass"
+    "    return"
    ]
   },
   {
@@ -1626,7 +1975,7 @@
     "tags": []
    },
    "source": [
-    "### Exercise 5: Binary format 🌶️🌶️🌶️"
+    "### Exercise 5: Binary format (hard)"
    ]
   },
   {
@@ -1678,14 +2027,14 @@
     "    Returns:\n",
     "        - The secret message\n",
     "    \"\"\"\n",
-    "    pass"
+    "    return"
    ]
   }
  ],
  "metadata": {
   "celltoolbar": "Slideshow",
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
    "name": "python3"
   },
@@ -1699,7 +2048,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.12.4"
+   "version": "3.13.5"
   }
  },
  "nbformat": 4,
diff --git a/05_object_oriented_programming.ipynb b/05_object_oriented_programming.ipynb
index afb772b5..17b8e713 100644
--- a/05_object_oriented_programming.ipynb
+++ b/05_object_oriented_programming.ipynb
@@ -1700,7 +1700,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.10.13"
+   "version": "3.13.5"
   }
  },
  "nbformat": 4,
diff --git a/tutorial/quiz/input_output.py b/tutorial/quiz/input_output.py
index 923b907e..9bd6a539 100644
--- a/tutorial/quiz/input_output.py
+++ b/tutorial/quiz/input_output.py
@@ -43,7 +43,7 @@ def __init__(self, title=""):
             question="What happens if you call <code>input()</code> in the middle of a function?",
             options={
                 "The function execution stops and it waits for the user to type an input": "Correct! Input is a blocking function which waits for user to enter a string in the console and press enter.",
-                "The function continues its execution": "Wrong!",
+                "The function continues its execution": "Wrong! Input is a blocking function which waits for user input.",
             },
             correct_answer="The function execution stops and it waits for the user to type an input",
             shuffle=True,
@@ -57,7 +57,7 @@ def __init__(self, title=""):
         q1 = Question(
             question="What does the operator <code>/</code> do when applied to two <code>Pathlib.Path</code> objects?",
             options={
-                "It removes the second path from the first": "Wrong, try it in the shell.",
+                "It removes the second path from the first": "Wrong, try it in a cell below.",
                 "It concatenates paths": "Correct, it lets you construct a path from different segments",
             },
             correct_answer="It concatenates paths",
@@ -68,7 +68,7 @@ def __init__(self, title=""):
             question="If you use Pathlib,  do you need to use different path separators on Windows and Linux to combine path segments?",
             options={
                 "No, you can combine Pathlib.Path objects with /": "Correct! Pathlib will then generate the correct path for your OS.",
-                "Yes": "Wrong! You can always use  <code>/</code>",
+                "Yes": "Wrong! You can always use <code>/</code>",
             },
             correct_answer="No, you can combine Pathlib.Path objects with /",
             shuffle=True,
@@ -78,7 +78,7 @@ def __init__(self, title=""):
             question="""The path </code>Pathlib.Path("./")</code> represent a relative path. What location does it refer to?""",
             options={
                 "Relative to the current working directory, the location of the current Python script being run": "Correct!",
-                "Relative to the user's home directory": "Wrong!",
+                "Relative to the user's home directory": "Wrong! It is relative to the current working directory.",
             },
             correct_answer="Relative to the current working directory, the location of the current Python script being run",
             shuffle=True,
diff --git a/tutorial/tests/data/example1.csv b/tutorial/tests/data/example1.csv
new file mode 100644
index 00000000..53f9e8ba
--- /dev/null
+++ b/tutorial/tests/data/example1.csv
@@ -0,0 +1,11 @@
+this,is,data

+0,1,2

+1,2,3

+2,3,4

+3,4,5

+4,5,6

+5,6,7

+6,7,8

+7,8,9

+8,9,10

+9,10,11

diff --git a/tutorial/tests/data/me.txt b/tutorial/tests/data/me.txt
new file mode 100644
index 00000000..2d5fcfd7
--- /dev/null
+++ b/tutorial/tests/data/me.txt
@@ -0,0 +1 @@
+Simone
\ No newline at end of file
diff --git a/tutorial/tests/data/numbers.txt b/tutorial/tests/data/numbers.txt
new file mode 100644
index 00000000..8b1acc12
--- /dev/null
+++ b/tutorial/tests/data/numbers.txt
@@ -0,0 +1,10 @@
+0
+1
+2
+3
+4
+5
+6
+7
+8
+9
diff --git a/tutorial/tests/data/output.txt b/tutorial/tests/data/output.txt
new file mode 100644
index 0000000000000000000000000000000000000000..df93f5f3f72487244976c34e85525cf445016566
GIT binary patch
literal 10
RcmZQzWMXDvWn<^y1ONc904@Lk

literal 0
HcmV?d00001

diff --git a/tutorial/tests/data/output1.txt b/tutorial/tests/data/output1.txt
new file mode 100644
index 0000000000000000000000000000000000000000..bf7fd73a844290ab930a8665635b465aec2c9e9f
GIT binary patch
literal 2048
zcmV~$17HvU00h8Cwr$(is%6`@ZM&9j+qP}nwr$-3AOs^Af+GY%A{0U+48kHD!XpAA
zA`&7a3Zfz!q9X=kA{JsJ4&ovn;v)ePA`ucJ36dfik|PCDA{A024bmbV(jx;hA`>zr
z3$h{`vLgp_A{TNa5Aq@(@}mF(P!NSs7=b8)q9}&qD1nkFh0-X4vM7i0sDO&7gvzLb
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literal 0
HcmV?d00001

diff --git a/tutorial/tests/test_03_functions.py b/tutorial/tests/test_03_functions.py
index 7f77ccaf..d093820f 100644
--- a/tutorial/tests/test_03_functions.py
+++ b/tutorial/tests/test_03_functions.py
@@ -95,10 +95,10 @@ def validate_basic_area_signature(function_to_test) -> None:
 @pytest.mark.parametrize(
     "length,width",
     [
-        (2.0, 3.0),
+        (2.123, 3.456),
         (5.0, 4.0),
-        (1.5, 2.5),
-        (0.1, 0.1),
+        (1.5, 2.57),
+        (0.109, 0.103),
     ],
 )
 def test_calculate_basic_area(length: float, width: float, function_to_test):
@@ -234,6 +234,28 @@ def test_calculate_area(length, width, unit, function_to_test):
     assert expected == result, "Incorrect area calculation or formatting"
 
 
+@pytest.mark.parametrize(
+    "length,width,unit",
+    [
+        (2.0, 3.0, "km"),  # Invalid unit
+        (2.0, 3.0, ""),  # Empty unit
+        (2.0, 3.0, "CM"),  # Case sensitive check
+        (2.0, 3.0, "inches"),  # Another invalid unit
+    ],
+)
+def test_calculate_area_invalid_units(length, width, unit, function_to_test):
+    """Test that the function properly handles invalid units."""
+    validate_area_signature(function_to_test)
+    result = function_to_test(length, width, unit)
+    expected = f"Invalid unit: {unit}"
+    assert isinstance(result, str), (
+        "Result should be a string like 'Invalid unit: <unit>'"
+    )
+    assert result == expected, (
+        f"Expected '{expected}' for invalid unit '{unit}', got '{result}'"
+    )
+
+
 #
 # Exercise 3: summing anything
 #

From 5f18cdab4ffe2f3e1c4834c9ea592a084efc0e66 Mon Sep 17 00:00:00 2001
From: Lopes <fabio.lopes@empa.ch>
Date: Tue, 4 Nov 2025 13:14:16 +0100
Subject: [PATCH 02/11] Corrected issues and tested functions in Issue #272

---
 04_input_output.ipynb                  | 491 ++++---------------------
 tutorial/tests/test_04_input_output.py |   4 +-
 2 files changed, 72 insertions(+), 423 deletions(-)

diff --git a/04_input_output.ipynb b/04_input_output.ipynb
index 4ce37f05..82ac0bb1 100644
--- a/04_input_output.ipynb
+++ b/04_input_output.ipynb
@@ -488,25 +488,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "b5d9190bff57413c8c14c640aa74557a",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "Paths(children=(Question(children=(HTML(value='<strong>Q1:</strong> What does the operator <code>/</code> do w…"
-      ]
-     },
-     "execution_count": 1,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "import tutorial.quiz.input_output as op\n",
     "op.Paths()"
@@ -522,34 +506,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "text/html": [
-       "<div style='background-color: #ffebee; border-radius: 5px; padding: 10px;'>🚫 <strong style='color: red;'>OpenAI API key is not provided.</strong><br>API key is missing.</div>"
-      ],
-      "text/plain": [
-       "<IPython.core.display.HTML object>"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    },
-    {
-     "data": {
-      "text/html": [
-       "<div style='background-color: #fffde7; border-radius: 5px; padding: 10px;'>🔄 <strong>IPytest extension (re)loaded.</strong></div>"
-      ],
-      "text/plain": [
-       "<IPython.core.display.HTML object>"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%reload_ext tutorial.tests.testsuite"
    ]
@@ -560,7 +519,7 @@
    "metadata": {},
    "source": [
     "\n",
-    "1. Modify the function `solution_find_all_files` to find all files and directories in the [data](./tutorial/tests/data/) (./tutorial/tests/data/) directory and return them as a list of `Path` objects\n",
+    "1. Modify the function `solution_find_all_files` to find all files and directories in the [data](./tutorial/tests/data) directory and return them as a list of `Path` objects\n",
     "\n",
     "<div class=\"alert alert-block alert-info\">\n",
     "    <b>Hint:</b> The path to the data directory is available as the argument <code>current_path</code> of the function <code>solution_find_all_files</code>\n",
@@ -569,24 +528,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "5a82cdcf4ce1468d8718502eafc1c89a",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -614,24 +558,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "2f2eb3ad53e4430b836b3fbcaa5f0f66",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -661,24 +590,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "5acc98c538244a7487e51251a8ce1b71",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -705,9 +619,9 @@
     "### Reading from a file\n",
     "\n",
     "We now want to learn how to read text from a file. \n",
-    "Let's see how to do this with an example: we want to open the file [hello.txt](./data/hello.txt) and read its contents.\n",
+    "Let's see how to do this with an example: we want to open the file [hello.txt](./tutorial/tests/data/hello.txt) and read its contents.\n",
     "\n",
-    "1. The path is already identified, we know the file is in `./data/hello.txt`. We save this in a variable `path`.\n",
+    "1. The path is already identified, we know the file is in `./tutorial/tests/data/hello.txt`. We save this in a variable `path`.\n",
     "2. We now can use the built-in function [`open`](https://docs.python.org/3/library/functions.html#open) to open the file. This function returns a [file object](https://docs.python.org/3/glossary.html#term-file-object) that we can use to further manipulate the file. To ensure we only open the file for reading, we pass the string \"r\" to the second argument of `open`.\n",
     "3. Now we can read the contents using `read`, `readline` or `readlines`. `read` reads the whole file content into a single string, `readline` reads one line, while `readlines` reads the whole file content as a list of strings, one item per line in the file. This knowledge is useful when we only want to read part of a file or when the file is too big to fit in memory and we can only read parts.\n",
     "4. Finally, we close the file using the `close` method on the file object.\n"
@@ -715,19 +629,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "['Hello, I am a file with some text.\\n']\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -748,20 +654,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 12,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "['Hello, I am a file with some text.\\n']\n",
-      "[]\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -784,34 +681,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "this\n",
-      "\n",
-      "file\n",
-      "\n",
-      "has multiple\n",
-      "\n",
-      "lines\n",
-      "\n",
-      "how many\n",
-      "\n",
-      "lines\n",
-      "\n",
-      "does this file\n",
-      "\n",
-      "have?\n",
-      "\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -839,25 +713,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "ad907828193c4bbaa30116d5342f87dd",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "ReadFiles(children=(Question(children=(HTML(value='<strong>Q1:</strong> Can you read from a file before callin…"
-      ]
-     },
-     "execution_count": 14,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "import tutorial.quiz.input_output as op\n",
     "op.ReadFiles()"
@@ -873,34 +731,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 15,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "text/html": [
-       "<div style='background-color: #ffebee; border-radius: 5px; padding: 10px;'>🚫 <strong style='color: red;'>OpenAI API key is not provided.</strong><br>API key is missing.</div>"
-      ],
-      "text/plain": [
-       "<IPython.core.display.HTML object>"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    },
-    {
-     "data": {
-      "text/html": [
-       "<div style='background-color: #fffde7; border-radius: 5px; padding: 10px;'>🔄 <strong>IPytest extension (re)loaded.</strong></div>"
-      ],
-      "text/plain": [
-       "<IPython.core.display.HTML object>"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%reload_ext tutorial.tests.testsuite"
    ]
@@ -915,24 +748,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "658982e189394032bd022f74294fd393",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -961,12 +779,12 @@
     "- We use `write` to write a *string* to the file. Other types of object should be converted to string before being written.\n",
     "\n",
     "\n",
-    "Let's see this in action by writing your name in a file called `me.txt` in [data](./data/)"
+    "Let's see this in action by writing your name in a file called `me.txt` in [./tutorial/tests/data](./tutorial/tests/data/)"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 19,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
@@ -992,7 +810,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 20,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
@@ -1023,25 +841,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 21,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "cb48e1322fe843a2ae8628f24d467a16",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "WriteFiles(children=(Question(children=(HTML(value='<strong>Q1:</strong> What does <code>w</code> in the secon…"
-      ]
-     },
-     "execution_count": 21,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "import tutorial.quiz.input_output as op\n",
     "op.WriteFiles()"
@@ -1057,34 +859,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 22,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "text/html": [
-       "<div style='background-color: #ffebee; border-radius: 5px; padding: 10px;'>🚫 <strong style='color: red;'>OpenAI API key is not provided.</strong><br>API key is missing.</div>"
-      ],
-      "text/plain": [
-       "<IPython.core.display.HTML object>"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    },
-    {
-     "data": {
-      "text/html": [
-       "<div style='background-color: #fffde7; border-radius: 5px; padding: 10px;'>🔄 <strong>IPytest extension (re)loaded.</strong></div>"
-      ],
-      "text/plain": [
-       "<IPython.core.display.HTML object>"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%reload_ext tutorial.tests.testsuite"
    ]
@@ -1099,24 +876,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 23,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "044f8550f1914cb49ee4d639a7d553c6",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -1161,24 +923,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 31,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "5ec927991895480bbfc1d720c592a674",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -1223,19 +970,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 32,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "['Hello, I am a file with some text.\\n']\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -1270,25 +1009,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 33,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "4a284a916de749929f85bee97e286c61",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "ContextManagers(children=(Question(children=(HTML(value='<strong>Q1:</strong> Do you need to call <code>close<…"
-      ]
-     },
-     "execution_count": 33,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "import tutorial.quiz.input_output as op\n",
     "op.ContextManagers()"
@@ -1313,19 +1036,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 34,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "b'\\x00\\x01\\x02\\x03\\x04\\x05\\x06\\x07\\x08\\t'\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -1348,19 +1063,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 35,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -1385,7 +1092,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 36,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
@@ -1414,19 +1121,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 37,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276, 277, 278, 279, 280, 281, 282, 283, 284, 285, 286, 287, 288, 289, 290, 291, 292, 293, 294, 295, 296, 297, 298, 299, 300, 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 311, 312, 313, 314, 315, 316, 317, 318, 319, 320, 321, 322, 323, 324, 325, 326, 327, 328, 329, 330, 331, 332, 333, 334, 335, 336, 337, 338, 339, 340, 341, 342, 343, 344, 345, 346, 347, 348, 349, 350, 351, 352, 353, 354, 355, 356, 357, 358, 359, 360, 361, 362, 363, 364, 365, 366, 367, 368, 369, 370, 371, 372, 373, 374, 375, 376, 377, 378, 379, 380, 381, 382, 383, 384, 385, 386, 387, 388, 389, 390, 391, 392, 393, 394, 395, 396, 397, 398, 399, 400, 401, 402, 403, 404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414, 415, 416, 417, 418, 419, 420, 421, 422, 423, 424, 425, 426, 427, 428, 429, 430, 431, 432, 433, 434, 435, 436, 437, 438, 439, 440, 441, 442, 443, 444, 445, 446, 447, 448, 449, 450, 451, 452, 453, 454, 455, 456, 457, 458, 459, 460, 461, 462, 463, 464, 465, 466, 467, 468, 469, 470, 471, 472, 473, 474, 475, 476, 477, 478, 479, 480, 481, 482, 483, 484, 485, 486, 487, 488, 489, 490, 491, 492, 493, 494, 495, 496, 497, 498, 499, 500, 501, 502, 503, 504, 505, 506, 507, 508, 509, 510, 511, 512, 513, 514, 515, 516, 517, 518, 519, 520, 521, 522, 523, 524, 525, 526, 527, 528, 529, 530, 531, 532, 533, 534, 535, 536, 537, 538, 539, 540, 541, 542, 543, 544, 545, 546, 547, 548, 549, 550, 551, 552, 553, 554, 555, 556, 557, 558, 559, 560, 561, 562, 563, 564, 565, 566, 567, 568, 569, 570, 571, 572, 573, 574, 575, 576, 577, 578, 579, 580, 581, 582, 583, 584, 585, 586, 587, 588, 589, 590, 591, 592, 593, 594, 595, 596, 597, 598, 599, 600, 601, 602, 603, 604, 605, 606, 607, 608, 609, 610, 611, 612, 613, 614, 615, 616, 617, 618, 619, 620, 621, 622, 623, 624, 625, 626, 627, 628, 629, 630, 631, 632, 633, 634, 635, 636, 637, 638, 639, 640, 641, 642, 643, 644, 645, 646, 647, 648, 649, 650, 651, 652, 653, 654, 655, 656, 657, 658, 659, 660, 661, 662, 663, 664, 665, 666, 667, 668, 669, 670, 671, 672, 673, 674, 675, 676, 677, 678, 679, 680, 681, 682, 683, 684, 685, 686, 687, 688, 689, 690, 691, 692, 693, 694, 695, 696, 697, 698, 699, 700, 701, 702, 703, 704, 705, 706, 707, 708, 709, 710, 711, 712, 713, 714, 715, 716, 717, 718, 719, 720, 721, 722, 723, 724, 725, 726, 727, 728, 729, 730, 731, 732, 733, 734, 735, 736, 737, 738, 739, 740, 741, 742, 743, 744, 745, 746, 747, 748, 749, 750, 751, 752, 753, 754, 755, 756, 757, 758, 759, 760, 761, 762, 763, 764, 765, 766, 767, 768, 769, 770, 771, 772, 773, 774, 775, 776, 777, 778, 779, 780, 781, 782, 783, 784, 785, 786, 787, 788, 789, 790, 791, 792, 793, 794, 795, 796, 797, 798, 799, 800, 801, 802, 803, 804, 805, 806, 807, 808, 809, 810, 811, 812, 813, 814, 815, 816, 817, 818, 819, 820, 821, 822, 823, 824, 825, 826, 827, 828, 829, 830, 831, 832, 833, 834, 835, 836, 837, 838, 839, 840, 841, 842, 843, 844, 845, 846, 847, 848, 849, 850, 851, 852, 853, 854, 855, 856, 857, 858, 859, 860, 861, 862, 863, 864, 865, 866, 867, 868, 869, 870, 871, 872, 873, 874, 875, 876, 877, 878, 879, 880, 881, 882, 883, 884, 885, 886, 887, 888, 889, 890, 891, 892, 893, 894, 895, 896, 897, 898, 899, 900, 901, 902, 903, 904, 905, 906, 907, 908, 909, 910, 911, 912, 913, 914, 915, 916, 917, 918, 919, 920, 921, 922, 923, 924, 925, 926, 927, 928, 929, 930, 931, 932, 933, 934, 935, 936, 937, 938, 939, 940, 941, 942, 943, 944, 945, 946, 947, 948, 949, 950, 951, 952, 953, 954, 955, 956, 957, 958, 959, 960, 961, 962, 963, 964, 965, 966, 967, 968, 969, 970, 971, 972, 973, 974, 975, 976, 977, 978, 979, 980, 981, 982, 983, 984, 985, 986, 987, 988, 989, 990, 991, 992, 993, 994, 995, 996, 997, 998, 999, 1000, 1001, 1002, 1003, 1004, 1005, 1006, 1007, 1008, 1009, 1010, 1011, 1012, 1013, 1014, 1015, 1016, 1017, 1018, 1019, 1020, 1021, 1022, 1023]\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "import pathlib as pl\n",
     "import struct\n",
@@ -1453,41 +1152,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 38,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "bytes: ['0x0', '0x0', '0x0', '0x0'], integer: 0, string: \u0000\n",
-      "bytes: ['0x1', '0x0', '0x0', '0x0'], integer: 1, string: \u0001\n",
-      "bytes: ['0x2', '0x0', '0x0', '0x0'], integer: 2, string: \u0002\n",
-      "bytes: ['0x3', '0x0', '0x0', '0x0'], integer: 3, string: \u0003\n",
-      "bytes: ['0x4', '0x0', '0x0', '0x0'], integer: 4, string: \u0004\n",
-      "bytes: ['0x5', '0x0', '0x0', '0x0'], integer: 5, string: \u0005\n",
-      "bytes: ['0x3c', '0x0', '0x0', '0x0'], integer: 60, string: <\n",
-      "bytes: ['0x3d', '0x0', '0x0', '0x0'], integer: 61, string: =\n",
-      "bytes: ['0x3e', '0x0', '0x0', '0x0'], integer: 62, string: >\n",
-      "bytes: ['0x3f', '0x0', '0x0', '0x0'], integer: 63, string: ?\n",
-      "bytes: ['0x40', '0x0', '0x0', '0x0'], integer: 64, string: @\n",
-      "bytes: ['0x41', '0x0', '0x0', '0x0'], integer: 65, string: A\n",
-      "bytes: ['0x42', '0x0', '0x0', '0x0'], integer: 66, string: B\n",
-      "bytes: ['0x43', '0x0', '0x0', '0x0'], integer: 67, string: C\n",
-      "bytes: ['0x44', '0x0', '0x0', '0x0'], integer: 68, string: D\n",
-      "bytes: ['0x45', '0x0', '0x0', '0x0'], integer: 69, string: E\n",
-      "bytes: ['0x46', '0x0', '0x0', '0x0'], integer: 70, string: F\n",
-      "bytes: ['0x47', '0x0', '0x0', '0x0'], integer: 71, string: G\n",
-      "bytes: ['0x48', '0x0', '0x0', '0x0'], integer: 72, string: H\n",
-      "bytes: ['0x49', '0x0', '0x0', '0x0'], integer: 73, string: I\n",
-      "bytes: ['0x0', '0x2', '0x0', '0x0'], integer: 512, string: Ȁ\n",
-      "bytes: ['0x1', '0x2', '0x0', '0x0'], integer: 513, string: ȁ\n",
-      "bytes: ['0x2', '0x2', '0x0', '0x0'], integer: 514, string: Ȃ\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "for i in range(0, 6):\n",
     "    bt = i.to_bytes(4, 'little')\n",
@@ -1520,22 +1189,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 46,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "The `uft8` codepoint  is = 67, the bytes representation = b'C\\x00\\x00\\x00', the representation is C\n",
-      "The `uft8` codepoint  is = 105, the bytes representation = b'i\\x00\\x00\\x00', the representation is i\n",
-      "The `uft8` codepoint  is = 97, the bytes representation = b'a\\x00\\x00\\x00', the representation is a\n",
-      "The `uft8` codepoint  is = 111, the bytes representation = b'o\\x00\\x00\\x00', the representation is o\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "message = \"Ciao\"\n",
     "message_secret = bytes(message, \"utf-8\")\n",
@@ -1565,26 +1223,16 @@
     "These packages are outside of the scope of this tutorial and will not be covered here.\n",
     "\n",
     "\n",
-    "Let's see how to read csv files using `csv` with an example by reading [example.csv](./data/example.csv):"
+    "Let's see how to read csv files using `csv` with an example by reading [example.csv](./tutorial/tests/data/example.csv):"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 47,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "['1', '2', 'some']\n",
-      "['3', '4', 'numbers']\n",
-      "['5', '6', 'here']\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "import csv\n",
     "import pathlib as pl\n",
@@ -1872,7 +1520,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "%%ipytest input_output\n",
+    "%%ipytest\n",
     "\n",
     "import pathlib as pl\n",
     "import string\n",
@@ -1908,7 +1556,7 @@
     "tags": []
    },
    "source": [
-    "Write a function which takes the words from the file `english.txt` and translates them to Italian using the dictionary file `dict.csv`. The output should be a **list of tuples** with the pair `italian, english` if the word is found and nothing otherwise.\n",
+    "Write a function which takes the words from the file `english.txt` and translates them to Italian using the dictionary file `dict.csv`. The output should be a **list of tuples** with the pair `italian, english` **if the word is found and nothing otherwise**.\n",
     "\n",
     "For example, given the `english.txt` file:\n",
     "\n",
@@ -1950,6 +1598,7 @@
    "source": [
     "%%ipytest\n",
     "\n",
+    "import csv\n",
     "import pathlib as pl\n",
     "\n",
     "def solution_exercise4(english: pl.Path, dictionary: pl.Path) -> list[(str, str)]:\n",
diff --git a/tutorial/tests/test_04_input_output.py b/tutorial/tests/test_04_input_output.py
index b7b9fa69..13fb902c 100644
--- a/tutorial/tests/test_04_input_output.py
+++ b/tutorial/tests/test_04_input_output.py
@@ -254,10 +254,10 @@ def reference_exercise5(secret_file: pl.Path) -> str:
 def test_exercise5(function_to_test):
     message = get_data("secret_message.dat")
     # Save the original content of the input file
-    original_content = message.read_text()
+    original_content = message.read_bytes()
 
     try:
         assert function_to_test(message) == reference_exercise5(message)
     finally:
         # Reset the input file to its original content
-        message.write_text(original_content)
+        message.write_bytes(original_content)

From 3e8c8d9b8d173599d2f3bee1baf73c5fed1748fd Mon Sep 17 00:00:00 2001
From: Lopes <fabio.lopes@empa.ch>
Date: Tue, 4 Nov 2025 13:15:52 +0100
Subject: [PATCH 03/11] Corrected directories hyperlinks

---
 04_input_output.ipynb | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/04_input_output.ipynb b/04_input_output.ipynb
index 82ac0bb1..6617a382 100644
--- a/04_input_output.ipynb
+++ b/04_input_output.ipynb
@@ -519,7 +519,7 @@
    "metadata": {},
    "source": [
     "\n",
-    "1. Modify the function `solution_find_all_files` to find all files and directories in the [data](./tutorial/tests/data) directory and return them as a list of `Path` objects\n",
+    "1. Modify the function `solution_find_all_files` to find all files and directories in the ```/tutorial/tests/data``` directory and return them as a list of `Path` objects\n",
     "\n",
     "<div class=\"alert alert-block alert-info\">\n",
     "    <b>Hint:</b> The path to the data directory is available as the argument <code>current_path</code> of the function <code>solution_find_all_files</code>\n",
@@ -779,7 +779,7 @@
     "- We use `write` to write a *string* to the file. Other types of object should be converted to string before being written.\n",
     "\n",
     "\n",
-    "Let's see this in action by writing your name in a file called `me.txt` in [./tutorial/tests/data](./tutorial/tests/data/)"
+    "Let's see this in action by writing your name in a file called `me.txt` in ```/tutorial/tests/data```"
    ]
   },
   {

From c13d7e2de53810d19df6d64b866c49163aeb1654 Mon Sep 17 00:00:00 2001
From: Lopes <fabio.lopes@empa.ch>
Date: Mon, 3 Nov 2025 18:08:26 +0100
Subject: [PATCH 04/11] Resolving part of the issue #272

---
 04_input_output.ipynb                | 559 ++++++++++++++++++++++-----
 05_object_oriented_programming.ipynb |   2 +-
 tutorial/quiz/input_output.py        |   8 +-
 tutorial/tests/data/example1.csv     |  11 +
 tutorial/tests/data/me.txt           |   1 +
 tutorial/tests/data/numbers.txt      |  10 +
 tutorial/tests/data/output.txt       | Bin 0 -> 10 bytes
 tutorial/tests/data/output1.txt      | Bin 0 -> 2048 bytes
 8 files changed, 481 insertions(+), 110 deletions(-)
 create mode 100644 tutorial/tests/data/example1.csv
 create mode 100644 tutorial/tests/data/me.txt
 create mode 100644 tutorial/tests/data/numbers.txt
 create mode 100644 tutorial/tests/data/output.txt
 create mode 100644 tutorial/tests/data/output1.txt

diff --git a/04_input_output.ipynb b/04_input_output.ipynb
index 7a4c3153..4ce37f05 100644
--- a/04_input_output.ipynb
+++ b/04_input_output.ipynb
@@ -40,11 +40,11 @@
     "      - [Reading/Writing CSV files](#Reading/Writing-CSV-files)\n",
     "        - [Quiz on CSV](#Quiz-on-CSV)\n",
     "    - [Exercises](#Exercises)\n",
-    "      - [Exercise 1: CSV to dictionary 🌶️](#Exercise-1:-CSV-to-dictionary-🌶️)\n",
-    "      - [Exercise 2: Counting words 🌶️](#Exercise-2:-Counting-words-🌶️)\n",
-    "      - [Exercise 3: Letter statistics 🌶️🌶️](#Exercise-3:-Letter-statistics-🌶️🌶️)\n",
-    "      - [Exercise 4: Translating words 🌶️🌶️](#Exercise-4:-Translating-words-🌶️🌶️)\n",
-    "      - [Exercise 5: Binary format 🌶️🌶️🌶️](#Exercise-5:-Binary-format-🌶️🌶️🌶️)"
+    "      - [Exercise 1: CSV to dictionary (easy)](#Exercise-1:-CSV-to-dictionary-(easy))\n",
+    "      - [Exercise 2: Counting words (easy)](#Exercise-2:-Counting-words-(easy))\n",
+    "      - [Exercise 3: Letter statistics (medium)](#Exercise-3:-Letter-statistics-(medium))\n",
+    "      - [Exercise 4: Translating words (medium)](#Exercise-4:-Translating-words-(medium))\n",
+    "      - [Exercise 5: Binary format (hard)](#Exercise-5:-Binary-format-(hard))"
    ]
   },
   {
@@ -75,13 +75,7 @@
     "- connecting to databases or other network services\n",
     "\n",
     "\n",
-    "The majority of these operations are covered by the Python standard library. We are going to see how to use them in this chapter.\n",
-    "\n",
-    "<div class=\"alert alert-block alert-info\">\n",
-    "    <h4><b>Note</b></h4>\n",
-    "In reference to the chapter on functional programming, it is interesting to note that these functions perform <b>side-effects</b>. Therefore, any code containing these operations is no longer <b>pure</b> and is not referentially transparent. The same function can return different values for the same argument if called multiple times, and the function can have <b>long-distance</b> effects. That means they can modify the program state elsewhere, leading to unexpected results.<br><br>\n",
-    "Therefore, we suggest separating input and output from the other computations in your program. For example, if you have a complex calculation requiring several user inputs at several stages of the process, consider writing a function that only performs the calculation given all inputs and then requires all inputs separately, for example, through a single file. This makes your code easier to debug, test and understand.\n",
-    "</div>"
+    "The majority of these operations are covered by the Python standard library. We are going to see how to use them in this chapter."
    ]
   },
   {
@@ -108,8 +102,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "It is also possible to print any other python object using `print`. \n",
-    "In that case, the `__str__` **magic method** on that object's class is [called](https://docs.python.org/3/reference/datamodel.html#object.__str__)."
+    "It is also possible to print any other python object using `print`."
    ]
   },
   {
@@ -154,7 +147,9 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "metadata": {},
+   "metadata": {
+    "scrolled": true
+   },
    "outputs": [],
    "source": [
     "import tutorial.quiz.input_output as op\n",
@@ -245,7 +240,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "%%ipytest debug\n",
+    "%%ipytest\n",
     "\n",
     "def solution_print_odd(n: int) -> None: \n",
     "    \"\"\"Prints all odd numbers from 1 to n\n",
@@ -255,8 +250,7 @@
     "\n",
     "    Returns:\n",
     "        - None (prints to console)\n",
-    "    \"\"\"\n",
-    "    pass"
+    "    \"\"\""
    ]
   },
   {
@@ -287,7 +281,6 @@
     "    Returns:\n",
     "        - None (prints to console)\n",
     "    \"\"\"\n",
-    "    pass\n",
     "\n",
     "solution_print_salutation()"
    ]
@@ -495,9 +488,25 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "b5d9190bff57413c8c14c640aa74557a",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "Paths(children=(Question(children=(HTML(value='<strong>Q1:</strong> What does the operator <code>/</code> do w…"
+      ]
+     },
+     "execution_count": 1,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "import tutorial.quiz.input_output as op\n",
     "op.Paths()"
@@ -513,9 +522,34 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "<div style='background-color: #ffebee; border-radius: 5px; padding: 10px;'>🚫 <strong style='color: red;'>OpenAI API key is not provided.</strong><br>API key is missing.</div>"
+      ],
+      "text/plain": [
+       "<IPython.core.display.HTML object>"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    },
+    {
+     "data": {
+      "text/html": [
+       "<div style='background-color: #fffde7; border-radius: 5px; padding: 10px;'>🔄 <strong>IPytest extension (re)loaded.</strong></div>"
+      ],
+      "text/plain": [
+       "<IPython.core.display.HTML object>"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%reload_ext tutorial.tests.testsuite"
    ]
@@ -535,9 +569,24 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 3,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "5a82cdcf4ce1468d8718502eafc1c89a",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -565,9 +614,24 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 9,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "2f2eb3ad53e4430b836b3fbcaa5f0f66",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -597,9 +661,24 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 10,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "5acc98c538244a7487e51251a8ce1b71",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -613,8 +692,7 @@
     "\n",
     "    Returns:\n",
     "        - The number of directories in the directory\n",
-    "    \"\"\"\n",
-    "    pass\n"
+    "    \"\"\""
    ]
   },
   {
@@ -637,11 +715,19 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 11,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "['Hello, I am a file with some text.\\n']\n"
+     ]
+    }
+   ],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -662,11 +748,20 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 12,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "['Hello, I am a file with some text.\\n']\n",
+      "[]\n"
+     ]
+    }
+   ],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -689,11 +784,34 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 13,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "this\n",
+      "\n",
+      "file\n",
+      "\n",
+      "has multiple\n",
+      "\n",
+      "lines\n",
+      "\n",
+      "how many\n",
+      "\n",
+      "lines\n",
+      "\n",
+      "does this file\n",
+      "\n",
+      "have?\n",
+      "\n"
+     ]
+    }
+   ],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -721,9 +839,25 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 14,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "ad907828193c4bbaa30116d5342f87dd",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "ReadFiles(children=(Question(children=(HTML(value='<strong>Q1:</strong> Can you read from a file before callin…"
+      ]
+     },
+     "execution_count": 14,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "import tutorial.quiz.input_output as op\n",
     "op.ReadFiles()"
@@ -739,9 +873,34 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 15,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "<div style='background-color: #ffebee; border-radius: 5px; padding: 10px;'>🚫 <strong style='color: red;'>OpenAI API key is not provided.</strong><br>API key is missing.</div>"
+      ],
+      "text/plain": [
+       "<IPython.core.display.HTML object>"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    },
+    {
+     "data": {
+      "text/html": [
+       "<div style='background-color: #fffde7; border-radius: 5px; padding: 10px;'>🔄 <strong>IPytest extension (re)loaded.</strong></div>"
+      ],
+      "text/plain": [
+       "<IPython.core.display.HTML object>"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%reload_ext tutorial.tests.testsuite"
    ]
@@ -756,9 +915,24 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 18,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "658982e189394032bd022f74294fd393",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -773,7 +947,7 @@
     "    Returns:\n",
     "        - A list of strings, each representing a line in the file\n",
     "    \"\"\"\n",
-    "    pass"
+    "    return"
    ]
   },
   {
@@ -792,7 +966,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 19,
    "metadata": {
     "tags": []
    },
@@ -818,7 +992,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 20,
    "metadata": {
     "tags": []
    },
@@ -849,9 +1023,25 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 21,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "cb48e1322fe843a2ae8628f24d467a16",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "WriteFiles(children=(Question(children=(HTML(value='<strong>Q1:</strong> What does <code>w</code> in the secon…"
+      ]
+     },
+     "execution_count": 21,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "import tutorial.quiz.input_output as op\n",
     "op.WriteFiles()"
@@ -867,9 +1057,34 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 22,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "<div style='background-color: #ffebee; border-radius: 5px; padding: 10px;'>🚫 <strong style='color: red;'>OpenAI API key is not provided.</strong><br>API key is missing.</div>"
+      ],
+      "text/plain": [
+       "<IPython.core.display.HTML object>"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    },
+    {
+     "data": {
+      "text/html": [
+       "<div style='background-color: #fffde7; border-radius: 5px; padding: 10px;'>🔄 <strong>IPytest extension (re)loaded.</strong></div>"
+      ],
+      "text/plain": [
+       "<IPython.core.display.HTML object>"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%reload_ext tutorial.tests.testsuite"
    ]
@@ -884,9 +1099,24 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 23,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "044f8550f1914cb49ee4d639a7d553c6",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -902,8 +1132,7 @@
     "\n",
     "    Returns:\n",
     "        - None (writes to file)\n",
-    "    \"\"\"\n",
-    "    pass"
+    "    \"\"\""
    ]
   },
   {
@@ -911,24 +1140,45 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "2. Modify the function `solution_read_write_file` to read the lines from the file `input_file` and write them in the form `line, length`, to the file `output_file`. Here `line` is the line of text in `input_file` **without the line ending**, `length` is **number of characters** in that line **without the line separator**.\n",
-    "If `input_file` contains these lines:\n",
+    "2. Modify the function `solution_read_write_file` to read the lines from the file `input_file` and write them in the form `line, length`, to the file `output_file`. Here `line` is the line of text in `input_file` **without the line ending (\\r\\n)**, `length` is **number of characters** in that line. The characters are added automatically by the operating system when reading a file. Windows uses **\\r\\n** whereas Linux and MacOS use only **\\n**. To remove the line ending characters, use ```strip(\"\\r\\n\")```, e.g.: ```line.strip(\"\\r\\n\")```.\n",
+    "\n",
+    "    If `input_file` contains these lines:\n",
+    "    \n",
     "    ```\n",
     "    first\n",
     "    second\n",
     "    ```\n",
+    "    \n",
     "    we expect the output file to contain these lines:\n",
+    "    \n",
     "    ```\n",
     "    first, 5\n",
     "    second, 6\n",
-    "    ```"
+    "    ```\n",
+    "    \n",
+    "    Do not forget to add a **\\n** when writing lines in the file."
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 31,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "5ec927991895480bbfc1d720c592a674",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -945,8 +1195,7 @@
     "\n",
     "    Returns:\n",
     "        - None (writes to file)\n",
-    "    \"\"\"\n",
-    "    pass"
+    "    \"\"\""
    ]
   },
   {
@@ -974,11 +1223,19 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 32,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "['Hello, I am a file with some text.\\n']\n"
+     ]
+    }
+   ],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -1013,9 +1270,25 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
+   "execution_count": 33,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/vnd.jupyter.widget-view+json": {
+       "model_id": "4a284a916de749929f85bee97e286c61",
+       "version_major": 2,
+       "version_minor": 0
+      },
+      "text/plain": [
+       "ContextManagers(children=(Question(children=(HTML(value='<strong>Q1:</strong> Do you need to call <code>close<…"
+      ]
+     },
+     "execution_count": 33,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "import tutorial.quiz.input_output as op\n",
     "op.ContextManagers()"
@@ -1040,11 +1313,19 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 34,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "b'\\x00\\x01\\x02\\x03\\x04\\x05\\x06\\x07\\x08\\t'\n"
+     ]
+    }
+   ],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -1067,11 +1348,19 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 35,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]\n"
+     ]
+    }
+   ],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -1096,7 +1385,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 36,
    "metadata": {
     "tags": []
    },
@@ -1125,11 +1414,19 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 37,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276, 277, 278, 279, 280, 281, 282, 283, 284, 285, 286, 287, 288, 289, 290, 291, 292, 293, 294, 295, 296, 297, 298, 299, 300, 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 311, 312, 313, 314, 315, 316, 317, 318, 319, 320, 321, 322, 323, 324, 325, 326, 327, 328, 329, 330, 331, 332, 333, 334, 335, 336, 337, 338, 339, 340, 341, 342, 343, 344, 345, 346, 347, 348, 349, 350, 351, 352, 353, 354, 355, 356, 357, 358, 359, 360, 361, 362, 363, 364, 365, 366, 367, 368, 369, 370, 371, 372, 373, 374, 375, 376, 377, 378, 379, 380, 381, 382, 383, 384, 385, 386, 387, 388, 389, 390, 391, 392, 393, 394, 395, 396, 397, 398, 399, 400, 401, 402, 403, 404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414, 415, 416, 417, 418, 419, 420, 421, 422, 423, 424, 425, 426, 427, 428, 429, 430, 431, 432, 433, 434, 435, 436, 437, 438, 439, 440, 441, 442, 443, 444, 445, 446, 447, 448, 449, 450, 451, 452, 453, 454, 455, 456, 457, 458, 459, 460, 461, 462, 463, 464, 465, 466, 467, 468, 469, 470, 471, 472, 473, 474, 475, 476, 477, 478, 479, 480, 481, 482, 483, 484, 485, 486, 487, 488, 489, 490, 491, 492, 493, 494, 495, 496, 497, 498, 499, 500, 501, 502, 503, 504, 505, 506, 507, 508, 509, 510, 511, 512, 513, 514, 515, 516, 517, 518, 519, 520, 521, 522, 523, 524, 525, 526, 527, 528, 529, 530, 531, 532, 533, 534, 535, 536, 537, 538, 539, 540, 541, 542, 543, 544, 545, 546, 547, 548, 549, 550, 551, 552, 553, 554, 555, 556, 557, 558, 559, 560, 561, 562, 563, 564, 565, 566, 567, 568, 569, 570, 571, 572, 573, 574, 575, 576, 577, 578, 579, 580, 581, 582, 583, 584, 585, 586, 587, 588, 589, 590, 591, 592, 593, 594, 595, 596, 597, 598, 599, 600, 601, 602, 603, 604, 605, 606, 607, 608, 609, 610, 611, 612, 613, 614, 615, 616, 617, 618, 619, 620, 621, 622, 623, 624, 625, 626, 627, 628, 629, 630, 631, 632, 633, 634, 635, 636, 637, 638, 639, 640, 641, 642, 643, 644, 645, 646, 647, 648, 649, 650, 651, 652, 653, 654, 655, 656, 657, 658, 659, 660, 661, 662, 663, 664, 665, 666, 667, 668, 669, 670, 671, 672, 673, 674, 675, 676, 677, 678, 679, 680, 681, 682, 683, 684, 685, 686, 687, 688, 689, 690, 691, 692, 693, 694, 695, 696, 697, 698, 699, 700, 701, 702, 703, 704, 705, 706, 707, 708, 709, 710, 711, 712, 713, 714, 715, 716, 717, 718, 719, 720, 721, 722, 723, 724, 725, 726, 727, 728, 729, 730, 731, 732, 733, 734, 735, 736, 737, 738, 739, 740, 741, 742, 743, 744, 745, 746, 747, 748, 749, 750, 751, 752, 753, 754, 755, 756, 757, 758, 759, 760, 761, 762, 763, 764, 765, 766, 767, 768, 769, 770, 771, 772, 773, 774, 775, 776, 777, 778, 779, 780, 781, 782, 783, 784, 785, 786, 787, 788, 789, 790, 791, 792, 793, 794, 795, 796, 797, 798, 799, 800, 801, 802, 803, 804, 805, 806, 807, 808, 809, 810, 811, 812, 813, 814, 815, 816, 817, 818, 819, 820, 821, 822, 823, 824, 825, 826, 827, 828, 829, 830, 831, 832, 833, 834, 835, 836, 837, 838, 839, 840, 841, 842, 843, 844, 845, 846, 847, 848, 849, 850, 851, 852, 853, 854, 855, 856, 857, 858, 859, 860, 861, 862, 863, 864, 865, 866, 867, 868, 869, 870, 871, 872, 873, 874, 875, 876, 877, 878, 879, 880, 881, 882, 883, 884, 885, 886, 887, 888, 889, 890, 891, 892, 893, 894, 895, 896, 897, 898, 899, 900, 901, 902, 903, 904, 905, 906, 907, 908, 909, 910, 911, 912, 913, 914, 915, 916, 917, 918, 919, 920, 921, 922, 923, 924, 925, 926, 927, 928, 929, 930, 931, 932, 933, 934, 935, 936, 937, 938, 939, 940, 941, 942, 943, 944, 945, 946, 947, 948, 949, 950, 951, 952, 953, 954, 955, 956, 957, 958, 959, 960, 961, 962, 963, 964, 965, 966, 967, 968, 969, 970, 971, 972, 973, 974, 975, 976, 977, 978, 979, 980, 981, 982, 983, 984, 985, 986, 987, 988, 989, 990, 991, 992, 993, 994, 995, 996, 997, 998, 999, 1000, 1001, 1002, 1003, 1004, 1005, 1006, 1007, 1008, 1009, 1010, 1011, 1012, 1013, 1014, 1015, 1016, 1017, 1018, 1019, 1020, 1021, 1022, 1023]\n"
+     ]
+    }
+   ],
    "source": [
     "import pathlib as pl\n",
     "import struct\n",
@@ -1156,11 +1453,41 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 38,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "bytes: ['0x0', '0x0', '0x0', '0x0'], integer: 0, string: \u0000\n",
+      "bytes: ['0x1', '0x0', '0x0', '0x0'], integer: 1, string: \u0001\n",
+      "bytes: ['0x2', '0x0', '0x0', '0x0'], integer: 2, string: \u0002\n",
+      "bytes: ['0x3', '0x0', '0x0', '0x0'], integer: 3, string: \u0003\n",
+      "bytes: ['0x4', '0x0', '0x0', '0x0'], integer: 4, string: \u0004\n",
+      "bytes: ['0x5', '0x0', '0x0', '0x0'], integer: 5, string: \u0005\n",
+      "bytes: ['0x3c', '0x0', '0x0', '0x0'], integer: 60, string: <\n",
+      "bytes: ['0x3d', '0x0', '0x0', '0x0'], integer: 61, string: =\n",
+      "bytes: ['0x3e', '0x0', '0x0', '0x0'], integer: 62, string: >\n",
+      "bytes: ['0x3f', '0x0', '0x0', '0x0'], integer: 63, string: ?\n",
+      "bytes: ['0x40', '0x0', '0x0', '0x0'], integer: 64, string: @\n",
+      "bytes: ['0x41', '0x0', '0x0', '0x0'], integer: 65, string: A\n",
+      "bytes: ['0x42', '0x0', '0x0', '0x0'], integer: 66, string: B\n",
+      "bytes: ['0x43', '0x0', '0x0', '0x0'], integer: 67, string: C\n",
+      "bytes: ['0x44', '0x0', '0x0', '0x0'], integer: 68, string: D\n",
+      "bytes: ['0x45', '0x0', '0x0', '0x0'], integer: 69, string: E\n",
+      "bytes: ['0x46', '0x0', '0x0', '0x0'], integer: 70, string: F\n",
+      "bytes: ['0x47', '0x0', '0x0', '0x0'], integer: 71, string: G\n",
+      "bytes: ['0x48', '0x0', '0x0', '0x0'], integer: 72, string: H\n",
+      "bytes: ['0x49', '0x0', '0x0', '0x0'], integer: 73, string: I\n",
+      "bytes: ['0x0', '0x2', '0x0', '0x0'], integer: 512, string: Ȁ\n",
+      "bytes: ['0x1', '0x2', '0x0', '0x0'], integer: 513, string: ȁ\n",
+      "bytes: ['0x2', '0x2', '0x0', '0x0'], integer: 514, string: Ȃ\n"
+     ]
+    }
+   ],
    "source": [
     "for i in range(0, 6):\n",
     "    bt = i.to_bytes(4, 'little')\n",
@@ -1193,15 +1520,28 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 46,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "The `uft8` codepoint  is = 67, the bytes representation = b'C\\x00\\x00\\x00', the representation is C\n",
+      "The `uft8` codepoint  is = 105, the bytes representation = b'i\\x00\\x00\\x00', the representation is i\n",
+      "The `uft8` codepoint  is = 97, the bytes representation = b'a\\x00\\x00\\x00', the representation is a\n",
+      "The `uft8` codepoint  is = 111, the bytes representation = b'o\\x00\\x00\\x00', the representation is o\n"
+     ]
+    }
+   ],
    "source": [
     "message = \"Ciao\"\n",
     "message_secret = bytes(message, \"utf-8\")\n",
-    "[print(f\"The `uft8` codepoint  is = {enc}, the bytes representation = {enc.to_bytes(4, 'little')}, the representation is {chr(enc)}\") for plain, enc in zip(message, message_secret)]"
+    "print_messages = [f\"The `uft8` codepoint  is = {enc}, the bytes representation = {enc.to_bytes(4, 'little')}, the representation is {chr(enc)}\" for plain, enc in zip(message, message_secret)]\n",
+    "for msg in print_messages:\n",
+    "    print(msg)"
    ]
   },
   {
@@ -1230,11 +1570,21 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 47,
    "metadata": {
     "tags": []
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "['1', '2', 'some']\n",
+      "['3', '4', 'numbers']\n",
+      "['5', '6', 'here']\n"
+     ]
+    }
+   ],
    "source": [
     "import csv\n",
     "import pathlib as pl\n",
@@ -1330,7 +1680,7 @@
     "tags": []
    },
    "source": [
-    "### Exercise 1: CSV to dictionary 🌶️"
+    "### Exercise 1: CSV to dictionary (easy)"
    ]
   },
   {
@@ -1404,7 +1754,7 @@
     "    Returns:\n",
     "        - A dictionary with each row represented as a key, value pair\n",
     "    \"\"\"\n",
-    "    pass"
+    "    return"
    ]
   },
   {
@@ -1414,7 +1764,7 @@
     "tags": []
    },
    "source": [
-    "### Exercise 2: Counting words 🌶️"
+    "### Exercise 2: Counting words (easy)"
    ]
   },
   {
@@ -1472,7 +1822,7 @@
     "    Returns:\n",
     "        - The number of words in the file\n",
     "    \"\"\"\n",
-    "    pass"
+    "    return"
    ]
   },
   {
@@ -1482,7 +1832,7 @@
     "tags": []
    },
    "source": [
-    "### Exercise 3: Letter statistics 🌶️🌶️"
+    "### Exercise 3: Letter statistics (medium)"
    ]
   },
   {
@@ -1538,7 +1888,7 @@
     "    Returns:\n",
     "        - A dictionary with a count of each letter\n",
     "    \"\"\"\n",
-    "    pass"
+    "    return"
    ]
   },
   {
@@ -1548,7 +1898,7 @@
     "tags": []
    },
    "source": [
-    "### Exercise 4: Translating words 🌶️🌶️"
+    "### Exercise 4: Translating words (medium)"
    ]
   },
   {
@@ -1615,8 +1965,7 @@
     "    Returns:\n",
     "        - A list of tuples with the english / italian words\n",
     "    \"\"\"\n",
-    "\n",
-    "    pass"
+    "    return"
    ]
   },
   {
@@ -1626,7 +1975,7 @@
     "tags": []
    },
    "source": [
-    "### Exercise 5: Binary format 🌶️🌶️🌶️"
+    "### Exercise 5: Binary format (hard)"
    ]
   },
   {
@@ -1678,14 +2027,14 @@
     "    Returns:\n",
     "        - The secret message\n",
     "    \"\"\"\n",
-    "    pass"
+    "    return"
    ]
   }
  ],
  "metadata": {
   "celltoolbar": "Slideshow",
   "kernelspec": {
-   "display_name": "Python 3",
+   "display_name": "Python 3 (ipykernel)",
    "language": "python",
    "name": "python3"
   },
@@ -1699,7 +2048,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.12.4"
+   "version": "3.13.5"
   }
  },
  "nbformat": 4,
diff --git a/05_object_oriented_programming.ipynb b/05_object_oriented_programming.ipynb
index afb772b5..17b8e713 100644
--- a/05_object_oriented_programming.ipynb
+++ b/05_object_oriented_programming.ipynb
@@ -1700,7 +1700,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.10.13"
+   "version": "3.13.5"
   }
  },
  "nbformat": 4,
diff --git a/tutorial/quiz/input_output.py b/tutorial/quiz/input_output.py
index 923b907e..9bd6a539 100644
--- a/tutorial/quiz/input_output.py
+++ b/tutorial/quiz/input_output.py
@@ -43,7 +43,7 @@ def __init__(self, title=""):
             question="What happens if you call <code>input()</code> in the middle of a function?",
             options={
                 "The function execution stops and it waits for the user to type an input": "Correct! Input is a blocking function which waits for user to enter a string in the console and press enter.",
-                "The function continues its execution": "Wrong!",
+                "The function continues its execution": "Wrong! Input is a blocking function which waits for user input.",
             },
             correct_answer="The function execution stops and it waits for the user to type an input",
             shuffle=True,
@@ -57,7 +57,7 @@ def __init__(self, title=""):
         q1 = Question(
             question="What does the operator <code>/</code> do when applied to two <code>Pathlib.Path</code> objects?",
             options={
-                "It removes the second path from the first": "Wrong, try it in the shell.",
+                "It removes the second path from the first": "Wrong, try it in a cell below.",
                 "It concatenates paths": "Correct, it lets you construct a path from different segments",
             },
             correct_answer="It concatenates paths",
@@ -68,7 +68,7 @@ def __init__(self, title=""):
             question="If you use Pathlib,  do you need to use different path separators on Windows and Linux to combine path segments?",
             options={
                 "No, you can combine Pathlib.Path objects with /": "Correct! Pathlib will then generate the correct path for your OS.",
-                "Yes": "Wrong! You can always use  <code>/</code>",
+                "Yes": "Wrong! You can always use <code>/</code>",
             },
             correct_answer="No, you can combine Pathlib.Path objects with /",
             shuffle=True,
@@ -78,7 +78,7 @@ def __init__(self, title=""):
             question="""The path </code>Pathlib.Path("./")</code> represent a relative path. What location does it refer to?""",
             options={
                 "Relative to the current working directory, the location of the current Python script being run": "Correct!",
-                "Relative to the user's home directory": "Wrong!",
+                "Relative to the user's home directory": "Wrong! It is relative to the current working directory.",
             },
             correct_answer="Relative to the current working directory, the location of the current Python script being run",
             shuffle=True,
diff --git a/tutorial/tests/data/example1.csv b/tutorial/tests/data/example1.csv
new file mode 100644
index 00000000..53f9e8ba
--- /dev/null
+++ b/tutorial/tests/data/example1.csv
@@ -0,0 +1,11 @@
+this,is,data

+0,1,2

+1,2,3

+2,3,4

+3,4,5

+4,5,6

+5,6,7

+6,7,8

+7,8,9

+8,9,10

+9,10,11

diff --git a/tutorial/tests/data/me.txt b/tutorial/tests/data/me.txt
new file mode 100644
index 00000000..2d5fcfd7
--- /dev/null
+++ b/tutorial/tests/data/me.txt
@@ -0,0 +1 @@
+Simone
\ No newline at end of file
diff --git a/tutorial/tests/data/numbers.txt b/tutorial/tests/data/numbers.txt
new file mode 100644
index 00000000..8b1acc12
--- /dev/null
+++ b/tutorial/tests/data/numbers.txt
@@ -0,0 +1,10 @@
+0
+1
+2
+3
+4
+5
+6
+7
+8
+9
diff --git a/tutorial/tests/data/output.txt b/tutorial/tests/data/output.txt
new file mode 100644
index 0000000000000000000000000000000000000000..df93f5f3f72487244976c34e85525cf445016566
GIT binary patch
literal 10
RcmZQzWMXDvWn<^y1ONc904@Lk

literal 0
HcmV?d00001

diff --git a/tutorial/tests/data/output1.txt b/tutorial/tests/data/output1.txt
new file mode 100644
index 0000000000000000000000000000000000000000..bf7fd73a844290ab930a8665635b465aec2c9e9f
GIT binary patch
literal 2048
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literal 0
HcmV?d00001


From 42f6da42c489cee2992f0b1ac5f74d297a05d88d Mon Sep 17 00:00:00 2001
From: Lopes <fabio.lopes@empa.ch>
Date: Tue, 4 Nov 2025 13:14:16 +0100
Subject: [PATCH 05/11] Corrected issues and tested functions in Issue #272

---
 04_input_output.ipynb                  | 491 ++++---------------------
 tutorial/tests/test_04_input_output.py |   4 +-
 2 files changed, 72 insertions(+), 423 deletions(-)

diff --git a/04_input_output.ipynb b/04_input_output.ipynb
index 4ce37f05..82ac0bb1 100644
--- a/04_input_output.ipynb
+++ b/04_input_output.ipynb
@@ -488,25 +488,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "b5d9190bff57413c8c14c640aa74557a",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "Paths(children=(Question(children=(HTML(value='<strong>Q1:</strong> What does the operator <code>/</code> do w…"
-      ]
-     },
-     "execution_count": 1,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "import tutorial.quiz.input_output as op\n",
     "op.Paths()"
@@ -522,34 +506,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "text/html": [
-       "<div style='background-color: #ffebee; border-radius: 5px; padding: 10px;'>🚫 <strong style='color: red;'>OpenAI API key is not provided.</strong><br>API key is missing.</div>"
-      ],
-      "text/plain": [
-       "<IPython.core.display.HTML object>"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    },
-    {
-     "data": {
-      "text/html": [
-       "<div style='background-color: #fffde7; border-radius: 5px; padding: 10px;'>🔄 <strong>IPytest extension (re)loaded.</strong></div>"
-      ],
-      "text/plain": [
-       "<IPython.core.display.HTML object>"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%reload_ext tutorial.tests.testsuite"
    ]
@@ -560,7 +519,7 @@
    "metadata": {},
    "source": [
     "\n",
-    "1. Modify the function `solution_find_all_files` to find all files and directories in the [data](./tutorial/tests/data/) (./tutorial/tests/data/) directory and return them as a list of `Path` objects\n",
+    "1. Modify the function `solution_find_all_files` to find all files and directories in the [data](./tutorial/tests/data) directory and return them as a list of `Path` objects\n",
     "\n",
     "<div class=\"alert alert-block alert-info\">\n",
     "    <b>Hint:</b> The path to the data directory is available as the argument <code>current_path</code> of the function <code>solution_find_all_files</code>\n",
@@ -569,24 +528,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "5a82cdcf4ce1468d8718502eafc1c89a",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -614,24 +558,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "2f2eb3ad53e4430b836b3fbcaa5f0f66",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -661,24 +590,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "5acc98c538244a7487e51251a8ce1b71",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -705,9 +619,9 @@
     "### Reading from a file\n",
     "\n",
     "We now want to learn how to read text from a file. \n",
-    "Let's see how to do this with an example: we want to open the file [hello.txt](./data/hello.txt) and read its contents.\n",
+    "Let's see how to do this with an example: we want to open the file [hello.txt](./tutorial/tests/data/hello.txt) and read its contents.\n",
     "\n",
-    "1. The path is already identified, we know the file is in `./data/hello.txt`. We save this in a variable `path`.\n",
+    "1. The path is already identified, we know the file is in `./tutorial/tests/data/hello.txt`. We save this in a variable `path`.\n",
     "2. We now can use the built-in function [`open`](https://docs.python.org/3/library/functions.html#open) to open the file. This function returns a [file object](https://docs.python.org/3/glossary.html#term-file-object) that we can use to further manipulate the file. To ensure we only open the file for reading, we pass the string \"r\" to the second argument of `open`.\n",
     "3. Now we can read the contents using `read`, `readline` or `readlines`. `read` reads the whole file content into a single string, `readline` reads one line, while `readlines` reads the whole file content as a list of strings, one item per line in the file. This knowledge is useful when we only want to read part of a file or when the file is too big to fit in memory and we can only read parts.\n",
     "4. Finally, we close the file using the `close` method on the file object.\n"
@@ -715,19 +629,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "['Hello, I am a file with some text.\\n']\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -748,20 +654,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 12,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "['Hello, I am a file with some text.\\n']\n",
-      "[]\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -784,34 +681,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "this\n",
-      "\n",
-      "file\n",
-      "\n",
-      "has multiple\n",
-      "\n",
-      "lines\n",
-      "\n",
-      "how many\n",
-      "\n",
-      "lines\n",
-      "\n",
-      "does this file\n",
-      "\n",
-      "have?\n",
-      "\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -839,25 +713,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 14,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "ad907828193c4bbaa30116d5342f87dd",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "ReadFiles(children=(Question(children=(HTML(value='<strong>Q1:</strong> Can you read from a file before callin…"
-      ]
-     },
-     "execution_count": 14,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "import tutorial.quiz.input_output as op\n",
     "op.ReadFiles()"
@@ -873,34 +731,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 15,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "text/html": [
-       "<div style='background-color: #ffebee; border-radius: 5px; padding: 10px;'>🚫 <strong style='color: red;'>OpenAI API key is not provided.</strong><br>API key is missing.</div>"
-      ],
-      "text/plain": [
-       "<IPython.core.display.HTML object>"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    },
-    {
-     "data": {
-      "text/html": [
-       "<div style='background-color: #fffde7; border-radius: 5px; padding: 10px;'>🔄 <strong>IPytest extension (re)loaded.</strong></div>"
-      ],
-      "text/plain": [
-       "<IPython.core.display.HTML object>"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%reload_ext tutorial.tests.testsuite"
    ]
@@ -915,24 +748,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "658982e189394032bd022f74294fd393",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -961,12 +779,12 @@
     "- We use `write` to write a *string* to the file. Other types of object should be converted to string before being written.\n",
     "\n",
     "\n",
-    "Let's see this in action by writing your name in a file called `me.txt` in [data](./data/)"
+    "Let's see this in action by writing your name in a file called `me.txt` in [./tutorial/tests/data](./tutorial/tests/data/)"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 19,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
@@ -992,7 +810,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 20,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
@@ -1023,25 +841,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 21,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "cb48e1322fe843a2ae8628f24d467a16",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "WriteFiles(children=(Question(children=(HTML(value='<strong>Q1:</strong> What does <code>w</code> in the secon…"
-      ]
-     },
-     "execution_count": 21,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "import tutorial.quiz.input_output as op\n",
     "op.WriteFiles()"
@@ -1057,34 +859,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 22,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "text/html": [
-       "<div style='background-color: #ffebee; border-radius: 5px; padding: 10px;'>🚫 <strong style='color: red;'>OpenAI API key is not provided.</strong><br>API key is missing.</div>"
-      ],
-      "text/plain": [
-       "<IPython.core.display.HTML object>"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    },
-    {
-     "data": {
-      "text/html": [
-       "<div style='background-color: #fffde7; border-radius: 5px; padding: 10px;'>🔄 <strong>IPytest extension (re)loaded.</strong></div>"
-      ],
-      "text/plain": [
-       "<IPython.core.display.HTML object>"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%reload_ext tutorial.tests.testsuite"
    ]
@@ -1099,24 +876,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 23,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "044f8550f1914cb49ee4d639a7d553c6",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -1161,24 +923,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 31,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "5ec927991895480bbfc1d720c592a674",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "VBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': 'HTML(value=\\'<div style…"
-      ]
-     },
-     "metadata": {},
-     "output_type": "display_data"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "%%ipytest\n",
     "\n",
@@ -1223,19 +970,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 32,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "['Hello, I am a file with some text.\\n']\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -1270,25 +1009,9 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 33,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "application/vnd.jupyter.widget-view+json": {
-       "model_id": "4a284a916de749929f85bee97e286c61",
-       "version_major": 2,
-       "version_minor": 0
-      },
-      "text/plain": [
-       "ContextManagers(children=(Question(children=(HTML(value='<strong>Q1:</strong> Do you need to call <code>close<…"
-      ]
-     },
-     "execution_count": 33,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
    "source": [
     "import tutorial.quiz.input_output as op\n",
     "op.ContextManagers()"
@@ -1313,19 +1036,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 34,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "b'\\x00\\x01\\x02\\x03\\x04\\x05\\x06\\x07\\x08\\t'\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -1348,19 +1063,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 35,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "import pathlib as pl\n",
     "\n",
@@ -1385,7 +1092,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 36,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
@@ -1414,19 +1121,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 37,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276, 277, 278, 279, 280, 281, 282, 283, 284, 285, 286, 287, 288, 289, 290, 291, 292, 293, 294, 295, 296, 297, 298, 299, 300, 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 311, 312, 313, 314, 315, 316, 317, 318, 319, 320, 321, 322, 323, 324, 325, 326, 327, 328, 329, 330, 331, 332, 333, 334, 335, 336, 337, 338, 339, 340, 341, 342, 343, 344, 345, 346, 347, 348, 349, 350, 351, 352, 353, 354, 355, 356, 357, 358, 359, 360, 361, 362, 363, 364, 365, 366, 367, 368, 369, 370, 371, 372, 373, 374, 375, 376, 377, 378, 379, 380, 381, 382, 383, 384, 385, 386, 387, 388, 389, 390, 391, 392, 393, 394, 395, 396, 397, 398, 399, 400, 401, 402, 403, 404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414, 415, 416, 417, 418, 419, 420, 421, 422, 423, 424, 425, 426, 427, 428, 429, 430, 431, 432, 433, 434, 435, 436, 437, 438, 439, 440, 441, 442, 443, 444, 445, 446, 447, 448, 449, 450, 451, 452, 453, 454, 455, 456, 457, 458, 459, 460, 461, 462, 463, 464, 465, 466, 467, 468, 469, 470, 471, 472, 473, 474, 475, 476, 477, 478, 479, 480, 481, 482, 483, 484, 485, 486, 487, 488, 489, 490, 491, 492, 493, 494, 495, 496, 497, 498, 499, 500, 501, 502, 503, 504, 505, 506, 507, 508, 509, 510, 511, 512, 513, 514, 515, 516, 517, 518, 519, 520, 521, 522, 523, 524, 525, 526, 527, 528, 529, 530, 531, 532, 533, 534, 535, 536, 537, 538, 539, 540, 541, 542, 543, 544, 545, 546, 547, 548, 549, 550, 551, 552, 553, 554, 555, 556, 557, 558, 559, 560, 561, 562, 563, 564, 565, 566, 567, 568, 569, 570, 571, 572, 573, 574, 575, 576, 577, 578, 579, 580, 581, 582, 583, 584, 585, 586, 587, 588, 589, 590, 591, 592, 593, 594, 595, 596, 597, 598, 599, 600, 601, 602, 603, 604, 605, 606, 607, 608, 609, 610, 611, 612, 613, 614, 615, 616, 617, 618, 619, 620, 621, 622, 623, 624, 625, 626, 627, 628, 629, 630, 631, 632, 633, 634, 635, 636, 637, 638, 639, 640, 641, 642, 643, 644, 645, 646, 647, 648, 649, 650, 651, 652, 653, 654, 655, 656, 657, 658, 659, 660, 661, 662, 663, 664, 665, 666, 667, 668, 669, 670, 671, 672, 673, 674, 675, 676, 677, 678, 679, 680, 681, 682, 683, 684, 685, 686, 687, 688, 689, 690, 691, 692, 693, 694, 695, 696, 697, 698, 699, 700, 701, 702, 703, 704, 705, 706, 707, 708, 709, 710, 711, 712, 713, 714, 715, 716, 717, 718, 719, 720, 721, 722, 723, 724, 725, 726, 727, 728, 729, 730, 731, 732, 733, 734, 735, 736, 737, 738, 739, 740, 741, 742, 743, 744, 745, 746, 747, 748, 749, 750, 751, 752, 753, 754, 755, 756, 757, 758, 759, 760, 761, 762, 763, 764, 765, 766, 767, 768, 769, 770, 771, 772, 773, 774, 775, 776, 777, 778, 779, 780, 781, 782, 783, 784, 785, 786, 787, 788, 789, 790, 791, 792, 793, 794, 795, 796, 797, 798, 799, 800, 801, 802, 803, 804, 805, 806, 807, 808, 809, 810, 811, 812, 813, 814, 815, 816, 817, 818, 819, 820, 821, 822, 823, 824, 825, 826, 827, 828, 829, 830, 831, 832, 833, 834, 835, 836, 837, 838, 839, 840, 841, 842, 843, 844, 845, 846, 847, 848, 849, 850, 851, 852, 853, 854, 855, 856, 857, 858, 859, 860, 861, 862, 863, 864, 865, 866, 867, 868, 869, 870, 871, 872, 873, 874, 875, 876, 877, 878, 879, 880, 881, 882, 883, 884, 885, 886, 887, 888, 889, 890, 891, 892, 893, 894, 895, 896, 897, 898, 899, 900, 901, 902, 903, 904, 905, 906, 907, 908, 909, 910, 911, 912, 913, 914, 915, 916, 917, 918, 919, 920, 921, 922, 923, 924, 925, 926, 927, 928, 929, 930, 931, 932, 933, 934, 935, 936, 937, 938, 939, 940, 941, 942, 943, 944, 945, 946, 947, 948, 949, 950, 951, 952, 953, 954, 955, 956, 957, 958, 959, 960, 961, 962, 963, 964, 965, 966, 967, 968, 969, 970, 971, 972, 973, 974, 975, 976, 977, 978, 979, 980, 981, 982, 983, 984, 985, 986, 987, 988, 989, 990, 991, 992, 993, 994, 995, 996, 997, 998, 999, 1000, 1001, 1002, 1003, 1004, 1005, 1006, 1007, 1008, 1009, 1010, 1011, 1012, 1013, 1014, 1015, 1016, 1017, 1018, 1019, 1020, 1021, 1022, 1023]\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "import pathlib as pl\n",
     "import struct\n",
@@ -1453,41 +1152,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 38,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "bytes: ['0x0', '0x0', '0x0', '0x0'], integer: 0, string: \u0000\n",
-      "bytes: ['0x1', '0x0', '0x0', '0x0'], integer: 1, string: \u0001\n",
-      "bytes: ['0x2', '0x0', '0x0', '0x0'], integer: 2, string: \u0002\n",
-      "bytes: ['0x3', '0x0', '0x0', '0x0'], integer: 3, string: \u0003\n",
-      "bytes: ['0x4', '0x0', '0x0', '0x0'], integer: 4, string: \u0004\n",
-      "bytes: ['0x5', '0x0', '0x0', '0x0'], integer: 5, string: \u0005\n",
-      "bytes: ['0x3c', '0x0', '0x0', '0x0'], integer: 60, string: <\n",
-      "bytes: ['0x3d', '0x0', '0x0', '0x0'], integer: 61, string: =\n",
-      "bytes: ['0x3e', '0x0', '0x0', '0x0'], integer: 62, string: >\n",
-      "bytes: ['0x3f', '0x0', '0x0', '0x0'], integer: 63, string: ?\n",
-      "bytes: ['0x40', '0x0', '0x0', '0x0'], integer: 64, string: @\n",
-      "bytes: ['0x41', '0x0', '0x0', '0x0'], integer: 65, string: A\n",
-      "bytes: ['0x42', '0x0', '0x0', '0x0'], integer: 66, string: B\n",
-      "bytes: ['0x43', '0x0', '0x0', '0x0'], integer: 67, string: C\n",
-      "bytes: ['0x44', '0x0', '0x0', '0x0'], integer: 68, string: D\n",
-      "bytes: ['0x45', '0x0', '0x0', '0x0'], integer: 69, string: E\n",
-      "bytes: ['0x46', '0x0', '0x0', '0x0'], integer: 70, string: F\n",
-      "bytes: ['0x47', '0x0', '0x0', '0x0'], integer: 71, string: G\n",
-      "bytes: ['0x48', '0x0', '0x0', '0x0'], integer: 72, string: H\n",
-      "bytes: ['0x49', '0x0', '0x0', '0x0'], integer: 73, string: I\n",
-      "bytes: ['0x0', '0x2', '0x0', '0x0'], integer: 512, string: Ȁ\n",
-      "bytes: ['0x1', '0x2', '0x0', '0x0'], integer: 513, string: ȁ\n",
-      "bytes: ['0x2', '0x2', '0x0', '0x0'], integer: 514, string: Ȃ\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "for i in range(0, 6):\n",
     "    bt = i.to_bytes(4, 'little')\n",
@@ -1520,22 +1189,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 46,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "The `uft8` codepoint  is = 67, the bytes representation = b'C\\x00\\x00\\x00', the representation is C\n",
-      "The `uft8` codepoint  is = 105, the bytes representation = b'i\\x00\\x00\\x00', the representation is i\n",
-      "The `uft8` codepoint  is = 97, the bytes representation = b'a\\x00\\x00\\x00', the representation is a\n",
-      "The `uft8` codepoint  is = 111, the bytes representation = b'o\\x00\\x00\\x00', the representation is o\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "message = \"Ciao\"\n",
     "message_secret = bytes(message, \"utf-8\")\n",
@@ -1565,26 +1223,16 @@
     "These packages are outside of the scope of this tutorial and will not be covered here.\n",
     "\n",
     "\n",
-    "Let's see how to read csv files using `csv` with an example by reading [example.csv](./data/example.csv):"
+    "Let's see how to read csv files using `csv` with an example by reading [example.csv](./tutorial/tests/data/example.csv):"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 47,
+   "execution_count": null,
    "metadata": {
     "tags": []
    },
-   "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "['1', '2', 'some']\n",
-      "['3', '4', 'numbers']\n",
-      "['5', '6', 'here']\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
     "import csv\n",
     "import pathlib as pl\n",
@@ -1872,7 +1520,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "%%ipytest input_output\n",
+    "%%ipytest\n",
     "\n",
     "import pathlib as pl\n",
     "import string\n",
@@ -1908,7 +1556,7 @@
     "tags": []
    },
    "source": [
-    "Write a function which takes the words from the file `english.txt` and translates them to Italian using the dictionary file `dict.csv`. The output should be a **list of tuples** with the pair `italian, english` if the word is found and nothing otherwise.\n",
+    "Write a function which takes the words from the file `english.txt` and translates them to Italian using the dictionary file `dict.csv`. The output should be a **list of tuples** with the pair `italian, english` **if the word is found and nothing otherwise**.\n",
     "\n",
     "For example, given the `english.txt` file:\n",
     "\n",
@@ -1950,6 +1598,7 @@
    "source": [
     "%%ipytest\n",
     "\n",
+    "import csv\n",
     "import pathlib as pl\n",
     "\n",
     "def solution_exercise4(english: pl.Path, dictionary: pl.Path) -> list[(str, str)]:\n",
diff --git a/tutorial/tests/test_04_input_output.py b/tutorial/tests/test_04_input_output.py
index b7b9fa69..13fb902c 100644
--- a/tutorial/tests/test_04_input_output.py
+++ b/tutorial/tests/test_04_input_output.py
@@ -254,10 +254,10 @@ def reference_exercise5(secret_file: pl.Path) -> str:
 def test_exercise5(function_to_test):
     message = get_data("secret_message.dat")
     # Save the original content of the input file
-    original_content = message.read_text()
+    original_content = message.read_bytes()
 
     try:
         assert function_to_test(message) == reference_exercise5(message)
     finally:
         # Reset the input file to its original content
-        message.write_text(original_content)
+        message.write_bytes(original_content)

From ee27b63b3ed704d12da02c4ec6cbe1570484df2c Mon Sep 17 00:00:00 2001
From: Lopes <fabio.lopes@empa.ch>
Date: Tue, 4 Nov 2025 13:15:52 +0100
Subject: [PATCH 06/11] Corrected directories hyperlinks

---
 04_input_output.ipynb | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/04_input_output.ipynb b/04_input_output.ipynb
index 82ac0bb1..6617a382 100644
--- a/04_input_output.ipynb
+++ b/04_input_output.ipynb
@@ -519,7 +519,7 @@
    "metadata": {},
    "source": [
     "\n",
-    "1. Modify the function `solution_find_all_files` to find all files and directories in the [data](./tutorial/tests/data) directory and return them as a list of `Path` objects\n",
+    "1. Modify the function `solution_find_all_files` to find all files and directories in the ```/tutorial/tests/data``` directory and return them as a list of `Path` objects\n",
     "\n",
     "<div class=\"alert alert-block alert-info\">\n",
     "    <b>Hint:</b> The path to the data directory is available as the argument <code>current_path</code> of the function <code>solution_find_all_files</code>\n",
@@ -779,7 +779,7 @@
     "- We use `write` to write a *string* to the file. Other types of object should be converted to string before being written.\n",
     "\n",
     "\n",
-    "Let's see this in action by writing your name in a file called `me.txt` in [./tutorial/tests/data](./tutorial/tests/data/)"
+    "Let's see this in action by writing your name in a file called `me.txt` in ```/tutorial/tests/data```"
    ]
   },
   {

From 5bd589eb6742c15e877451b291ee8d04a405d4b1 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 4 Nov 2025 12:31:55 +0000
Subject: [PATCH 07/11] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 04_input_output.ipynb            |   4 +---
 tutorial/tests/data/example1.csv |  22 +++++++++++-----------
 tutorial/tests/data/me.txt       |   2 +-
 tutorial/tests/data/output.txt   | Bin 10 -> 10 bytes
 tutorial/tests/data/output1.txt  | Bin 2048 -> 2049 bytes
 5 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/04_input_output.ipynb b/04_input_output.ipynb
index 6617a382..6c94bd5d 100644
--- a/04_input_output.ipynb
+++ b/04_input_output.ipynb
@@ -147,9 +147,7 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "metadata": {
-    "scrolled": true
-   },
+   "metadata": {},
    "outputs": [],
    "source": [
     "import tutorial.quiz.input_output as op\n",
diff --git a/tutorial/tests/data/example1.csv b/tutorial/tests/data/example1.csv
index 53f9e8ba..97cf6750 100644
--- a/tutorial/tests/data/example1.csv
+++ b/tutorial/tests/data/example1.csv
@@ -1,11 +1,11 @@
-this,is,data

-0,1,2

-1,2,3

-2,3,4

-3,4,5

-4,5,6

-5,6,7

-6,7,8

-7,8,9

-8,9,10

-9,10,11

+this,is,data
+0,1,2
+1,2,3
+2,3,4
+3,4,5
+4,5,6
+5,6,7
+6,7,8
+7,8,9
+8,9,10
+9,10,11
\ No newline at end of file
diff --git a/tutorial/tests/data/me.txt b/tutorial/tests/data/me.txt
index 2d5fcfd7..e09cfaf8 100644
--- a/tutorial/tests/data/me.txt
+++ b/tutorial/tests/data/me.txt
@@ -1 +1 @@
-Simone
\ No newline at end of file
+Simone
diff --git a/tutorial/tests/data/output.txt b/tutorial/tests/data/output.txt
index df93f5f3f72487244976c34e85525cf445016566..6a1b60378403dc4bfc05a02f2d0992d4d46b82c6 100644
GIT binary patch
literal 10
RcmZQzWMXDvWn<^y0ssK8051Rl

literal 10
RcmZQzWMXDvWn<^y1ONc904@Lk

diff --git a/tutorial/tests/data/output1.txt b/tutorial/tests/data/output1.txt
index bf7fd73a844290ab930a8665635b465aec2c9e9f..f7dff7ae65669a88e2b23c35bf3c5282b6b38f1a 100644
GIT binary patch
delta 8
PcmZn=XcSn$!N>&w3UUF}

delta 6
NcmZn^Xb@Py0RRTn0m=XX


From 4717bf309ceaa7ed1423ac1f96da250ac5f9fe92 Mon Sep 17 00:00:00 2001
From: Lopes <fabio.lopes@empa.ch>
Date: Tue, 4 Nov 2025 13:33:02 +0100
Subject: [PATCH 08/11] Running pre-commit

---
 04_input_output.ipynb            |   4 +---
 tutorial/tests/data/example1.csv |  22 +++++++++++-----------
 tutorial/tests/data/me.txt       |   2 +-
 tutorial/tests/data/output.txt   | Bin 10 -> 10 bytes
 tutorial/tests/data/output1.txt  | Bin 2048 -> 2049 bytes
 5 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/04_input_output.ipynb b/04_input_output.ipynb
index 6617a382..6c94bd5d 100644
--- a/04_input_output.ipynb
+++ b/04_input_output.ipynb
@@ -147,9 +147,7 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "metadata": {
-    "scrolled": true
-   },
+   "metadata": {},
    "outputs": [],
    "source": [
     "import tutorial.quiz.input_output as op\n",
diff --git a/tutorial/tests/data/example1.csv b/tutorial/tests/data/example1.csv
index 53f9e8ba..0c6b9092 100644
--- a/tutorial/tests/data/example1.csv
+++ b/tutorial/tests/data/example1.csv
@@ -1,11 +1,11 @@
-this,is,data

-0,1,2

-1,2,3

-2,3,4

-3,4,5

-4,5,6

-5,6,7

-6,7,8

-7,8,9

-8,9,10

-9,10,11

+this,is,data
+0,1,2
+1,2,3
+2,3,4
+3,4,5
+4,5,6
+5,6,7
+6,7,8
+7,8,9
+8,9,10
+9,10,11
\ No newline at end of file
diff --git a/tutorial/tests/data/me.txt b/tutorial/tests/data/me.txt
index 2d5fcfd7..e09cfaf8 100644
--- a/tutorial/tests/data/me.txt
+++ b/tutorial/tests/data/me.txt
@@ -1 +1 @@
-Simone
\ No newline at end of file
+Simone
diff --git a/tutorial/tests/data/output.txt b/tutorial/tests/data/output.txt
index df93f5f3f72487244976c34e85525cf445016566..6a1b60378403dc4bfc05a02f2d0992d4d46b82c6 100644
GIT binary patch
literal 10
RcmZQzWMXDvWn<^y0ssK8051Rl

literal 10
RcmZQzWMXDvWn<^y1ONc904@Lk

diff --git a/tutorial/tests/data/output1.txt b/tutorial/tests/data/output1.txt
index bf7fd73a844290ab930a8665635b465aec2c9e9f..f7dff7ae65669a88e2b23c35bf3c5282b6b38f1a 100644
GIT binary patch
delta 8
PcmZn=XcSn$!N>&w3UUF}

delta 6
NcmZn^Xb@Py0RRTn0m=XX


From 500e08347ecd451f26bbee26e9795ab943cf2516 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 4 Nov 2025 12:37:34 +0000
Subject: [PATCH 09/11] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 tutorial/tests/data/example1.csv | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tutorial/tests/data/example1.csv b/tutorial/tests/data/example1.csv
index 3870be47..ab2340cd 100644
--- a/tutorial/tests/data/example1.csv
+++ b/tutorial/tests/data/example1.csv
@@ -21,4 +21,4 @@ this,is,data
 7,8,9
 8,9,10
 >>>>>>> 5bd589eb6742c15e877451b291ee8d04a405d4b1
-9,10,11
\ No newline at end of file
+9,10,11

From 6ab78a7cccbb8e715acb123eda8dc2ee6d914e10 Mon Sep 17 00:00:00 2001
From: Lopes <fabio.lopes@empa.ch>
Date: Tue, 11 Nov 2025 14:07:17 +0100
Subject: [PATCH 10/11] Correct filepath

---
 04_input_output.ipynb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/04_input_output.ipynb b/04_input_output.ipynb
index 6c94bd5d..c77e582f 100644
--- a/04_input_output.ipynb
+++ b/04_input_output.ipynb
@@ -619,7 +619,7 @@
     "We now want to learn how to read text from a file. \n",
     "Let's see how to do this with an example: we want to open the file [hello.txt](./tutorial/tests/data/hello.txt) and read its contents.\n",
     "\n",
-    "1. The path is already identified, we know the file is in `./tutorial/tests/data/hello.txt`. We save this in a variable `path`.\n",
+    "1. The path is already identified, we know the file is in [hello.txt](./tutorial/tests/data/hello.txt). We save this in a variable `path`.\n",
     "2. We now can use the built-in function [`open`](https://docs.python.org/3/library/functions.html#open) to open the file. This function returns a [file object](https://docs.python.org/3/glossary.html#term-file-object) that we can use to further manipulate the file. To ensure we only open the file for reading, we pass the string \"r\" to the second argument of `open`.\n",
     "3. Now we can read the contents using `read`, `readline` or `readlines`. `read` reads the whole file content into a single string, `readline` reads one line, while `readlines` reads the whole file content as a list of strings, one item per line in the file. This knowledge is useful when we only want to read part of a file or when the file is too big to fit in memory and we can only read parts.\n",
     "4. Finally, we close the file using the `close` method on the file object.\n"

From 9c639fa33573d2c6ed953446443de468b51f5bff Mon Sep 17 00:00:00 2001
From: Despina Adamopoulou <despoina.adamopoulou@empa.ch>
Date: Tue, 11 Nov 2025 16:41:47 +0100
Subject: [PATCH 11/11] final fixes

---
 04_input_output.ipynb | 37 +++++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/04_input_output.ipynb b/04_input_output.ipynb
index c77e582f..0666a1d6 100644
--- a/04_input_output.ipynb
+++ b/04_input_output.ipynb
@@ -40,11 +40,11 @@
     "      - [Reading/Writing CSV files](#Reading/Writing-CSV-files)\n",
     "        - [Quiz on CSV](#Quiz-on-CSV)\n",
     "    - [Exercises](#Exercises)\n",
-    "      - [Exercise 1: CSV to dictionary (easy)](#Exercise-1:-CSV-to-dictionary-(easy))\n",
-    "      - [Exercise 2: Counting words (easy)](#Exercise-2:-Counting-words-(easy))\n",
-    "      - [Exercise 3: Letter statistics (medium)](#Exercise-3:-Letter-statistics-(medium))\n",
-    "      - [Exercise 4: Translating words (medium)](#Exercise-4:-Translating-words-(medium))\n",
-    "      - [Exercise 5: Binary format (hard)](#Exercise-5:-Binary-format-(hard))"
+    "      - [Exercise 1: CSV to dictionary](#Exercise-1:-CSV-to-dictionary)\n",
+    "      - [Exercise 2: Counting words](#Exercise-2:-Counting-words)\n",
+    "      - [Exercise 3: Letter statistics](#Exercise-3:-Letter-statistics)\n",
+    "      - [Exercise 4: Translating words](#Exercise-4:-Translating-words)\n",
+    "      - [Exercise 5: Binary format](#Exercise-5:-Binary-format)"
    ]
   },
   {
@@ -1326,7 +1326,7 @@
     "tags": []
    },
    "source": [
-    "### Exercise 1: CSV to dictionary (easy)"
+    "### Exercise 1: CSV to dictionary"
    ]
   },
   {
@@ -1336,6 +1336,8 @@
     "tags": []
    },
    "source": [
+    "**Difficulty: 🌶️**\n",
+    "\n",
     "Write a function that reads a CSV file and returns a dictionary.\n",
     "\n",
     "- The dictionary keys are in the first **column**\n",
@@ -1410,7 +1412,7 @@
     "tags": []
    },
    "source": [
-    "### Exercise 2: Counting words (easy)"
+    "### Exercise 2: Counting words"
    ]
   },
   {
@@ -1420,6 +1422,8 @@
     "tags": []
    },
    "source": [
+    "**Difficulty: 🌶️**\n",
+    "\n",
     "Write a function  to read all the lines from `input_file` and count the number of words in the file. The solution should be a single number.\n",
     "\n",
     "For example, for the file\n",
@@ -1439,7 +1443,7 @@
     "            The file is available as the parameter <code>input_file</code> of <code>solution_exercise2</code> function\n",
     "        </li>\n",
     "        <li>\n",
-    "           A word consists of <b>printable</b> characters without whitespaces, line breaks etc. Have a look at the basic_datatypes notebook if you forgot how to split a text into it's words.\n",
+    "           A word consists of <b>printable</b> characters without whitespaces, line breaks etc. Have a look at the basic_datatypes notebook if you forgot how to split a text into its words.\n",
     "        </li>\n",
     "    </ul>\n",
     "</div>\n",
@@ -1478,7 +1482,7 @@
     "tags": []
    },
    "source": [
-    "### Exercise 3: Letter statistics (medium)"
+    "### Exercise 3: Letter statistics"
    ]
   },
   {
@@ -1488,7 +1492,9 @@
     "tags": []
    },
    "source": [
-    "Write a function that reads all the lines from `lines.txt` and counts the occurences of every letter present in all the words.\n",
+    "**Difficulty: 🌶️🌶️**\n",
+    "\n",
+    "Write a function that reads all the lines from [lines.txt](./tutorial/tests/data/lines.txt) and counts the occurences of every letter present in all the words.\n",
     "\n",
     "The result should be a dictionary, where each key-value pair is like `{letter: count}`. For example, `{a: 5}` means that the letter `a` appeared five times in this file.\n",
     "\n",
@@ -1544,7 +1550,7 @@
     "tags": []
    },
    "source": [
-    "### Exercise 4: Translating words (medium)"
+    "### Exercise 4: Translating words"
    ]
   },
   {
@@ -1554,7 +1560,9 @@
     "tags": []
    },
    "source": [
-    "Write a function which takes the words from the file `english.txt` and translates them to Italian using the dictionary file `dict.csv`. The output should be a **list of tuples** with the pair `italian, english` **if the word is found and nothing otherwise**.\n",
+    "**Difficulty: 🌶️🌶️**\n",
+    "\n",
+    "Write a function which takes the words from the file [english.txt](./tutorial/tests/data/english.txt) and translates them to Italian using the dictionary file [dict.csv](./tutorial/tests/data/dict.csv). The output should be a **list of tuples** with the pair `italian, english` **if the word is found and nothing otherwise**.\n",
     "\n",
     "For example, given the `english.txt` file:\n",
     "\n",
@@ -1622,7 +1630,7 @@
     "tags": []
    },
    "source": [
-    "### Exercise 5: Binary format (hard)"
+    "### Exercise 5: Binary format"
    ]
   },
   {
@@ -1632,8 +1640,9 @@
     "tags": []
    },
    "source": [
+    "**Difficulty: 🌶️🌶️🌶️**\n",
     "\n",
-    "The file `super_secret.dat` contains a secret message. We know that the message is stored in binary format as a sequence of bytes. The message starts with the byte sequence `b'\\xff\\xee\\xdd\\xcc\\xbb\\xaa'` and finishes with `b'\\xaa\\xbb\\xcc\\xdd\\xee\\xff'`. \n",
+    "The file `secret_file` contains a secret message. We know that the message is stored in binary format as a sequence of bytes. The message starts with the byte sequence `b'\\xff\\xee\\xdd\\xcc\\xbb\\xaa'` and finishes with `b'\\xaa\\xbb\\xcc\\xdd\\xee\\xff'`. \n",
     "Write a function that reads the file and returns **only** the secret message as a string.\n",
     "\n",
     "\n",