Class design (Book, Member, Librarian, Loan) in LLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a class for Book with a constructor.

LLD

class Book:
    def __init__(self, title, author):
        self.title = title
        self.author = [1]

Drag options to blanks, or click blank then click option'

Aauthor

Btitle

Cself

Dbook

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning title to self.author by mistake.

The constructor assigns the parameter author to the instance variable self.author.

2fill in blank

medium

Complete the code to add a method that returns the member's name.

LLD

class Member:
    def __init__(self, name):
        self.name = name
    
    def get_name(self):
        return [1]

Drag options to blanks, or click blank then click option'

Aname

Bself.name

Cself

Dmember_name

Attempts:

3 left

💡 Hint

Common Mistakes

Returning just name without self. causes an error.

The method should return the instance variable self.name to access the member's name.

3fill in blank

hard

Fix the error in the Loan class constructor to correctly assign the book and member.

LLD

class Loan:
    def __init__(self, book, member):
        self.book = book
        self.member = [1]

Drag options to blanks, or click blank then click option'

Amember

Bself.member

Cself.book

Dbook

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning self.member to itself causes no change.

The constructor should assign the parameter member to self.member.

4fill in blank

hard

Fill both blanks to complete the method that checks if a book is available (not loaned).

LLD

class Librarian:
    def __init__(self):
        self.loans = []
    
    def is_book_available(self, book):
        for loan in self.loans:
            if loan.[1] == book:
                return [2]
        return True

Drag options to blanks, or click blank then click option'

Abook

BFalse

CTrue

Dmember

Attempts:

3 left

💡 Hint

Common Mistakes

Returning True inside the loop causes wrong availability.

The method checks if any loan's book matches the given book. If yes, it returns False meaning not available.

5fill in blank

hard

Fill all three blanks to create a method that adds a new loan if the book is available.

LLD

class Librarian:
    def __init__(self):
        self.loans = []
    
    def add_loan(self, book, member):
        if self.is_book_available(book):
            new_loan = Loan([1], [2])
            self.loans.[3](new_loan)
            return True
        return False

Drag options to blanks, or click blank then click option'

Abook

Bmember

Cappend

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove instead of append causes errors.

The method creates a new Loan with book and member, then appends it to self.loans.

Practice

1. Which class should be responsible for storing information about a book's title, author, and ISBN in a library system?

easy

A. Member

B. Book

C. Librarian

D. Loan

Solution

1. Step 1: Identify the class representing a book

   The class named Book logically holds details about books such as title, author, and ISBN.

2. Step 2: Confirm other classes' roles

   Member is for library users, Librarian manages operations, and Loan tracks borrowing, so they don't store book details.

3. Final Answer:

   Book -> Option B

4. Quick Check:

   Book class stores book info [OK]

Hint: Book class holds book details like title and author [OK]

Common Mistakes:

• Confusing Member with Book class
• Assigning book details to Loan class
• Thinking Librarian stores book info

2. Which of the following is the correct way to define a method named borrowBook inside the Member class in Python?

easy

A. def borrowBook():

B. def borrowBook(book):

C. def borrowBook(self):

D. def borrowBook(self, book):

Solution

1. Step 1: Understand method definition in Python classes

   Instance methods must have self as the first parameter to access object data.

2. Step 2: Check method parameters for borrowing a book

   The method needs the book to borrow, so it should accept a book parameter after self.

3. Final Answer:

   def borrowBook(self, book): -> Option D

4. Quick Check:

   Instance method with self and book param [OK]

Hint: Instance methods always start with self parameter [OK]

Common Mistakes:

• Omitting self parameter
• Not passing book argument
• Defining method without parameters

3. Given the following Python code snippet, what will be the output?

class Loan:
    def __init__(self, book, member):
        self.book = book
        self.member = member

loan = Loan('1984', 'Alice')
print(loan.book, loan.member)

medium

A. 1984 Alice

B. book member

C. Loan object memory address

D. Error: missing parameters

Solution

1. Step 1: Analyze the Loan class constructor

   The constructor __init__ assigns book and member to instance variables.

2. Step 2: Check the print statement output

   Printing loan.book and loan.member outputs the strings '1984' and 'Alice' separated by space.

3. Final Answer:

   1984 Alice -> Option A

4. Quick Check:

   loan.book and loan.member print values [OK]

Hint: Print instance variables to see stored values [OK]

Common Mistakes:

• Expecting object memory address output
• Confusing variable names with strings
• Assuming error due to parameters

4. Identify the error in this Python class design snippet for the Librarian class:

class Librarian:
    def __init__(self, name):
        self.name = name
    def addBook(book):
        print(f"Adding {book} to library")

medium

A. Missing self parameter in addBook method

B. Incorrect print statement syntax

C. Constructor missing return statement

D. Class name should be lowercase

Solution

1. Step 1: Check method parameters in class

   Instance methods must include self as the first parameter to access instance data.

2. Step 2: Verify addBook method signature

   addBook lacks self, so it will cause an error when called on an instance.

3. Final Answer:

   Missing self parameter in addBook method -> Option A

4. Quick Check:

   Instance methods need self param [OK]

Hint: Instance methods always start with self parameter [OK]

Common Mistakes:

• Thinking print syntax is wrong
• Expecting constructor to return value
• Believing class names must be lowercase

5. In designing a library system, which class should handle the logic to check if a book is currently loaned out before allowing a member to borrow it?

hard

A. Book

B. Member

C. Loan

D. Librarian

Solution

1. Step 1: Understand responsibilities of each class

   Book stores book info, Member represents users, Loan tracks borrow records, and Librarian manages library operations.

2. Step 2: Identify who controls borrowing rules

   The Loan class should handle checking if a book is currently loaned out before allowing borrowing, as it tracks loan records.

3. Final Answer:

   Loan -> Option C

4. Quick Check:

   Loan class tracks loan status [OK]

Hint: Loan class tracks if a book is loaned out [OK]

Common Mistakes:

• Putting borrowing logic inside Book class
• Assigning loan status check to Member
• Expecting Librarian class to enforce borrowing rules