Chapter 10

Question 1

What is an object?

Answer 1

An object is a software entity that contains both data and procedures.

Question 2

What is encapsulation?

Answer 2

Encapsulation is the combining of data and code into a single object.

Question 3

Why is an object’s internal data usually hidden from outside code?

Answer 3

The data is protected from accidental corruption.

In addition, the programming code outside the object does not need to know about the format or internal structure of the object’s data.

Question 4

What are public methods? What are private methods?

Answer 4

Public methods can be accessed by entities outside the object.

Private methods cannot be accessed by entities outside the object. They are designed to be accessed internally.

Question 5

You hear someone make the following comment: “A blueprint is a design for a house. A carpenter can use the blueprint to build the house. If the carpenter wishes, he or she can build several identical houses from the same blueprint.” Think of this as a metaphor for classes and objects. Does the blueprint represent a class, or does it represent an object?

Answer 5

The metaphor of a blueprint represents a class.

Question 6

In this chapter, we use the metaphor of a cookie cutter and cookies that are made from the cookie cutter to describe classes and objects. In this metaphor, are objects the cookie cutter, or the cookies?

Answer 6

Objects are the cookies.

Question 7

What is the purpose of the _ init _ method? When does it execute?

Answer 7

Its purpose is to initialize an object’s data attributes. It executes immediately after the object is created.

Question 8

What is the purpose of the self parameter in a method?

Answer 8

When a method executes, it must have a way of knowing which object’s data attributes it is supposed to operate on. That’s where the self parameter comes in. When a method is called, Python automatically makes its self parameter reference the specific object that the method is supposed to operate on.

Question 9

In a Python class, how do you hide an attribute from code outside the class?

Answer 9

By starting the attribute’s name with two underscores

Question 10

What is the purpose of the _ str _ method?

Answer 10

It returns a string representation of the object.

Question 11

How do you call the _ str _ method?

Answer 11

By passing the object to the built-in str method

Question 12

What is an instance attribute?

Answer 12

An attribute that belongs to a specific instance of a class

Question 13

A program creates 10 instances of the Coin class. How many _ _sideup attributes exist in memory?

Answer 13

10

Question 14

What is an accessor method? What is a mutator method?

Answer 14

Accessor method (getter) returns a value from a class’s attribute but does not change it

Mutator method(setter) stores a value in a data attribute or changes the value of a data attribute in some other way

Question 15

The typical UML diagram for a class has three sections. What appears in these three sections?

Answer 15

The top section is where you write the name of the class.
The middle section holds a list of the class’s fields.
The bottom section holds a list of the class’s methods.

Question 16

What is a problem domain?

Answer 16

A written description of the real-world objects, parties, and major events related to the problem

Question 17

When designing an object-oriented application, who should write a description of the problem domain?

Answer 17

yourself or an expert

Question 18

How do you identify the potential classes in a problem domain description?

Answer 18

First, identify the nouns, pronouns, and pronoun phrases in the problem domain description. Then, refine the list to eliminate duplicates, items that you do not need to be concerned with in the problem, items that represent objects instead of classes, and items that represent simple values that can be stored in variables.

Question 19

What are a class’s responsibilities?

Answer 19

The things that the class is responsible for knowing and the actions that the class is responsible for doing

Question 20

What two questions should you ask to determine a class’s responsibilities?

Answer 20

In the context of this problem, what must the class know? What must the class do?

Question 21

Will all of a class’s actions always be directly mentioned in the problem domain description?

Answer 21

No, not always

Question 22

The                programming practice is centered on creating functions that are separate from the data that they work on.

Answer 22

procedural

Question 23

The                programming practice is centered on creating objects.

Answer 23

object-oriented

Question 24

A(n)                is a component of a class that references data.

Answer 24

data attribute

Question 25

An object is a(n)               .

Answer 25

instance

Question 26

By doing this, you can hide a class’s attribute from code outside the class.

Answer 26

begin the attribute’s name with two underscores

Question 27

A(n)                method gets the value of a data attribute but does not change it.

Answer 27

accessor

Question 28

A(n)                method stores a value in a data attribute or changes its value in some other way.

Answer 28

mutator

Question 29

The                method is automatically called when an object is created.

Answer 29

__init__

Question 30

If a class has a method named _ str _, which of these is a way to call the method?

Answer 30

by passing an instance of the class to the built in str function

class MyClass:
def __str__(self):
return “This is my custom string representation”

obj = MyClass()
string_representation = str(obj)
print(string_representation)

Output:

This is my custom string representation

Question 31

A set of standard diagrams for graphically depicting object-oriented systems is provided by               .

Answer 31

the Unified Modeling Language

Question 32

In one approach to identifying the classes in a problem, the programmer identifies the                in a description of the problem domain.

Answer 32

nouns

Question 33

In one approach to identifying a class’s data attributes and methods, the programmer identifies the class’s               .

Answer 33

responsibilities