Exercises: full OOP design

These exercises combine everything covered in the OOP chapter — classes, inheritance, encapsulation, properties, magic methods, and ABCs. No scaffolding, no hints — just the requirements and the expected output.

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Exercise 9 — Library management system Advanced

Design a Library Management System with the following classes:

• Book — title, author, ISBN, available (bool)
• Member — name, member ID, list of borrowed books (max 3)
• Library — collection of books and members, with:
  • add_book(book) / remove_book(isbn)
  • register_member(member) / remove_member(member_id)
  • borrow_book(member_id, isbn) — with proper error handling
  • return_book(member_id, isbn)
  • search_by_author(author) — returns list of matching books
  • available_books() — returns all books not currently borrowed
  • __str__ showing library stats

Expected output

lib = Library("City Library")
lib.add_book(Book("1984", "Orwell", "ISBN001"))
lib.add_book(Book("Dune", "Herbert", "ISBN002"))
lib.register_member(Member("Alice", "M001"))

lib.borrow_book("M001", "ISBN001")
print(lib.available_books())    # [Dune by Herbert]
lib.return_book("M001", "ISBN001")
print(lib.available_books())    # [1984 by Orwell, Dune by Herbert]
print(lib)                      # City Library — 2 books, 1 members

Solution

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Exercise 10 — Challenge: Matrix Advanced

Implement a Matrix class that behaves like a mathematical matrix:

• __init__ takes a 2D list
• __add__, __sub__, __mul__ (matrix × matrix AND matrix × scalar)
• __eq__, __repr__
• __getitem__ so m[row][col] works
• transpose() returning a new Matrix
• determinant() for 2×2 and 3×3 matrices
• is_square(), rows, cols as properties
• Raise ValueError for incompatible dimensions

Expected output

m1 = Matrix([[1, 2], [3, 4]])
m2 = Matrix([[5, 6], [7, 8]])

print(m1 + m2)          # Matrix([[6, 8], [10, 12]])
print(m1 * m2)          # Matrix([[19, 22], [43, 50]])
print(m1 * 2)           # Matrix([[2, 4], [6, 8]])
print(m1.transpose())   # Matrix([[1, 3], [2, 4]])
print(m1.determinant()) # -2.0
print(m1[0][1])         # 2
print(m1.rows)          # 2
print(m1.cols)          # 2
print(m1.is_square())   # True

Solution