20.10. Multiple Choice Questions

Q-1: Given the below code, what would be printed (ignore newlines and spacing between sentences)?

class Person:
    def work(self):
        print("A person can work.")

    def food(self):
        print("A person eats food.")

class Employee(Person):
    def work(self):
        print("An employee works.")

p1 = Person()
p2 = Employee()
p1.work()
p2.work()
p1.food()
p2.food()

• A person can work. A person can work. An employee works. A person eats food.
• Try again!
• A person can work. An employee works. A person eats food.
• Try again!
• The code won't compile.
• Try again!
• A person can work. An employee works. A person eats food. A person eats food.
• Correct! Since Employee inherited from Person, the food method works for the Employee class as well.
• A person can work. A person can work. An employee works. A person eats food. A person eats food.
• Try again!

Q-2: Given the below code, what would be printed (ignore newlines and spacing between sentences)?

class Person:
   def work(self):
      print("A person can work.")

   def food(self):
      print("A person eats food.")

class Employee(Person):
   pass

p1 = Person()
p2 = Employee()
p1.work()
p2.work()
p1.food()
p2.food()

• A person can work. None. A person eats food. None.
• Try again!
• A person can work. A person can work. A person eats food. A person eats food.
• Correct! Since Employee inherited from Person, the methods work and food work for Employee as well.
• The code won't compile.
• Try again!
• A person can work. A person eats food.
• Try again!

Q-3: Given the below code, what would be printed (ignore newlines and spacing between sentences)?

class Person:
   def work(self):
      print("A person can work.")

   def food(self):
      print("A person eats food.")

class Employee(Person):
   def work(self):
      super().work()
      print("I can work.")

   def food(self):
      super().food()
      print("I can eat.")

p1 = Person()
p2 = Employee()
p1.work()
p2.work()
p1.food()
p2.food()

• A person can work. I can work. A person eats food. I can eat.
• Try again! There are 2 sentences missing: "A person can work." and "A person eats food.".
• A person can work. None. I can work. A person eats food. None. I can eat.
• Try again! Using super().method in the child class Employee method inherits the method (print statements, in this case) from the parent class Person.
• The code won't compile.
• Try again! The code compiles.
• A person can work. A person can work. I can work. A person eats food. A person eats food. I can eat.
• Correct! Using super() reduces code duplication, and the child class method can duplicate the functionality of the parent class method.

Q-4: For which of the following can inheritance be used?

• Keyboard inherits from Computer.
• Try again! Keyboard isn't a type of Computer, so inheritance can't be used.
• Student inherits from Person.
• Correct! Student is a type of Person, so inheritance can be used.
• Encyclopedia inherits from Book.
• Correct! Encyclopedia is a type of Book, so inheritance can be used.
• Person inherits House.
• Try again! Person isn't a type of House, so inheritance can't be used.

Q-5: Can a class only inherit from another class if it is a type of the class?

• Yes, a class can only inherit from another class if it is a type of the class.
• Correct! A class can only inherit from another class if it is a type of the class. For example, an encyclopedia is a type of book.
• No, a class can inherit from another class if they're associated.
• Try again!
• Yes and no. A class can inherit from another class if they're associated or if it is a type of the class.
• Try again!

Q-6: What phrases represent inheritance?

• A (class) has a (class).
• Try again! Classes that are associated can't use inheritance.
• A (class) can be substituted with (another class).
• Correct! Classes that can be substituted can use inheritance.
• A (class) can be associated with (another class).
• Try again! Classes that are associated can't use inheritance.
• A (class) is a type of (other class).
• Correct! Classes that can be substituted can use inheritance.
• A (class) is a specialization of (other class).
• Correct! Classes that can be substituted can use inheritance.

Q-7: How do you call a method in a parent class?

• parent().method
• Do not use parent.
• parent.method
• Do not use parent. Do use ().
• super().method
• Correct! Use super().method to call parent class methods.
• super.method
• You need the ()

Q-8: If Dictionary is a subclass of Book, what line of code is needed to invoke the __init__ method in Book to Dictionary?

• Book.__init__(self)
• Correct! Using ParentClass.method is one way to invoke a method in the ParentClass to the ChildClass.
• Dictionary.__init__(self)
• Try again!
• super().__init__()
• Correct! Using super().method is one way to invoke a method in the ParentClass to the ChildClass.
• Book.super().__init__(self)
• Try again!
• Book.__init__(Dictionary)
• Try again!

Q-9: What will be printed?

class Person:
   pass

class Employee(Person):
   pass

p2 = Employee()
print(isinstance(p2, Person))

• True
• Correct! p2 is assigned to an Employee object, and the Employee object inherits from Person. Therefore, p2 is an instance of Person.
• False
• Try again!
• The code won't compile.
• Try again! The code compiles even with the pass statements.
• None
• Try again! Printing isinstance() will print either True or False if it compiles.

Q-10: Which statement about inheritance is incorrect?

• Inheritance is a key idea of Object-oriented programming (OOP).
• Try again! This statement about inheritance is correct.
• The child class is also called a subclass or a derived class.
• Try again! This statement about inheritance is correct.
• Private members of a class can be inherited.
• Correct! This statement about inheritance is incorrect. Private members of a class can't be inherited.
• Protected members of a class can be inherited.
• Try again! This statement about inheritance is correct.

Q-11: Given that there is an Item class with a name and price with a __str__ method that returns "name: price", which of the following is correct?

I

class TestItem(unittest.TestCase):

    def setUp():
        i1 = Item("Coke", 2.99)
        i2 = Item("Burger", 6.99)

    def test_str_item():
        self.assertEqual(i1.__str__(), "Coke: 2.99")
        self.assertEqual(i2.__str__(), "Burger: 6.99")

II

class TestItem(unittest.TestCase):

    def setUp(self):
        self.i1 = Item("Coke", 2.99)
        self.i2 = Item("Burger", 6.99)

    def test_str_item():
        self.assertEqual(i1.__str__(), "Coke: 2.99")
        self.assertEqual(i2.__str__(), "Burger: 6.99")

III

class TestItem(unittest.TestCase):

    def setUp(self):
        self.i1 = Item("Coke", 2.99)
        self.i2 = Item("Burger", 6.99)

    def test_str_item(self):
        self.assertEqual(self.i1.__str__(), "Coke: 2.99")
        self.assertEqual(self.i2.__str__(), "Burger: 6.99")

IV

class TestItem(unittest.TestCase):

    def setUp():
        i1 = Item("Coke", 2.99)
        i2 = Item("Burger", 6.99)

    def test_str_item(self):
        self.assertEqual(self.i1.__str__(), "Coke: 2.99")
        self.assertEqual(self.i2.__str__(), "Burger: 6.99")

• I
• All methods take self (the current object).
• II
• The test_create method takes self and you must use self to access i1 and i2.
• III
• Correct! Remember to pass in self to methods and use self when accessing attributes.
• IV
• The setUp method takes self and you must use self in the setUp so other methods will still have access.

Q-12: Given that there is an Car class with attributes of make and color, which of the following is correct?

I

class TestCar(unittest.TestCase):

    def setUp():
         c1 = Car("Ford", "blue")
         c2 = Car("Toyota", "red")

     def test_create_car():
         assertEqual(c1.make, "Ford")
         assertEqual(c1.color, "blue")
         assertEqual(c2.make, "Toyota")
         assertEqual(c2.color, "red")

II

class TestCar(unittest.TestCase):

    def setUp(self):
        self.c1 = Car("Ford", "blue")
        self.c2 = Car("Toyota", "red")

    def test_create_car(self):
        assertEqual(self.c1.make, "Ford")
        assertEqual(self.c1.color, "blue")
        assertEqual(self.c2.make, "Toyota")
        assertEqual(self.c2.color, "red")

III

class TestCar(unittest.TestCase):

    def setUp(self):
        self.c1 = Car("Ford", "blue")
        self.c2 = Car("Toyota", "red")

    def test_create_car():
        self.assertEqual(self.c1.make, "Ford")
        self.assertEqual(self.c1.color, "blue")
        self.assertEqual(self.c2.make, "Toyota")
        self.assertEqual(self.c2.color, "red")

IV

class TestCar(unittest.TestCase):

    def setUp(self):
        self.c1 = Car("Ford", "blue")
        self.c2 = Car("Toyota", "red")

    def test_create_car(self):
        self.assertEqual(self.c1.make, "Ford")
        self.assertEqual(self.c1.color, "blue")
        self.assertEqual(self.c2.make, "Toyota")
        self.assertEqual(self.c2.color, "red")

• I
• All methods take self (the current object).
• II
• The assertEqual methods need to be called on self (the current object).
• III
• All methods take self (the current object).
• IV
• Correct! All methods take self and you must call assertEqual on self and use self for accessing attributes.

Q-13: Given that there is an Car class with attributes of make and color and a method set_color which changes the color, which of the following is correct?

I

class TestCar(unittest.TestCase):

    def setUp():
         c1 = Car("Ford", "blue")
         c2 = Car("Toyota", "red")

     def test_change_color():
         assertEqual(c1.color, "blue")
         c1.set_color("yellow")
         assertEqual(c1.color, "yellow")
         assertEqual(c2.color, "red")
         c2.set_color("blue")
         assertEqual(c2.color, "blue")

II

class TestCar(unittest.TestCase):

    def setUp(self):
         self.c1 = Car("Ford", "blue")
         self.c2 = Car("Toyota", "red")

     def test_change_color(self):
         self.assertEqual(self.c1.color, "yellow")
         self.c1.set_color("yellow")
         self.assertEqual(self.c1.color, "blue")
         self.assertEqual(self.c2.color, "red")
         self.c2.set_color("blue")
         self.assertEqual(self.c2.color, "blue")

III

class TestCar(unittest.TestCase):

    def setUp(self):
         self.c1 = Car("Ford", "blue")
         self.c2 = Car("Toyota", "red")

     def test_change_color(self):
         self.assertEqual(self.c1.color, "blue")
         self.c1.set_color("yellow")
         self.assertEqual(self.c1.color, "yellow")
         self.assertEqual(self.c2.color, "red")
         self.c2.set_color("blue")
         self.assertEqual(self.c2.color, "blue")

IV

class TestCar(unittest.TestCase):

    def setUp(self):
         self.c1 = Car("Ford", "blue")
         self.c2 = Car("Toyota", "red")

     def test_change_color(self):
         self.assertEqual(self.c1.color, "blue")
         self.c1.set_color("yellow")
         self.assertEqual(self.c1.color, "yellow")
         self.assertEqual(self.c2.color, "blue")
         self.c2.set_color("blue")
         self.assertEqual(self.c2.color, "red")

• I
• All methods take self (the current object).
• II
• Check the original and changed color on each car object.
• III
• Correct!
• IV
• Check the original and changed color on each car object.

Q-14: Given that there is an Car class with attributes of make and color and a method set_make which changes the make, which of the following is correct?

I

class TestCar(unittest.TestCase):

    def setUp():
         c1 = Car("Ford", "blue")
         c2 = Car("Toyota", "red")

     def test_change_make():
         assertEqual(c1.make, "Ford"")
         c1.set_make("Toyota")
         assertEqual(c1.make, "Toyota")
         assertEqual(c2.make, "Toyota")
         c2.set_make("Ford")
         assertEqual(c2.make, "Ford")

II

class TestCar(unittest.TestCase):

    def setUp(self):
         self.c1 = Car("Ford", "blue")
         self.c2 = Car("Toyota", "red")

     def test_change_make():
         self.assertEqual(self.c1.make, "Toyota")
         self.c1.set_make("Ford")
         self.assertEqual(self.c1.make, "Ford")
         self.assertEqual(self.c2.make, "Ford")
         self.c2.set_make("Toyota")
         self.assertEqual(self.c2.make, "Toyota")

III

class TestCar(unittest.TestCase):

    def setUp(self):
         self.c1 = Car("Ford", "blue")
         self.c2 = Car("Toyota", "red")

     def test_change_make(self):
         self.assertEqual(c1.make, "Toyota")
         self.c1.set_make("Ford")
         self.assertEqual(c1.make, "Ford")
         self.assertEqual(c2.make, "Ford")
         self.c2.set_make("Toyota")
         self.assertEqual(c2.make, "Toyota")

IV

class TestCar(unittest.TestCase):

    def setUp(self):
         self.c1 = Car("Ford", "blue")
         self.c2 = Car("Toyota", "red")

     def test_change_make(self):
         self.assertEqual(self.c1.make, "Ford"")
         self.c1.set_make("Toyota")
         self.assertEqual(self.c1.make, "Toyota")
         self.assertEqual(self.c2.make, "Toyota")
         self.c2.set_make("Ford")
         self.assertEqual(self.c2.make, "Ford")

• I
• All methods take self (the current object).
• II
• All methods take self (the current object).
• III
• Are the test cases correct? What was the original make and changed make for each?
• IV
• Correct!

Q-15: Given that there is an Item class with a name and price and an Order class that takes a list of Item objects and has a total method which returns the total price for all items, which of the following is correct?

I

class TestItem(unittest.TestCase):

    def setUp(self):
        i1 = Item("Coke", 2.99)
        i2 = Item("Burger", 6.99)
        self.o1 = Order([i1, i2])

    def test_create_order_total(self):
        self.assertAlmostEqual(self.o1.total(), 9.98, 2)

II

class TestItem(unittest.TestCase):

    def setUp(self):
        i1 = Item("Coke", 2.99)
        i2 = Item("Burger", 6.99)
        self.o1 = Order([i1, i2])

    def test_create_order_total(self):
        self.assertAlmostEqual(self.o1.total(), 9.99, 2)

III

class TestItem(unittest.TestCase):

    def setUp(self):
        i1 = Item("Coke", 2.99)
        i2 = Item("Burger", 6.99)
        self.o1 = Order([i1, i2])

    def test_create_order_total(self):
        self.assertAlmostEqual(self.o1.total(), "8.98", 2)

IV

class TestItem(unittest.TestCase):
class TestItem(unittest.TestCase):

    def setUp(self):
        i1 = Item("Coke", 2.99)
        i2 = Item("Burger", 6.99)
        self.o1 = Order([i1, i2])

    def test_create_order_total(self):
        self.assertAlmostEqual(self.o1.total(), 8.98, 2)

• I
• Correct!
• II
• Is 9.99 correct?
• III
• The method total returns a number, not a string.
• IV
• Is 8.98 correct?

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