Lesson 7.03: Methods

Learning Objectives

Students will be able to...

Define and identify: method, __str__, __add__, operator overloading
Create a class with an __init__ method
Understand and use the self argument
Instantiate a class with an argument

Do Now
Lab - Kangaroo Class
Associated Reading - section 6.3 of Book
Read through the handout, lesson, and lab so that you are familiar with the requirements and can assist students

Do Now
- Display the Do Now on the board.
- Students will find that when they try to print the two different Time objects, it produces output that's not particularly useful or readable.
- Students will also discover that adding objects doesn't work...yet!
Lesson
- Discuss the Do Now.
  - method: a function inside of a class.
  - The first argument is always self.
  - Ask students what method we have already seen and used previously. (init)
  - Ask students how they would distinguish between the two time variables.
  - __str__: Need a method called __str__. This will get called when you print an object, and it returns a string that is easy to read and understand.
    - Have the students practice writing __str__ for the Time class for 5 minutes.
    - Have a student write up their string method on the board.
  - __add__: add is another method that gets called when the plus sign is used. It takes in another two time objects and returns a time object that is the sum of both.
    - Overwriting add is called operator overloading because you are re-writing the code used to make the + work.
    - Work together with students to come up with the add time algorithm.
Lab
- Have students finish up the time adding method.
- Have students work on kanga roo lab.
Debrief
- Go over students' questions and demonstrate some students' successfully completed labs.
- Review what methods are generally, and what specific methods were used in today's lab.

Students that are moving quickly should work on the bonus assignment in the lab or assist a partner that is struggling.