23_列表.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 1. 为什么用列表"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "1532445696968\n",
      "<class 'list'>\n",
      "['hello', 'world', 98]\n"
     ]
    }
   ],
   "source": [
    "a = 10  # 变量存储的是一个对象的引用\n",
    "# 列表存储的是多个对象的引用，每个对象有自己单独的id，type，value\n",
    "lst = ['hello', 'world', 98]\n",
    "print(id(lst))\n",
    "print(type(lst))\n",
    "print(lst)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 2. 列表对象创建"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "['hello', 'world', 98]\n",
      "hello 98\n"
     ]
    }
   ],
   "source": [
    "# 创建列表的第一种方式：[]\n",
    "lst1 = ['hello', 'world', 98]\n",
    "print(lst1)\n",
    "print(lst1[0], lst1[-1])  # -1为最后一个元素"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "['hello', 'world', 98, 'hello']\n",
      "hello hello\n"
     ]
    }
   ],
   "source": [
    "# 创建列表的第一种方式：[]\n",
    "lst1 = ['hello', 'world', 98, 'hello']\n",
    "print(lst1)\n",
    "print(lst1[0], lst1[-4])  # -4为重复元素"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [],
   "source": [
    "# 创建列表的第二种方式：使用内置函数list()\n",
    "lst2 = list(['hello', 'world', 98])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 3. 列表的特点"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'\\n列表的特点：\\n1.列表元素按照顺序有序排序\\n2.索引映射唯一一个数据\\n3.列表可以存储重复数据\\n4.任意数据类型混存\\n5.根据需要动态分配和回收内存\\n'"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "'''\n",
    "列表的特点：\n",
    "1.列表元素按照顺序有序排序\n",
    "2.索引映射唯一一个数据\n",
    "3.列表可以存储重复数据\n",
    "4.任意数据类型混存\n",
    "5.根据需要动态分配和回收内存\n",
    "'''"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 4. 获取指定元素的索引"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0\n",
      "3\n",
      "0\n"
     ]
    }
   ],
   "source": [
    "lst = ['hello', 'world', 98, 'hello']\n",
    "print(lst.index('hello'))  # 如果列表中有相同元素，只返回列表中相同元素的第一个元素的索引\n",
    "# print(list.index('Python'))  # 找不到\n",
    "# 在指定的start和stop之间进行查找\n",
    "# print(lst.index('hello', 1, 3))  # 找不到\n",
    "print(lst.index('hello', 1, 4))\n",
    "print(lst.index('hello', 0, 4))  # 找第一个"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 5. 获取列表中单个元素"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "98\n",
      "hello\n"
     ]
    }
   ],
   "source": [
    "lst = ['hello', 'world', 98, 'hello', 'world', 234]\n",
    "# 获取索引为2的元素（正向索引从0到N-1）\n",
    "print(lst[2])\n",
    "# 获取索引为-3的元素（逆向索引从-N到-1）\n",
    "print(lst[-3])\n",
    "# 获取索引为10的元素（指定索引不存在，抛出异常）\n",
    "# print(lst[10])  # IndexError: list index out of range"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 6. 获取列表中多个元素"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "原列表 1532445706440\n",
      "切的片段： 1532445697544\n",
      "[20, 30, 40, 50, 60]\n",
      "[20, 30, 40, 50, 60]\n",
      "[20, 40, 60]\n",
      "[10, 30, 50]\n",
      "[20, 40, 60, 80]\n",
      "[80, 70, 60, 50, 40, 30, 20, 10]\n",
      "[80, 70, 60, 50, 40, 30, 20, 10]\n",
      "[70, 50, 30]\n"
     ]
    }
   ],
   "source": [
    "# 切片操作\n",
    "lst = [10, 20, 30, 40, 50, 60, 70, 80]\n",
    "# start=1,stop=6,step=1\n",
    "# print(lst[1:6:1])\n",
    "print('原列表', id(lst))\n",
    "lst2 = lst[1:6:1]\n",
    "print('切的片段：', id(lst2))\n",
    "print(lst[1:6])  # 默认步长为1\n",
    "print(lst[1:6:])  # 默认步长为1\n",
    "# start=1,stop=6,step=2\n",
    "print(lst[1:6:2])\n",
    "# stop=6,step=2,start采用默认,0\n",
    "print(lst[:6:2])\n",
    "# start=1,step=2,stop采用默认，最后一个元素N-1\n",
    "print(lst[1::2])\n",
    "\n",
    "# step为负数\n",
    "print(lst[::-1])\n",
    "# start=7,stop省略,step=-1\n",
    "print(lst[7::-1])\n",
    "# start=6,stop=0,step=-2\n",
    "print(lst[6:0:-2])\n",
    "# stop，start不能是负数"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 7. 列表元素判断及遍历"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "True\n",
      "True\n",
      "True\n",
      "False\n",
      "False\n",
      "True\n",
      "10\n",
      "20\n",
      "python\n",
      "hello\n"
     ]
    }
   ],
   "source": [
    "print('p' in 'python')\n",
    "print('k' not in 'python')\n",
    "\n",
    "lst = [10, 20, 'python', 'hello']\n",
    "# 判断\n",
    "print(10 in lst)\n",
    "print(100 in lst)\n",
    "print(10 not in lst)\n",
    "print(100 not in lst)\n",
    "# 遍历\n",
    "for item in lst:\n",
    "    print(item)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 8. 列表元素添加"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[10, 20, 30, 100]\n",
      "[10, 20, 30, 100, 'hello', 'world']\n",
      "[10, 90, 20, 30, 100, 'hello', 'world']\n",
      "[10, True, False, 'hello']\n"
     ]
    }
   ],
   "source": [
    "# 向列表末尾添加一个元素，标识相同，同一个列表对象\n",
    "lst = [10, 20, 30]\n",
    "lst.append(100)\n",
    "print(lst)\n",
    "\n",
    "# 列表末尾至少添加一个元素\n",
    "lst2 = ['hello', 'world']\n",
    "# lst.append(lst2)   # lst2作为一个元素放入lst末尾\n",
    "lst.extend(lst2)  # 添加lst2每个元素分别添加到lst末尾\n",
    "print(lst)\n",
    "\n",
    "# 列表的任意位置添加一个元素\n",
    "lst.insert(1, 90)\n",
    "print(lst)\n",
    "\n",
    "# 列表的任意位置添加至少一个元素（切片，切掉的位置用新的list代替）\n",
    "lst3 = [True, False, 'hello']\n",
    "lst[1:] = lst3\n",
    "print(lst)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 9. 列表元素删除"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[10, 20, 40, 50, 60, 30]\n",
      "[10, 40, 50, 60, 30]\n",
      "[10, 40, 50, 60]\n",
      "原列表 [10, 40, 50, 60]\n",
      "切片后的列表 [40, 50]\n",
      "[10, 60]\n",
      "[]\n"
     ]
    }
   ],
   "source": [
    "lst = [10, 20, 30, 40, 50, 60, 30]\n",
    "lst.remove(30)  # 从列表中溢出一个元素，如果有重复元素只移除第一个元素\n",
    "print(lst)\n",
    "# lst.remove(100)  # ValueError: list.remove(x): x not in list\n",
    "\n",
    "# pop()根据索引移除元素\n",
    "lst.pop(1)\n",
    "print(lst)\n",
    "# lst.pop(5)  # IndexError: pop index out of range 指定的索引位置不存在，抛出异常\n",
    "lst.pop()  # 不写参数，默认删除最后一个元素\n",
    "print(lst)\n",
    "\n",
    "# 切片操作，删除至少一个元素，将产生一个新的列表对象\n",
    "new_lst = lst[1:3]\n",
    "print('原列表', lst)\n",
    "print('切片后的列表', new_lst)\n",
    "\n",
    "# 不产生新的列表对象，而是删除原列表中的内容（用空列表进行替代）\n",
    "lst[1:3] = []\n",
    "print(lst)\n",
    "\n",
    "# clear()清空列表  元素\n",
    "lst.clear()\n",
    "print(lst)  # []\n",
    "\n",
    "# del删除列表  对象\n",
    "del lst\n",
    "# print(lst)  # NameError: name 'lst' is not defined"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 10. 列表元素修改"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[10, 20, 100, 40]\n",
      "[10, 300, 400, 500, 600, 40]\n"
     ]
    }
   ],
   "source": [
    "lst = [10, 20, 30, 40]\n",
    "# 一次修改一个值\n",
    "lst[2] = 100\n",
    "print(lst)\n",
    "\n",
    "# 切片操作\n",
    "lst[1:3] = [300, 400, 500, 600]\n",
    "print(lst)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 11. 列表元素排序"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "排序前的列表 [20, 40, 10, 98, 54] 1532445713608\n",
      "排序后的列表 [10, 20, 40, 54, 98] 1532445713608\n",
      "[98, 54, 40, 20, 10]\n",
      "[10, 20, 40, 54, 98]\n",
      "排序前的列表 [20, 40, 10, 98, 54]\n",
      "[10, 20, 40, 54, 98]\n",
      "[98, 54, 40, 20, 10]\n"
     ]
    }
   ],
   "source": [
    "lst = [20, 40, 10, 98, 54]\n",
    "print('排序前的列表', lst, id(lst))\n",
    "# 开始排序，调用列表对象的sort方法，升序排序\n",
    "lst.sort()\n",
    "print('排序后的列表', lst, id(lst))  # 标识未更改，在原列表上进行的排序\n",
    "\n",
    "# 通过指定关键字参数，将列表中的元素进行降序排序\n",
    "# reverse=True 表示降序排序\n",
    "lst.sort(reverse=True)\n",
    "print(lst)\n",
    "# reverse=False 表示降序排序\n",
    "lst.sort(reverse=False)\n",
    "print(lst)\n",
    "\n",
    "# 使用内置函数sorted()对列表进行排序，将产生一个新的列表对象，原列表不发生改变\n",
    "lst = [20, 40, 10, 98, 54]\n",
    "print('排序前的列表', lst)\n",
    "# 开始排序\n",
    "new_lst = sorted(lst)  # 产生新的列表对象\n",
    "print(new_lst)\n",
    "# 指定关键字参数，实现列表元素降序排序\n",
    "desc_lst = sorted(lst, reverse=True)\n",
    "print(desc_lst)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 12. 列表生成式"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[1, 2, 3, 4, 5, 6, 7, 8, 9]\n",
      "[1, 4, 9, 16, 25, 36, 49, 64, 81]\n",
      "[2, 4, 6, 8, 10]\n"
     ]
    }
   ],
   "source": [
    "# 使用列表生成式要求列表中的元素都有一定的规则\n",
    "lst = [i for i in range(1, 10)]\n",
    "print(lst)\n",
    "lst1 = [i*i for i in range(1, 10)]\n",
    "print(lst1)\n",
    "\n",
    "# 要求：列表中的元素的值为2,4,6,8,10\n",
    "lst2 = [i*2 for i in range(1, 6)]\n",
    "print(lst2)"
   ]
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Python 3.6.3",
   "language": "python",
   "name": "python3.6.3"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 3
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython3",
   "version": "3.6.3"
  },
  "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": "480px"
   },
   "toc_section_display": true,
   "toc_window_display": true
  }
 },
 "nbformat": 4,
 "nbformat_minor": 4
}