{
"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": []
}
],
"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": "3.9.10"
}
},
"nbformat": 4,
"nbformat_minor": 5
}