Category Archives: Lesson

Parsons Problem Lesson: quad_functions

Learning Programming is Hard

Many challenges face the new Computer Science learner. One of the most interesting times for students learning to program is that period after they’ve learned a new feature or programming strategy, but before they’ve had a chance to really master it. The syntax may still be unfamiliar, or the strategy is “the same, but different” as something that they’ve seen before.

A Parsons Puzzle

I first stumbled upon the “Parsons Problem” type of question in a paper by researchers Denny, Luxton-Reilly, and Simon, Evaluating a New Exam Question: Parsons Problems, published in 2008, which led me to Parsons and Haden’s original paper Parsons’ programming puzzles: a fun and effective learning tool for first programming courses.

A “Parson’s Puzzle” is a programming problem delivered via computer, in which code fragments, manipulated via a drag-and-drop interface, may be assembled to form a correct, working program. Clicking a “Check” button would provide some sort of feedback. Parsons and Haden proposed that the nature of the puzzle would improve engagement with the topic, provide better structure for students still struggling to understand fundamental logic, strategies, or algorithms, and even intentionally allow for common errors so that a student could get immediate feedback on fundamental misunderstandings.

Parsons and Haden’s original idea of helping to teach students with an automated system was adapted to a paper-based means of assessing students by Denny, Luxton-Reilly, and Simon. Along the same lines, it’s certainly possible to use a paper-based strategy of helping students develop and clarify their thinking on any given computer programming topic.

A Paper-Based Parsons Problem in the Classroom

In an introductory computer science course taught using Python, students had recently learned about functions, and had had the chance to learn how to use functions in several different contexts. Students were paired randomly and given a paper copy of the activity here [PDF], and asked to a) arrange the lines of code into strips of paper that they would assemble into a working version of the program, and then b) enter their code into the computer to verify that it works as intended.

"""
quad_functions.py
This program solves quadratic equations using three functions:
* one function to get the coefficients a, b, and c
* one function to calculate the two roots, and
* one function to print out the results
@author You
@version 1.0
"""

def get_coeffs():

def get_coeffs(a, b, c):

def calculate_roots(a,b,c):

def main():

def calculate_roots():

def display_solutions(root1, root2):

def display_solutions():

main()

a, b, c = get_coeffs()

root1 = (-b + (b * b - 4 * a * c) ** (1/2)) / (2 * a)

root2 = (-b - (b * b - 4 * a * c) ** (1/2)) / (2 * a)

x, y, z = get_coeffs(a, b, c)

display_solutions(r1, r2)

return root1, root2

display_solutions()

display_solutions(a, b, c)

print(root1, root2)

return a, b, c

print("The solutions are: ")

a = eval(input("Enter coefficient a: "))

b = eval(input("Enter coefficient b: "))

c = eval(input("Enter coefficient c: "))

r1, r2 = calculate_roots()

a, b, c = get_coeffs()

r1, r2 = calculate_roots(a, b, c)

if __name__ == "__main__":

#!/usr/bin/env python3

Observations

Students took the assignment seriously, and seemed to appreciate the nature of the puzzle, and the fact that all of the information was available to them—they just had to (literally) put the pieces together. There were some lively discussions—”Do we need a function header with parameters or not? Do we need the function to return a value or not?”—as well as a desire to get done with the puzzle-solving as quickly as possible in order to move onto entering the code into the computer to test their program.

For a larger assignment or project with many variations, the Parsons approach is not well-suited: there are too many variations that need to be considered. For students just learning to master a new topic, however—functions, conditionals, while-loops, for-loops, etc—the Parsons Problem strategy is a great way to build students’ skills and confidence in programming.

References

Paul Denny, Andrew Luxton-Reilly, and Beth Simon. 2008. Evaluating a new exam question: Parsons problems. In Proceedings of the Fourth international Workshop on Computing Education Research (ICER ’08). ACM, New York, NY, USA, 113-124.

Dale Parsons and Patricia Haden. 2006. Parson’s programming puzzles: a fun and effective learning tool for first programming courses. In Proceedings of the 8th Australasian Conference on Computing Education – Volume 52 (ACE ’06), Denise Tolhurst and Samuel Mann (Eds.), Vol. 52. Australian Computer Society, Inc., Darlinghurst, Australia, Australia, 157-163.

Pair Programming

As a Science teacher I am well-acquainted with the idea of students working as partners in a lab setting. It’s a time-honored practice based on a variety of rationales, depending on the setting. Lab partners, or indeed partners in any academic setting, might be placed together for logistical reasons: there may be multiple responsibilities that need to be shared, there may be limited equipment, limited lab supplies, limited computers, or limited space. There may be pedagogical reasons as well: students can assist each other in learning material, or learning to work together may even be the goal of the lesson.

In computer programming classes, “pair programming” may be used, with one student typically “driving” (entering code on the computer), and another “navigating” (dictating code, catching typos, etc.) There are variations on the specific responsibilities of each role, but the general idea is that two heads are better than one, and that an ongoing conversation as the code is developed will produce a stronger product. Pair Programming isn’t just for classes–it’s actually used in the software industry by some organizations.

Regardless of the context, there are bound to be challenges when two people are asked to work together in a demanding situation. One common challenge is when two students have varying abilities or levels of success. Sometimes teachers will even pair students with this in mind, either placing students of similar level with each other, or pairing a successful student with a challenged student with the hope of fostering some impromptu peer tutoring. (I’d suggest that there are issues with both of these strategies, but we’ll leave that for another time.)

In my courses I’ve developed a Pairing Strategy that seems to be working well for my students based on the success I’ve seen in their assignments and their behaviors in the classroom. It works like this:

1. Introduce the idea of Paired Work.
Discuss the benefits and talk about the challenges. Mention the fact that there may be different roles to be played, and that those roles will likely change over the course of the experience.

2. Discuss behavior.
Point out that people need to be on their best behavior when working as a pair. Respect is an important part of this process, and that includes during that first moment when you learn who you’re going to be working with. A loud cry of “Oh, man, I got stuck with Christine??!” doesn’t get you off to a great start, and celebrating that you got paired with the person with the highest test average isn’t appropriate either.

Code.org’s video on Pair Programming, while a bit cheesy and clearly intended for a more Middle School audience, pretty much nails it.

3. Explain the Pairing process.
Very often I’ll use this computer program to pair students randomly. They’ve come to appreciate the excitement of finding out who they’re going to be working with.

In the case of Pair Programming, I’ll be very specific. Just before running the program so that students can see the results on the overhead projector, I’ll say that the partner listed on the left side of list will be the first “driver,” and that students will be using that person’s computer for the project. The person listed on the right side of the list will be the navigator, and will get up and move over to where the driver is sitting to get started.

#!/usr/bin/env python3

"""
random_partners.py
This program takes a list of students in the class and assigns them randomly
to a series of groups of a specified size.
@author Richard White
@version 2018-10-10
"""

import random,os

def main():
    all_students = ["Kareem","Lucas","Marcela","Dylan","Gwen","Ella","Adam","Carrie","Patty","Annie","Audrey","Aidin","Sinjin","Henry","Robby","Sean","Ms. Dunham"]
    students_present = ["Kareem","Lucas","Marcela","Dylan","Gwen","Ella","Adam","Carrie","Patty","Annie","Audrey","Aidin","Sinjin","Henry","Robby","Sean","Ms. Dunham"]
    os.system("clear")
    groupsize = eval(input("Enter # of people in a group: "))
    os.system("clear")
    i = 0
    print("PARTNERS:")
    while len(students_present) > 0:
        if i > 0 and i % groupsize != 0:        # Print commas after first one in group, 
            print(", ", end='')                 # but not if done with group
        random_student = random.choice(students_present)    # Pick random student
        print(random_student,end='')
        students_present.remove(random_student)             # Remove name from list
        i += 1
        if i % groupsize == 0:
            print()             # Space down at end of members
    print()

if __name__ == "__main__":
    main()

4. Run the program
Here’s a sample run from running this program in my Introductory Computer Science course:

PARTNERS:
Robby, Adam
Kareem, Aidin
Ella, Annie
Henry, Patty
Gwen, Ms. Dunham
Lucas, Carrie
Dylan, Audrey
Sean, Sinjin
Marcela

5. At an opportune time, have students exchange roles.
During every assignment, assuming I’ve done a good job of building in an unexpected challenge or new idea, I’ll ask for attention: “Hands off the keyboard!” or something similar. I’ll pose a question regarding the work that they’ve done, or share some observations I’ve made, or ask if anyone has come across the difficulty that I’ll expect they’re going to have. After this brief interruption, I’ll ask them to change roles and continue their work.

Sometimes the process doesn’t work quite right the first time, or there may be mid-course corrections required if students get a little sloppy in their treatment of each other. That can happen in any classroom environment. The fact that students are truly randomly assigned, however, seems to keep them on their best behavior. They know that I don’t have any intentions in assigning them to a given partner–this is just who they’re going to be working with today.

Here’s a video clip of my students working on a programming assignment in a Paired environment.

Overall, I’ve been very pleased with how this process has worked with my students over time. Give it a try in your classroom and see what you think!