Creating a program that compares test scores to answers

Python Help
,
1

Hey guys, so the issue I’m having is the program I’ve written seems to kind of do what it’s intended to do. The problem, though, is that I can’t seem to get it to compare the answers correctly, resulting in false scores.

def Main():

    total = 0
    answers = ['A','C','A','A','D','B','C','A','C','B','A','D','C','A','D','C','B','B','D','A']

    infile = open('Scores.txt', 'r')
    student_answers = infile.readline()
    infile.close()
    print(student_answers)

    for answer in student_answers:
        for S in range(len(answer)):
            if answer[S] == answers[S]:
                total += 1


    print('Total correct answers: ', total)
    print('Total of incorrect answers: ', 20 - total)

    if total >= 15:
            print('Congratulations! You passed the exam.')
    elif total < 15:
            print('Sorry, you have failed the exam.')
Main()

What’s happening is when answers which are the answer key, are compared to the answers in the Scores.txt file, it keeps giving me 7 correct and 13 wrong even if the file has the same answers as the answer key. It seems to be counting only the A’s as correct, as there are 7 of those in the answers list.

Any and all help is appreciated thank you.

2

What does Scores.txt look like? I would guess something like “ACAADBC…”, since you’re calling readline() once and then iterating over the resulting string.

In any event, let’s assume you have student_answers that is an iterable of one-character strings (whether that’s a string or a list of strings). And let’s further assume that the answers are all correct.

This loop will proceed as follows:

answer S answers[S] answer[S] answer[S] == answers[S]
"A" 0 "A" "A" True
"C" 0 "A" "C" False
"A" 0 "A" "A" True
"A" 0 "A" "A" True
"C" 0 "A" "D" False

Your outer loop seems fine, but your inner loop is just always a range(1). And while I’m sure there’s a way to do this with a nested loop, it will almost certainly be doing more work than you really need.

I think the zip() builtin function could be useful here.

1 Like
3

Assuming that the Score.txt file is ACAADBCACBADCADCBBDA, you can create a student_answers list object with student_answers = [answer for answer in infile.readline()]

Also, you don’t need a nested loop:

for index, _ in enumerate(answers):
        if student_answers[index] == answers[index]:
            total += 1
4

or even better:

for student, correct in zip(students_answers, answers):
    if student == correct:
        total += 1

To be really cleaver, you could take advantage of TRue being of value 1:

total += student == correct

But I really don’t like that – a bit too magic :slight_smile:

BTW: basic "print debugging is a critical skill tyr adding a print to your code:

    for answer in student_answers:
        for S in range(len(answer)):
            print(answer[S], answers[S])
            if answer[S] == answers[S]:
                total += 1

and you’d probably see the issue, if not the solution …