Exercise: Encapsulation

Questions for: Encapsulation

What is the purpose of the following Python code? 
class Employee:
    def __init__(self, name, __salary):
        self.name = name
        self.__salary = __salary

    @property
    def salary(self):
        return self.__salary
A:
To create a new instance of the class
B:
To define a public variable 'salary'
C:
To allow unrestricted access to the 'salary' variable
D:
To provide read-only access to the 'salary' variable
Answer: D
The @property decorator creates a read-only property 'salary', providing controlled access to the private variable '__salary'.
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How can encapsulation be enhanced in the following Python class to provide write access to the 'price' variable? 
class Product:
    def __init__(self, name, price):
        self.name = name
        self.__price = price
A:
Use a double underscore prefix for 'price'
B:
Create a setter method for 'price'
C:
Make 'price' a global variable
D:
Use a single underscore prefix for 'price'
Answer: B
To provide write access to a private variable, a setter method can be created for 'price'.
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What does the following Python code demonstrate? 
class Book:
    def __init__(self, title, __author):
        self.title = title
        self.__author = __author

    def get_author(self):
        return self.__author
A:
Public access specifier
B:
Private access specifier
C:
Protected access specifier
D:
Global variable
Answer: B
The double underscore prefix before 'author' indicates that it is a private variable, demonstrating encapsulation by hiding the implementation details.
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In Python, what is the primary benefit of using a property with a setter method? 
class Rectangle:
    def __init__(self, width, height):
        self._width = width
        self._height = height

    @property
    def area(self):
        return self._width * self._height

    @property
    def width(self):
        return self._width

    @width.setter
    def width(self, value):
        if value > 0:
            self._width = value
        else:
            raise ValueError("Width must be greater than 0.")
A:
It allows read-only access to the width property
B:
It provides write access to the width property with validation
C:
It creates a new instance of the class
D:
It exposes all internal details of the class
Answer: B
The @width.setter decorator allows write access to the 'width' property with the provided validation in the setter method.
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How can encapsulation be enforced to make a variable 'password' accessible only within its own class? 
class User:
    def __init__(self, username, password):
        self.username = username
        self.__password = password
A:
Add a single underscore prefix before 'password'
B:
Add a double underscore prefix before 'password'
C:
Use a getter method for 'password'
D:
Make 'password' a global variable
Answer: B
Adding a double underscore prefix before 'password' makes it a private variable, enforcing encapsulation within the class.
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