machinelearning_notebook/0_python/4_Data_Structure_2.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 1. 字符串"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "字符串是基于文本的有序数据，用单/双/三重引号括起来表示。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "10\n"
     ]
    }
   ],
   "source": [
    "String0 = 'Taj Mahal is beautiful'\n",
    "String1 = \"Taj Mahal is beautiful\"\n",
    "String2 = '''Taj Mahal\n",
    "is\n",
    "beautiful'''"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Taj Mahal is beautiful <class 'str'>\n",
      "Taj Mahal is beautiful <class 'str'>\n",
      "Taj Mahal\n",
      "is\n",
      "beautiful <class 'str'>\n"
     ]
    }
   ],
   "source": [
    "print(String0, type(String0))\n",
    "print(String1, type(String1))\n",
    "print(String2, type(String2))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "字符串索引和分段类似于前面详细解释过的列表。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "M\n",
      "Mahal is beautiful\n"
     ]
    }
   ],
   "source": [
    "print(String0[4])\n",
    "print(String0[4:])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 1.1 内置函数"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**find( )** 函数返回要在字符串中找到的给定数据的索引值。如果没有找到它，它返回 **-1**。记住不要将返回的-1与反向索引值混淆。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "7\n",
      "-1\n"
     ]
    }
   ],
   "source": [
    "print(String0.find('al'))\n",
    "print(String0.find('am'))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "返回的索引值是输入数据中第一个元素的索引。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "a\n"
     ]
    }
   ],
   "source": [
    "print(String0[7])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "还可以输入**find()** 函数，在它们之间搜索索引值。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "2\n",
      "2\n"
     ]
    }
   ],
   "source": [
    "print(String0.find('j',1))\n",
    "print(String0.find('j',1,3))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**capitalize( )** 用于将字符串中的第一个元素大写。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Observe the first letter in this sentence. can you change this sentence\n"
     ]
    }
   ],
   "source": [
    "String3 = 'observe the first letter in this sentence. can you change this sentence'\n",
    "print(String3.capitalize())"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**center( )** 用于通过指定字段宽度将字符串居中对齐。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'                        Taj Mahal is beautiful                        '"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "String0.center(70)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "One can also fill the left out spaces with any other character."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'------------------------Taj Mahal is beautiful------------------------'"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "String0.center(70,'-')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**zfill( )** 通过指定字段宽度来填充零。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'00000000Taj Mahal is beautiful'"
      ]
     },
     "execution_count": 12,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "String0.zfill(30)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**expandtabs( )** 允许您更改制表符的间距。'\\t'默认设置为8个空格。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "h\te\tl\tl\to\n",
      "h e l l o\n",
      "h       e       l       l       o\n"
     ]
    }
   ],
   "source": [
    "s = 'h\\te\\tl\\tl\\to'\n",
    "print(s)\n",
    "print(s.expandtabs(1))\n",
    "print(s.expandtabs())"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "collapsed": true
   },
   "source": [
    "**index( )** 和 **find( )** 函数的工作方式相同，唯一的区别在于 **find( )** 返回'-1'，当输入元素在字符串中没有找到，但是**index( )** 函数会抛出一个ValueError。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0\n",
      "4\n"
     ]
    },
    {
     "ename": "ValueError",
     "evalue": "substring not found",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mValueError\u001b[0m                                Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-14-a7d6b97b4839>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mString0\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mindex\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'Taj'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      2\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mString0\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mindex\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'Mahal'\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;36m0\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 3\u001b[0;31m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mString0\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mindex\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'Mahal'\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;36m10\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;36m20\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;31mValueError\u001b[0m: substring not found"
     ]
    }
   ],
   "source": [
    "print(String0.index('Taj'))\n",
    "print(String0.index('Mahal',0))\n",
    "print(String0.index('Mahal',10,20))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**endswith( )** 函数用于检查给定字符串是否以作为输入的特定字符结尾。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "False\n"
     ]
    }
   ],
   "source": [
    "print(String0.endswith('y'))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "还可以指定开始和停止索引值。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "True\n",
      "True\n"
     ]
    }
   ],
   "source": [
    "print(String0.endswith('l',0))\n",
    "print(String0.endswith('M',0,5))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**count( )** 函数计算给定字符串中的字符数。也可以指定开始和停止索引或将其留空。(这些是隐式参数，将在函数中处理)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "4\n",
      "2\n"
     ]
    }
   ],
   "source": [
    "print(String0.count('a',0))\n",
    "print(String0.count('a',5,10))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**join( )** 函数在输入字符串的元素之间添加一个字符。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'*a_a-'"
      ]
     },
     "execution_count": 16,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "'a'.join('*_-')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'1\\n2'"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "'\\n'.join(['1', '2'])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "'*_-' 是输入字符串而字符'a'被添加在每一个元素之间。"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**join( )** 函数也可以被用来将列表转化为字符串。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "['T', 'a', 'j', ' ', 'M', 'a', 'h', 'a', 'l', ' ', 'i', 's', ' ', 'b', 'e', 'a', 'u', 't', 'i', 'f', 'u', 'l']\n",
      "Taj Mahal is beautiful\n"
     ]
    }
   ],
   "source": [
    "a = list(String0)\n",
    "print(a)\n",
    "b = ''.join(a)\n",
    "print(b)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "在将它转化成字符串之前，**join( )** 函数可以被用来在列表元素中插入任意的字符。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      " /i/s/ /b/e/a/u/t/i/f/u/l\n"
     ]
    }
   ],
   "source": [
    "c = '/'.join(a)[18:]\n",
    "print(c)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**split( )** 函数被用来将一个字符串转化为列表。把它想成与**join()** 相反地函数。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[' ', 'i', 's', ' ', 'b', 'e', 'a', 'u', 't', 'i', 'f', 'u', 'l']\n"
     ]
    }
   ],
   "source": [
    "d = c.split('/')\n",
    "print(d)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "在 **split( )** 函数中，还可以指定分割字符串的次数，或者新返回列表应该包含的元素数量。元素的数量总是比指定的数量多1，这是因为它被分割了指定的次数。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[' ', 'i', 's', ' /b/e/a/u/t/i/f/u/l']\n",
      "4\n"
     ]
    }
   ],
   "source": [
    "e = c.split('/',3)\n",
    "print(e)\n",
    "print(len(e))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**lower( )** 将任何大写字母转换为小写字母。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Taj Mahal is beautiful\n",
      "taj mahal is beautiful\n"
     ]
    }
   ],
   "source": [
    "print(String0)\n",
    "print(String0.lower())"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**upper( )** 将任何小写字母转换为大写字母。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'TAJ MAHAL IS BEAUTIFUL'"
      ]
     },
     "execution_count": 12,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "String0.upper()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**replace( )** 函数将该元素替换为另一个元素。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'Bengaluru is beautiful'"
      ]
     },
     "execution_count": 22,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "String0.replace('Taj Mahal','Bengaluru')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**strip( )** 函数用于从右端和左端删除不需要的元素。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [],
   "source": [
    "f = '    hello      '"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "如果没有指定字符，那么它将删除数据左边和右边的所有空格。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'hello'"
      ]
     },
     "execution_count": 17,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "f.strip()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**strip( )** 函数，当指定字符时，如果该字符出现在指定字符串的两端，则删除该字符。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "metadata": {},
   "outputs": [],
   "source": [
    "f = '   ***----hello---*******     '"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'   ***----hello---*******     '"
      ]
     },
     "execution_count": 21,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "f.strip('*')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "必须删除星号，但没有。这是因为在左边和右边都有一个空格。在strip函数中。字符需要按照它们出现的特定顺序输入。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "----hello---\n",
      "hello\n"
     ]
    }
   ],
   "source": [
    "print(f.strip(' *'))\n",
    "print(f.strip(' *-'))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**lstrip( )** 和 **rstrip( )** 函数具有与strip函数相同的功能，但唯一的区别是**lstrip()** 只删除左边的内容，而**rstrip()** 只删除右边的内容。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 28,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "----hello---*******     \n",
      "   ***----hello---\n"
     ]
    }
   ],
   "source": [
    "print(f.lstrip(' *'))\n",
    "print(f.rstrip(' *'))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 2. 词典"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "字典更像数据库，因为在这里您可以用用户定义的字符串索引特定的序列。"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "为了定义一个词典，让一个变量和{ }或dict()相等。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 24,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<class 'dict'> <class 'dict'>\n"
     ]
    }
   ],
   "source": [
    "d0 = {}\n",
    "d1 = dict()\n",
    "print(type(d0), type(d1))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "词典的工作方式有点像列表，但增加了分配自己索引样式的功能。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{'OneTwo': 12, 'One': 1}\n"
     ]
    }
   ],
   "source": [
    "d0['One'] = 1\n",
    "d0['OneTwo'] = 12 \n",
    "print(d0)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 26,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{'key2': [1, 2, 4], 'key1': 1, 3: (1, 4, 6)}\n"
     ]
    }
   ],
   "source": [
    "d1 = {\"key1\":1, \"key2\":[1,2,4], 3:(1, 4, 6)}\n",
    "print(d1)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "这就是字典的样子。现在你可以通过设为'One'的索引值来访问'1'了"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 27,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "1\n"
     ]
    }
   ],
   "source": [
    "print(d0['One'])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "两个相关的列表可以合并成一个字典。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "names = ['One', 'Two', 'Three', 'Four', 'Five']\n",
    "numbers = [1, 2, 3, 4, 5]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**zip( )** 函数用来结合两个列表。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{'One': 1, 'Four': 4, 'Three': 3, 'Five': 5, 'Two': 2}\n"
     ]
    }
   ],
   "source": [
    "d2 = zip(names,numbers)\n",
    "print(dict(d2))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "这两个列表组合成一个列表，每个元素都与元组中来自另一个列表的各自元素相连。元组，因为它是被分配的，而且值不应该改变。\n",
    "\n",
    "进一步地，为了将上面的内容转化为词典。我们可以使用 **dict( )** 函数。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{'One': 1, 'Four': 4, 'Three': 3, 'Five': 5, 'Two': 2}\n"
     ]
    }
   ],
   "source": [
    "d2 = zip(names,numbers)\n",
    "\n",
    "a1 = dict(d2)\n",
    "print(a1)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 2.1 内置函数"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**clear( )** 函数被用于擦除所创建的整个数据库。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{}\n"
     ]
    }
   ],
   "source": [
    "a1.clear()\n",
    "print(a1)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "字典也可以使用循环来构建。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{'One': 1, 'Four': 4, 'Three': 3, 'Five': 5, 'Two': 2}\n"
     ]
    }
   ],
   "source": [
    "a1 = {names[i]:numbers[i] for i in range(len(names))}\n",
    "print(a1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{'One': 1, 'Four': 4, 'Three': 3, 'Five': 5, 'Two': 2}\n"
     ]
    }
   ],
   "source": [
    "for i in range(len(names)):\n",
    "    a1[names[i]] = numbers[i]\n",
    "print(a1)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**values( )** 函数返回了一个包含字典中所有赋值的列表"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "dict_values([1, 4, 3, 5, 2])"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a1.values()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**keys( )** 函数返回包含赋值的所有索引或键。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "dict_keys(['One', 'Four', 'Three', 'Five', 'Two'])"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a1.keys()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**items()** 返回一个列表同时也包含该列表，但是字典中的每个元素都在一个元组中。这与使用zip函数得到的结果相同。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[   One] 1\n",
      "[  Four] 4\n",
      "[ Three] 3\n",
      "[  Five] 5\n",
      "[   Two] 2\n"
     ]
    }
   ],
   "source": [
    "a1.items()\n",
    "\n",
    "for (k,v) in a1.items():\n",
    "    print(\"[%6s] %d\" % (k, v))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**pop()** 函数用于删除特定的元素，并且这个删除的元素可以被分配给一个新的变量。但是请记住，只存储值而不存储键。因为它只是一个索引值。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{'One': 1, 'Three': 3, 'Five': 5, 'Two': 2}\n",
      "4\n"
     ]
    }
   ],
   "source": [
    "a2 = a1.pop('Four')\n",
    "print(a1)\n",
    "print(a2)"
   ]
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Python 3",
   "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": "3.6.8"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 1
}