{"cells": [{"cell_type": "markdown", "metadata": {}, "source": ["# 1A.e - Correction de l'interrogation \u00e9crite du 26 septembre 2015\n", "\n", "tests, boucles, fonctions"]}, {"cell_type": "code", "execution_count": 1, "metadata": {}, "outputs": [{"data": {"text/html": ["<div id=\"my_id_menu_nb\">run previous cell, wait for 2 seconds</div>\n", "<script>\n", "function repeat_indent_string(n){\n", "    var a = \"\" ;\n", "    for ( ; n > 0 ; --n)\n", "        a += \"    \";\n", "    return a;\n", "}\n", "var update_menu_string = function(begin, lfirst, llast, sformat, send, keep_item, begin_format, end_format) {\n", "    var anchors = document.getElementsByClassName(\"section\");\n", "    if (anchors.length == 0) {\n", "        anchors = document.getElementsByClassName(\"text_cell_render rendered_html\");\n", "    }\n", "    var i,t;\n", "    var text_menu = begin;\n", "    var text_memo = \"<pre>\\nlength:\" + anchors.length + \"\\n\";\n", "    var ind = \"\";\n", "    var memo_level = 1;\n", "    var href;\n", "    var tags = [];\n", "    var main_item = 0;\n", "    var format_open = 0;\n", "    for (i = 0; i <= llast; i++)\n", "        tags.push(\"h\" + i);\n", "\n", "    for (i = 0; i < anchors.length; i++) {\n", "        text_memo += \"**\" + anchors[i].id + \"--\\n\";\n", "\n", "        var child = null;\n", "        for(t = 0; t < tags.length; t++) {\n", "            var r = anchors[i].getElementsByTagName(tags[t]);\n", "            if (r.length > 0) {\n", "child = r[0];\n", "break;\n", "            }\n", "        }\n", "        if (child == null) {\n", "            text_memo += \"null\\n\";\n", "            continue;\n", "        }\n", "        if (anchors[i].hasAttribute(\"id\")) {\n", "            // when converted in RST\n", "            href = anchors[i].id;\n", "            text_memo += \"#1-\" + href;\n", "            // passer \u00e0 child suivant (le chercher)\n", "        }\n", "        else if (child.hasAttribute(\"id\")) {\n", "            // in a notebook\n", "            href = child.id;\n", "            text_memo += \"#2-\" + href;\n", "        }\n", "        else {\n", "            text_memo += \"#3-\" + \"*\" + \"\\n\";\n", "            continue;\n", "        }\n", "        var title = child.textContent;\n", "        var level = parseInt(child.tagName.substring(1,2));\n", "\n", "        text_memo += \"--\" + level + \"?\" + lfirst + \"--\" + title + \"\\n\";\n", "\n", "        if ((level < lfirst) || (level > llast)) {\n", "            continue ;\n", "        }\n", "        if (title.endsWith('\u00b6')) {\n", "            title = title.substring(0,title.length-1).replace(\"<\", \"&lt;\")\n", "         .replace(\">\", \"&gt;\").replace(\"&\", \"&amp;\");\n", "        }\n", "        if (title.length == 0) {\n", "            continue;\n", "        }\n", "\n", "        while (level < memo_level) {\n", "            text_menu += end_format + \"</ul>\\n\";\n", "            format_open -= 1;\n", "            memo_level -= 1;\n", "        }\n", "        if (level == lfirst) {\n", "            main_item += 1;\n", "        }\n", "        if (keep_item != -1 && main_item != keep_item + 1) {\n", "            // alert(main_item + \" - \" + level + \" - \" + keep_item);\n", "            continue;\n", "        }\n", "        while (level > memo_level) {\n", "            text_menu += \"<ul>\\n\";\n", "            memo_level += 1;\n", "        }\n", "        text_menu += repeat_indent_string(level-2);\n", "        text_menu += begin_format + sformat.replace(\"__HREF__\", href).replace(\"__TITLE__\", title);\n", "        format_open += 1;\n", "    }\n", "    while (1 < memo_level) {\n", "        text_menu += end_format + \"</ul>\\n\";\n", "        memo_level -= 1;\n", "        format_open -= 1;\n", "    }\n", "    text_menu += send;\n", "    //text_menu += \"\\n\" + text_memo;\n", "\n", "    while (format_open > 0) {\n", "        text_menu += end_format;\n", "        format_open -= 1;\n", "    }\n", "    return text_menu;\n", "};\n", "var update_menu = function() {\n", "    var sbegin = \"\";\n", "    var sformat = '<a href=\"#__HREF__\">__TITLE__</a>';\n", "    var send = \"\";\n", "    var begin_format = '<li>';\n", "    var end_format = '</li>';\n", "    var keep_item = -1;\n", "    var text_menu = update_menu_string(sbegin, 2, 4, sformat, send, keep_item,\n", "       begin_format, end_format);\n", "    var menu = document.getElementById(\"my_id_menu_nb\");\n", "    menu.innerHTML=text_menu;\n", "};\n", "window.setTimeout(update_menu,2000);\n", "            </script>"], "text/plain": ["<IPython.core.display.HTML object>"]}, "execution_count": 2, "metadata": {}, "output_type": "execute_result"}], "source": ["from jyquickhelper import add_notebook_menu\n", "add_notebook_menu()"]}, {"cell_type": "markdown", "metadata": {}, "source": ["### Enonc\u00e9 1"]}, {"cell_type": "markdown", "metadata": {}, "source": ["#### Q1\n", "\n", "Le programme suivant provoque une erreur pourquoi ?"]}, {"cell_type": "code", "execution_count": 2, "metadata": {}, "outputs": [{"name": "stdout", "output_type": "stream", "text": ["4\n"]}, {"ename": "IndexError", "evalue": "list index out of range", "output_type": "error", "traceback": ["\u001b[1;31m---------------------------------------------------------------------------\u001b[0m", "\u001b[1;31mIndexError\u001b[0m                                Traceback (most recent call last)", "\u001b[1;32m<ipython-input-4-6893f4ac9402>\u001b[0m in \u001b[0;36m<module>\u001b[1;34m()\u001b[0m\n\u001b[0;32m      1\u001b[0m \u001b[0mtab\u001b[0m \u001b[1;33m=\u001b[0m \u001b[1;33m[\u001b[0m\u001b[1;36m1\u001b[0m\u001b[1;33m,\u001b[0m \u001b[1;36m3\u001b[0m\u001b[1;33m]\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m      2\u001b[0m \u001b[1;32mfor\u001b[0m \u001b[0mi\u001b[0m \u001b[1;32min\u001b[0m \u001b[0mrange\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;36m0\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0mlen\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mtab\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m:\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[1;32m----> 3\u001b[1;33m     \u001b[0mprint\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mtab\u001b[0m\u001b[1;33m[\u001b[0m\u001b[0mi\u001b[0m\u001b[1;33m]\u001b[0m \u001b[1;33m+\u001b[0m \u001b[0mtab\u001b[0m\u001b[1;33m[\u001b[0m\u001b[0mi\u001b[0m\u001b[1;33m+\u001b[0m\u001b[1;36m1\u001b[0m\u001b[1;33m]\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m", "\u001b[1;31mIndexError\u001b[0m: list index out of range"]}], "source": ["tab = [1, 3]\n", "for i in range(0, len(tab)):\n", "    print(tab[i] + tab[i+1])"]}, {"cell_type": "markdown", "metadata": {}, "source": ["On d\u00e9couvre le probl\u00e8me en ajoutant des affichages interm\u00e9diaires :"]}, {"cell_type": "code", "execution_count": 3, "metadata": {}, "outputs": [{"name": "stdout", "output_type": "stream", "text": ["0 1 2\n", "4\n", "1 2 2\n"]}, {"ename": "IndexError", "evalue": "list index out of range", "output_type": "error", "traceback": ["\u001b[1;31m---------------------------------------------------------------------------\u001b[0m", "\u001b[1;31mIndexError\u001b[0m                                Traceback (most recent call last)", "\u001b[1;32m<ipython-input-5-58b7566d9294>\u001b[0m in \u001b[0;36m<module>\u001b[1;34m()\u001b[0m\n\u001b[0;32m      2\u001b[0m \u001b[1;32mfor\u001b[0m \u001b[0mi\u001b[0m \u001b[1;32min\u001b[0m \u001b[0mrange\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;36m0\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0mlen\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mtab\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m:\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m      3\u001b[0m     \u001b[0mprint\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mi\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0mi\u001b[0m\u001b[1;33m+\u001b[0m\u001b[1;36m1\u001b[0m\u001b[1;33m,\u001b[0m \u001b[0mlen\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mtab\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[1;32m----> 4\u001b[1;33m     \u001b[0mprint\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0mtab\u001b[0m\u001b[1;33m[\u001b[0m\u001b[0mi\u001b[0m\u001b[1;33m]\u001b[0m \u001b[1;33m+\u001b[0m \u001b[0mtab\u001b[0m\u001b[1;33m[\u001b[0m\u001b[0mi\u001b[0m\u001b[1;33m+\u001b[0m\u001b[1;36m1\u001b[0m\u001b[1;33m]\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m", "\u001b[1;31mIndexError\u001b[0m: list index out of range"]}], "source": ["tab = [1, 3]\n", "for i in range(0, len(tab)):\n", "    print(i, i+1, len(tab))\n", "    print(tab[i] + tab[i+1])"]}, {"cell_type": "markdown", "metadata": {}, "source": ["A la derni\u00e8re it\u00e9ration, $i+1$ d\u00e9vient \u00e9gal \u00e0 la longueur de la liste ``tab`` or le dernier indice d'un tableau est ``len(tab)-1``."]}, {"cell_type": "markdown", "metadata": {}, "source": ["#### Q2\n", "\n", "O\u00f9 est l'erreur de syntaxe ?"]}, {"cell_type": "code", "execution_count": 4, "metadata": {}, "outputs": [{"ename": "SyntaxError", "evalue": "invalid syntax (<ipython-input-6-2f84bd962211>, line 2)", "output_type": "error", "traceback": ["\u001b[1;36m  File \u001b[1;32m\"<ipython-input-6-2f84bd962211>\"\u001b[1;36m, line \u001b[1;32m2\u001b[0m\n\u001b[1;33m    if n = 1:\u001b[0m\n\u001b[1;37m         ^\u001b[0m\n\u001b[1;31mSyntaxError\u001b[0m\u001b[1;31m:\u001b[0m invalid syntax\n"]}], "source": ["n = 1\n", "if n = 1:\n", "    y = 0\n", "else:\n", "    y = 1"]}, {"cell_type": "markdown", "metadata": {}, "source": ["Le test d'\u00e9galit\u00e9 s'\u00e9crit ``==``."]}, {"cell_type": "markdown", "metadata": {}, "source": ["#### Q3\n", "\n", "On associe la valeur 1 \u00e0 la lettre *a*, 2 \u00e0 *b* et ainsi de suite. Ecrire une fonction qui fait la somme de ces valeurs pour une cha\u00eene de caract\u00e8res.\n", "\n", "Exemple :  elu  $\\rightarrow$ 5 + 12 + 21 = 38"]}, {"cell_type": "code", "execution_count": 5, "metadata": {}, "outputs": [{"data": {"text/plain": ["38"]}, "execution_count": 6, "metadata": {}, "output_type": "execute_result"}], "source": ["def somme_caracteres(mot):\n", "    s = 0\n", "    for c in mot :\n", "        s += ord(c) - ord(\"a\") + 1\n", "    return s\n", "\n", "somme_caracteres(\"elu\")"]}, {"cell_type": "markdown", "metadata": {}, "source": ["On peut l'\u00e9crire de fa\u00e7on plus courte :"]}, {"cell_type": "code", "execution_count": 6, "metadata": {}, "outputs": [{"data": {"text/plain": ["38"]}, "execution_count": 7, "metadata": {}, "output_type": "execute_result"}], "source": ["def somme_caracteres(mot):\n", "    return sum(ord(c) - ord(\"a\") + 1 for c in mot)\n", "\n", "somme_caracteres(\"elu\")"]}, {"cell_type": "markdown", "metadata": {}, "source": ["### Enonc\u00e9 2"]}, {"cell_type": "markdown", "metadata": {}, "source": ["#### Q1\n", "\n", "Barrez les lignes qui produiraient une erreur \u00e0 l'ex\u00e9cution et dire pourquoi ?"]}, {"cell_type": "code", "execution_count": 7, "metadata": {}, "outputs": [{"ename": "TypeError", "evalue": "Can't convert 'int' object to str implicitly", "output_type": "error", "traceback": ["\u001b[1;31m---------------------------------------------------------------------------\u001b[0m", "\u001b[1;31mTypeError\u001b[0m                                 Traceback (most recent call last)", "\u001b[1;32m<ipython-input-10-225cea37f121>\u001b[0m in \u001b[0;36m<module>\u001b[1;34m()\u001b[0m\n\u001b[1;32m----> 1\u001b[1;33m \u001b[0my\u001b[0m \u001b[1;33m=\u001b[0m \u001b[1;34m\"a\"\u001b[0m \u001b[1;33m*\u001b[0m \u001b[1;36m3\u001b[0m \u001b[1;33m+\u001b[0m \u001b[1;36m1\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m\u001b[0;32m      2\u001b[0m \u001b[0mz\u001b[0m \u001b[1;33m=\u001b[0m \u001b[1;36m3\u001b[0m \u001b[1;33m*\u001b[0m \u001b[1;34m\"a\"\u001b[0m \u001b[1;33m+\u001b[0m \u001b[1;36m1\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0;32m      3\u001b[0m \u001b[0mprint\u001b[0m\u001b[1;33m(\u001b[0m\u001b[0my\u001b[0m\u001b[1;33m,\u001b[0m\u001b[0mz\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n", "\u001b[1;31mTypeError\u001b[0m: Can't convert 'int' object to str implicitly"]}], "source": ["y = \"a\" * 3 + 1\n", "z = 3 * \"a\" + 1\n", "print(y,z)"]}, {"cell_type": "markdown", "metadata": {}, "source": ["Les deux premi\u00e8res lignes sont incorrects car on essaye d'ajouter une cha\u00eene de caract\u00e8res \u00e0 un nombre. La premi\u00e8re op\u00e9ration est correcte ``\"a\" * 3``. Dans un sens comme dans l'autre, elle donne ``\"aaa\"``. Mais on ne peut ajouter 1 \u00e0 ``\"aaa\"``."]}, {"cell_type": "markdown", "metadata": {}, "source": ["#### Q2\n", "\n", "Que vaut ``l`` \u00e0 la fin du programme ?"]}, {"cell_type": "code", "execution_count": 8, "metadata": {}, "outputs": [{"name": "stdout", "output_type": "stream", "text": ["[[0], [1], [2], [3], [4], [5], [6], [7], [8], [9]]\n"]}], "source": ["l = []\n", "for i in range(0, 10):\n", "    l.append([i])\n", "print(l)"]}, {"cell_type": "markdown", "metadata": {}, "source": ["Il ne faut pas confondre la m\u00e9thode [append](https://docs.python.org/3.4/tutorial/datastructures.html#more-on-lists) et [extend](https://docs.python.org/3.4/tutorial/datastructures.html#more-on-lists)."]}, {"cell_type": "code", "execution_count": 9, "metadata": {}, "outputs": [{"name": "stdout", "output_type": "stream", "text": ["[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]\n"]}], "source": ["l = []\n", "for i in range(0, 10):\n", "    l.extend([i])\n", "print(l)"]}, {"cell_type": "markdown", "metadata": {}, "source": ["#### Q3\n", "\n", "Ecrire une fonction qui prend une cha\u00eene de caract\u00e8res et qui lui enl\u00e8ve une lettre sur 2."]}, {"cell_type": "code", "execution_count": 10, "metadata": {}, "outputs": [{"data": {"text/plain": ["'pto'"]}, "execution_count": 11, "metadata": {}, "output_type": "execute_result"}], "source": ["def un_sur_deux(mot):\n", "    s = \"\"\n", "    for i,c in enumerate(mot):\n", "        if i % 2 == 0:\n", "            s += c\n", "    return s\n", "\n", "un_sur_deux(\"python\")"]}, {"cell_type": "markdown", "metadata": {}, "source": ["Ou plus court encore :"]}, {"cell_type": "code", "execution_count": 11, "metadata": {}, "outputs": [{"data": {"text/plain": ["'pto'"]}, "execution_count": 12, "metadata": {}, "output_type": "execute_result"}], "source": ["def un_sur_deux(mot):\n", "    return \"\".join( c for i,c in enumerate(mot) if i % 2 == 0 )\n", "\n", "un_sur_deux(\"python\")"]}, {"cell_type": "code", "execution_count": 12, "metadata": {"collapsed": true}, "outputs": [], "source": []}], "metadata": {"kernelspec": {"display_name": "Python 3", "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": "3.6.1"}}, "nbformat": 4, "nbformat_minor": 2}