{ "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "###

✅ **Put your name here**

\n", "####

✅ Put your group member names here

" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "# Day 16 In-Class Assignment: More OOP\n", " " ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Agenda for today's class\n", "\n", "

\n", "\n", "1. More about standard methods\n" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "# 1 More standard methods\n", "\n", "Still working with our `Point` class below." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Standard operators\n", "Python has two classes of standard operators:\n", "\n", "* math operations (+, -, *, /, etc.)\n", "* collection operations ([], iteration, etc.)\n", "\n", "It maps the symbols used (such as +) to a set of pre-defined methods. There are well over 60 such methods, but we can get the basic ideas with just a few\n", "\n", "How does Python map + to a method?\n", "\n", "\"add-method\"" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "There are two important points in the above diagram:\n", "\n", "* every operator has an associated method as provided by Python. For example:\n", " * `+:__add__`\n", " * `-:__sub__`\n", " * etc. All begin and end with two underlines.\n", " * you can only connect an operator to one of the existing methods (you can't make them up)\n", "* in a binary operator calling sequence (as the figure shows), the left-hand-side (*lhs*) of the operator is used to call the method and the right-hand-side (*rhs*) is passed as a parameter.\n", " * Python does this translation automatically\n", " * both forms are **exactly** equivalent, but the binary operator form is more convenient." ] }, { "cell_type": "code", "execution_count": 1, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Init called\n", "Add called\n", "Init called\n", "Result type is: \n", "String called\n", "(01:01) String called\n", "(02:02)\n" ] } ], "source": [ "class Point(object):\n", " def __init__(self,x=0,y=0): \n", " self.x_coord = x\n", " self.y_coord = y\n", " print(\"Init called\")\n", " def __str__(self):\n", " print(\"String called\")\n", " return \"({:02d}:{:02d})\".format(self.x_coord, self.y_coord)\n", " def translate(self,x=0,y=0): \n", " self.x_coord += x\n", " self.y_coord += y\n", " def __add__ (self, rhs):\n", " x = self.x_coord + rhs.x_coord\n", " y = self.y_coord + rhs.y_coord\n", " print(\"Add called\")\n", " return Point(x,y)\n", "\n", "my_point = Point(1,1)\n", "result = my_point + my_point\n", "# result = my_point.__add__(my_point) # same thing!!!\n", "print(\"Result type is: \", type(result))\n", "print(my_point, result)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "In the `Point` class, we now include an `__add__` method. When we call the `__add__` method a new `Point` instance is made. Note the second call of `__init__`, that is from inside the `__add__` method when the new `Point` is returned. Also notice that the original `my_point` is not changed as a result of the call." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "Copy the `Point` code above in the cell below but modify the `__add__` method to be a single line (which is all it needs to be)." ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "# your code here" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "# 2 Updating our Clock class\n", "\n", "OK, let's update our `Clock` class. New elements are marked with a *\n", "- each `Clock` instance will represent the present time in hours, minutes and seconds.\n", " - thus each instance will have three data attributes: `hours`, `minutes` and `seconds`\n", "- the default instance will have all attributes set to 0\n", "- provide a `__str__` method\n", "- provide an `__add__` such that we can add two clock instances, yielding a new clock instance:\n", " - no hour will be greater than 23, no minute or second greater than 59\n", " - we will use clock arithmetic: when a sum is larger than the limit, a carry is added\n", " - as our `Clock` instance has no days represented, there is no carry recorded for hours.\n", " \n", " Do it in stages. Copy from your previous `Clock` class" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "# your code here" ] }, { "cell_type": "code", "execution_count": 4, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "01:00\n", "01:01\n", "02:01\n" ] } ], "source": [ "# some test code\n", "c1 = Clock(24,60) \n", "print(c1) # should be 01:00\n", "c2 = Clock(1,1)\n", "print(c2) # should be 01:01\n", "c3 = c1 + c2\n", "print(c3) # should be 02:01" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "-----\n", "### Congratulations, we're done!\n", "\n", "Now, you just need to submit this assignment by uploading it to the course Desire2Learn web page for today's submission folder (Don't forget to add your names in the first cell).\n" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "© Copyright Michigan State University Board of Trustees" ] } ], "metadata": { "anaconda-cloud": {}, "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": "3.7.6" } }, "nbformat": 4, "nbformat_minor": 4 }