Section 20.10 Multiple Choice Questions

Activity 20.10.1.

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!

Activity 20.10.2.

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!

Activity 20.10.3.

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.

Activity 20.10.4.

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.

Activity 20.10.5.

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!

Activity 20.10.6.

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.

Activity 20.10.7.

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 ()

Activity 20.10.8.

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!

Activity 20.10.9.

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.

Activity 20.10.10.

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.

Activity 20.10.11.

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.

Activity 20.10.12.

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.

Activity 20.10.13.

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.

Activity 20.10.14.

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!

Activity 20.10.15.

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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