{ "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "# 列表（list）是什么\n", "**Python的列表：list。**list是一种有序的集合，可以随时添加和删除其中的元素。\n", "\n", "列表由一系列按特定顺序排列的元素组成。你可以创建包含字母表中所有字母、数字0~9或\n", "所有家庭成员姓名的列表；也可以将任何东西加入列表中，其中的元素之间可以没有任何关系。\n", "鉴于列表通常包含多个元素，给列表指定一个表示复数的名称（如letters、 digits或names）是\n", "个不错的主意。\n", "\n", "比如，列出班里所有同学的名字，就可以用一个list表示：" ] }, { "cell_type": "code", "execution_count": 1, "metadata": {}, "outputs": [], "source": [ "classmates = ['Michael', 'Bob', 'Tracy']" ] }, { "cell_type": "code", "execution_count": 2, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "3" ] }, "execution_count": 2, "metadata": {}, "output_type": "execute_result" } ], "source": [ "# 用len()函数可以获得list元素的个数：\n", "len(classmates)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "# 1.1 **访问列表元素**" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "列表是有序集合，因此要访问列表的任何元素，只需将该元素的位置或索引告诉Python即可。
\n", "要访问列表元素，可指出列表的名称，再指出元素的索引，并将其放在方括号内。
\n", "例如，下面的代码从列表bicycles中提取第一款自行车：" ] }, { "cell_type": "code", "execution_count": 3, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Trek\n" ] } ], "source": [ "bicycles = ['trek', 'cannondale', 'redline', 'specialized']\n", "print(bicycles[0].title())" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "用**索引**访问list中的元素，索引是从$0$开始,而不是1" ] }, { "cell_type": "code", "execution_count": 4, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['Michael', 'Bob', 'Tracy']" ] }, "execution_count": 4, "metadata": {}, "output_type": "execute_result" } ], "source": [ "classmates" ] }, { "cell_type": "code", "execution_count": 5, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "'Michael'" ] }, "execution_count": 5, "metadata": {}, "output_type": "execute_result" } ], "source": [ "classmates[0]" ] }, { "cell_type": "code", "execution_count": 6, "metadata": {}, "outputs": [ { "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\u001b[0m in \u001b[0;36m\u001b[1;34m\u001b[0m\n\u001b[0;32m 1\u001b[0m \u001b[1;31m# 当索引超出了范围时，Python会报一个IndexError错误，所以，要确保索引不要越界，记得最后一个元素的索引是len(classmates) - 1\u001b[0m\u001b[1;33m\u001b[0m\u001b[1;33m\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[1;32m----> 2\u001b[1;33m \u001b[0mclassmates\u001b[0m\u001b[1;33m[\u001b[0m\u001b[1;36m3\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": [ "# 当索引超出了范围时，Python会报一个IndexError错误，所以，要确保索引不要越界，记得最后一个元素的索引是len(classmates) - 1\n", "classmates[3]" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "如果要**取最后一个元素**，除了计算索引位置外，还可以用$-1$做索引，直接获取最后一个元素：" ] }, { "cell_type": "code", "execution_count": 7, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "'Tracy'" ] }, "execution_count": 7, "metadata": {}, "output_type": "execute_result" } ], "source": [ "classmates[-1]" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "取倒数第2个、倒数第3个：" ] }, { "cell_type": "code", "execution_count": 8, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "'Bob'" ] }, "execution_count": 8, "metadata": {}, "output_type": "execute_result" } ], "source": [ "classmates[-2]" ] }, { "cell_type": "code", "execution_count": 9, "metadata": {}, "outputs": [ { "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\u001b[0m in \u001b[0;36m\u001b[1;34m\u001b[0m\n\u001b[1;32m----> 1\u001b[1;33m \u001b[0mclassmates\u001b[0m\u001b[1;33m[\u001b[0m\u001b[1;33m-\u001b[0m\u001b[1;36m4\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": [ "classmates[-4]" ] }, { "cell_type": "code", "execution_count": 10, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "My first bicycle was a Trek.\n" ] } ], "source": [ "bicycles = ['trek', 'cannondale', 'redline', 'specialized']\n", "message = \"My first bicycle was a \" + bicycles[0].title() + \".\"\n", "print(message)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "# **从列表中插入元素**
\n", "list是一个可变的有序表，所以，可以往list中追加元素到末尾：" ] }, { "cell_type": "code", "execution_count": 11, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['Michael', 'Bob', 'Tracy']" ] }, "execution_count": 11, "metadata": {}, "output_type": "execute_result" } ], "source": [ "classmates" ] }, { "cell_type": "code", "execution_count": 12, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['Michael', 'Bob', 'Tracy', 'Adam']" ] }, "execution_count": 12, "metadata": {}, "output_type": "execute_result" } ], "source": [ "classmates.append('Adam')\n", "classmates" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "可以把元素插入到指定的位置，比如索引号为1的位置：" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "也可以把元素插入到指定的位置，比如索引号为1的位置：" ] }, { "cell_type": "code", "execution_count": 13, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['Michael', 'Jack', 'Bob', 'Tracy', 'Adam']" ] }, "execution_count": 13, "metadata": {}, "output_type": "execute_result" } ], "source": [ "classmates.insert(1, 'Jack')\n", "classmates" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "# **从列表中删除元素**
\n", "你经常需要从列表中删除一个或多个元素,你可以根据位置或值来删除列表中的元素。" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "删除list**末尾**的元素，用$pop()$方法：\n", "\n", "有时候，你要将元素从列表中删除，并接着使用它的值。" ] }, { "cell_type": "code", "execution_count": 14, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['Michael', 'Jack', 'Bob', 'Tracy', 'Adam']" ] }, "execution_count": 14, "metadata": {}, "output_type": "execute_result" } ], "source": [ "classmates" ] }, { "cell_type": "code", "execution_count": 15, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['Michael', 'Jack', 'Bob', 'Tracy']" ] }, "execution_count": 15, "metadata": {}, "output_type": "execute_result" } ], "source": [ "aaa = classmates.pop()\n", "classmates" ] }, { "cell_type": "code", "execution_count": 16, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "'Adam'" ] }, "execution_count": 16, "metadata": {}, "output_type": "execute_result" } ], "source": [ "aaa" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "要删除指定位置的元素，用$pop(i)$方法，其中i是索引位置：" ] }, { "cell_type": "code", "execution_count": 17, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['Michael', 'Bob', 'Tracy']" ] }, "execution_count": 17, "metadata": {}, "output_type": "execute_result" } ], "source": [ "classmates = ['Michael', 'Bob', 'Tracy']\n", "classmates" ] }, { "cell_type": "code", "execution_count": 18, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Bob\n" ] }, { "data": { "text/plain": [ "['Michael', 'Tracy']" ] }, "execution_count": 18, "metadata": {}, "output_type": "execute_result" } ], "source": [ "a = classmates.pop(1)\n", "print(a)\n", "classmates" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "使用**del语句**删除元素" ] }, { "cell_type": "code", "execution_count": 19, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "['honda', 'yamaha', 'suzuki']\n", "['yamaha', 'suzuki']\n" ] } ], "source": [ "motorcycles = ['honda', 'yamaha', 'suzuki']\n", "print(motorcycles)\n", "del motorcycles[0]\n", "print(motorcycles)" ] }, { "cell_type": "code", "execution_count": 20, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "['honda', 'yamaha', 'suzuki']\n", "['honda', 'suzuki']\n" ] } ], "source": [ "motorcycles = ['honda', 'yamaha', 'suzuki']\n", "print(motorcycles)\n", "del motorcycles[1]\n", "print(motorcycles)" ] }, { "cell_type": "code", "execution_count": 21, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "The first motorcycle I owned was a Honda.\n" ] } ], "source": [ "motorcycles = ['honda', 'yamaha', 'suzuki']\n", "first_owned = motorcycles.pop(0)\n", "print('The first motorcycle I owned was a ' + first_owned.title() + '.')" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "**根据值删除元素**
\n", "有时候，你不知道要从列表中删除的值所处的位置。如果你只知道要删除的元素的值，可使\n", "用方法remove()" ] }, { "cell_type": "code", "execution_count": 22, "metadata": { "scrolled": true }, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "['honda', 'yamaha', 'suzuki']\n", "\n", "A Ducati is too expensive for me.\n" ] } ], "source": [ "motorcycles = ['honda', 'yamaha', 'suzuki', 'ducati']\n", "too_expensive = 'ducati'\n", "motorcycles.remove(too_expensive)\n", "print(motorcycles)\n", "print(\"\\nA \" + too_expensive.title() + \" is too expensive for me.\")" ] }, { "cell_type": "code", "execution_count": 23, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "0" ] }, "execution_count": 23, "metadata": {}, "output_type": "execute_result" } ], "source": [ "motorcycles.index('honda')" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "**注意：
**方法remove()只删除第一个指定的值。如果要删除的值可能在列表中出现多次，就需要\n", "使用循环来判断是否删除了所有这样的值。" ] }, { "cell_type": "code", "execution_count": 24, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "[2, 1, 3]\n" ] } ], "source": [ "a = [1,2,1,3]\n", "a.remove(1)\n", "print(a)" ] }, { "cell_type": "code", "execution_count": 25, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "[2, 3]" ] }, "execution_count": 25, "metadata": {}, "output_type": "execute_result" } ], "source": [ "a = [1,2,1,3]\n", "x = 1\n", "for x in a:\n", " a.remove(x)\n", "a" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "**把某个元素替换成别的元素，可以直接赋值给对应的索引位置：**" ] }, { "cell_type": "code", "execution_count": 26, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['Michael', 'Tracy']" ] }, "execution_count": 26, "metadata": {}, "output_type": "execute_result" } ], "source": [ "classmates" ] }, { "cell_type": "code", "execution_count": 27, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['Michael', 'Sarah']" ] }, "execution_count": 27, "metadata": {}, "output_type": "execute_result" } ], "source": [ "classmates[1] = 'Sarah'\n", "classmates" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "list里面的**元素的数据类型**也可以不同：" ] }, { "cell_type": "code", "execution_count": 28, "metadata": {}, "outputs": [], "source": [ "L = ['Apple', 123, True]" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "list元素也可以是另一个list，比如：" ] }, { "cell_type": "code", "execution_count": 29, "metadata": {}, "outputs": [], "source": [ "s = ['python', 'java', ['asp', 'php'], 'scheme']" ] }, { "cell_type": "code", "execution_count": 30, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "4" ] }, "execution_count": 30, "metadata": {}, "output_type": "execute_result" } ], "source": [ "len(s)" ] }, { "cell_type": "code", "execution_count": 31, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "'asp'" ] }, "execution_count": 31, "metadata": {}, "output_type": "execute_result" } ], "source": [ "s[2][0]" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "s只有4个元素，其中s[2]又是一个list，拆开写：" ] }, { "cell_type": "code", "execution_count": 32, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['python', 'java', ['asp', 'php'], 'scheme']" ] }, "execution_count": 32, "metadata": {}, "output_type": "execute_result" } ], "source": [ "p = ['asp', 'php']\n", "s = ['python', 'java', p, 'scheme']\n", "s" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "要拿到'php'可以写$p[1]$或者$s[2][1]$，因此$s$可以看成是一个二维数组，类似的还有三维、四维……数组，不过很少用到。\n", "\n", "如果一个list中一个元素也没有，就是一个空的list，它的长度为$0$：" ] }, { "cell_type": "code", "execution_count": 33, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "'asp'" ] }, "execution_count": 33, "metadata": {}, "output_type": "execute_result" } ], "source": [ "s[2][0]" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ " # 组织列表" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "在你创建的列表中，元素的排列顺序常常是无法预测的，因为你并非总能控制用户提供数据\n", "的顺序。这虽然在大多数情况下都是不可避免的，但你经常需要以特定的顺序呈现信息。 有时候，\n", "你希望保留列表元素最初的排列顺序，而有时候又需要调整排列顺序。 Python提供了很多组织列\n", "表的方式，可根据具体情况选用" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "**使用方法 sort()对列表进行永久性排序**" ] }, { "cell_type": "code", "execution_count": 34, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "['audi', 'bmw', 'subaru', 'toyota']\n" ] } ], "source": [ "cars = ['bmw', 'audi', 'toyota', 'subaru']\n", "cars.sort()\n", "print(cars)" ] }, { "cell_type": "code", "execution_count": 35, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['audi', 'bmw', 'subaru', 'toyota']" ] }, "execution_count": 35, "metadata": {}, "output_type": "execute_result" } ], "source": [ "cars" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "你还可以按与字母顺序相反的顺序排列列表元素，为此，只需向sort()方法传递参数\n", "reverse=True。下面的示例将汽车列表按与字母顺序相反的顺序排列：" ] }, { "cell_type": "code", "execution_count": 36, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "['toyota', 'subaru', 'bmw', 'audi']\n" ] } ], "source": [ "cars = ['bmw', 'audi', 'toyota', 'subaru']\n", "cars.sort(reverse=True)\n", "print(cars)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "**使用函数 sorted()对列表进行临时排序**
\n", "要保留列表元素原来的排列顺序，同时以特定的顺序呈现它们，可使用函数sorted()。
函数\n", "sorted()让你能够按特定顺序显示列表元素，同时不影响它们在列表中的原始排列顺序" ] }, { "cell_type": "code", "execution_count": 37, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Here is the original list:\n", "['bmw', 'audi', 'toyota', 'subaru']\n", "\n", "Here is the sorted list:\n", "['audi', 'bmw', 'subaru', 'toyota']\n", "\n", "Here is the original list again:\n", "['bmw', 'audi', 'toyota', 'subaru']\n" ] } ], "source": [ "cars = ['bmw', 'audi', 'toyota', 'subaru']\n", "print(\"Here is the original list:\")\n", "print(cars)\n", "print(\"\\nHere is the sorted list:\")\n", "print(sorted(cars))\n", "print(\"\\nHere is the original list again:\")\n", "print(cars)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "**倒着打印列表**\n", "要反转列表元素的排列顺序，可使用方法reverse()。
假设汽车列表是按购买时间排列的，
\n", "可轻松地按相反的顺序排列其中的汽车：" ] }, { "cell_type": "code", "execution_count": 38, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "['bmw', 'audi', 'toyota', 'subaru']\n", "['subaru', 'toyota', 'audi', 'bmw']\n" ] } ], "source": [ "cars = ['bmw', 'audi', 'toyota', 'subaru']\n", "print(cars)\n", "cars.reverse()\n", "print(cars)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "注意， reverse()不是指按与字母顺序相反的顺序排列列表元素，而只是反转列表元素的排\n", "列顺序：
\n", "['bmw', 'audi', 'toyota', 'subaru']
\n", "['subaru', 'toyota', 'audi', 'bmw']" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "方法reverse()永久性地修改列表元素的排列顺序，
但可随时恢复到原来的排列顺序，为此\n", "只需对列表再次调用reverse()即可。" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "# 遍历整个列表\n" ] }, { "cell_type": "code", "execution_count": 39, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "alice\n", "david\n", "carolina\n" ] } ], "source": [ "magicians = ['alice', 'david', 'carolina']\n", "for magician in magicians:\n", " print(magician)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "# 创建数值列表" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "需要存储一组数字的原因有很多，例如，在游戏中，需要跟踪每个角色的位置，还可能需要
\n", "跟踪玩家的几个最高得分。在数据可视化中，处理的几乎都是由数字（如温度、距离、人口数量、
\n", "经度和纬度等）组成的集合。\n", "列表非常适合用于存储数字集合，而Python提供了很多工具，可帮助你高效地处理数字列表。
\n", "明白如何有效地使用这些工具后，即便列表包含数百万个元素，你编写的代码也能运行得很好。" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "**使用函数 range()**
\n", "Python函数range()让你能够轻松地生成一系列的数字。
例如，可以像下面这样使用函数\n", "range()来打印一系列的数字：" ] }, { "cell_type": "code", "execution_count": 40, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "1\n", "2\n", "3\n", "4\n" ] } ], "source": [ "for value in range(1,5):\n", " print(value)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "**使用 range()创建数字列表**
\n", "要创建数字列表，可使用函数list()将range()的结果直接转换为列表。\n", "
如果将range()作为list()的参数，输出将为一个数字列表。" ] }, { "cell_type": "code", "execution_count": 42, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "range(1, 6)" ] }, "execution_count": 42, "metadata": {}, "output_type": "execute_result" } ], "source": [ "range(1,6)" ] }, { "cell_type": "code", "execution_count": 41, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "[1, 2, 3, 4, 5]\n" ] } ], "source": [ "numbers = list(range(1,6))\n", "print(numbers)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "使用函数range()时，还可指定步长。
例如，下面的代码打印1~10内的偶数：" ] }, { "cell_type": "code", "execution_count": 43, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "[2, 4, 6, 8, 10]\n" ] } ], "source": [ "even_numbers = list(range(2,11,2))\n", "print(even_numbers)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "使用函数range()几乎能够创建任何需要的数字集，例如，如何创建一个列表，其中包含前\n", "10个整数（即1~10）的平方呢？" ] }, { "cell_type": "code", "execution_count": 44, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]\n" ] } ], "source": [ "squares = []\n", "for value in range(1,11): #1,2,3.....10\n", " square = value**2\n", " squares.append(square)\n", "print(squares)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "**列表解析**" ] }, { "cell_type": "code", "execution_count": 45, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]\n" ] } ], "source": [ "squares = [value**2 for value in range(1,11)]\n", "print(squares)" ] }, { "cell_type": "code", "execution_count": 46, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "range(1, 10)" ] }, "execution_count": 46, "metadata": {}, "output_type": "execute_result" } ], "source": [ "range(1,10)" ] }, { "cell_type": "code", "execution_count": 47, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "[1, 2, 3, 4, 5, 6, 7, 8, 9]" ] }, "execution_count": 47, "metadata": {}, "output_type": "execute_result" } ], "source": [ "list(range(1,10))" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "# 对数字列表执行简单的统计计算" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "有几个专门用于处理数字列表的Python函数。\n", "
例如，你可以轻松地找出数字列表的最大值、最小值和总和：" ] }, { "cell_type": "code", "execution_count": 48, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "0\n", "9\n" ] } ], "source": [ "digits = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0]\n", "print(min(digits))\n", "print(max(digits))" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "# 使用列表的一部分\n", "
处理列表的部分元素——Python称之为切片。" ] }, { "cell_type": "code", "execution_count": 49, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "['charles', 'martina', 'michael']\n" ] } ], "source": [ "players = ['charles', 'martina', 'michael', 'florence', 'eli']\n", "print(players[0:3])" ] }, { "cell_type": "code", "execution_count": 50, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "['martina', 'michael', 'florence']\n" ] } ], "source": [ "players = ['charles', 'martina', 'michael', 'florence', 'eli']\n", "print(players[1:4])" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "如果你没有指定第一个索引， Python将自动从列表开头开始：" ] }, { "cell_type": "code", "execution_count": 51, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "['charles', 'martina', 'michael', 'florence']\n" ] } ], "source": [ "players = ['charles', 'martina', 'michael', 'florence', 'eli']\n", "print(players[:4])" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "要让切片终止于列表末尾，也可使用类似的语法。例如，
如果要提取从第3个元素到列表末\n", "尾的所有元素，可将起始索引指定为2， 并省略终止索引：" ] }, { "cell_type": "code", "execution_count": 52, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "['michael', 'florence', 'eli']\n" ] } ], "source": [ "players = ['charles', 'martina', 'michael', 'florence', 'eli']\n", "print(players[2:])" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "输出名单上的最后三名队员" ] }, { "cell_type": "code", "execution_count": 53, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "['michael', 'florence', 'eli']\n" ] } ], "source": [ "players = ['charles', 'martina', 'michael', 'florence', 'eli']\n", "print(players[-3:])" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "**遍历切片**
\n", "如果要遍历列表的部分元素，可在for循环中使用切片。
在下面的示例中，我们遍历前三名\n", "队员，并打印他们的名字：" ] }, { "cell_type": "code", "execution_count": 54, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Here are the first three players on my team:\n", "Charles\n", "Martina\n", "Michael\n" ] } ], "source": [ "players = ['charles', 'martina', 'michael', 'florence', 'eli']\n", "print(\"Here are the first three players on my team:\")\n", "for player in players[:3]:\n", " print(player.title())" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "# 复制列表" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "要复制列表，可创建一个包含整个列表的切片，方法是同时省略起始索引和终止索引（ [:]）。
\n", "这让Python创建一个始于第一个元素，终止于最后一个元素的切片，即复制整个列表。" ] }, { "cell_type": "code", "execution_count": 1, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "My favorite foods are:\n", "['pizza', 'falafel', 'carrot cake']\n", "\n", "My friend's favorite foods are:\n", "['pizza', 'falafel', 'carrot cake']\n" ] } ], "source": [ "my_foods = ['pizza', 'falafel', 'carrot cake']\n", "friend_foods = my_foods[:]\n", "# friend_foods = my_foods\n", "print(\"My favorite foods are:\")\n", "print(my_foods)\n", "\n", "print(\"\\nMy friend's favorite foods are:\")\n", "print(friend_foods)" ] }, { "cell_type": "code", "execution_count": 2, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['pizza', 'falafel', 'carrot cake']" ] }, "execution_count": 2, "metadata": {}, "output_type": "execute_result" } ], "source": [ "my_foods[0]='aaa'\n", "friend_foods" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "注意：" ] }, { "cell_type": "code", "execution_count": 55, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "['a', 2, 3]\n" ] } ], "source": [ "a = [1,2,3]\n", "b = a\n", "b[0] = \"a\"\n", "print(a)" ] }, { "cell_type": "code", "execution_count": 3, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "My favorite foods are:\n", "['pizza', 'falafel', 'carrot cake', 'cannoli']\n", "\n", "My friend's favorite foods are:\n", "['pizza', 'falafel', 'carrot cake', 'ice cream']\n" ] } ], "source": [ "my_foods = ['pizza', 'falafel', 'carrot cake']\n", "friend_foods = my_foods[:]\n", "my_foods.append('cannoli')\n", "friend_foods.append('ice cream')\n", "print(\"My favorite foods are:\")\n", "print(my_foods)\n", "print(\"\\nMy friend's favorite foods are:\")\n", "print(friend_foods)" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [] }, { "cell_type": "markdown", "metadata": {}, "source": [ "# tuple\n", "**tuple(元组)**是另一种有序列表。
\n", "tuple和list非常类似，但是tuple一旦初始化就不能修改，比如同样是列出同学的名字:" ] }, { "cell_type": "code", "execution_count": 56, "metadata": {}, "outputs": [], "source": [ "classmates = ('Michael', 'Bob', 'Tracy')" ] }, { "cell_type": "code", "execution_count": 57, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "('Michael', 'Bob', 'Tracy')" ] }, "execution_count": 57, "metadata": {}, "output_type": "execute_result" } ], "source": [ "classmates" ] }, { "cell_type": "code", "execution_count": 58, "metadata": {}, "outputs": [ { "ename": "TypeError", "evalue": "'tuple' object does not support item assignment", "output_type": "error", "traceback": [ "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m", "\u001b[1;31mTypeError\u001b[0m Traceback (most recent call last)", "\u001b[1;32m\u001b[0m in \u001b[0;36m\u001b[1;34m\u001b[0m\n\u001b[1;32m----> 1\u001b[1;33m \u001b[0mclassmates\u001b[0m\u001b[1;33m[\u001b[0m\u001b[1;36m0\u001b[0m\u001b[1;33m]\u001b[0m \u001b[1;33m=\u001b[0m \u001b[1;34m'aaa'\u001b[0m\u001b[1;33m\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m", "\u001b[1;31mTypeError\u001b[0m: 'tuple' object does not support item assignment" ] } ], "source": [ "classmates[0] = 'aaa'" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "这里**classmates**这个$tuple$不能变了，它也没有**append()，insert()**这样的方法。
\n", "其他获取元素的方法和list是一样的，你可以正常地使用**classmates[0]，classmates[-1]**，但不能赋值成另外的元素。
\n", "**不可变的tuple有什么意义？**:因为tuple不可变，所以代码更安全。如果可能，能用tuple代替list就尽量用tuple。" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "tuple的陷阱：**当你定义一个tuple时，在定义的时候，tuple的元素就必须被确定下来，比如：**" ] }, { "cell_type": "code", "execution_count": 4, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "(1, 2)" ] }, "execution_count": 4, "metadata": {}, "output_type": "execute_result" } ], "source": [ "t = (1, 2)\n", "t" ] }, { "cell_type": "code", "execution_count": 5, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "1" ] }, "execution_count": 5, "metadata": {}, "output_type": "execute_result" } ], "source": [ "t[0]" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "定义一个空的tuple，可以写成()：" ] }, { "cell_type": "code", "execution_count": 6, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "()" ] }, "execution_count": 6, "metadata": {}, "output_type": "execute_result" } ], "source": [ "t = ()\n", "t" ] }, { "cell_type": "markdown", "metadata": {}, "source": [] }, { "cell_type": "code", "execution_count": 62, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "1" ] }, "execution_count": 62, "metadata": {}, "output_type": "execute_result" } ], "source": [ "# 定义的不是tuple，er而是1这个数！ 这是因为括号()既可以表示tuple，又可以表示数学公式中的小括号，这就产生了歧义\n", "t = (1)\n", "t" ] }, { "cell_type": "code", "execution_count": 63, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "int" ] }, "execution_count": 63, "metadata": {}, "output_type": "execute_result" } ], "source": [ "type(t)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "因此，Python规定，这种情况下，按小括号进行计算，计算结果自然是1。\n", "所以，只有1个元素的tuple定义时必须加一个逗号,，来消除歧义：" ] }, { "cell_type": "code", "execution_count": 64, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "(1,)" ] }, "execution_count": 64, "metadata": {}, "output_type": "execute_result" } ], "source": [ "# 所以，只有1个元素的tuple定义时必须加一个逗号,，来消除歧义：\n", "t = (1,)\n", "t" ] }, { "cell_type": "code", "execution_count": 65, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "tuple" ] }, "execution_count": 65, "metadata": {}, "output_type": "execute_result" } ], "source": [ "type(t)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "**修改元组变量**
\n", "虽然不能修改元组的元素，但可以给存储元组的变量赋值。
因此，如果要修改前述矩形的尺\n", "寸，可重新定义整个元组：" ] }, { "cell_type": "code", "execution_count": 66, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Original dimensions:\n", "200\n", "50\n", "\n", "Modified dimensions:\n", "400\n", "100\n" ] } ], "source": [ "dimensions = (200, 50)\n", "print(\"Original dimensions:\")\n", "for dimension in dimensions:\n", " print(dimension)\n", " \n", "dimensions = (400, 100)\n", "print(\"\\nModified dimensions:\")\n", "for dimension in dimensions:\n", " print(dimension)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "**“可变的”tuple：**" ] }, { "cell_type": "code", "execution_count": 8, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "('a', 'b', ['A', 'B'])" ] }, "execution_count": 8, "metadata": {}, "output_type": "execute_result" } ], "source": [ "t = ('a', 'b', ['A', 'B'])\n", "t" ] }, { "cell_type": "code", "execution_count": 9, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "('a', 'b', ['X', 'Y'])" ] }, "execution_count": 9, "metadata": {}, "output_type": "execute_result" } ], "source": [ "ar_1 = t[2][0]\n", "t[2][0] = 'X'\n", "ar_2 = t[2][0]\n", "t[2][1] = 'Y'\n", "t" ] }, { "cell_type": "code", "execution_count": 69, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "1899709865856" ] }, "execution_count": 69, "metadata": {}, "output_type": "execute_result" } ], "source": [ "ar_0 = t[2][0]\n", "id(ar_0)" ] }, { "cell_type": "code", "execution_count": 70, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "1899709865856" ] }, "execution_count": 70, "metadata": {}, "output_type": "execute_result" } ], "source": [ "id(t[2][0])" ] }, { "cell_type": "code", "execution_count": 71, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "1899709865856" ] }, "execution_count": 71, "metadata": {}, "output_type": "execute_result" } ], "source": [ "t[2][0] = 'X'\n", "id(t[2][0])" ] }, { "cell_type": "code", "execution_count": 72, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "1899710605216" ] }, "execution_count": 72, "metadata": {}, "output_type": "execute_result" } ], "source": [ "t[2][0] = 'A'\n", "id(t[2][0])" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "**原始的内存结构：**
\n", "![alt text](002List-Tuple1.png)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "**把list的元素'A'和'B'修改为'X'和'Y'后：**
\n", "![alt text](002List-Tuple2.png)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "表面上看，tuple的元素确实变了，但其实变的不是tuple的元素，而是list的元素。
\n", "tuple一开始指向的list并没有改成别的list，所以，tuple所谓的“不变”是说**tuple的每个元素，指向永远不变。**即指向'a'，就不能改成指向'b'，指向一个list，就不能改成指向其他对象，**但指向的这个list本身是可变的！**\n", "\n", "要创建一个内容也不变的tuple怎么做？那就必须保证tuple的每一个元素本身也不能变。" ] }, { "cell_type": "code", "execution_count": 11, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "('a', 'b', ['X', 'Y'])\n" ] } ], "source": [ "t = ('a', 'b', ['A', 'B'])\n", "ar_1 = t[2][0]\n", "t[2][0] = 'X'\n", "ar_2 = t[2][0]\n", "t[2][1] = 'Y'\n", "\n", "print(t)\n", "\n", "# t[2] = [\"t\",\"t\"]" ] }, { "cell_type": "code", "execution_count": 12, "metadata": {}, "outputs": [ { "ename": "TypeError", "evalue": "'tuple' object does not support item assignment", "output_type": "error", "traceback": [ "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m", "\u001b[1;31mTypeError\u001b[0m Traceback (most recent call last)", "\u001b[1;32m\u001b[0m in \u001b[0;36m\u001b[1;34m\u001b[0m\n\u001b[1;32m----> 1\u001b[1;33m \u001b[0mt\u001b[0m\u001b[1;33m[\u001b[0m\u001b[1;36m2\u001b[0m\u001b[1;33m]\u001b[0m \u001b[1;33m=\u001b[0m \u001b[1;33m[\u001b[0m\u001b[1;34m\"t\"\u001b[0m\u001b[1;33m,\u001b[0m\u001b[1;34m\"t\"\u001b[0m\u001b[1;33m]\u001b[0m\u001b[1;33m\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m", "\u001b[1;31mTypeError\u001b[0m: 'tuple' object does not support item assignment" ] } ], "source": [ "t[2] = [\"t\",\"t\"]" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "# 遍历元组中的所有值" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "像列表一样，也可以使用for循环来遍历元组中的所有值：" ] }, { "cell_type": "code", "execution_count": 1, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "200\n", "50\n" ] } ], "source": [ "dimensions = (200, 50)\n", "for dimension in dimensions:\n", " print(dimension)" ] }, { "cell_type": "code", "execution_count": 2, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "[200, 50]" ] }, "execution_count": 2, "metadata": {}, "output_type": "execute_result" } ], "source": [ "[dimension for dimension in dimensions]" ] }, { "cell_type": "code", "execution_count": 7, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]\n" ] } ], "source": [ "squares = [value**2 for value in range(1,11)]\n", "print(squares)" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "a = 2\n", "b = 2" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "id(a),id(b)" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "a=3\n", "b" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "id(a)" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "b=3\n", "id(b)" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "c=2\n", "id(c)" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "s1 = 'ab'\n", "id(s1)" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "s2 = 'ab'\n", "id(s2)" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "s3 = 'a'\n", "id(s3)" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "id('a')" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "id('ab')" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "id('abc')" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "id('abc')" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "id(2.0)" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "id(2.0)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "# list 练习" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "**1. 在列表末尾添加元素
**\n", "在列表中添加新元素时，最简单的方式是将元素附加到列表末尾。给列表附加元素时，它将
\n", "添加到列表末尾。继续使用前一个示例中的列表，在其末尾添加新元素'ducati'：" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "motorcycles = ['honda', 'yamaha', 'suzuki']\n", "print(motorcycles)\n", "motorcycles.append('ducati')\n", "print(motorcycles)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "方法append()让动态地创建列表易如反掌，例如，你可以先创建一个空列表，再使用一系列的\n", "append()语句添加元素。下面来创建一个空列表，再在其中添加元素'honda'、 'yamaha'和'suzuki'：" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "motorcycles = []\n", "motorcycles.append('honda')\n", "motorcycles.append('yamaha')\n", "motorcycles.append('suzuki')\n", "print(motorcycles)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "使用方法insert()可在列表的任何位置添加新元素。为此，你需要指定新元素的索引和值。" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "motorcycles = ['honda', 'yamaha', 'suzuki']\n", "motorcycles.insert(0, 'ducati')\n", "print(motorcycles)" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "x = ['ab111','abc','ab1211','abcd']\t\t\t#创建列表并赋值\n", "x.sort(key=len,reverse=True)\t\t#使用sort()方法对变量x中元素进行长度逆序排序\n", "print(x)\t" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "sorted??" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [] } ], "metadata": { "kernelspec": { "display_name": "Python 3 (ipykernel)", "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": "3.8.20" }, "toc": { "base_numbering": 1, "nav_menu": {}, "number_sections": false, "sideBar": true, "skip_h1_title": false, "title_cell": "Table of Contents", "title_sidebar": "Contents", "toc_cell": false, "toc_position": { "height": "calc(100% - 180px)", "left": "10px", "top": "150px", "width": "406.237px" }, "toc_section_display": true, "toc_window_display": true } }, "nbformat": 4, "nbformat_minor": 4 }