Exercise: Grade overview – Hands-on Computer Science

Download as a script python-exercise-grades.py with the task as comments, to run in VS Code or Positron

Task

Ten exams have been marked, and their points from 0 to 100 are already in the program. First write a function grade(points) that returns the grade for the points: from 90 points a 1, from 75 a 2, from 60 a 3, from 50 a 4 and below that a 5. The main program main then prints every exam with its number, its points and its grade. At the end it writes how many exams have passed, that is have a 4 or better, and how many points there were on average, with one decimal place.

What it should look like

Exam 1: 95 points, grade 1
Exam 2: 72 points, grade 3
Exam 3: 48 points, grade 5
Exam 4: 88 points, grade 2
Exam 5: 61 points, grade 3
Exam 6: 50 points, grade 4
Exam 7: 30 points, grade 5
Exam 8: 79 points, grade 2
Exam 9: 90 points, grade 1
Exam 10: 66 points, grade 3
8 of 10 passed
Average: 67.9 points

Your program

def main():
    exams = [95, 72, 48, 88, 61, 50, 30, 79, 90, 66]
    passed = 0

    # Print every exam with number, points and grade
    # and count on the way how many have passed.

    # Print the number of passes and the average.


def grade(points):
    # Return the grade 1 to 5 for the points.
    return 5


main()

Because grade returns its result, you can check it on its own before you write the loop. To do so, replace the last line for the time being with print(grade(90), grade(89), grade(50), grade(49)); the result should be 1 2 4 5.

SHOW HINT 1

In grade the order matters: check points >= 90 first, then the condition points >= 75 with elif and so on downwards, and whatever is left ends up in the else. Python takes the first branch whose condition holds, so 95 points get only the 1, even though 95 is also greater than 75.

SHOW HINT 2

for number, points in enumerate(exams, start=1): gives the number and the points of an exam in every round. In the body, call grade(points), keep the grade in a variable and count passed up by one if the grade is 4 or smaller.

SHOW THE SOLUTION

def main():
    exams = [95, 72, 48, 88, 61, 50, 30, 79, 90, 66]
    passed = 0

    for number, points in enumerate(exams, start=1):
        mark = grade(points)
        print(f"Exam {number}: {points} points, grade {mark}")
        if mark <= 4:
            passed += 1

    average = sum(exams) / len(exams)
    print(f"{passed} of {len(exams)} passed")
    print(f"Average: {average:.1f} points")


def grade(points):
    if points >= 90:
        return 1
    elif points >= 75:
        return 2
    elif points >= 60:
        return 3
    elif points >= 50:
        return 4
    else:
        return 5


main()

A single loop prints every line and counts the passes along the way, while sum() and len() give the average without any loop. In main the grade is called mark and not grade, because that name already belongs to the function: a variable grade in main would hide the function there, and Python would report an error at the call.

For the quick ones

Also print how often each grade occurs, such as Grade 1: 2 times. For this, create a list counts = [0, 0, 0, 0, 0] before the loop, whose first place counts the ones, the second the twos and so on, and in the loop increase the right place with counts[mark - 1] += 1. A second loop with enumerate(counts, start=1) then prints the five lines.