04-estructuras-datos.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Estructuras de Datos\n",
    "===\n",
    "\n",
    "**Juan David Velásquez Henao**  \n",
    "jdvelasq@unal.edu.co   \n",
    "Universidad Nacional de Colombia, Sede Medellín  \n",
    "Facultad de Minas  \n",
    "Medellín, Colombia\n",
    "\n",
    "---\n",
    "\n",
    "Haga click [aquí](https://github.com/jdvelasq/Python-for-ETL-processes/tree/master/) para acceder al repositorio online.\n",
    "\n",
    "Haga click [aquí](http://nbviewer.jupyter.org/github/jdvelasq/Python-for-ETL-processes/tree/master/) para explorar el repositorio usando `nbviewer`. "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "---"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Listas"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Las principales funciones de las listas son las siguientes:\n",
    "\n",
    "* `list.`**`append`**`(`*`x`*`)`  -- agrega el elemento `x` al final de la lista. \n",
    "* `list.`**`extend`**`(`*`L`*`)`  -- agrega la lista `L` al final de la lista.\n",
    "* `list.`**`insert`**`(`*`i`*`,`*`x`*`)` -- inserta el elemento `x` en la posición `i`.\n",
    "* `list.`**`remove`**`(`*`x`*`)`  -- remueve el elemento `x`.\n",
    "* `list.`**`pop`**`([`*`j`*`])`   -- remueve el elemento en la posición `j` de la lista. \n",
    "* `list.`**`clear`**`()`  -- borra la lista; elimina todos los elementos de la lista.\n",
    "* `list.`**`index`**`(`*`x`*`)`  -- devuelve el indice del elemento `x`\n",
    "* `list.`**`count`**`(`*`x`*`)`  -- Cuenta las veces que aparece el elemento `x`.\n",
    "* `list.`**`sort`**`(`*`key=None`*`, `*`reverse=False`*`)` -- ordena los elementos de la lista.\n",
    "* `list.`**`copy`**`()` -- crea una copia de la lista."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[1, 2, 3, 4, 5]"
      ]
     },
     "execution_count": 1,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a = [1, 2, 3, 4, 5] # creación de la lista\n",
    "a"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[1, 2, 3, 4, 5, 6]"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a.append(6) # agrega el elemento al final\n",
    "a"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[1, 2, 3, 4, 5, 6, 7, 8, 9]"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "b = [7, 8, 9]  # crea una nueva lista\n",
    "a.extend(b)    # pega la nueva lista al final de la anterior\n",
    "a"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['a', 1, 2, 3, 4, 5, 6, 7, 8, 9]"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a.insert(0, 'a')  # las listas pueden contener elementos con diferentes tipos de datos\n",
    "a"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "1 2 3 4\n"
     ]
    }
   ],
   "source": [
    "x = ['a', 'b', 'b', 'c', 'c', 'c', 'd', 'd', 'd', 'd'] # cuenta la cantidad de veces que aparece cada elemento\n",
    "print(x.count('a'), x.count('b'), x.count('c'), x.count('d'))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['a', 'b', 'b', 'c', 'c', 'd', 'd', 'd', 'd']"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "x.remove('c')  # borra una de las veces que aparece el elemento\n",
    "x"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[9, 8, 7, 6, 5, 4, 3, 2, 1, 'a']"
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a.reverse()  # invierte la lista\n",
    "a"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[1, 2, 3, 4, 5]"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "v = [2, 4, 1, 5, 3]  \n",
    "v.sort()  # ordena la lista\n",
    "v"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[1, 2, 3, 4, 5]"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "sorted([2, 4, 1, 5, 3])  # devuelve una copia ordenada de la lista original"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[1, 2, 3, 4]"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "v.pop() # remueve el último elemento de la lista (extremo derecho).\n",
    "v"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[9, 8, 6, 5, 4, 3, 2, 1, 'a']"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a.pop(2) # remueve el elemento en la posición 2 de la lista\n",
    "a"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]"
      ]
     },
     "execution_count": 12,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "x = list(range(10)) # convierte un objeto rango en lista\n",
    "x"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]"
      ]
     },
     "execution_count": 13,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "y = x  # `y` apunta en memoria a la misma lista que `x`.\n",
    "y"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[0, 1, 2, 3, 4, 5, 6, 7, 8]"
      ]
     },
     "execution_count": 14,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "y.pop()  # si se remueve un elemento en la lista `y`, también se remueve en la lista `x`\n",
    "x"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]"
      ]
     },
     "execution_count": 15,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "x = list(range(10))  \n",
    "y = x.copy()         # para evitar el problema anterior se usa `copy()`\n",
    "x.pop()\n",
    "y"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Funciones `filter` y  `map` "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[5]\n"
     ]
    }
   ],
   "source": [
    "# Filtra los elementos mayores que 4\n",
    "# MAL\n",
    "a = [3, 4, 5]\n",
    "b = []\n",
    "for i in a:\n",
    "    if i > 4:\n",
    "        b.append(i)\n",
    "print(b)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [],
   "source": [
    "# BIEN\n",
    "a = [3, 4, 5]\n",
    "b = [i for i in a if i > 4]\n",
    "# O:\n",
    "b = filter(lambda x: x > 4, a)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[6, 7, 8]\n"
     ]
    }
   ],
   "source": [
    "# Sume 3 a todos los elementos de una lista\n",
    "# MAL\n",
    "a = [3, 4, 5]\n",
    "for i in range(len(a)):\n",
    "    a[i] += 3\n",
    "print(a)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[6, 7, 8]"
      ]
     },
     "execution_count": 19,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# BIEN\n",
    "a = [3, 4, 5]\n",
    "a = [i + 3 for i in a]\n",
    "a"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[6, 7, 8]"
      ]
     },
     "execution_count": 20,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# BIEN\n",
    "a = [3, 4, 5]\n",
    "a = map(lambda i: i + 3, a)\n",
    "list(a)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Desempaquetado de listas"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[2, 3]\n"
     ]
    }
   ],
   "source": [
    "a, *rest = [1, 2, 3]    # a = 1, rest = [2, 3]\n",
    "print(rest)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[2, 3]\n"
     ]
    }
   ],
   "source": [
    "a, *middle, c = [1, 2, 3, 4] # a = 1, middle = [2, 3], c = 4\n",
    "print(middle)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Uso de listas como stacks"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Una lista es una estructura de datos LIFO (Last In First Out): el último elemento en entrar es el primer elemento en salir. Para simular este funcionamiento se usan las funciones `append` y `pop`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[3, 4, 5, 6, 7]"
      ]
     },
     "execution_count": 23,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "stack = [3, 4, 5] # se crea una lista con elementos\n",
    "stack.append(6)   # se agrega el 6 al final de la lista\n",
    "stack.append(7)   # se agrega el 7 al final de la lista\n",
    "stack"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 24,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "7"
      ]
     },
     "execution_count": 24,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "stack.pop()  # al llamar a `pop` sale primero el 7 que fue el último elemento en entrar."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[3, 4, 5, 6]"
      ]
     },
     "execution_count": 25,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "stack"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 26,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "6"
      ]
     },
     "execution_count": 26,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "stack.pop()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 27,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "5"
      ]
     },
     "execution_count": 27,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "stack.pop()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 28,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[3, 4]"
      ]
     },
     "execution_count": 28,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "stack"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Uso de listas como colas"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Esta estructura de datos simula la cola de un supermercado. Los elementos entran por la cola y salen por la cabeza (popleft -- pop() por el inicio de la lista). Para ello, se debe importar la función `deque` de la librería `collections`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 29,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'a'"
      ]
     },
     "execution_count": 29,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "from collections import deque\n",
    "queue = deque([\"a\", \"b\", \"c\"])  # se crea una cola con elementos.\n",
    "queue.append(\"d\")               # la `d` entra por el extremo derecho\n",
    "queue.append(\"e\")               # la `e` entra por el extremo derecho\n",
    "queue.popleft()                 # la `a` sale por el extremo izquierdo."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 30,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'b'"
      ]
     },
     "execution_count": 30,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "queue.popleft()                 # la `b` sale por el extremo izquierdo"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 31,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "deque(['c', 'd', 'e'])"
      ]
     },
     "execution_count": 31,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "queue                           # imprime el contenido de la variable queue"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# List comprenhensions"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Este es un mecanismo para definir la composición de una lista de forma compacta. En el siguiente ejemplo se crea una lista con los cuadrados de los números del 0 al 9."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 32,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]"
      ]
     },
     "execution_count": 32,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "squares = []\n",
    "for x in range(10):\n",
    "    squares.append(x**2)\n",
    "    \n",
    "squares"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Un mecanismo más simple consiste en aplicar la función `lambda x:x**2` a los elementos de la lista `[0, ..., 9]`. Para que la función anónima sea aplicada a cada elemento de la lista se usa la función `map`. "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 33,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]"
      ]
     },
     "execution_count": 33,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "squares = list(map(lambda x: x**2, range(10)))\n",
    "squares"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Un mecanismo mucho más simple es integrar la definición de los elementos de la lista en el ciclo `for`: "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 34,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]"
      ]
     },
     "execution_count": 34,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "squares = [x**2 for x in range(10)]\n",
    "squares"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "En una comprenhension, se pueden anidar ciclos `for` tal como se muestra a continuación. Adicionalmente, se pueden agregar condiciones usando la palabra reservada `if`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 35,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[(1, 3), (1, 4), (2, 3), (2, 1), (2, 4), (3, 1), (3, 4)]"
      ]
     },
     "execution_count": 35,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "[(x, y) for x in [1,2,3] for y in [3,1,4] if x != y]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Note que el codigo anterior es mucho más simple que el equivalente usando ciclos `for` anidados como se ilustra en el siguiente código."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 36,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[(1, 3), (1, 4), (2, 3), (2, 1), (2, 4), (3, 1), (3, 4)]"
      ]
     },
     "execution_count": 36,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "combs = []\n",
    "for x in [1,2,3]:\n",
    "    for y in [3,1,4]:\n",
    "        if x != y:\n",
    "            combs.append((x, y))\n",
    "\n",
    "combs\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Ya que este es un mecanismo para crear listas, tambien puede ser aplicado sobre elementos del tipo string. En el siguiente ejemplo, la función `strip` elimina los espacio en blanco al principio y al final de la cadena de caracteres."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 37,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['a a', 'a a', 'a a']"
      ]
     },
     "execution_count": 37,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# llamada de un metodo sobre cada elemento\n",
    "x = ['  a a', '  a a  ', 'a a  ']\n",
    "[y.strip() for y in x]  # elimina los espacios en blanco que delimitan la cadena"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 38,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['linea 1', 'linea 2', 'linea 3', 'linea 4', 'linea 5']"
      ]
     },
     "execution_count": 38,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "['linea ' + str(i) for i in range(1, 6)]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 39,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "linea 1\n",
      "linea 2\n",
      "linea 3\n",
      "linea 4\n",
      "linea 5\n"
     ]
    }
   ],
   "source": [
    "for x in ['linea ' + str(i) for i in range(1, 6)]: print(x)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 40,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['1', '10', '11', '12', '13', '14', '15', '16', '17', '18', '19']"
      ]
     },
     "execution_count": 40,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# numeros del 1 al 20 que contienen un '1'\n",
    "import re\n",
    "[str(x) for x in range(1,21) if re.search('1', str(x))]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 41,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['1', '11']"
      ]
     },
     "execution_count": 41,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# números del 1 al 20 que finanlizan con un '1'\n",
    "import re\n",
    "[str(x) for x in range(1,21) if re.search('1$', str(x))]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 42,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "11"
      ]
     },
     "execution_count": 42,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# cantidad de números del 1 al 20 que contienen un '1'\n",
    "import re\n",
    "len([str(x) for x in range(1,21) if re.search('1', str(x))])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 43,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['345', 'cde', 'lmn']"
      ]
     },
     "execution_count": 43,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# extrae los caracteres en las posiciones 2, 3 y 4\n",
    "x = [\"123456790\",\n",
    "     \"abcdefghi\",\n",
    "     \"jklmnopqr\" ]\n",
    "[m[2:5] for m in x]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 44,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['456', 'def', 'nop', '123456']"
      ]
     },
     "execution_count": 44,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# extrae los caracteres entre corchetes `[` y `]`.\n",
    "x = [\"-->[456]<--\",\n",
    "     \"-->[def]<--\",\n",
    "     \"-->[nop]<--\",\n",
    "    \"-------->[123456]<---------\"]\n",
    "[m[(m.find('[')+1):m.find(']')] for m in x]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 45,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['is', 'by', 'Project', 'for']"
      ]
     },
     "execution_count": 45,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# extrae la segunda palabra de cada línea\n",
    "x = [\"Bash is a Unix shell and command language\",\n",
    "     \"written by Brian Fox for the \", \n",
    "     \"GNU Project as a free software\",\n",
    "     \"replacement for the Bourne shell.\"]\n",
    "[m.split(' ')[1] for m in x]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "A continuación se presentan varios ejemplos de iteración sobre strings."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 46,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "012345678910111213141516171819\n"
     ]
    }
   ],
   "source": [
    "# iteracción sobre strings -- MAL\n",
    "nums = \"\"\n",
    "for n in range(20):\n",
    "  nums += str(n)   # Lento e ineficiente\n",
    "print(nums)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 47,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "012345678910111213141516171819\n"
     ]
    }
   ],
   "source": [
    "# iteración sobre strings -- BIEN\n",
    "nums = []\n",
    "for n in range(20):\n",
    "  nums.append(str(n))\n",
    "print(\"\".join(nums))  # más eficiente"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 48,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "012345678910111213141516171819\n"
     ]
    }
   ],
   "source": [
    "# iteración sobre strings -- MEJOR\n",
    "nums = [str(n) for n in range(20)]\n",
    "print(\"\".join(nums))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 49,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[(0, 0), (1, 1), (2, 4), (3, 9), (4, 16), (5, 25)]"
      ]
     },
     "execution_count": 49,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# también se pueden crear tuplas.\n",
    "[(x, x**2) for x in range(6)]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "En el siguiente ejemplo, el primer `for` recorre los elementos de la lista `vec` mientras que el segundo ciclo `for` recorre las componentes de dicho elemento."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 50,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[1, 2, 3, 4, 5, 6, 7, 8, 9]"
      ]
     },
     "execution_count": 50,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "vec = [[1,2,3], [4,5,6], [7,8,9]]\n",
    "[num for elem in vec for num in elem]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 51,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['3.1', '3.14', '3.142', '3.1416', '3.14159']"
      ]
     },
     "execution_count": 51,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "from math import pi  # otro ejemplo\n",
    "[str(round(pi, i)) for i in range(1, 6)]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 52,
   "metadata": {},
   "outputs": [],
   "source": [
    "# se simula una matriz como una lista cuyos elementos son listas de números.\n",
    "matrix = [\n",
    "    [1, 2, 3, 4],\n",
    "    [5, 6, 7, 8],\n",
    "    [9, 10, 11, 12],\n",
    "]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 53,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[[1, 5, 9], [2, 6, 10], [3, 7, 11], [4, 8, 12]]"
      ]
     },
     "execution_count": 53,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# se calcula la transpuesta \n",
    "[[row[i] for row in matrix] for i in range(4)]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 54,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[[1, 5, 9], [2, 6, 10], [3, 7, 11], [4, 8, 12]]"
      ]
     },
     "execution_count": 54,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# este es el codigo equivalente tradicional.\n",
    "transposed = []\n",
    "for i in range(4):\n",
    "    transposed.append([row[i] for row in matrix])\n",
    "\n",
    "transposed"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 55,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[[1, 5, 9], [2, 6, 10], [3, 7, 11], [4, 8, 12]]"
      ]
     },
     "execution_count": 55,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# otro codigo equivalente.\n",
    "transposed = []\n",
    "for i in range(4):\n",
    "    # the following 3 lines implement the nested listcomp\n",
    "    transposed_row = []\n",
    "    for row in matrix:\n",
    "        transposed_row.append(row[i])\n",
    "    transposed.append(transposed_row)\n",
    "\n",
    "transposed"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 56,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[(1, 5, 9), (2, 6, 10), (3, 7, 11), (4, 8, 12)]"
      ]
     },
     "execution_count": 56,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# otra forma\n",
    "list(zip(*matrix))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Borrado de elementos de una lista"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "El comando `del` permite borar elementos de una lista."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 57,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[1, 66.25, 333, 333, 1234.5]"
      ]
     },
     "execution_count": 57,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a = [-1, 1, 66.25, 333, 333, 1234.5]\n",
    "del a[0]\n",
    "a"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 58,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[1, 66.25, 1234.5]"
      ]
     },
     "execution_count": 58,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "del a[2:4]\n",
    "a"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 59,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[]"
      ]
     },
     "execution_count": 59,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "del a[:]\n",
    "a"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 60,
   "metadata": {},
   "outputs": [],
   "source": [
    "del a"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Tuplas y secuencias"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Una tupla es una secuencia de elementos separados por comas. "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 61,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "12345"
      ]
     },
     "execution_count": 61,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "t = 12345, 54321, 'hello!'\n",
    "t[0]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 62,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "(12345, 54321, 'hello!')"
      ]
     },
     "execution_count": 62,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "t  # una tupla se diferencia de una lista porque se imprime entre paréntesis. "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 63,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "((12345, 54321, 'hello!'), (1, 2, 3, 4, 5))"
      ]
     },
     "execution_count": 63,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Las tuplas pueden anidarse.\n",
    "u = t, (1, 2, 3, 4, 5)\n",
    "u"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 64,
   "metadata": {},
   "outputs": [],
   "source": [
    "x, y, z = t # asignación de los elementos de una tupla."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 65,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "12345"
      ]
     },
     "execution_count": 65,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "x"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 66,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "54321"
      ]
     },
     "execution_count": 66,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "y"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 67,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'hello!'"
      ]
     },
     "execution_count": 67,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "z"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Conjuntos"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Un conjunto es una estructura de datos cuyos elementos no se repiten."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 68,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{'pear', 'orange', 'apple', 'banana'}\n"
     ]
    }
   ],
   "source": [
    "basket = {'apple', 'orange', 'apple', 'pear', 'orange', 'banana'}\n",
    "print(basket)                      # los elmentos duplicados se removieron."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 69,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 69,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "'orange' in basket # `in` se usa para determinar si el elemento está en el conjunto"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 70,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "False"
      ]
     },
     "execution_count": 70,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "'crabgrass' in basket"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 71,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'a', 'b', 'c', 'd', 'r'}"
      ]
     },
     "execution_count": 71,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a = set('abracadabra')    # el string se descompone en sus letras.\n",
    "b = set('alacazam')\n",
    "a                         # letras únicas en el string `a`."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "A continuación se presentan las principales operaciones entre conjuntos."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 72,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'b', 'd', 'r'}"
      ]
     },
     "execution_count": 72,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a - b                              # letras en a pero no en b (diferencia)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 73,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'a', 'b', 'c', 'd', 'l', 'm', 'r', 'z'}"
      ]
     },
     "execution_count": 73,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a | b                              # letras en a o en b (OR)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 74,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'a', 'c'}"
      ]
     },
     "execution_count": 74,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a & b                              # letras en a y en b (intersección)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 75,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'b', 'd', 'l', 'm', 'r', 'z'}"
      ]
     },
     "execution_count": 75,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a ^ b                              # letras en a o en b pero no en ambos"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 76,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'d', 'r'}"
      ]
     },
     "execution_count": 76,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# List comprenhensions en conjuntos\n",
    "a = {x for x in 'abracadabra' if x not in 'abc'} # letras que estan en `abracadabra` y no están en `abc`.\n",
    "a"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Diccionarios"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Un dicionario es una estructura de datos en que cada elemento contiene una clave y un valor. Los diccionarios pueden crearse usando `{` y `}`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 77,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'a': 1, 'b': 2, 'c': 3}"
      ]
     },
     "execution_count": 77,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "x = {'b': 2, 'a': 1} # 'a'  y 'b'  son las claves y 1 y 2 son los valores\n",
    "x['c'] = 3  # se agrega un neuvo elemento al dicicionario.\n",
    "x"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 78,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "2"
      ]
     },
     "execution_count": 78,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "x['b']  # se obtiene el valor asociado a la clave 'b'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 79,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'a': 1, 'c': 3, 'd': 4}"
      ]
     },
     "execution_count": 79,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "del x['b']      # se elimina el elemento.\n",
    "x['d'] = 4    # se agrega un nuevo elemento.\n",
    "x"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 80,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['a', 'c', 'd']"
      ]
     },
     "execution_count": 80,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "list(x.keys())    # la función `keys` imprime las claves."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 81,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['a', 'c', 'd']"
      ]
     },
     "execution_count": 81,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "sorted(x.keys())  # claves ordenadas."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 82,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 82,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "'a' in x  # "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 83,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "False"
      ]
     },
     "execution_count": 83,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "'a' not in x"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 84,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'a': 1, 'b': 2, 'd': 4}"
      ]
     },
     "execution_count": 84,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# un diccionario también puee crearse con `dict` a partir de una lista de tuplas.\n",
    "dict([('d', 4), ('a', 1), ('b', 2)]) "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 85,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{2: 4, 4: 16, 6: 36}"
      ]
     },
     "execution_count": 85,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# también se pueden crear diccionarios usando comprenhensions\n",
    "{x: x**2 for x in (2, 4, 6)}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 86,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'a': 1, 'b': 2, 'c': 3}"
      ]
     },
     "execution_count": 86,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dict(c=3, b=2, a=1) # creación del diccionario usando `=`"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 87,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'a': 1, 'c': 3, 'd': 4}"
      ]
     },
     "execution_count": 87,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "x.copy()  # devuelve una copia del diccionario"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 88,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "dict_items([('a', 1), ('c', 3), ('d', 4)])"
      ]
     },
     "execution_count": 88,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "x.items() # retorna una nueva vista de los items en el diccionario."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Comparación de secuencias y otros tipos de datos"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "A continuación se presentan varios ejemplos de comparación entre secuencias."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 89,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 89,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "(1, 2, 3) < (1, 2, 4)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 90,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 90,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "[1, 2, 3] < [1, 2, 4]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 91,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 91,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "'ABC' < 'C' < 'Pascal' < 'Python'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 92,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 92,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "(1, 2, 3, 4) < (1, 2, 4)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 93,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 93,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "(1, 2) < (1, 2, -1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 94,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 94,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "(1, 2, 3) == (1.0, 2.0, 3.0)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 95,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 95,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "(1, 2, ('aa', 'ab')) < (1, 2, ('abc', 'a'), 4)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Representación de objectos (estructuras de datos) como texto"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "La función `repr()` produce la representación de un objeto en forma de string para su impresión. La función `str()` convierte un objeto a una cadena de caracteres."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 96,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Hola, mundo.\n"
     ]
    }
   ],
   "source": [
    "s = 'Hola, mundo.'\n",
    "print(s) # note que aca lo imprime sin las comillas"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 97,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'Hola, mundo.'"
      ]
     },
     "execution_count": 97,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "str(s) # imprime las comillas"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 98,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "\"'Hola, mundo.'\""
      ]
     },
     "execution_count": 98,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "repr(s) # note las comillas dobles"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 99,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'1'"
      ]
     },
     "execution_count": 99,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a = 1  \n",
    "str(a)  # convierte al 1 de número a string."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 100,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'0.14285714285714285'"
      ]
     },
     "execution_count": 100,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "str(1/7)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "La función `repr()` es usualmente usada para impresión, tal como se ilustra en el siguiente ejemplo."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 101,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "El valor de \"x\" es 32.5, y el de \"y\" es 40000...\n"
     ]
    }
   ],
   "source": [
    "x = 10 * 3.25\n",
    "y = 200 * 200\n",
    "s = 'El valor de \"x\" es ' + repr(x) + ', y el de \"y\" es ' + repr(y) + '...'\n",
    "print(s)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 102,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "'hola, mundo, feliz\\n'\n"
     ]
    }
   ],
   "source": [
    "hello = 'hola, mundo, feliz\\n' \n",
    "hellos = repr(hello) # agrega comillas\n",
    "print(hellos)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 103,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "\"(32.5, 40000, ('a', 'b'))\""
      ]
     },
     "execution_count": 103,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "repr((x, y, ('a', 'b')))  # la función `repr()` recibe cualquier objeto de Python"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 104,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      " 1   1    1\n",
      " 2   4    8\n",
      " 3   9   27\n",
      " 4  16   64\n",
      " 5  25  125\n",
      " 6  36  216\n",
      " 7  49  343\n",
      " 8  64  512\n",
      " 9  81  729\n",
      "10 100 1000\n"
     ]
    }
   ],
   "source": [
    "for x in range(1, 11):\n",
    "    print(repr(x).rjust(2), repr(x*x).rjust(3), end=' ') # imprime las dos primeras columnas\n",
    "    print(repr(x*x*x).rjust(4))                          # imprime la tercera columna"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 105,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      " 1   1    1\n",
      " 2   4    8\n",
      " 3   9   27\n",
      " 4  16   64\n",
      " 5  25  125\n",
      " 6  36  216\n",
      " 7  49  343\n",
      " 8  64  512\n",
      " 9  81  729\n",
      "10 100 1000\n"
     ]
    }
   ],
   "source": [
    "# forma alternativa\n",
    "for x in range(1, 11): \n",
    "    print('{0:2d} {1:3d} {2:4d}'.format(x, x*x, x*x*x))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "La función `zfill()` permite rellenar un número con ceros a la izquierda."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 106,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'00012'"
      ]
     },
     "execution_count": 106,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "'12'.zfill(5)  # el número debe tener 5 caracteres de longitud en total"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 107,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'-003.14'"
      ]
     },
     "execution_count": 107,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "'-3.14'.zfill(7) # el número debe tener 7 caracteres de longitud en total, teniendo en cuenta el signo - "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 108,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'3.14159265359'"
      ]
     },
     "execution_count": 108,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "'3.14159265359'.zfill(5) # si la cadena ya excede la longitud, zfill() no la recorta."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "La función `print()` admite argumentos para la impresión. En su forma más simple, los argumentos son impresos en orden y su lugar se indica mediante los caracteres `{}`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 109,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Este es el argumento -1- y este el \"-2-\"\n"
     ]
    }
   ],
   "source": [
    "print('Este es el argumento {} y este el \"{}\"'.format('-1-', '-2-'))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "En los ejemplos anteriores, los argumentos se imprimen por posición: el primer argumetno de format se imprime en el primer `{}` y asi sucesivamente. Python permite numerar o dar nombre a los argumentos para su impresión."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 110,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "-0- y -1-\n"
     ]
    }
   ],
   "source": [
    "print('{0} y {1}'.format('-0-', '-1-'))  # {0} es '-0-'  y {1} es '-1-'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 111,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "-1- y -0-\n"
     ]
    }
   ],
   "source": [
    "print('{1} y {0}'.format('-0-', '-1-')) # {0} es '-0-'  y {1} es '-1-'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 112,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "-0- y -1-.\n"
     ]
    }
   ],
   "source": [
    "print('{arg0} y {arg1}.'.format(arg1='-1-', arg0='-0-')) # se da nombre a los argumentos "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 113,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "-0-, -1-, y -2-.\n"
     ]
    }
   ],
   "source": [
    "print('{0}, {1}, y {a}.'.format('-0-', '-1-', a='-2-'))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 114,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Este es el argumento -0-.\n"
     ]
    }
   ],
   "source": [
    "x = '-0-'\n",
    "print('Este es el argumento {}.'.format(x))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 115,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Este es el argumento '-0-'.\n"
     ]
    }
   ],
   "source": [
    "print('Este es el argumento {!r}.'.format(x)) # aca agrega comillas alrededor de x"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "El formato `{0:.3f}`indica lo siguiente: `0` es el número del argumento; `.3f` indica un número en punto flotante (un real) con tres decimales después del punto."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 116,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Valor de PI con tres decimales: 3.142.\n"
     ]
    }
   ],
   "source": [
    "import math\n",
    "print('Valor de PI con tres decimales: {0:.3f}.'.format(math.pi))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 117,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "hola mundo ---- 1.23456789\n"
     ]
    }
   ],
   "source": [
    "print('{} ---- {}'.format('hola mundo', 1.23456789))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 118,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "hola mundo      ----     1.23\n"
     ]
    }
   ],
   "source": [
    "print('{0:15s} ---- {1:8.2f}'.format('hola mundo', 1.23456789))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 119,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "     hola mundo ----     1.23\n"
     ]
    }
   ],
   "source": [
    "print('{0:>15s} ---- {1:8.2f}'.format('hola mundo', 1.23456789))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "En el siguiente ejemplo se ilustra la ipmpresión de un diccionario. El formato `{0:10}` indica que el argumento `0` tiene diez caracteres de longitud; la cadena de caracteres se alinea por la izquierda. El formato `{1:10d}` señala que el argumento 1 es entero ('d') y tiene diez caracteres de longitud; se hace la alineación por la derecha. "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 120,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "a          --->        100\n",
      "b          --->        101\n",
      "c          --->        102\n"
     ]
    }
   ],
   "source": [
    "z = {'a': 100, 'b': 101, 'c': 102}\n",
    "for x, y in z.items():\n",
    "    print('{0:10} ---> {1:10d}'.format(x, y))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 121,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "a: 100; b: 101; c: 102\n"
     ]
    }
   ],
   "source": [
    "# este ejemplo muestra como imprimir un diccionario.\n",
    "z = {'a': 100, 'b': 101, 'c': 102}\n",
    "print('a: {0[a]:d}; '\n",
    "      'b: {0[b]:d}; '\n",
    "      'c: {0[c]:d}'.format(z))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 122,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "a: 100; b: 101; c: 102\n"
     ]
    }
   ],
   "source": [
    "# otra forma de imprimir un diccionario.\n",
    "z = {'a': 100, 'b': 101, 'c': 102}\n",
    "print('a: {a:d}; b: {b:d}; c: {c:d}'.format(**z))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Por compatibilidad con versiones anteriores, Python conserva la impresión usando el operador `%`. En el siguiente ejemplo, la especificación `%5.3f` indica que se imprimirá un número real de cinco caracteres de longitud y tres posiciones decimales."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 123,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "--> 3.142 <--\n"
     ]
    }
   ],
   "source": [
    "import math\n",
    "print('--> %5.3f <--' % math.pi)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "---"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**Bibliografía**.\n",
    "\n",
    "> [The Python Tutorial](https://docs.python.org/3/tutorial/index.html) by Python Software Fundation\n",
    "\n",
    "> [IPython in deep](https://github.com/ipython/ipython-in-depth/blob/master/examples/Index.ipynb) at GitHub\n",
    "\n",
    "> [IPython wiki](https://github.com/ipython/ipython/wiki) at GitHub"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "---"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Estructuras de Datos\n",
    "===\n",
    "\n",
    "**Juan David Velásquez Henao**  \n",
    "jdvelasq@unal.edu.co   \n",
    "Universidad Nacional de Colombia, Sede Medellín  \n",
    "Facultad de Minas  \n",
    "Medellín, Colombia\n",
    "\n",
    "---\n",
    "\n",
    "Haga click [aquí](https://github.com/jdvelasq/Python-for-ETL-processes/tree/master/) para acceder al repositorio online.\n",
    "\n",
    "Haga click [aquí](http://nbviewer.jupyter.org/github/jdvelasq/Python-for-ETL-processes/tree/master/) para explorar el repositorio usando `nbviewer`. "
   ]
  }
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