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| { | |
| "cells": [ | |
| { | |
| "metadata": {}, | |
| "id": "cc5e76ab", | |
| "cell_type": "markdown", | |
| "source": "# A Bit of Gymnastics in Python (Problems + Solutions)" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "5c4c70bb", | |
| "cell_type": "markdown", | |
| "source": "In this interactive session, I will propose exercises inspired by the most popular questions about Python in Stack Overflow: https://stackoverflow.com/questions/tagged/python?tab=votes.\n\nHere is the approach of the session:\n\n* For beginners, search answers on the web, discover some elements of the Python syntax;\n* For more advanced users, try to do as much as possible without any help from the web, gain speed and agility, find several answers to the same question.\n\nRequirements: a computer with a Python installation + Jupyter Notebook. Only a minimal knowledge of Python is necessary." | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "0230edac", | |
| "cell_type": "markdown", | |
| "source": "## Ternary operator" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "fb7a1bb4", | |
| "cell_type": "markdown", | |
| "source": "### Problem" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.159225Z", | |
| "end_time": "2023-04-19T11:33:51.174226Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "afcdfd0a", | |
| "cell_type": "code", | |
| "source": "def foo():\n print('Long computation of foo()...')\n return 'foo'", | |
| "execution_count": 1, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.175228Z", | |
| "end_time": "2023-04-19T11:33:51.190226Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "6564eaaf", | |
| "cell_type": "code", | |
| "source": "def bar():\n print('Long computation of bar()...')\n return 'bar'", | |
| "execution_count": 2, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "858733ea", | |
| "cell_type": "markdown", | |
| "source": "Implement the following function:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.191238Z", | |
| "end_time": "2023-04-19T11:33:51.206233Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "c7c5e29e", | |
| "cell_type": "code", | |
| "source": "def h(x):\n \"\"\"If x, then foo(), else bar().\n \n Evaluation is lazy: for example, if x is True, then only foo() is computed, not bar().\n \n Parameters\n ----------\n x: bool\n \n Returns\n -------\n str\n If x, then foo(), else bar().\n \n Examples\n --------\n >>> h(True)\n Long computation of foo()...\n 'foo'\n\n >>> h(False)\n Long computation of bar()...\n 'bar'\n \"\"\"\n pass", | |
| "execution_count": 3, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "330d5cf4", | |
| "cell_type": "markdown", | |
| "source": "### Solution" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.207226Z", | |
| "end_time": "2023-04-19T11:33:51.222226Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "5c1d6db8", | |
| "cell_type": "code", | |
| "source": "def h(x):\n return foo() if x else bar()", | |
| "execution_count": 4, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.223226Z", | |
| "end_time": "2023-04-19T11:33:51.237237Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "617c0a86", | |
| "cell_type": "code", | |
| "source": "h(True)", | |
| "execution_count": 5, | |
| "outputs": [ | |
| { | |
| "output_type": "stream", | |
| "text": "Long computation of foo()...\n", | |
| "name": "stdout" | |
| }, | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 5, | |
| "data": { | |
| "text/plain": "'foo'" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.238240Z", | |
| "end_time": "2023-04-19T11:33:51.252183Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "493654ec", | |
| "cell_type": "code", | |
| "source": "h(False)", | |
| "execution_count": 6, | |
| "outputs": [ | |
| { | |
| "output_type": "stream", | |
| "text": "Long computation of bar()...\n", | |
| "name": "stdout" | |
| }, | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 6, | |
| "data": { | |
| "text/plain": "'bar'" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.253204Z", | |
| "end_time": "2023-04-19T11:33:51.267690Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "f6d74144", | |
| "cell_type": "code", | |
| "source": "def h(x):\n if x:\n return foo()\n return bar()", | |
| "execution_count": 7, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.269733Z", | |
| "end_time": "2023-04-19T11:33:51.282814Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "0bb6a01a", | |
| "cell_type": "code", | |
| "source": "h(True)", | |
| "execution_count": 8, | |
| "outputs": [ | |
| { | |
| "output_type": "stream", | |
| "text": "Long computation of foo()...\n", | |
| "name": "stdout" | |
| }, | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 8, | |
| "data": { | |
| "text/plain": "'foo'" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.284818Z", | |
| "end_time": "2023-04-19T11:33:51.298560Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "7f0dedde", | |
| "cell_type": "code", | |
| "source": "h(False)", | |
| "execution_count": 9, | |
| "outputs": [ | |
| { | |
| "output_type": "stream", | |
| "text": "Long computation of bar()...\n", | |
| "name": "stdout" | |
| }, | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 9, | |
| "data": { | |
| "text/plain": "'bar'" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "3841f32e", | |
| "cell_type": "markdown", | |
| "source": "## Check whether a file exists when opening it" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "8f4d5cd5", | |
| "cell_type": "markdown", | |
| "source": "### Problem" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "11e8fed8", | |
| "cell_type": "markdown", | |
| "source": "Implement the following function:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.299549Z", | |
| "end_time": "2023-04-19T11:33:51.314676Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "9f260a4b", | |
| "cell_type": "code", | |
| "source": "def read_file(file_name):\n \"\"\"Read a file if it exists.\n \n Print each line of the file. If the file does not exist, print 'File not found'.\n \n Parameters\n ----------\n file_name: str\n Name of the file.\n \n Examples\n --------\n >>> read_file('existing_file.txt')\n This is the first line in the file.\n This is the second line in the file.\n \n >>> read_file('non_existing_file.txt')\n File not found\n \"\"\"\n pass", | |
| "execution_count": 10, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "309828ab", | |
| "cell_type": "markdown", | |
| "source": "### Solution" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.315669Z", | |
| "end_time": "2023-04-19T11:33:51.330083Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "d6e44af8", | |
| "cell_type": "code", | |
| "source": "def read_file(file_name):\n try:\n with open(file_name) as f:\n for line in f:\n print(line.strip())\n except FileNotFoundError:\n print('File not found')", | |
| "execution_count": 11, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.331075Z", | |
| "end_time": "2023-04-19T11:33:51.345293Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "631c3024", | |
| "cell_type": "code", | |
| "source": "read_file('existing_file.txt')", | |
| "execution_count": 12, | |
| "outputs": [ | |
| { | |
| "output_type": "stream", | |
| "text": "This is the first line in the file.\nThis is the second line in the file.\n", | |
| "name": "stdout" | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.346293Z", | |
| "end_time": "2023-04-19T11:33:51.360455Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "d68e60fc", | |
| "cell_type": "code", | |
| "source": "read_file('non_existing_file.txt')", | |
| "execution_count": 13, | |
| "outputs": [ | |
| { | |
| "output_type": "stream", | |
| "text": "File not found\n", | |
| "name": "stdout" | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.361448Z", | |
| "end_time": "2023-04-19T11:33:51.376462Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "c47ee603", | |
| "cell_type": "code", | |
| "source": "from pathlib import Path", | |
| "execution_count": 14, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.377447Z", | |
| "end_time": "2023-04-19T11:33:51.392553Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "6c2dfddc", | |
| "cell_type": "code", | |
| "source": "def read_file(file_name):\n my_file = Path(file_name)\n try:\n with my_file.open() as f:\n for line in f:\n print(line.strip())\n except FileNotFoundError:\n print('File not found')", | |
| "execution_count": 15, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.393553Z", | |
| "end_time": "2023-04-19T11:33:51.408562Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "295a1768", | |
| "cell_type": "code", | |
| "source": "read_file('existing_file.txt')", | |
| "execution_count": 16, | |
| "outputs": [ | |
| { | |
| "output_type": "stream", | |
| "text": "This is the first line in the file.\nThis is the second line in the file.\n", | |
| "name": "stdout" | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.409556Z", | |
| "end_time": "2023-04-19T11:33:51.424562Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "d56b76cf", | |
| "cell_type": "code", | |
| "source": "read_file('non_existing_file.txt')", | |
| "execution_count": 17, | |
| "outputs": [ | |
| { | |
| "output_type": "stream", | |
| "text": "File not found\n", | |
| "name": "stdout" | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "86bfe67b", | |
| "cell_type": "markdown", | |
| "source": "## Merge two dictionaries" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "80e8cff2", | |
| "cell_type": "markdown", | |
| "source": "### Problem" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.425554Z", | |
| "end_time": "2023-04-19T11:33:51.439832Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "48d23d74", | |
| "cell_type": "code", | |
| "source": "x = {'a': 'value_a', 'b': 'old_value_b'}\ny = {'b': 'new_value_b', 'c': 'value_c'}", | |
| "execution_count": 18, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "1a4072f8", | |
| "cell_type": "markdown", | |
| "source": "Merge `x` and `y` into a new dictionary `z`, such that `z = {'a': 'value_a', 'b': 'new_value_b', 'c': 'value_c'}`." | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "219ce410", | |
| "cell_type": "markdown", | |
| "source": "### Solution" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.440833Z", | |
| "end_time": "2023-04-19T11:33:51.455233Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "de18ed44", | |
| "cell_type": "code", | |
| "source": "z = x.copy()\nz.update(y)\nz", | |
| "execution_count": 19, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 19, | |
| "data": { | |
| "text/plain": "{'a': 'value_a', 'b': 'new_value_b', 'c': 'value_c'}" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.456249Z", | |
| "end_time": "2023-04-19T11:33:51.471225Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "4b7a5281", | |
| "cell_type": "code", | |
| "source": "z = {**x, **y}\nz", | |
| "execution_count": 20, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 20, | |
| "data": { | |
| "text/plain": "{'a': 'value_a', 'b': 'new_value_b', 'c': 'value_c'}" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.472224Z", | |
| "end_time": "2023-04-19T11:33:51.487232Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "a280fff6", | |
| "cell_type": "code", | |
| "source": "z = x | y\nz", | |
| "execution_count": 21, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 21, | |
| "data": { | |
| "text/plain": "{'a': 'value_a', 'b': 'new_value_b', 'c': 'value_c'}" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "a96cfdd0", | |
| "cell_type": "markdown", | |
| "source": "## Execute an external program or call a system command" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "388b7b6a", | |
| "cell_type": "markdown", | |
| "source": "### Problem" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "2783ad05", | |
| "cell_type": "markdown", | |
| "source": "Execute a shell command (for example `dir` in Windows or `ls` in Linux), and get the output." | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "b253d50a", | |
| "cell_type": "markdown", | |
| "source": "Remark: for this precise use case, i.e. to handle files and directories, it is better to use Pathlib. This is just an toy example of how to call an external program or system command." | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "d91f4f45", | |
| "cell_type": "markdown", | |
| "source": "### Solution" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.488228Z", | |
| "end_time": "2023-04-19T11:33:51.503233Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "2fa39f77", | |
| "cell_type": "code", | |
| "source": "import subprocess", | |
| "execution_count": 22, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.504227Z", | |
| "end_time": "2023-04-19T11:33:51.519371Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "2bc747f3", | |
| "cell_type": "code", | |
| "source": "output = subprocess.run(\"dir\", shell=True, capture_output=True).stdout", | |
| "execution_count": 23, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.520361Z", | |
| "end_time": "2023-04-19T11:33:51.534500Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "cell_type": "code", | |
| "source": "print(output.decode('utf-8', errors='ignore'))", | |
| "execution_count": 24, | |
| "outputs": [ | |
| { | |
| "output_type": "stream", | |
| "text": " Volume in drive C is OS\r\n Volume Serial Number is 562B-1B7F\r\n\r\n Directory of c:\\Dropbox\\A\\01_Recherche\\Groupe de lecture\\2023 04 19 Fanfan\r\n\r\n04/19/2023 01:33 PM <DIR> .\r\n04/14/2023 01:14 PM <DIR> ..\r\n04/19/2023 10:50 AM <DIR> .ipynb_checkpoints\r\n04/14/2023 05:29 PM 24,931 a_bit_of_gymnastics_in_python_problems_only.ipynb\r\n04/19/2023 11:29 AM 44,854 a_bit_of_gymnastics_in_python_with_solutions.ipynb\r\n04/14/2023 05:19 PM 8,091 draft.ipynb\r\n04/14/2023 02:28 PM 73 existing_file.txt\r\n04/14/2023 04:16 PM <DIR> my\r\n 4 File(s) 77,949 bytes\r\n 4 Dir(s) 2,747,672,657,920 bytes free\r\n\n", | |
| "name": "stdout" | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "b99c68a0", | |
| "cell_type": "markdown", | |
| "source": "## Create a directory if it does not exist (with its parent directories if needed)" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "269fd227", | |
| "cell_type": "markdown", | |
| "source": "### Problem" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "28c51765", | |
| "cell_type": "markdown", | |
| "source": "Inside the current working directory, create the directory `my/nice/directory`, but only if needed: the proposed solution should work even if the directory `my`, `my/nice` or `my/nice/directory` already exists." | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "9a98a2f8", | |
| "cell_type": "markdown", | |
| "source": "### Solution" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.535488Z", | |
| "end_time": "2023-04-19T11:33:51.549712Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "7c891e59", | |
| "cell_type": "code", | |
| "source": "from pathlib import Path", | |
| "execution_count": 25, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.550703Z", | |
| "end_time": "2023-04-19T11:33:51.565834Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "934b910b", | |
| "cell_type": "code", | |
| "source": "Path(\"my/nice/directory\").mkdir(parents=True, exist_ok=True)", | |
| "execution_count": 26, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "ffdcd801", | |
| "cell_type": "markdown", | |
| "source": "## Access the index in 'for' loops" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "26c93a02", | |
| "cell_type": "markdown", | |
| "source": "### Problem" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.567831Z", | |
| "end_time": "2023-04-19T11:33:51.581834Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "5747dadd", | |
| "cell_type": "code", | |
| "source": "nephews = ['Huey', 'Dewey', 'Louie']", | |
| "execution_count": 27, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "633b27e2", | |
| "cell_type": "markdown", | |
| "source": "Using the above list, write a code that prints:\n\n 0 Huey\n 1 Dewey\n 2 Louie" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "f746be49", | |
| "cell_type": "markdown", | |
| "source": "### Solution" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.582827Z", | |
| "end_time": "2023-04-19T11:33:51.596835Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "55963901", | |
| "cell_type": "code", | |
| "source": "for i, nephew in enumerate(nephews):\n print(i, nephew)", | |
| "execution_count": 28, | |
| "outputs": [ | |
| { | |
| "output_type": "stream", | |
| "text": "0 Huey\n1 Dewey\n2 Louie\n", | |
| "name": "stdout" | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "941a85ea", | |
| "cell_type": "markdown", | |
| "source": "## Flatten a list of lists" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "6c6d4892", | |
| "cell_type": "markdown", | |
| "source": "### Problem" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.597826Z", | |
| "end_time": "2023-04-19T11:33:51.612834Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "6f1b5bea", | |
| "cell_type": "code", | |
| "source": "lst_of_lsts = [[1, 2, 3], [4, 5, 6], [7], [8, 9]]", | |
| "execution_count": 29, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "98321de7", | |
| "cell_type": "markdown", | |
| "source": "Using the above list of lists, output the flattened list `[1, 2, 3, 4, 5, 6, 7, 8, 9]`." | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "5796e9ec", | |
| "cell_type": "markdown", | |
| "source": "### Solution" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.613826Z", | |
| "end_time": "2023-04-19T11:33:51.628835Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "1720d030", | |
| "cell_type": "code", | |
| "source": "[x\n for lst in lst_of_lsts\n for x in lst\n]", | |
| "execution_count": 30, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 30, | |
| "data": { | |
| "text/plain": "[1, 2, 3, 4, 5, 6, 7, 8, 9]" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.629831Z", | |
| "end_time": "2023-04-19T11:33:51.644838Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "dfb83b3d", | |
| "cell_type": "code", | |
| "source": "result = []\nfor lst in lst_of_lsts:\n result.extend(lst)\nresult", | |
| "execution_count": 31, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 31, | |
| "data": { | |
| "text/plain": "[1, 2, 3, 4, 5, 6, 7, 8, 9]" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.645826Z", | |
| "end_time": "2023-04-19T11:33:51.660037Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "39fe9e72", | |
| "cell_type": "code", | |
| "source": "from itertools import chain", | |
| "execution_count": 32, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.661035Z", | |
| "end_time": "2023-04-19T11:33:51.676034Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "c2cdfc38", | |
| "cell_type": "code", | |
| "source": "list(chain(*lst_of_lsts))", | |
| "execution_count": 33, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 33, | |
| "data": { | |
| "text/plain": "[1, 2, 3, 4, 5, 6, 7, 8, 9]" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.677036Z", | |
| "end_time": "2023-04-19T11:33:51.692032Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "9c12fa1a", | |
| "cell_type": "code", | |
| "source": "list(chain.from_iterable(lst_of_lsts))", | |
| "execution_count": 34, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 34, | |
| "data": { | |
| "text/plain": "[1, 2, 3, 4, 5, 6, 7, 8, 9]" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.693034Z", | |
| "end_time": "2023-04-19T11:33:51.707181Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "5dc147bb", | |
| "cell_type": "code", | |
| "source": "from functools import reduce\nfrom operator import iconcat", | |
| "execution_count": 35, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.709186Z", | |
| "end_time": "2023-04-19T11:33:51.723190Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "5b3a3258", | |
| "cell_type": "code", | |
| "source": "reduce(iconcat, lst_of_lsts, [])", | |
| "execution_count": 36, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 36, | |
| "data": { | |
| "text/plain": "[1, 2, 3, 4, 5, 6, 7, 8, 9]" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "end_time": "2023-04-14T13:20:42.498869Z", | |
| "start_time": "2023-04-14T13:20:42.481874Z" | |
| } | |
| }, | |
| "id": "e224d17a", | |
| "cell_type": "markdown", | |
| "source": "## Slicing" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "3798b291", | |
| "cell_type": "markdown", | |
| "source": "### Problem" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.724182Z", | |
| "end_time": "2023-04-19T11:33:51.739318Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "ff00e73c", | |
| "cell_type": "code", | |
| "source": "lst = [x**2 for x in range(10)]\nlst", | |
| "execution_count": 37, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 37, | |
| "data": { | |
| "text/plain": "[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "74db9925", | |
| "cell_type": "markdown", | |
| "source": "Use slicing to produce the following desired results..." | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "1548c419", | |
| "cell_type": "markdown", | |
| "source": "### Solution" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "7748909a", | |
| "cell_type": "markdown", | |
| "source": "`lst[i]` for `i` even, from `i=4` to `i=8` included:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.740311Z", | |
| "end_time": "2023-04-19T11:33:51.755314Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "2f0f05c7", | |
| "cell_type": "code", | |
| "source": "lst[4:9:2]", | |
| "execution_count": 38, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 38, | |
| "data": { | |
| "text/plain": "[16, 36, 64]" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "end_time": "2023-04-14T13:24:53.288770Z", | |
| "start_time": "2023-04-14T13:24:53.283770Z" | |
| } | |
| }, | |
| "id": "a5c0fbd5", | |
| "cell_type": "markdown", | |
| "source": "`lst[i]` from `i=4` to `i=8` included: " | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.756311Z", | |
| "end_time": "2023-04-19T11:33:51.771319Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "361178fb", | |
| "cell_type": "code", | |
| "source": "lst[4:9]", | |
| "execution_count": 39, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 39, | |
| "data": { | |
| "text/plain": "[16, 25, 36, 49, 64]" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "a760936f", | |
| "cell_type": "markdown", | |
| "source": "`lst[i]` from the beginning to `i=3` included:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.772311Z", | |
| "end_time": "2023-04-19T11:33:51.787312Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "ac33e2a3", | |
| "cell_type": "code", | |
| "source": "lst[:4]", | |
| "execution_count": 40, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 40, | |
| "data": { | |
| "text/plain": "[0, 1, 4, 9]" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "1faeeffb", | |
| "cell_type": "markdown", | |
| "source": "`lst[i]` from `i=4` included to the end:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.788524Z", | |
| "end_time": "2023-04-19T11:33:51.802534Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "dae97f8f", | |
| "cell_type": "code", | |
| "source": "lst[4:]", | |
| "execution_count": 41, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 41, | |
| "data": { | |
| "text/plain": "[16, 25, 36, 49, 64, 81]" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "19545ff3", | |
| "cell_type": "markdown", | |
| "source": "`lst[i]` for any `i`:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.803535Z", | |
| "end_time": "2023-04-19T11:33:51.817735Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "3443cfe9", | |
| "cell_type": "code", | |
| "source": "lst[:]", | |
| "execution_count": 42, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 42, | |
| "data": { | |
| "text/plain": "[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "8ffb5445", | |
| "cell_type": "markdown", | |
| "source": "Last value of `lst`:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.818725Z", | |
| "end_time": "2023-04-19T11:33:51.833807Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "feae4fc6", | |
| "cell_type": "code", | |
| "source": "lst[-1]", | |
| "execution_count": 43, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 43, | |
| "data": { | |
| "text/plain": "81" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "end_time": "2023-04-14T13:27:12.682960Z", | |
| "start_time": "2023-04-14T13:27:12.677041Z" | |
| } | |
| }, | |
| "id": "bb6a6d7c", | |
| "cell_type": "markdown", | |
| "source": "Second-to-last value of `lst`:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.834799Z", | |
| "end_time": "2023-04-19T11:33:51.849890Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "83af658d", | |
| "cell_type": "code", | |
| "source": "lst[-2]", | |
| "execution_count": 44, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 44, | |
| "data": { | |
| "text/plain": "64" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "b4adda59", | |
| "cell_type": "markdown", | |
| "source": "Three last values of `lst`:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.850878Z", | |
| "end_time": "2023-04-19T11:33:51.865020Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "9118774e", | |
| "cell_type": "code", | |
| "source": "lst[-3:]", | |
| "execution_count": 45, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 45, | |
| "data": { | |
| "text/plain": "[49, 64, 81]" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "0daf1fe3", | |
| "cell_type": "markdown", | |
| "source": "All values of `lst`, except the three last ones:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.866011Z", | |
| "end_time": "2023-04-19T11:33:51.881019Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "b234e821", | |
| "cell_type": "code", | |
| "source": "lst[:-3]", | |
| "execution_count": 46, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 46, | |
| "data": { | |
| "text/plain": "[0, 1, 4, 9, 16, 25, 36]" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "3248c0e1", | |
| "cell_type": "markdown", | |
| "source": "All values of `lst` in reverse order:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.882012Z", | |
| "end_time": "2023-04-19T11:33:51.896019Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "56302035", | |
| "cell_type": "code", | |
| "source": "lst[::-1]", | |
| "execution_count": 47, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 47, | |
| "data": { | |
| "text/plain": "[81, 64, 49, 36, 25, 16, 9, 4, 1, 0]" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "8e5f716f", | |
| "cell_type": "markdown", | |
| "source": "The last three items of `lst`, in reverse order:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.897012Z", | |
| "end_time": "2023-04-19T11:33:51.911145Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "cb514309", | |
| "cell_type": "code", | |
| "source": "lst[:-4:-1]", | |
| "execution_count": 48, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 48, | |
| "data": { | |
| "text/plain": "[81, 64, 49]" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "f7d24af6", | |
| "cell_type": "markdown", | |
| "source": "Everything except the last three items, in reverse order:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.912147Z", | |
| "end_time": "2023-04-19T11:33:51.927146Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "5d17240f", | |
| "cell_type": "code", | |
| "source": "lst[-4::-1]", | |
| "execution_count": 49, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 49, | |
| "data": { | |
| "text/plain": "[36, 25, 16, 9, 4, 1, 0]" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "b4410b6c", | |
| "cell_type": "markdown", | |
| "source": "## Find the (first) index of an item in a list" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "f4829840", | |
| "cell_type": "markdown", | |
| "source": "### Problem" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.928147Z", | |
| "end_time": "2023-04-19T11:33:51.943151Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "b58e6ae6", | |
| "cell_type": "code", | |
| "source": "lst = ['a', 'b', 'c']", | |
| "execution_count": 50, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "01c8944d", | |
| "cell_type": "markdown", | |
| "source": "Implement the following function:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.945156Z", | |
| "end_time": "2023-04-19T11:33:51.958395Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "f5fa3e70", | |
| "cell_type": "code", | |
| "source": "def find_first_index(l, x):\n \"\"\"Find the first index of an item in a list.\n \n Parameters\n ----------\n l: lst\n The list where to search.\n x: object\n The searched element.\n \n Returns\n -------\n int\n Index of `x` in `l`. If `x` is not found, return `len(l)`.\n \n Examples\n --------\n >>> lst = ['a', 'b', 'c']\n >>> find_first_index(lst, 'c')\n 2\n >>> find_first_index(lst, 'z')\n 3\n \"\"\"\n pass", | |
| "execution_count": 51, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "c0ad67cc", | |
| "cell_type": "markdown", | |
| "source": "### Solution" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.959456Z", | |
| "end_time": "2023-04-19T11:33:51.973619Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "53fc523e", | |
| "cell_type": "code", | |
| "source": "def find_first_index(l, x):\n try:\n return l.index(x)\n except ValueError:\n return len(l)", | |
| "execution_count": 52, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.974047Z", | |
| "end_time": "2023-04-19T11:33:51.989256Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "0d62f87a", | |
| "cell_type": "code", | |
| "source": "find_first_index(lst, 'c')", | |
| "execution_count": 53, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 53, | |
| "data": { | |
| "text/plain": "2" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:51.990284Z", | |
| "end_time": "2023-04-19T11:33:52.004466Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "46bdf09b", | |
| "cell_type": "code", | |
| "source": "find_first_index(lst, 'z')", | |
| "execution_count": 54, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 54, | |
| "data": { | |
| "text/plain": "3" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "72352e49", | |
| "cell_type": "markdown", | |
| "source": "## Iterate over a dictionary" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "a51f65d4", | |
| "cell_type": "markdown", | |
| "source": "### Problem" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:52.005481Z", | |
| "end_time": "2023-04-19T11:33:52.019799Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "7b55efbe", | |
| "cell_type": "code", | |
| "source": "d = {'a': 0, 'b': 1, 'c': 2}", | |
| "execution_count": 55, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "84a04bf2", | |
| "cell_type": "markdown", | |
| "source": "Using the above dictionary, write code that prints the keys:\n\n a\n b\n c" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "end_time": "2023-04-14T14:28:09.384125Z", | |
| "start_time": "2023-04-14T14:28:09.366127Z" | |
| } | |
| }, | |
| "id": "1a5ea89c", | |
| "cell_type": "markdown", | |
| "source": "Idem with the values:\n \n 0\n 1\n 2" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "cc58e550", | |
| "cell_type": "markdown", | |
| "source": "Idem with the pairs (key, value):\n\n a 0\n b 1\n c 2" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "ea2264cb", | |
| "cell_type": "markdown", | |
| "source": "### Solution" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:52.020717Z", | |
| "end_time": "2023-04-19T11:33:52.035717Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "f2e9b381", | |
| "cell_type": "code", | |
| "source": "for k in d.keys():\n print(k)", | |
| "execution_count": 56, | |
| "outputs": [ | |
| { | |
| "output_type": "stream", | |
| "text": "a\nb\nc\n", | |
| "name": "stdout" | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:52.036716Z", | |
| "end_time": "2023-04-19T11:33:52.050880Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "f85dadc8", | |
| "cell_type": "code", | |
| "source": "for v in d.values():\n print(v)", | |
| "execution_count": 57, | |
| "outputs": [ | |
| { | |
| "output_type": "stream", | |
| "text": "0\n1\n2\n", | |
| "name": "stdout" | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:52.051896Z", | |
| "end_time": "2023-04-19T11:33:52.066021Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "7555e2be", | |
| "cell_type": "code", | |
| "source": "for k, v in d.items():\n print(k, v)", | |
| "execution_count": 58, | |
| "outputs": [ | |
| { | |
| "output_type": "stream", | |
| "text": "a 0\nb 1\nc 2\n", | |
| "name": "stdout" | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "2c5abcfc", | |
| "cell_type": "markdown", | |
| "source": "## Bonus problem: global variables" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "2fe06b98", | |
| "cell_type": "markdown", | |
| "source": "### Problem" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "cb235801", | |
| "cell_type": "markdown", | |
| "source": "One of the most popular questions about Python in Stack Overflow deals with global variables." | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "427e0d73", | |
| "cell_type": "markdown", | |
| "source": "It is easy to find quite reasonable examples where a global variable is **read** in a function. This mechanism can be used to store and then access the value of a constant:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:52.067237Z", | |
| "end_time": "2023-04-19T11:33:52.081963Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "c4863567", | |
| "cell_type": "code", | |
| "source": "SPEED_OF_LIGHT = 299792458\ndef energy_of_mass(m):\n return m * SPEED_OF_LIGHT**2", | |
| "execution_count": 59, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "f5cb7e10", | |
| "cell_type": "markdown", | |
| "source": "But if you try to find an example where a function **writes** on a global variable, you might find something like this:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:52.082965Z", | |
| "end_time": "2023-04-19T11:33:52.097943Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "ba1a5ac8", | |
| "cell_type": "code", | |
| "source": "climate_warming = 0\n\ndef use_car():\n print('Vroom vroom')\n global climate_warming\n climate_warming += 1\n \ndef use_coal_power_plant():\n print('Chug chug')\n global climate_warming\n climate_warming += 1\n \nuse_car()\nuse_car()\nuse_coal_power_plant()\nprint(f\"{climate_warming=}\")", | |
| "execution_count": 60, | |
| "outputs": [ | |
| { | |
| "output_type": "stream", | |
| "text": "Vroom vroom\nVroom vroom\nChug chug\nclimate_warming=3\n", | |
| "name": "stdout" | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "2a4e11f9", | |
| "cell_type": "markdown", | |
| "source": "However, this is not very clean, and it would be better to do as in the following (extended) example:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:52.098935Z", | |
| "end_time": "2023-04-19T11:33:52.113930Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "d79d3bb8", | |
| "cell_type": "code", | |
| "source": "class Planet():\n def __init__(self):\n self.climate_warming = 0\n\ndef use_car(planet):\n print('Vroom vroom')\n planet.climate_warming += 1\n \ndef use_coal_power_plant(planet):\n print('Chug chug')\n planet.climate_warming += 1\n\ndef capture_co2(planet):\n print('Swoosh')\n planet.climate_warming -= 1\n\nprint('Earth...')\nearth = Planet()\nuse_car(planet=earth)\nuse_car(planet=earth)\nuse_coal_power_plant(planet=earth)\n\nprint('\\nAlternate Earth...')\nalternate_earth = Planet()\nuse_car(alternate_earth)\nuse_coal_power_plant(alternate_earth)\ncapture_co2(alternate_earth)\n\nprint('\\nResults')\nprint(f\"{earth.climate_warming=}\")\nprint(f\"{alternate_earth.climate_warming=}\")", | |
| "execution_count": 61, | |
| "outputs": [ | |
| { | |
| "output_type": "stream", | |
| "text": "Earth...\nVroom vroom\nVroom vroom\nChug chug\n\nAlternate Earth...\nVroom vroom\nChug chug\nSwoosh\n\nResults\nearth.climate_warming=3\nalternate_earth.climate_warming=1\n", | |
| "name": "stdout" | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "27e6c9f4", | |
| "cell_type": "markdown", | |
| "source": "So here is the question: try to find a reasonable example where to use global variables and modify them inside one or several functions." | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "f239e26f", | |
| "cell_type": "markdown", | |
| "source": "### Proposed solution" | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "fedea631", | |
| "cell_type": "markdown", | |
| "source": "Imagine that I have a (badly programmed) Fibonacci function:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:52.114930Z", | |
| "end_time": "2023-04-19T11:33:52.129175Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "27037843", | |
| "cell_type": "code", | |
| "source": "def fibo(n):\n if n in {0, 1}:\n return 1\n return fibo(n - 2) + fibo(n - 1)", | |
| "execution_count": 62, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": {}, | |
| "id": "b99c2d81", | |
| "cell_type": "markdown", | |
| "source": "In a \"quick and dirty\" way, I would like to count how many times `fibo` is called. Here is a way to do it:" | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:52.131166Z", | |
| "end_time": "2023-04-19T11:33:52.144979Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "67034f6e", | |
| "cell_type": "code", | |
| "source": "def fibo(n):\n global count \n count += 1\n if n in {0, 1}:\n return 1\n return fibo(n - 2) + fibo(n - 1)", | |
| "execution_count": 63, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:52.145979Z", | |
| "end_time": "2023-04-19T11:33:52.160257Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "faf50fdf", | |
| "cell_type": "code", | |
| "source": "def fibo_count(n):\n global count\n count = 0\n return fibo(n), count", | |
| "execution_count": 64, | |
| "outputs": [] | |
| }, | |
| { | |
| "metadata": { | |
| "ExecuteTime": { | |
| "start_time": "2023-04-19T11:33:52.161259Z", | |
| "end_time": "2023-04-19T11:33:52.176118Z" | |
| }, | |
| "trusted": true | |
| }, | |
| "id": "5ec3ddfb", | |
| "cell_type": "code", | |
| "source": "fibo_count(10)", | |
| "execution_count": 65, | |
| "outputs": [ | |
| { | |
| "output_type": "execute_result", | |
| "execution_count": 65, | |
| "data": { | |
| "text/plain": "(89, 177)" | |
| }, | |
| "metadata": {} | |
| } | |
| ] | |
| }, | |
| { | |
| "metadata": { | |
| "trusted": true | |
| }, | |
| "cell_type": "code", | |
| "source": "", | |
| "execution_count": null, | |
| "outputs": [] | |
| } | |
| ], | |
| "metadata": { | |
| "kernelspec": { | |
| "name": "python3", | |
| "display_name": "Python 3 (ipykernel)", | |
| "language": "python" | |
| }, | |
| "language_info": { | |
| "name": "python", | |
| "version": "3.9.7", | |
| "mimetype": "text/x-python", | |
| "codemirror_mode": { | |
| "name": "ipython", | |
| "version": 3 | |
| }, | |
| "pygments_lexer": "ipython3", | |
| "nbconvert_exporter": "python", | |
| "file_extension": ".py" | |
| }, | |
| "toc": { | |
| "nav_menu": {}, | |
| "number_sections": true, | |
| "sideBar": true, | |
| "skip_h1_title": true, | |
| "base_numbering": 1, | |
| "title_cell": "Table of Contents", | |
| "title_sidebar": "Contents", | |
| "toc_cell": false, | |
| "toc_position": {}, | |
| "toc_section_display": true, | |
| "toc_window_display": true | |
| }, | |
| "gist": { | |
| "id": "a3886e8772c603561fa825651ab2b253", | |
| "data": { | |
| "description": "a_bit_of_gymnastics_in_python_with_solutions.ipynb", | |
| "public": true | |
| } | |
| }, | |
| "_draft": { | |
| "nbviewer_url": "https://gist.github.com/francois-durand/a3886e8772c603561fa825651ab2b253" | |
| } | |
| }, | |
| "nbformat": 4, | |
| "nbformat_minor": 5 | |
| } |
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