ing Lec 3: Classes and Ob Classes around him To mind map Classes are created using the keyword class. A class declaration defines a new type that links code and data. This new type is then used to declare objects of that class. Thus, a class is a logical abstraction, but an object has physical existence. A programmer can create many instances of a class. Creating an instance of a class interchangeably. An object is an instance and an instance is an object. is referred to as instantiation. The terms object and instance are often used Every element in a Python program is an object of a class. A number, string, list, dictionary, etc., used in a program is an object of a corresponding built-in class. The followings are class members: 1. Class Attributes: the variables defined directly in the class that are shared by all objects of the class. Class attributes can be accessed using the class name as well as using the objects. 2. Constructor: the constructor method is invoked automatically whenever a new object of a class is instantiated, The constructor must have a special name _init_() and a special parameter called self. 3. Instance Attributes: attributes or properties attached to an instance of a class. Instance attributes are defined in the constructor. 4. Class Methods: You can define as many methods as you want in a class using the def keyword. Each method must have the first parameter, generally named as self, which refers to the calling instance.

Using classes, design an online address book to keep track of the names, addresses, phone numbers, and dates of birth of family members, close friends, and certain business associates. Your program should be able to handle a maximum of 500 entries. Define a class addressType that can store a street address, city, state, and ZIP code. Use the appropriate functions to print and store the address. Also, use constructors to automatically initialize the member variables. Define a class extPersonType using the class personType (as defined in Example 10-10, Chapter 10), the class dateType (as designed in this chapters Programming Exercise 2), and the class addressType. Add a member variable to this class to classify the person as a family member, friend, or business associate. Also, add a member variable to store the phone number. Add (or override) the functions to print and store the appropriate information. Use constructors to automatically initialize the member variables. Define the class addressBookType using the previously defined classes. An object of the type addressBookType should be able to process a maximum of 500 entries. The program should perform the following operations: Load the data into the address book from a disk. Sort the address book by last name. Search for a person by last name. Print the address, phone number, and date of birth (if it exists) of a given person. Print the names of the people whose birthdays are in a given month. Print the names of all the people between two last names. Depending on the users request, print the names of all family members, friends, or business associates.

The technique of packaging an objects attributes into a cohesive unit that can be used as an undivided entity is ____________. a. inheritance b. encapsulation c. polymorphism d. interfacing

Chapter 10 defined the class circleType to implement the basic properties of a circle. (Add the function print to this class to output the radius, area, and circumference of a circle.) Now every cylinder has a base and height, where the base is a circle. Design a class cylinderType that can capture the properties of a cylinder and perform the usual operations on the cylinder. Derive this class from the class circleType designed in Chapter 10. Some of the operations that can be performed on a cylinder are as follows: calculate and print the volume, calculate and print the surface area, set the height, set the radius of the base, and set the center of the base. Also, write a program to test various operations on a cylinder.