6. Classes.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "# Classes"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "source": [
    "### A class is a template or blueprint that can be used to create certain objects. The class can for instance define what special properties these objects have and which functions can operate on these objects."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "## Class syntax"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "source": [
    "```\n",
    "class Name_of_class:\n",
    "    \"\"\"Documentation string for this class\"\"\"\n",
    "    <statement-1>\n",
    "    .\n",
    "    .\n",
    "    .\n",
    "    <statement-N>\n",
    "```"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "## Extremely simple class"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 50,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [],
   "source": [
    "class Person:\n",
    "    def say(self, text):\n",
    "        print(text)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 93,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [],
   "source": [
    "# Create a new Person object/instance using the class definition specified in the previous cell.\n",
    "p1 = Person()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 94,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Hello!\n"
     ]
    }
   ],
   "source": [
    "p1.say('Hello!')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "## Class with additional properties and functions"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [],
   "source": [
    "class Ball:\n",
    "    color = 'white'\n",
    "    \n",
    "    def __init__(self, x, y):\n",
    "        self.x = x\n",
    "        self.y = y\n",
    "        \n",
    "    def print_position(self):\n",
    "        print('Current location: (', self.x, ',', self.y, ')')\n",
    "        \n",
    "    def get_position(self):\n",
    "        return (self.x, self.y)\n",
    "        \n",
    "    def move(self, x, y):\n",
    "        self.x += x\n",
    "        self.y += y\n",
    "        \n",
    "    def change_color(self, new_color):\n",
    "        self.color = new_color"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 98,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [],
   "source": [
    "b = Ball(0, 0)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 99,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Current location: ( 0 , 0 )\n"
     ]
    }
   ],
   "source": [
    "b.print_position()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 100,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Current location: ( 1 , 3 )\n"
     ]
    }
   ],
   "source": [
    "b.move(1, 2)\n",
    "b.print_position()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'white'"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "b.color"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [],
   "source": [
    "b.color = 'yellow'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'black'"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "b.change_color('black')\n",
    "b.color"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[<__main__.Ball object at 0x7f0dc807b898>, <__main__.Ball object at 0x7f0dc807b4a8>, <__main__.Ball object at 0x7f0dc807b518>, <__main__.Ball object at 0x7f0dc807b8d0>]\n",
      "Current location: ( 0 , 5 )\n",
      "Current location: ( 1 , 6 )\n",
      "Current location: ( 2 , 4 )\n",
      "Current location: ( 3 , 7 )\n",
      "[(0, 5), (1, 6), (2, 4), (3, 7)]\n"
     ]
    }
   ],
   "source": [
    "import random\n",
    "\n",
    "balls = []\n",
    "for i in range(4):\n",
    "    balls.append( Ball(i, random.randint(0, 10)) )\n",
    "    \n",
    "print(balls)\n",
    "\n",
    "for ball in balls:\n",
    "    ball.print_position()\n",
    "    \n",
    "positions = [ball.get_position() for ball in balls]\n",
    "print(positions)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "## Generic class functionality"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "### \\_\\_init\\_\\_(self [,arguments] ): constructor, defines how a new object is instantiated"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [],
   "source": [
    "class Building:\n",
    "    def __init__(self, name, address):\n",
    "        self.name = name\n",
    "        self.address = address\n",
    "        \n",
    "    def print_information(self):\n",
    "        print(self.name, '\\n', self.address)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Smitsborg \n",
      " Nettelbosje 1, Groningen\n"
     ]
    }
   ],
   "source": [
    "zb = Building('Smitsborg', 'Nettelbosje 1, Groningen')\n",
    "zb.print_information()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "### \\_\\_del\\_\\_: destructor, defines additional steps to be taken when an object is removed"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 74,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [],
   "source": [
    "class Garbage:\n",
    "    def __init__(self):\n",
    "        print('Creating garbage')\n",
    "        \n",
    "    def __del__(self):\n",
    "        print('Cleaning up garbage')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 81,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Creating garbage\n"
     ]
    }
   ],
   "source": [
    "g = Garbage()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 82,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Cleaning up garbage\n"
     ]
    }
   ],
   "source": [
    "del(g)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "### \\_\\_str\\_\\_(self): printable string representation"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 52,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<__main__.Building object at 0x57075d0>\n"
     ]
    }
   ],
   "source": [
    "print(zb)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 73,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [],
   "source": [
    "class Test:\n",
    "    def __str__(self):\n",
    "        return 'This is a Test object'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 56,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "This is a Test object\n"
     ]
    }
   ],
   "source": [
    "print(Test())"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "<h3>Comparison methods:</h3>\n",
    "<pre>\n",
    "     __lt__(self, other)\n",
    "     __le__(self, other)\n",
    "     __eq__(self, other)\n",
    "     __ne__(self, other)\n",
    "     __gt__(self, other)\n",
    "     __ge__(self, other)\n",
    "</pre>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 83,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [],
   "source": [
    "class Record:\n",
    "    def __init__(self, id):\n",
    "        self.id = id\n",
    "        \n",
    "    def __lt__(self, other):\n",
    "        return self.id < other.id\n",
    "    \n",
    "    def __eq__(self, other):\n",
    "        return self.id == other.id"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 84,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "True\n",
      "False\n"
     ]
    }
   ],
   "source": [
    "r1 = Record(1)\n",
    "r2 = Record(2)\n",
    "print(r1 < r2)\n",
    "print(r1 == r2)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "<h3>Operators:</h3>\n",
    "<pre>\n",
    "    __add__(self, other)\n",
    "    __sub__(self, other)\n",
    "    __mul__(self, other)\n",
    "    __truediv__(self, other)\n",
    "    __floordiv__(self, other)\n",
    "    __mod__(self, other)\n",
    "    __divmod__(self, other)\n",
    "    __pow__(self, other[, modulo])\n",
    "    __lshift__(self, other)\n",
    "    __rshift__(self, other)\n",
    "    __and__(self, other)\n",
    "    __xor__(self, other)\n",
    "    __or__(self, other)\n",
    "</pre>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 86,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [],
   "source": [
    "class MyNumber:\n",
    "    def __init__(self, value):\n",
    "        self.value = value\n",
    "        \n",
    "    def __add__(self, number2):\n",
    "        return self.value + number2.value\n",
    "    \n",
    "    def __sub__(self, number2):\n",
    "        return self.value - number2.value"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 88,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "25\n",
      "-5\n"
     ]
    }
   ],
   "source": [
    "n1 = MyNumber(10)\n",
    "n2 = MyNumber(15)\n",
    "print(n1 + n2)\n",
    "print(n1 - n2)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "## Inheritance\n",
    "\n",
    "### Creating a new class by extending the definition of an existing class"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "source": [
    "```\n",
    "class DerivedClassName(BaseClassName1, ..., BaseClassNameM):\n",
    "    <statement-1>\n",
    "    .\n",
    "    .\n",
    "    .\n",
    "    <statement-N>\n",
    "```"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [],
   "source": [
    "class Publication:\n",
    "    def set_author(self, author):\n",
    "        self.author = author\n",
    "        \n",
    "    def __str__(self):\n",
    "        return 'Author: ' + self.author\n",
    "        \n",
    "class Book(Publication):\n",
    "    def set_isbn(self, isbn):\n",
    "        self.isbn = isbn\n",
    "        \n",
    "    def __str__(self):\n",
    "        # Get the output of the __str__() method\n",
    "        # of the superclass (parent / base class)\n",
    "        publication_info = super().__str__()\n",
    "        # Add the specific Book information to this\n",
    "        # string and return the result\n",
    "        return publication_info + '\\n' + 'ISBN: ' + self.isbn"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Author: My name\n"
     ]
    }
   ],
   "source": [
    "publ = Publication()\n",
    "publ.set_author('My name')\n",
    "print(publ)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {
    "collapsed": false,
    "slideshow": {
     "slide_type": "fragment"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Author: My name\n",
      "ISBN: 9789027439642\n"
     ]
    }
   ],
   "source": [
    "book = Book()\n",
    "book.set_author('My name')\n",
    "book.set_isbn('9789027439642')\n",
    "print(book)"
   ]
  }
 ],
 "metadata": {
  "celltoolbar": "Slideshow",
  "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": "3.4.0"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 0
}