vault backup: 2024-12-05 23:59:54

WS2425/Data Science/Ue_P/exercise_1/p01_crash_course_python.ipynb

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+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "id": "753cfea7-6082-484d-a916-50554ca4cb9c",
+   "metadata": {},
+   "source": [
+    "# Crash Course Python\n",
+    "During this session, you will get a brief introduction into Python. Therefore, follow the instructions in this notebook step by step. Do not hesitate to ask questions! The instruction given are not complete, therefore: Try it on your own, play a little with the code and take a look at the official documentation of python:\n",
+    "https://docs.python.org/3.11/"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "beb6f785-e6a0-48e8-b838-a0e5a0987f8e",
+   "metadata": {},
+   "source": [
+    "## Data types\n",
+    "There are different built in data types in python. A variable takes the corresponding data type, if it is assigned to an instance of this type. with the Python command `type` one can check the type of a given variable or value."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "0f529564-bfee-4d55-8110-8be138863d75",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "type(5)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "5f40d465-531f-420a-8442-6875e877bb5e",
+   "metadata": {},
+   "source": [
+    "### Boolean, Numbers & Strings\n",
+    "In Python one can easily work with boolean, numbers and strings. \n",
+    " - True and False are the constants for boolean. Operators are often written out (not False, True or False ...)\n",
+    " - Strings can be defined by \"...\" and '...', but also \"\"\"...\"\"\" for multi-line strings."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "962dfa3d-90b5-4ed8-b5f5-f32093f1daf7",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "long_string = \"\"\"Hallo,\n",
+    "I'm a long string\"\"\""
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "8592fb25-7882-456e-8418-b02ac9f0140c",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "A = True\n",
+    "B = False\n",
+    "\n",
+    "not (A or B)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "3ac1a2e0-a7ec-43d2-90f6-220a717a3415",
+   "metadata": {},
+   "source": [
+    "**Task:** Play around with numbers, strings an boolean. Sum up some strings, define numbers and perform some basic math."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "db978452-f0d4-4511-9fba-e0d4231e3e6d",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "markdown",
+   "id": "7142dffd-b4f0-40ea-8d0c-fee412705ab9",
+   "metadata": {},
+   "source": [
+    "Especially strings, have some built in functions. E.g. with upper() one can convert a string in only upper letters."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "c1292afe-e088-4ca7-a32c-8026d68e37e5",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "\"hallo\".upper()"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "af78c85f-4e66-45f5-a114-4f8c992b8b07",
+   "metadata": {},
+   "source": [
+    "**Task:** Take a look into the documentation for strings and check some further functions one can directly use."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "b297a9b2-a72d-477d-81aa-97c4af6f4d39",
+   "metadata": {},
+   "source": [
+    "### Lists\n",
+    "One special data type are lists. Similar to an array, a list is a chain of values. In Python a list is defined by [] and can store different data types."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "48d27fe8-609d-4f9a-9f50-03c221dad093",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "[0, \"hallo\", False]"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "6ce9c921-ff6a-4539-b0b8-b3c19f155bca",
+   "metadata": {},
+   "source": [
+    "A value in a list can be accessed by given the position in brackets []. E.g. in the following example the second (index 1) element is requested. One can also access elements backwards by using a negative index."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "7ed90d0e-9181-46ea-9d07-19cdc8d75538",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "[0, \"hallo\", False][1]"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "4a3bea0f-1f45-4131-bb20-2fc30ce459a8",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "[0, \"hallo\", False][-2]"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "de6acc40-a65f-45cc-8cb6-8e77a5cdb79f",
+   "metadata": {},
+   "source": [
+    "One can also access a range of elements, by using the following notation in the brackets: start:end. The result is a list again. \n",
+    "\n",
+    "**Task** Take the upper list and access the first two elements of the list."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "2d1a5e9d-43a3-4793-9064-2b1f001923d4",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "markdown",
+   "id": "3ebe85d9-5735-45c8-9aec-7e88732ce585",
+   "metadata": {},
+   "source": [
+    "Elements can be deleted from a list with the `del` command."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "cda33a05-45eb-4463-a6d8-ebad296719d9",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "tmp_list = [0, \"hallo\", False]\n",
+    "del tmp_list[-2]\n",
+    "\n",
+    "tmp_list"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "813ffc8e-9d2f-4cb1-bd2e-34b66a2541bc",
+   "metadata": {},
+   "source": [
+    "### Dictionaries\n",
+    "Next to lists (tuples and sets - not handled here), Python offers Dictionaries as an additional data type. A dictionary is a list of key-value pairs, where a value is accessed by the value. A dictionary is defined by {...}, keys are typically strings, values can be nearly anything one like."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "74b09698-9fb5-4fe0-9402-cee7085f637d",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "some_functions = {\n",
+    "    \"print\": print,\n",
+    "    \"input\": input,\n",
+    "}\n",
+    "\n",
+    "some_functions[\"print\"](\"dictionaries can store nearly everything\")"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "b1306508-e1a2-43da-a995-4fb09acc5fba",
+   "metadata": {},
+   "source": [
+    "**Task:** Create a dictionary which stores for a semester a list of lectures."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "d693c391-727f-4da9-83e5-a8efb0395d34",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "markdown",
+   "id": "66f74d92-497a-433c-9026-267308114e40",
+   "metadata": {},
+   "source": [
+    "## If statement\n",
+    "The if statement has the following structure: `if` CONDITION: Where condition is something evaluating to `True` or `False`. After the : a intended block begins, which is evaluated if the CONDITION is True. With else: and `elif` CONDITION the else or else if case can be used."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "cb3755b6-109f-419b-8ed2-0102a89479b9",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "tmp_number = 3\n",
+    "\n",
+    "if tmp_number > 4:\n",
+    "    print(f\"{tmp_number} is larger than 4\")\n",
+    "elif tmp_number < 4:\n",
+    "    print(f\"{tmp_number} is smaller than 4\")\n",
+    "else:\n",
+    "    print(f\"{tmp_number} equals 4\")"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "c6ba6285-5228-4140-b03e-44733dddac05",
+   "metadata": {},
+   "source": [
+    "**Task:** Create an if statement which checks if a given number is even or odd. "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "4a4d25b0-f476-4201-9f78-781a3d38b7c3",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "markdown",
+   "id": "64fb2bdf-e2e2-428b-9ef1-bf79a296086d",
+   "metadata": {},
+   "source": [
+    "## for statement\n",
+    "The `for` statement has the following structure: for VALUE in ITERATOR: Where VALUE takes all values given in ITERATOR. After the : a intended block begins, which is evaluated for every step. ITERATOR can be everything one can iterate over. There are plenty functions like range to iterate over a list of numbers, but one can also use a list to iterate over."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "3a4c109c-0966-4343-b4f3-c4a692adf52a",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "for i in range(10):\n",
+    "    print(i**2)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "5848b9ff-5a7d-4299-b9d2-fb0fc92fa455",
+   "metadata": {},
+   "source": [
+    "**Task:** Create a loop which iterates of every entry in a list of lectures and checks if the lecture is called \"Data Science\"."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "debf84c2-79cf-4b2b-9420-28c1a9ededf1",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "markdown",
+   "id": "7650dc1e-8521-4ae2-b63f-d6954805385d",
+   "metadata": {},
+   "source": [
+    "## Functions\n",
+    "A function has the following structure: def NAME(VAR1,VAR2,VAR3=DEFAULTVAL3): Where after the : a intended block starts, which is evaluated when the function is called. The parameters is a list of Variables, where a variable can also have a default value. The returned value is given by a return statement."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "d739bd2e-bfc7-4256-a9a5-947f7de0ada9",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "2f725e9f-9c99-417c-8911-439c96e33e24",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "a3eabab2-7e88-428f-b81f-2b910d61af74",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def my_add(x,y=2):\n",
+    "    return x+y\n",
+    "\n",
+    "print(my_add(2,4))\n",
+    "print(my_add(2))"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "5f5fca24-7b2c-493c-bd0e-af649ac89a0e",
+   "metadata": {},
+   "source": [
+    "**Task:** Create a function which takes a list of numbers and returns a list where every number is multiplied with a factor."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "1f1d96ed-9af3-435c-8df1-d15c89a83e6c",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "markdown",
+   "id": "e7b67ab6-b009-414b-8f35-da4b1ec09564",
+   "metadata": {},
+   "source": [
+    "## Classes\n",
+    "Take a look into the official Python tutorial for the way how a class is defined in Python:\n",
+    "https://docs.python.org/3/tutorial/classes.html"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "430b950b-b9a8-4e42-8f71-9dd938959ac5",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "markdown",
+   "id": "85f4f762-c825-4865-abab-74509038fbc2",
+   "metadata": {},
+   "source": [
+    "**Task:** Create a class which represents a lecture. Every lecture has a list of students and a title. Furthermore create a function which adds students to a lecture and a function which returns the number of students. "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "1efbb8a3-938a-4ebe-b05c-88687a49a6d6",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "markdown",
+   "id": "04d85fef-d5eb-4c9a-aea3-c4647777d58b",
+   "metadata": {},
+   "source": [
+    "## Modules\n",
+    "Python has a lot of modules included, but there is also a huge amount of models which can be installed. A modul can be imported with the import command. A module can be installed with the help of pip (command line tool). "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "b8b0d5b5-ec05-4c29-948b-a9c09a7944c1",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import tqdm\n",
+    "\n",
+    "r = 0\n",
+    "for i in tqdm.tqdm(range(10000000)):\n",
+    "    r += i\n",
+    "\n",
+    "print(r)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "f5c40f75-f103-47c6-b5ca-a7fae135bd2f",
+   "metadata": {},
+   "source": [
+    "In jupyter a command line command can be executed in a code cell if it starts with a !."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "42c49615-29ef-40b3-9954-8cf589bd505b",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "!cmd"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "cbcc2c40-05c9-42cc-9281-51fd307d44f9",
+   "metadata": {},
+   "source": [
+    "**Task:** Take a look on PyPI and search for an interesting module. Install the module and try it out. Some example modules:\n",
+    " - tensorflow (deep learning)\n",
+    " - numpy (numerical methods)\n",
+    " - sklearn (machine learning)\n",
+    " - ..."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "93cf0ef8-c5a6-4e6b-b7d8-9d55728e4ff4",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3 (ipykernel)",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.11.9"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}