Introduction to Computer Science and Programming in Python

Lecture 9

1. Getters and Setters

   Which of the below is a getter method for the number of wheels?

   ----------------------------------
   ----------- Given ------------
   ----------------------------------
   class Car(object):
       def __init__(self, w, d):
           self.wheels = w
           self.doors = d
           self.color = ""
   ----------------------------------
   
   (A)    def get_wheels():
               return wheels
   
   (B)    def get_wheels():
               return self.wheels
   
   (C)    def get_wheels(self):
               return wheels
   
   (D)    def get_wheels(self):
               return self.wheels
   

   def get_wheels():
       return wheels
   

   close

   def get_wheels():
       return self.wheels
   

   close

   def get_wheels(self):
       return wheels 
   

   close

   def get_wheels(self):
       return self.wheels
   

   check

   Check   Show Solution

2. Subclass

   What line could replace ____blank____ to create a class that inherits from Animal in the code below?

   ____blank____
       def speak(self):
           print("ruff ruff")
   
   (line1) d = Dog(7)
   (line2) d.set_name("Ruffles")
   (line3) d.speak()
   

   class Dog(Animal): check

   class Animal(Dog): close

   class Dog(object) close

   Check

   With this definition of Dog, you run a program with line1, line2, and line3 above. What happens? Refer to the lecture slides for the code making up the “Animal” class.

   Error on (line1) because Dog does not have an __init__ close

   Uses the __init__ from Animal, but then an error (line2) because Dog does not have a set_name method. close

   Uses the __init__ and set_name from Animal, but then an error (line3) because all methods must return something. close

   Runs, creates a Dog object with age=7 and name=“Ruffles”, and prints “ruff ruff” check

   Check   Show Solution