ch04-Python面向对象编程/04-01面向对象简介.ipynb

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 "cells": [
  {
   "cell_type": "markdown",
   "id": "8a5d82b9",
   "metadata": {},
   "source": [
    "# 面向对象简介\n",
    "\n",
    "对象一般是指一个类的实例，具有相关的成员变量和成员函数，在Python中成员变量叫做属性，成员函数叫做方法。\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "7c2c9e49",
   "metadata": {},
   "source": [
    "## 什么是对象\n",
    "\n",
    "Python中几乎所有的东西都是对象。基本类型是对象，如整数："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "21ffb0a2",
   "metadata": {},
   "outputs": [],
   "source": [
    "a = 10"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "d67f6220",
   "metadata": {},
   "source": [
    "其属性与方法："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "f8d025b8",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "10"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a.real"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "7e227da7",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "10"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a.conjugate()"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "e666906e",
   "metadata": {},
   "source": [
    "对象在内存中有一个地址与之对应，这个地址可以用id()函数查看："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "73e18793",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "4514492720"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "id(len)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "80760e35",
   "metadata": {},
   "source": [
    "同一个对象的内存地址一致："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "6715c20b",
   "metadata": {},
   "outputs": [],
   "source": [
    "b = a"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "id": "b2b0f179",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "id(b) == id(a)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "ea101f3e",
   "metadata": {},
   "source": [
    "id()函数本身也是对象："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "id": "2d4c1062",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "4514488128"
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "id(id)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "8c9a076b",
   "metadata": {},
   "source": [
    "在Python中，只有一些保留的关键字和符号不是对象。"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "31b5ecc1",
   "metadata": {},
   "source": [
    "## 自定义类型\n",
    "\n",
    "基本形式为：\n",
    "```python\n",
    "class ClassName(ParentClass):\n",
    "    \"\"\"class docstring\"\"\"\n",
    "    def some_method(self, ...):\n",
    "        return ...\n",
    "```\n",
    "具体规律为：\n",
    "- class关键字在最开始。\n",
    "- ClassName是自定义类型的名称， Python对类型名称没有规定，流行的做法是用大骆驼拼写法（Upper Camel Case）的记法，即每个单词的首字母大写，中间不留空格。\n",
    "- “()”中的ParentClass用来表示继承关系，可省略，默认为object。\n",
    "- “:”不能缺少，之后的内容要进行缩进。\n",
    "- 三引号包含的部分是类型的文档即docstring，可以省略。\n",
    "- 类型的方法定义与函数定义类似，第一个参数表示是对象本身，通常用self表示。\n",
    "\n",
    "例如："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "id": "2e678cc3",
   "metadata": {},
   "outputs": [],
   "source": [
    "class Leaf(object):\n",
    "    \"\"\"A leaf falling in the woods.\"\"\"\n",
    "    pass"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "8b1b43d9",
   "metadata": {},
   "source": [
    "其中，pass是一个特殊的关键词，用来占位，表示什么都不做。"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "2ae4ea06",
   "metadata": {},
   "source": [
    "新类型Leaf继承了Python中最基本的类型，即object。事实上所有的对象都是object："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "id": "1e0a28eb",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "isinstance(10, object)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "id": "5a775665",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "isinstance([], object)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "31ccd183",
   "metadata": {},
   "source": [
    "三引号的部分是对Leaf类的说明文档，可以调用Leaf的`.__doc__`属性查看："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "id": "11ddc382",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'A leaf falling in the woods.'"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "Leaf.__doc__"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "a32d330c",
   "metadata": {},
   "source": [
    "Leaf对象的产生："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "id": "afb454d1",
   "metadata": {},
   "outputs": [],
   "source": [
    "leaf = Leaf()"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "35b34c33",
   "metadata": {},
   "source": [
    "在Python里，变量是区分大小写的，因此，leaf和Leaf是不同的变量。\n",
    "\n",
    "再次调用生成的对象是不同的："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "id": "01c581c4",
   "metadata": {},
   "outputs": [],
   "source": [
    "leaf2 = Leaf()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "id": "fedbbba1",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "False"
      ]
     },
     "execution_count": 14,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "leaf is leaf2"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "ae2a7981",
   "metadata": {},
   "outputs": [],
   "source": []
  }
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