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   "source": [
    "Side effects en funciones\n",
    "===\n",
    "\n",
    "* Duración de la lección: 6:17 min"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "47a2e6c7-0a78-4b9c-9992-7b2731b6d032",
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   "source": [
    "#\n",
    "# Side effects con variables\n",
    "# =============================================================================\n",
    "#\n",
    "a = 1\n",
    "b = 2\n",
    "\n",
    "\n",
    "def a_plus_b():\n",
    "    return a + b\n",
    "\n",
    "\n",
    "a_plus_b()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "c6cb6dfa-c836-48ac-bbbd-e45a05a3b5ce",
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       "5"
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     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "#\n",
    "# Side effect: \n",
    "# Un cambio inadvertido cambia cambios no esperados en el resultado de la\n",
    "# función (indeseado!)\n",
    "#\n",
    "a = 3\n",
    "\n",
    "a_plus_b()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "e915c250-7c54-44cc-9635-ec44153f4236",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[1, 2, 'a']\n"
     ]
    }
   ],
   "source": [
    "#\n",
    "# Side effects con listas\n",
    "# =============================================================================\n",
    "#\n",
    "my_list = [1, 2]\n",
    "\n",
    "\n",
    "def my_function(a_list):\n",
    "    a_list.append(\"a\")\n",
    "\n",
    "\n",
    "my_function(my_list)\n",
    "#\n",
    "# Efecto indeseado:\n",
    "#\n",
    "print(my_list)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "bd84eefc-cbf4-4c82-9e9a-64ba95327191",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[1, 2]\n"
     ]
    }
   ],
   "source": [
    "#\n",
    "# Corrección: no se debe modificar la lista externa\n",
    "#\n",
    "my_list = [1, 2]\n",
    "\n",
    "\n",
    "def my_function(a_list):\n",
    "    a_list = a_list.copy()\n",
    "    a_list.append(\"a\")\n",
    "\n",
    "\n",
    "my_function(my_list)\n",
    "print(my_list)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "eb3f3ef4-fbc8-4c00-99d5-5a21afce628e",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[1, 2]\n",
      "[1, 2, 'a']\n"
     ]
    }
   ],
   "source": [
    "#\n",
    "# Si se desea modificar la lista\n",
    "#\n",
    "my_list = [1, 2]\n",
    "\n",
    "\n",
    "def my_function(a_list):\n",
    "    a_list = a_list.copy()\n",
    "    a_list.append(\"a\")\n",
    "    return a_list\n",
    "\n",
    "\n",
    "my_new_list = my_function(my_list)\n",
    "print(my_list)\n",
    "print(my_new_list)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "id": "0afb0cd9-5437-4eab-b7c0-26326ae321cf",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[1]\n",
      "[1, 2]\n",
      "[1, 2, 3]\n"
     ]
    }
   ],
   "source": [
    "#\n",
    "# Side effects con listas\n",
    "# =============================================================================\n",
    "# La variable L no debería acumular la lista ya que el valor por defecto \n",
    "# de L es []\n",
    "#\n",
    "def f(a, L=[]):\n",
    "    L.append(a)\n",
    "    return L\n",
    "\n",
    "\n",
    "print(f(1))\n",
    "print(f(2))\n",
    "print(f(3))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "id": "23dfe8f4-bdd9-4a09-a6c8-6bf439ffae7e",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[1]\n",
      "[2]\n",
      "[3]\n"
     ]
    }
   ],
   "source": [
    "#\n",
    "# Corrección del side effect usando None\n",
    "#\n",
    "def f(a, L=None):\n",
    "    if L is None:\n",
    "        L = []\n",
    "    L.append(a)\n",
    "    return L\n",
    "\n",
    "\n",
    "print(f(1))\n",
    "print(f(2))\n",
    "print(f(3))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "id": "ebe21557-6c75-4ab7-b731-3d449d68554c",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{0: 'A', 1: 'b'}\n"
     ]
    }
   ],
   "source": [
    "#\n",
    "# Side effects con diccionarios\n",
    "# =============================================================================\n",
    "#\n",
    "my_dict = {\n",
    "    0: \"a\",\n",
    "    1: \"b\",\n",
    "}\n",
    "\n",
    "\n",
    "def my_function(a_dict):\n",
    "    a_dict[0] = \"A\"\n",
    "\n",
    "\n",
    "my_function(my_dict)\n",
    "#\n",
    "# Efecto indeseado:\n",
    "#\n",
    "print(my_dict)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "id": "d98c9143-a95a-4077-a43a-1c994c0e3aa5",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{0: 'a', 1: 'b'}\n"
     ]
    }
   ],
   "source": [
    "my_dict = {\n",
    "    0: \"a\",\n",
    "    1: \"b\",\n",
    "}\n",
    "\n",
    "\n",
    "def my_function(a_dict):\n",
    "    a_dict = a_dict.copy()\n",
    "    a_dict[0] = \"A\"\n",
    "\n",
    "\n",
    "my_function(my_dict)\n",
    "print(my_dict)"
   ]
  }
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