05.02 Encapsulation And State - Quiz

Check your understanding

1. What is encapsulation in object-oriented programming?

   • Hiding all methods from external access
   • Bundling data and methods together while controlling access to internal details { data-correct }
   • Making all attributes public
   • Converting objects to strings

2. Which Python naming convention indicates a protected attribute?

   • attribute
   • _attribute { data-correct }
   • __attribute
   • ATTRIBUTE

3. What is an invariant in object-oriented programming?

   • A method that never changes
   • A variable that cannot be modified
   • A condition that must always be true for an object to be in a valid state { data-correct }
   • A type of loop

4. Look at this code. What’s the problem with direct attribute access?

   class BankAccount:
       def __init__(self, balance):
           self._balance = balance
   
   account = BankAccount(100)
   account._balance = -500  # Problem here
   

   • It’s perfectly fine
   • It bypasses validation and can create invalid state { data-correct }
   • It’s too slow
   • It uses too much memory

5. What is the purpose of a getter method?

   • To delete an attribute
   • To provide controlled access to internal data { data-correct }
   • To create new objects
   • To sort data

6. When should you use a setter method?

   • When you need to validate input before storing it { data-correct }
   • When you want to make data public
   • When you need to delete an object
   • When you want to slow down your program

7. What does this Python property decorator do?

   @property
   def temperature(self):
       return self._celsius
   

   • Makes the method private
   • Allows the method to be accessed like an attribute { data-correct }
   • Deletes the attribute
   • Makes the method static

8. Which of these demonstrates good encapsulation?

   • student.name = "John"
   • student._grades[0] = 100
   • student.add_grade(85) { data-correct }
   • student.__secret = "hidden"

9. What happens if you violate an object’s invariants?

   • The program runs faster
   • The object may be in an invalid or inconsistent state { data-correct }
   • Nothing changes
   • The object becomes more secure

10. Which statement about public vs private interfaces is correct?

    • All methods should be private
    • The public interface should be stable while internal implementation can change { data-correct }
    • Private methods are faster than public methods
    • Public methods are automatically validated