{ "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "###
San Jose State University
Department of Applied Data Science

**DATA 200
Computational Programming for Data Analytics**

Spring 2024
Instructor: Ron Mak
" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## 10.4.2 Class `Time` Definition\n", "#### We define class `Time` is in module `timewithproperties` (Python source file `timewithproperties.py`)." ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "from timewithproperties import Time" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Class Time: `__init__` Method with Default Parameter Values\n", "```python\n", "class Time:\n", " \"\"\"\n", " Class Time with read-write properties.\n", " \"\"\"\n", "\n", " def __init__(self, hour=0, minute=0, second=0):\n", " \"\"\"\n", " Constructor of a Time object with default values.\n", " \"\"\"\n", " self._hour = hour # 0-23\n", " self._minute = minute # 0-59\n", " self._second = second # 0-59\n", "```" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Class `Time`: `hour` Read-Write Property\n", "#### We designate `hour` to be a publicly accessible **read-write property** and implement it as a **getter** method that access the value of the private attribute `_hour`. In this example, we return the hour in the 12-hour format.\n", "```python\n", " @property\n", " def hour(self):\n", " \"\"\"\n", " @return the hour in the 12-hour format.\n", " \"\"\"\n", " return self._hour if self._hour <= 12 else self._hour - 12" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "#### We can also define a **setter** method for the property which **validates** its parameter value.\n", "```python\n", " @hour.setter\n", " def hour(self, hour):\n", " \"\"\"\n", " Set the hour.\n", " @param hour the hour to set.\n", " \"\"\"\n", " if not (0 <= hour < 24):\n", " raise ValueError(f'Hour ({hour}) must be 0-23')\n", "\n", " self._hour = hour\n", "```" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "#### At run time, `wake_up.hour` implicitly calls the property's getter method and `wake_up.hour = 100` implicitly calls its setter method." ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "wake_up = Time(hour=6, minute=30)\n", "wake_up.hour" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "bedtime = Time(hour=22)\n", "bedtime" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "bedtime.hour" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "wake_up.hour = 100" ] }, { "attachments": {}, "cell_type": "markdown", "metadata": {}, "source": [ "### Class `Time`: `minute` and `second` Read-Write Properties\n", "```python\n", " @property\n", " def minute(self):\n", " \"\"\"\n", " @return the minute.\n", " \"\"\"\n", " return self._minute\n", "\n", " @minute.setter\n", " def minute(self, minute):\n", " \"\"\"\n", " Set the minute.\n", " @param minute the minute to set.\n", " \"\"\"\n", " if not (0 <= minute < 60):\n", " raise ValueError(f'Minute ({minute}) must be 0-59')\n", "\n", " self._minute = minute\n", "\n", " @property\n", " def second(self):\n", " \"\"\"\n", " @return the second.\n", " \"\"\"\n", " return self._second\n", "\n", " @second.setter\n", " def second(self, second):\n", " \"\"\"\n", " Set the second.\n", " @param second the second to set.\n", " \"\"\"\n", " if not (0 <= second < 60):\n", " raise ValueError(f'Second ({second}) must be 0-59')\n", "\n", " self._second = second\n", "```" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Class `Time`: Method `set_time` \n", "```python\n", " def set_time(self, hour=0, minute=0, second=0):\n", " \"\"\"\n", " Set the hour, minute, and second by invoking the setters.\n", " @param hour the hour to set.\n", " @param minute the minute to set.\n", " @param second the second to set.\n", " \"\"\"\n", " self.hour = hour\n", " self.minute = minute\n", " self.second = second\n", "```" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Class `Time`: Special Method `__repr__()`\n", "#### Every class has a method `__repr__()` the is implicitly called to return an object's \"official\" string representation. You can **override** its default code.\n", "```python\n", " def __repr__(self):\n", " \"\"\"\n", " @return the string representation of the Time object.\n", " \"\"\"\n", " return (f'Time(hour={self._hour}, minute={self._minute}, ' + \n", " f'second={self._second})')\n", "```\n", "#### The string representation is supposed to look like a constuctor call. The method is also implicitly called when you display an object." ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "wake_up" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "display(wake_up)" ] }, { "attachments": {}, "cell_type": "markdown", "metadata": {}, "source": [ "### Class `Time`: Special Method `__str__()`\n", "#### Every class has a method `__str__()` that is implicitly called to return a formmatted string for calls to str() or print().\n", "\n", "```python\n", " def __str__(self):\n", " \"\"\"\n", " @return a Time string in 12-hour clock format \n", " for calls to str() or to print().\n", " \"\"\"\n", " return (('12' if self.hour in (0, 12) else str(self.hour%12)) + \n", " f':{self.minute:0>2}:{self.second:0>2}' + \n", " (' AM' if self.hour < 12 else ' PM'))\n", "```" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "print(wake_up)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Built-in function`eval()`\n", "#### We can call the built-in `eval()` function to parse a string similar to one returned by `__repr__()` and return an object." ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "bedtime" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "bedtime_string = 'Time(hour=23, minute=30, second=10)'\n", "bedtime = eval(bedtime_string)\n", "\n", "bedtime" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "##########################################################################\n", "# (C) Copyright 2019 by Deitel & Associates, Inc. and #\n", "# Pearson Education, Inc. All Rights Reserved. #\n", "# #\n", "# DISCLAIMER: The authors and publisher of this book have used their #\n", "# best efforts in preparing the book. These efforts include the #\n", "# development, research, and testing of the theories and programs #\n", "# to determine their effectiveness. The authors and publisher make #\n", "# no warranty of any kind, expressed or implied, with regard to these #\n", "# programs or to the documentation contained in these books. The authors #\n", "# and publisher shall not be liable in any event for incidental or #\n", "# consequential damages in connection with, or arising out of, the #\n", "# furnishing, performance, or use of these programs. #\n", "##########################################################################\n" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [ "# Additional material (C) Copyright 2024 by Ronald Mak" ] } ], "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": "3.11.5" } }, "nbformat": 4, "nbformat_minor": 4 }