06.01 Building Classes And Composition - Quiz

Check your understanding

1. What is the primary purpose of the __init__ method in a Python class?

   • To delete objects when they’re no longer needed
   • To initialize a new object’s attributes and set up its initial state { data-correct }
   • To define what methods the class can use
   • To create multiple copies of the class

2. Which parameter must always be the first parameter in instance methods?

   • cls
   • self { data-correct }
   • this
   • instance

3. What does this code create?

   student = Student("Alice", "S12345")
   

   • A class definition
   • An instance (object) of the Student class { data-correct }
   • A method call
   • A constructor definition

4. What is composition in object-oriented programming?

   • Inheriting from multiple parent classes
   • Building complex objects by combining simpler component objects { data-correct }
   • Writing longer methods with more functionality
   • Using global variables in classes

5. Why is “composition over inheritance” often preferred?

   • Composition is always faster than inheritance
   • Composition provides more flexibility and looser coupling { data-correct }
   • Inheritance is deprecated in modern programming
   • Composition uses less memory

6. Look at this class structure. What principle does it demonstrate?

   class Car:
       def __init__(self, engine, wheels):
           self.engine = engine
           self.wheels = wheels
   

   • Inheritance
   • Composition { data-correct }
   • Encapsulation
   • Polymorphism

7. What makes a class “cohesive”?

   • It has many different responsibilities
   • It has a single, well-defined purpose with related methods { data-correct }
   • It inherits from multiple parent classes
   • It has more than 10 methods

8. Which constructor design is better?

   def __init__(self, name, age):
       self.name = name
       self.age = age
   
   def __init__(self, name, age):
       if not name or age < 0:
           raise ValueError("Invalid input")
       self.name = name
       self.age = age
   

   • Option A - simpler code
   • Option B - includes validation { data-correct }
   • Both are equally good
   • Neither is correct

9. What relationship does composition represent?

   • “is-a” relationship
   • “has-a” relationship { data-correct }
   • “uses-a” relationship
   • “extends-a” relationship

10. In this example, what type of _calculate_total?method is

    class ShoppingCart:
        def add_item(self, item): pass
        def _calculate_total(self): pass
        def get_total(self): return self._calculate_total()
    

    • Public method intended for external use
    • Private helper method for internal use { data-correct }
    • Static method that doesn’t use instance data
    • Abstract method that must be overridden