machinelearning_notebook/0_python/7_Class.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 1. 类"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python中的变量、列表、字典等其实都是对象。不涉及面向对象编程的理论部分，在本教程中对概念进行解释。"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "类声明如下"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "class class_name:\n",
    "\n",
    "    Functions"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "class FirstClass:\n",
    "    pass\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**pass** 在python中意味着什么都不做。 "
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "上面声明了一个名为“FirstClass”的类对象，现在考虑一个具有“FirstClass”所有特征的“egclass”。所以你所要做的就是，将“egclass”等同于“FirstClass”。在python术语中，这称为创建实例。“egclass”是“FirstClass”的实例"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [],
   "source": [
    "egclass = FirstClass()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "__main__.FirstClass"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "type(egclass)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "type"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "type(FirstClass)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "现在让我们向类中添加一些“功能”。这样我们的FirstClass就有了更好的定义。类内的函数被称为该类的“方法”"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "大多数类都有一个名为`__init__`的函数。这些被称为魔术方法。在这个方法中，你基本上初始化了这个类的变量，或者任何适用于这个方法中指定的所有方法的初始化算法。类中的变量称为属性。"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "这有助于简化实例的初始化过程。例如,\n",
    "\n",
    "在不使用魔法方法或被成为构造函数的`__init__`的情况下，我们必须定义一个**init()** 方法并调用**init()** 函数。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "ename": "AttributeError",
     "evalue": "'FirstClass' object has no attribute 'init'",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-8-d15e7b8e3d78>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0meg0\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mFirstClass\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0meg0\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0minit\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;31mAttributeError\u001b[0m: 'FirstClass' object has no attribute 'init'"
     ]
    }
   ],
   "source": [
    "eg0 = FirstClass()\n",
    "eg0.init()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "但是当构造函数被定义后，`__init__`被调用，这样初始化实例被创建。"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "我们构造我们的`FirstClass`去接受两个变量名称和符号。\n",
    "\n",
    "我将会在稍后解释`self`。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [],
   "source": [
    "class FirstClass:\n",
    "    \"\"\"My first class\"\"\"\n",
    "    def __init__(self,name,symbol):\n",
    "        self.name = name\n",
    "        self.symbol = symbol"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "现在我们已经定义了一个函数而且添加了`__init__`方法。我们可以创建一个名为FirstClass的实例，该实例现在接受两个参数。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {},
   "outputs": [],
   "source": [
    "eg1 = FirstClass('one',1)\n",
    "eg2 = FirstClass('two',2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "onex 11\n",
      "two 2\n",
      "My first class\n"
     ]
    }
   ],
   "source": [
    "print(eg1.name, eg1.symbol)\n",
    "print(eg2.name, eg2.symbol)\n",
    "print(eg1.__doc__)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**dir( )** 函数在查看类包含什么以及它提供了什么方法时非常方便。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {
    "scrolled": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['__class__',\n",
       " '__delattr__',\n",
       " '__dict__',\n",
       " '__dir__',\n",
       " '__doc__',\n",
       " '__eq__',\n",
       " '__format__',\n",
       " '__ge__',\n",
       " '__getattribute__',\n",
       " '__gt__',\n",
       " '__hash__',\n",
       " '__init__',\n",
       " '__le__',\n",
       " '__lt__',\n",
       " '__module__',\n",
       " '__ne__',\n",
       " '__new__',\n",
       " '__reduce__',\n",
       " '__reduce_ex__',\n",
       " '__repr__',\n",
       " '__setattr__',\n",
       " '__sizeof__',\n",
       " '__str__',\n",
       " '__subclasshook__',\n",
       " '__weakref__']"
      ]
     },
     "execution_count": 16,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dir(FirstClass)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 24,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'My first class'"
      ]
     },
     "execution_count": 24,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "FirstClass.__doc__"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "实例的**dir()** 也显示了它定义的属性。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['__class__',\n",
       " '__delattr__',\n",
       " '__dict__',\n",
       " '__dir__',\n",
       " '__doc__',\n",
       " '__eq__',\n",
       " '__format__',\n",
       " '__ge__',\n",
       " '__getattribute__',\n",
       " '__gt__',\n",
       " '__hash__',\n",
       " '__init__',\n",
       " '__le__',\n",
       " '__lt__',\n",
       " '__module__',\n",
       " '__ne__',\n",
       " '__new__',\n",
       " '__reduce__',\n",
       " '__reduce_ex__',\n",
       " '__repr__',\n",
       " '__setattr__',\n",
       " '__sizeof__',\n",
       " '__str__',\n",
       " '__subclasshook__',\n",
       " '__weakref__',\n",
       " 'name',\n",
       " 'symbol']"
      ]
     },
     "execution_count": 25,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dir(eg1)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "稍微改变一下FirstClass函数，"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {},
   "outputs": [],
   "source": [
    "class FirstClass:\n",
    "    def __init__(self,name,symbol):\n",
    "        self.n = name\n",
    "        self.s = symbol"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "将self.name和self.symbol转化成self.n和self.s会得到："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "metadata": {},
   "outputs": [],
   "source": [
    "eg1 = FirstClass('one',1)\n",
    "eg2 = FirstClass('two',2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "metadata": {},
   "outputs": [
    {
     "ename": "AttributeError",
     "evalue": "'FirstClass' object has no attribute 'name'",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-23-4ab7dec1c737>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0meg1\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mname\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0meg1\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0msymbol\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      2\u001b[0m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0meg2\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mname\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0meg2\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0msymbol\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
      "\u001b[0;31mAttributeError\u001b[0m: 'FirstClass' object has no attribute 'name'"
     ]
    }
   ],
   "source": [
    "print(eg1.name, eg1.symbol)\n",
    "print(eg2.name, eg2.symbol)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "AttributeError, 还记得变量就是类中的属性吗?因此，这意味着我们没有为实例提供正确的属性。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 24,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['__class__',\n",
       " '__delattr__',\n",
       " '__dict__',\n",
       " '__dir__',\n",
       " '__doc__',\n",
       " '__eq__',\n",
       " '__format__',\n",
       " '__ge__',\n",
       " '__getattribute__',\n",
       " '__gt__',\n",
       " '__hash__',\n",
       " '__init__',\n",
       " '__le__',\n",
       " '__lt__',\n",
       " '__module__',\n",
       " '__ne__',\n",
       " '__new__',\n",
       " '__reduce__',\n",
       " '__reduce_ex__',\n",
       " '__repr__',\n",
       " '__setattr__',\n",
       " '__sizeof__',\n",
       " '__str__',\n",
       " '__subclasshook__',\n",
       " '__weakref__',\n",
       " 'n',\n",
       " 's']"
      ]
     },
     "execution_count": 24,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dir(eg1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "one 1\n",
      "two 2\n"
     ]
    }
   ],
   "source": [
    "print(eg1.n, eg1.s)\n",
    "print(eg2.n, eg2.s)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "现在我们解决了这个错误。现在让我们比较一下我们看到的两个例子。\n",
    "\n",
    "当我声明self.name和self.symbol时，使用eg1.name和eg1.symbol没有属性错误。当我声明self.n和self.s时，使用eg1.n和eg1.s没有属性错误。\n",
    "\n",
    "从以上我们可以得出self就是实例本身。\n",
    "\n",
    "记住，self不是预定义的，它是用户定义的。你可以利用任何你觉得舒服的东西。但是使用self已经成为一种常见的做法。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "class FirstClass:\n",
    "    def __init__(asdf1234,name,symbol):\n",
    "        asdf1234.n = name\n",
    "        asdf1234.s = symbol"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "eg1 = FirstClass('one',1)\n",
    "eg2 = FirstClass('two',2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "one 1\n",
      "two 2\n"
     ]
    }
   ],
   "source": [
    "print(eg1.n, eg1.s)\n",
    "print(eg2.n, eg2.s)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "因为eg1和eg2是FirstClass的实例，所以它不需要被限制在FirstClass本身。它可以通过声明其他属性来扩展自己，而不需要在FirstClass中声明属性。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "metadata": {},
   "outputs": [],
   "source": [
    "eg1.cube = 1\n",
    "eg2.cube = 8"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 26,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['__class__',\n",
       " '__delattr__',\n",
       " '__dict__',\n",
       " '__dir__',\n",
       " '__doc__',\n",
       " '__eq__',\n",
       " '__format__',\n",
       " '__ge__',\n",
       " '__getattribute__',\n",
       " '__gt__',\n",
       " '__hash__',\n",
       " '__init__',\n",
       " '__le__',\n",
       " '__lt__',\n",
       " '__module__',\n",
       " '__ne__',\n",
       " '__new__',\n",
       " '__reduce__',\n",
       " '__reduce_ex__',\n",
       " '__repr__',\n",
       " '__setattr__',\n",
       " '__sizeof__',\n",
       " '__str__',\n",
       " '__subclasshook__',\n",
       " '__weakref__',\n",
       " 'cube',\n",
       " 'n',\n",
       " 's']"
      ]
     },
     "execution_count": 26,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dir(eg1)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "collapsed": true
   },
   "source": [
    "就像我们前面看到的全局变量和局部变量一样，即使类也有自己的变量类型。\n",
    "\n",
    "**类属性**:在方法外部定义的属性，适用于所有实例。\n",
    "\n",
    "**实例属性**:在方法内部定义的属性，只适用于该方法，并且对每个实例都是唯一的。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 27,
   "metadata": {},
   "outputs": [],
   "source": [
    "class FirstClass:\n",
    "    test = 'test'\n",
    "    def __init__(self,name,symbol):\n",
    "        self.name = name\n",
    "        self.symbol = symbol"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "这里test是一个类属性，而name是一个实例属性。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 28,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "test4\n"
     ]
    }
   ],
   "source": [
    "eg3 = FirstClass('Three',3)\n",
    "eg4 = FirstClass('Four', 4)\n",
    "eg4.test = 'test4'\n",
    "print(eg4.test)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 30,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "test Three\n"
     ]
    }
   ],
   "source": [
    "print(eg3.test, eg3.name)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "让我们添加更多的方法到FirstClass。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 34,
   "metadata": {},
   "outputs": [],
   "source": [
    "class FirstClass:\n",
    "    def __init__(self,name,symbol):\n",
    "        self.name = name\n",
    "        self.symbol = symbol\n",
    "    def square(self):\n",
    "        return self.symbol * self.symbol\n",
    "    def cube(self):\n",
    "        return self.symbol * self.symbol * self.symbol\n",
    "    def multiply(self, x):\n",
    "        return self.symbol * x"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 35,
   "metadata": {},
   "outputs": [],
   "source": [
    "eg4 = FirstClass('Five',5)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 37,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "25\n",
      "125\n"
     ]
    }
   ],
   "source": [
    "print(eg4.square())\n",
    "print(eg4.cube())"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 27,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "10"
      ]
     },
     "execution_count": 27,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "eg4.multiply(2)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "以上也可以写成："
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "ename": "AttributeError",
     "evalue": "type object 'FirstClass' has no attribute 'multiply'",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-5-448ee6ad2a26>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mFirstClass\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mmultiply\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0meg4\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;36m2\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;31mAttributeError\u001b[0m: type object 'FirstClass' has no attribute 'multiply'"
     ]
    }
   ],
   "source": [
    "FirstClass.multiply(eg4,2)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 2. 继承"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "在某些情况下，新类需要具有已定义类的所有特征。因此，新类可以“继承”前一个类，并向其添加自己的方法，这称为继承。"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "考虑类Person类具有薪水的方法。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [],
   "source": [
    "class Person:\n",
    "    def __init__(self,name,age):\n",
    "        self.name = name\n",
    "        self.age = age\n",
    "    def salary(self, value):\n",
    "        self.money = value\n",
    "        print(self.name,\"earns\",self.money)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [],
   "source": [
    "a = Person('Kartik',26)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Kartik earns 40000\n"
     ]
    }
   ],
   "source": [
    "a.salary(40000)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['__class__',\n",
       " '__delattr__',\n",
       " '__dict__',\n",
       " '__dir__',\n",
       " '__doc__',\n",
       " '__eq__',\n",
       " '__format__',\n",
       " '__ge__',\n",
       " '__getattribute__',\n",
       " '__gt__',\n",
       " '__hash__',\n",
       " '__init__',\n",
       " '__init_subclass__',\n",
       " '__le__',\n",
       " '__lt__',\n",
       " '__module__',\n",
       " '__ne__',\n",
       " '__new__',\n",
       " '__reduce__',\n",
       " '__reduce_ex__',\n",
       " '__repr__',\n",
       " '__setattr__',\n",
       " '__sizeof__',\n",
       " '__str__',\n",
       " '__subclasshook__',\n",
       " '__weakref__',\n",
       " 'salary']"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dir(Person)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "现在考虑另一个Artist类，告诉我们艺术家挣的钱的数量和他的艺术形式。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 42,
   "metadata": {},
   "outputs": [],
   "source": [
    "class Artist:\n",
    "    def __init__(self,name,age):\n",
    "        self.name = name\n",
    "        self.age = age\n",
    "    def salary(self,value):\n",
    "        self.money = value\n",
    "        print(self.name,\"earns\",self.money)\n",
    "    def artform(self, job):\n",
    "        self.job = job\n",
    "        print(self.name,\"is a\", self.job)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 43,
   "metadata": {},
   "outputs": [],
   "source": [
    "b = Artist('Nitin',20)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 44,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Nitin earns 50000\n",
      "Nitin is a Musician\n"
     ]
    }
   ],
   "source": [
    "b.salary(50000)\n",
    "b.artform('Musician')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 45,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['__class__',\n",
       " '__delattr__',\n",
       " '__dict__',\n",
       " '__dir__',\n",
       " '__doc__',\n",
       " '__eq__',\n",
       " '__format__',\n",
       " '__ge__',\n",
       " '__getattribute__',\n",
       " '__gt__',\n",
       " '__hash__',\n",
       " '__init__',\n",
       " '__le__',\n",
       " '__lt__',\n",
       " '__module__',\n",
       " '__ne__',\n",
       " '__new__',\n",
       " '__reduce__',\n",
       " '__reduce_ex__',\n",
       " '__repr__',\n",
       " '__setattr__',\n",
       " '__sizeof__',\n",
       " '__str__',\n",
       " '__subclasshook__',\n",
       " '__weakref__',\n",
       " 'artform',\n",
       " 'money']"
      ]
     },
     "execution_count": 45,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dir(Artist)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "money 方法和salary 方法是一样的。因此，我们可以将该方法推广到工资类，并将软件工程师类继承到美术师类。现在艺术类变成了，"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [],
   "source": [
    "class Artist(Person):\n",
    "    def artform(self, job):\n",
    "        self.job = job\n",
    "        print(self.name,\"is a\", self.job)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [],
   "source": [
    "c = Artist('Nishanth',21)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 48,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "['__class__',\n",
       " '__delattr__',\n",
       " '__dict__',\n",
       " '__dir__',\n",
       " '__doc__',\n",
       " '__eq__',\n",
       " '__format__',\n",
       " '__ge__',\n",
       " '__getattribute__',\n",
       " '__gt__',\n",
       " '__hash__',\n",
       " '__init__',\n",
       " '__le__',\n",
       " '__lt__',\n",
       " '__module__',\n",
       " '__ne__',\n",
       " '__new__',\n",
       " '__reduce__',\n",
       " '__reduce_ex__',\n",
       " '__repr__',\n",
       " '__setattr__',\n",
       " '__sizeof__',\n",
       " '__str__',\n",
       " '__subclasshook__',\n",
       " '__weakref__',\n",
       " 'artform',\n",
       " 'salary']"
      ]
     },
     "execution_count": 48,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dir(Artist)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Nishanth earns 60000\n",
      "Nishanth is a Dancer\n"
     ]
    }
   ],
   "source": [
    "c.salary(60000)\n",
    "c.artform('Dancer')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "假设在继承一个特定方法的时候，该方法不适合新类。可以通过在新类中用相同的名称再次定义该方法来重写该方法。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [],
   "source": [
    "class Artist(Person):\n",
    "    def artform(self, job):\n",
    "        self.job = job\n",
    "        print(self.name,\"is a\", self.job)\n",
    "    def salary(self, value):\n",
    "        self.money = value\n",
    "        print(self.name,\"earns\",self.money)\n",
    "        print(\"I am overriding the SoftwareEngineer class's salary method\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 51,
   "metadata": {},
   "outputs": [],
   "source": [
    "c = Artist('Nishanth',21)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 52,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Nishanth earns 60000\n",
      "I am overriding the SoftwareEngineer class's salary method\n",
      "Nishanth is a Dancer\n"
     ]
    }
   ],
   "source": [
    "c.salary(60000)\n",
    "c.artform('Dancer')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "如果不确定方法将被调用多少次，那么就很难声明那么多变量来携带每个结果，因此最好声明一个列表并附加结果。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [],
   "source": [
    "class EmptyList:\n",
    "    def __init__(self):\n",
    "        self.data = []\n",
    "    def one(self,x):\n",
    "        self.data.append(x)\n",
    "    def two(self, x ):\n",
    "        self.data.append(x**2)\n",
    "    def three(self, x):\n",
    "        self.data.append(x**3)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [],
   "source": [
    "xc = EmptyList()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[1]\n"
     ]
    }
   ],
   "source": [
    "xc.one(1)\n",
    "print(xc.data)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "因为xc.data是一个列表，直接的列表操作也是可以进行的。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 60,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[1, 8]\n"
     ]
    }
   ],
   "source": [
    "xc.data.append(8)\n",
    "print(xc.data)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 61,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[1, 8, 9]\n"
     ]
    }
   ],
   "source": [
    "xc.two(3)\n",
    "print(xc.data)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "如果输入参数的数量因实例而异，则可以使用星号。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 62,
   "metadata": {},
   "outputs": [],
   "source": [
    "class NotSure:\n",
    "    def __init__(self, *args):\n",
    "        self.data = ''.join(list(args)) "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 63,
   "metadata": {},
   "outputs": [],
   "source": [
    "yz = NotSure('I', 'Do' , 'Not', 'Know', 'What', 'To','Type')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 64,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'IDoNotKnowWhatToType'"
      ]
     },
     "execution_count": 64,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "yz.data"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 3. 接下来应该怎么做"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "单独练习可以帮助你掌握python的窍门。给自己一个问题陈述并解决它们。您还可以在任何竞争的编码平台上提交问题求解。你编写的代码越多，你发现的越多，你就越开始欣赏这门语言。\n",
    "\n",
    "现在已经向您介绍了python，您可以尝试您感兴趣的领域中的不同python库。我强烈建议您查看这个Python框架、库和软件列表http://awesome-python.com\n",
    "\n",
    "\n",
    "python官方文档: https://docs.python.org/3/\n",
    "\n",
    "Pyton 教程:\n",
    "* [Python tutorial (廖雪峰）](https://www.liaoxuefeng.com/wiki/1016959663602400)\n",
    "* [Python基础教程](https://www.runoob.com/python/python-tutorial.html)\n",
    "* [Python官方教程（中文版)](https://docs.python.org/zh-cn/3/tutorial/index.html)\n",
    "\n",
    "你也可以参考一些Python的练习程序，是由 Kartik Kannapur所写的。 Github Repo : https://github.com/rajathkumarmp/Python-Lectures \n",
    "\n",
    "\n",
    "享受解决问题陈述，因为生命短暂，你需要python!"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
 ],
 "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": "3.6.9"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 1
}