Lab 11: Object Oriented Programming
Overview
This week's lab focuses on object oriented programming, primarily on
- familiarizing yourself with the syntax and organization of classes
- getting comfortable with creating objects or instances of a class
- understanding the concepts of methods
- using methods to manipulate properties of a class
Refer to lecture 18 for examples of Python objects and methods.
How Big is this Lab?
The lab contains 5 questions. If you have questions about the expected level of detail for any of the questions, please ask your lab staff.
Assignment
1. Create an Instance of a Class (1 point)
This question is just a refresher on class and object syntax. Consider the following Student class:
class Student:
def __init__(self, name, courses):
self.name = name
self.courses = courses
Write one line of Python code which initializes a new student object with its name property set to "Ben Burns" and its courses property set to {"CICS 110", "MATH 131"}.
As a reminder, the __init__() method is called the Constructorm it is the Python method that runs every time we want to make a new instance of the Student class. You should not be calling __init__() directly, refer back to the slides if needed for examples.
2. Course Enrollment (1 point)
Now that we have our Student class set up, we want to allow our students to enroll in new courses. Here, we're going to add a method to the Student class to help our students enroll in a single new course.
Write a new method for a Student class named enroll, which takes in a string new_course and adds it to the Student's course property. For example, if we run the following code
bburns = Student("Ben Burns", {"CICS 110"})
bburns.enroll("MATH 131")
the name property of bburns should be set to "Ben Burns", and the value of the courses property should be {"CICS 110", "MATH 131"}.
3. Course Adjustment (1 point)
Similarly, we also would like to allow our students to drop courses. The goal is to add another method to the Student class so our students can drop a course.
Write a new method for a Student class named drop, which takes in a string course and attempts to remove it from the Student's course property. For example, if we run the following code
bburns = Student("Ben Burns", {"CICS 110", "MATH 131"})
bburns.drop("CICS 110")
the value of the courses property should now become {"MATH 131"}
Hint: Use .discard() for removing an item from a set. This ensures no exception will occur if a non-existent item is removed from a set.
4. Discussion (1 point)
In questions 2 and 3, you created two different methods within the Student class. Now, consider you do not have any methods defined within the Student class. Instead, you only have a single function called enroll_student(Student, new_course) defined outside the Student class to perform the enrollment operation. Discuss with your peers why do you need methods? What are the advantages and disadvantages of having methods?
Hint: Review Lecture 18 slides 7-11 and section 12.1 in zyBooks.
5. (Challenge) Dictionaries vs. Classes (1 point)
I don't know about you, but I personally find objects to be very confusing, especially all this self and __init__() syntax. However, I am really comfortable with dictionaries, including how to define a dictionary, how to work with key-value pairs, and how to use dictionaries in functions.
To my surprise, classes and dictionaries are actually extremely similar. In fact, an object's properties and their values are actually stored (under the hood) as a dictionary! That being said, why might I want to use a dictionary instead of a class? Why I might want to use a class instead of a dictionary?
Grading Scale
Below are how many points are required for each level on the 5-point scale.