{
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  {
   "cell_type": "markdown",
   "metadata": {
    "nbsphinx": "hidden"
   },
   "source": [
    "[prev: Structuration du code](code-block.ipynb) | [home](../index.ipynb)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Lire les erreurs\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Qu'est-ce c'est ?\n",
    "\n",
    "- L'erreur apparait au moment où l'instruction erronée est exécutée dans le cours du programme.\n",
    "- A priori, l'apparition d'une erreur interrompt le programme immédiatement -> plantage.\n",
    "- (il est quand même possible de [gérer les exceptions](../more-python/exceptions.ipynb))\n",
    "\n",
    "\n",
    "## Les informations fournies par une erreur\n",
    "\n",
    "- le type d'erreur\n",
    "- le message d'erreur\n",
    "- la ligne de code en jeu\n",
    "- la pile d'appel -> *traceback*\n",
    "\n",
    "Coder == Débugger, autant utiliser l'information qu'on nous donne."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Exemples classiques d'erreurs"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### NameError"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "tags": [
     "raises-exception"
    ]
   },
   "outputs": [
    {
     "ename": "NameError",
     "evalue": "name 'nexistepas' is not defined",
     "output_type": "error",
     "traceback": [
      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[1;31mNameError\u001b[0m                                 Traceback (most recent call last)",
      "Cell \u001b[1;32mIn[1], line 1\u001b[0m\n\u001b[1;32m----> 1\u001b[0m \u001b[43mnexistepas\u001b[49m\n",
      "\u001b[1;31mNameError\u001b[0m: name 'nexistepas' is not defined"
     ]
    }
   ],
   "source": [
    "nexistepas"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### ZeroDivisionError"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "scrolled": true,
    "tags": [
     "raises-exception"
    ]
   },
   "outputs": [
    {
     "ename": "ZeroDivisionError",
     "evalue": "division by zero",
     "output_type": "error",
     "traceback": [
      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[1;31mZeroDivisionError\u001b[0m                         Traceback (most recent call last)",
      "Cell \u001b[1;32mIn[2], line 1\u001b[0m\n\u001b[1;32m----> 1\u001b[0m \u001b[38;5;241;43m2\u001b[39;49m\u001b[43m \u001b[49m\u001b[38;5;241;43m/\u001b[39;49m\u001b[43m \u001b[49m\u001b[38;5;241;43m0\u001b[39;49m\n",
      "\u001b[1;31mZeroDivisionError\u001b[0m: division by zero"
     ]
    }
   ],
   "source": [
    "2 / 0"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### TypeError"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "tags": [
     "raises-exception"
    ]
   },
   "outputs": [
    {
     "ename": "TypeError",
     "evalue": "can only concatenate str (not \"int\") to str",
     "output_type": "error",
     "traceback": [
      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[1;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
      "Cell \u001b[1;32mIn[3], line 1\u001b[0m\n\u001b[1;32m----> 1\u001b[0m \u001b[38;5;124;43m'\u001b[39;49m\u001b[38;5;124;43mun\u001b[39;49m\u001b[38;5;124;43m'\u001b[39;49m\u001b[43m \u001b[49m\u001b[38;5;241;43m+\u001b[39;49m\u001b[43m \u001b[49m\u001b[38;5;241;43m2\u001b[39;49m\n",
      "\u001b[1;31mTypeError\u001b[0m: can only concatenate str (not \"int\") to str"
     ]
    }
   ],
   "source": [
    "'un' + 2"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### IndexError"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "tags": [
     "raises-exception"
    ]
   },
   "outputs": [
    {
     "ename": "IndexError",
     "evalue": "string index out of range",
     "output_type": "error",
     "traceback": [
      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[1;31mIndexError\u001b[0m                                Traceback (most recent call last)",
      "Cell \u001b[1;32mIn[4], line 2\u001b[0m\n\u001b[0;32m      1\u001b[0m hey \u001b[38;5;241m=\u001b[39m \u001b[38;5;124m'\u001b[39m\u001b[38;5;124mbonjour\u001b[39m\u001b[38;5;124m'\u001b[39m\n\u001b[1;32m----> 2\u001b[0m \u001b[43mhey\u001b[49m\u001b[43m[\u001b[49m\u001b[38;5;241;43m9\u001b[39;49m\u001b[43m]\u001b[49m\n",
      "\u001b[1;31mIndexError\u001b[0m: string index out of range"
     ]
    }
   ],
   "source": [
    "hey = 'bonjour'\n",
    "hey[9]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### KeyError"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "tags": [
     "raises-exception"
    ]
   },
   "outputs": [
    {
     "ename": "KeyError",
     "evalue": "'deux'",
     "output_type": "error",
     "traceback": [
      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[1;31mKeyError\u001b[0m                                  Traceback (most recent call last)",
      "Cell \u001b[1;32mIn[5], line 2\u001b[0m\n\u001b[0;32m      1\u001b[0m foobar\u001b[38;5;241m=\u001b[39m{\u001b[38;5;124m'\u001b[39m\u001b[38;5;124mun\u001b[39m\u001b[38;5;124m'\u001b[39m: \u001b[38;5;241m1\u001b[39m}\n\u001b[1;32m----> 2\u001b[0m \u001b[43mfoobar\u001b[49m\u001b[43m[\u001b[49m\u001b[38;5;124;43m'\u001b[39;49m\u001b[38;5;124;43mdeux\u001b[39;49m\u001b[38;5;124;43m'\u001b[39;49m\u001b[43m]\u001b[49m\n",
      "\u001b[1;31mKeyError\u001b[0m: 'deux'"
     ]
    }
   ],
   "source": [
    "foobar={'un': 1}\n",
    "foobar['deux']"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## *Traceback* et imbrication d'appels"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "La *Traceback* permet de suivre l'imbrication des appels au moment de l'erreur."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "tags": [
     "raises-exception"
    ]
   },
   "outputs": [
    {
     "ename": "ZeroDivisionError",
     "evalue": "division by zero",
     "output_type": "error",
     "traceback": [
      "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[1;31mZeroDivisionError\u001b[0m                         Traceback (most recent call last)",
      "Cell \u001b[1;32mIn[6], line 13\u001b[0m\n\u001b[0;32m     10\u001b[0m \u001b[38;5;28;01mdef\u001b[39;00m \u001b[38;5;21mf3\u001b[39m(x):\n\u001b[0;32m     11\u001b[0m     \u001b[38;5;28;01mreturn\u001b[39;00m f2(x) \u001b[38;5;241m/\u001b[39m \u001b[38;5;241m3\u001b[39m\n\u001b[1;32m---> 13\u001b[0m \u001b[43mf3\u001b[49m\u001b[43m(\u001b[49m\u001b[38;5;241;43m1\u001b[39;49m\u001b[43m)\u001b[49m\n",
      "Cell \u001b[1;32mIn[6], line 11\u001b[0m, in \u001b[0;36mf3\u001b[1;34m(x)\u001b[0m\n\u001b[0;32m     10\u001b[0m \u001b[38;5;28;01mdef\u001b[39;00m \u001b[38;5;21mf3\u001b[39m(x):\n\u001b[1;32m---> 11\u001b[0m     \u001b[38;5;28;01mreturn\u001b[39;00m \u001b[43mf2\u001b[49m\u001b[43m(\u001b[49m\u001b[43mx\u001b[49m\u001b[43m)\u001b[49m \u001b[38;5;241m/\u001b[39m \u001b[38;5;241m3\u001b[39m\n",
      "Cell \u001b[1;32mIn[6], line 8\u001b[0m, in \u001b[0;36mf2\u001b[1;34m(x)\u001b[0m\n\u001b[0;32m      7\u001b[0m \u001b[38;5;28;01mdef\u001b[39;00m \u001b[38;5;21mf2\u001b[39m(x):\n\u001b[1;32m----> 8\u001b[0m     \u001b[38;5;28;01mreturn\u001b[39;00m \u001b[43mf1\u001b[49m\u001b[43m(\u001b[49m\u001b[43mx\u001b[49m\u001b[43m)\u001b[49m \u001b[38;5;241m/\u001b[39m \u001b[38;5;241m2\u001b[39m\n",
      "Cell \u001b[1;32mIn[6], line 5\u001b[0m, in \u001b[0;36mf1\u001b[1;34m(x)\u001b[0m\n\u001b[0;32m      4\u001b[0m \u001b[38;5;28;01mdef\u001b[39;00m \u001b[38;5;21mf1\u001b[39m(x):\n\u001b[1;32m----> 5\u001b[0m     \u001b[38;5;28;01mreturn\u001b[39;00m \u001b[43mf0\u001b[49m\u001b[43m(\u001b[49m\u001b[43mx\u001b[49m\u001b[43m)\u001b[49m \u001b[38;5;241m/\u001b[39m \u001b[38;5;241m1\u001b[39m\n",
      "Cell \u001b[1;32mIn[6], line 2\u001b[0m, in \u001b[0;36mf0\u001b[1;34m(x)\u001b[0m\n\u001b[0;32m      1\u001b[0m \u001b[38;5;28;01mdef\u001b[39;00m \u001b[38;5;21mf0\u001b[39m(x):\n\u001b[1;32m----> 2\u001b[0m     \u001b[38;5;28;01mreturn\u001b[39;00m \u001b[43mx\u001b[49m\u001b[43m \u001b[49m\u001b[38;5;241;43m/\u001b[39;49m\u001b[43m \u001b[49m\u001b[38;5;241;43m0\u001b[39;49m\n",
      "\u001b[1;31mZeroDivisionError\u001b[0m: division by zero"
     ]
    }
   ],
   "source": [
    "def f0(x):\n",
    "    return x / 0\n",
    "\n",
    "def f1(x):\n",
    "    return f0(x) / 1\n",
    "\n",
    "def f2(x):\n",
    "    return f1(x) / 2\n",
    "\n",
    "def f3(x):\n",
    "    return f2(x) / 3\n",
    "\n",
    "f3(1)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Exercices"
   ]
  }
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