Как рассчитать процент и среднее значение тестов в 2D-списке без использования таких библиотек, как pandas или numpy

Конечно, есть много способов сделать это, но вот одно из возможных решений. Я использовал только списки и кортежи. Используя словари, у вас будет более элегантный способ доступа к данным.

students = []
reference_scores = []

def get_data():
    with open("./data/testscores.csv", "r") as file:
        lineArray = file.read().splitlines()        

        for line in lineArray:
            raw_data = line.split(",")
            name = raw_data[0]
            scores = []
            percentages = []
            average_percentage = 0

            if name != 'Testoutof':
                scores = raw_data[1:]

                for index, score in enumerate(scores):
                    percentage = get_percentage(int(score), int(reference_scores[index]))
                    average_percentage += percentage
                    percentages.append(percentage)
                average_percentage //= len(scores)
                students.append( (name, percentages, average_percentage) )
            else:
                reference_scores = raw_data[1:]
    return students

def get_percentage(score, reference):
    return (score * 100) // reference

def print_scores(data):
    for obj in data:
        score_string = ''
        for score in obj[1]:
            score_string += f'{score}% '    
        print(f'{obj[0]} {score_string} Average = {obj[2]}')

students = get_data()
print_scores(students)

# Output
Bob 100% 81% 58% 72% 100% 81% 100% 90% 100% 72% 80% 83% 90% 100%  Average = 86
Sue 80% 72% 66% 81% 40% 72% 100% 70% 80% 27% 100% 83% 70% 100%  Average = 74
Jan 60% 54% 0% 45% 70% 81% 44% 70% 80% 45% 70% 8% 50% 100%  Average = 55    
Sam 80% 72% 66% 63% 70% 63% 100% 90% 90% 81% 80% 75% 100% 88%  Average = 79 
Tom 90% 81% 75% 81% 90% 81% 100% 90% 90% 90% 90% 75% 90% 100%  Average = 87

Использование list comprehension может дать вам тот же результат без какого-либо определения функции:

file=open("testscores.csv","r")
matrix=[line.strip().split(",") for line in file.readlines()[1:]]

for row in matrix:
  data=[int(i)*10 for i in row[1:]]
  print(row[0], "% ".join(map(str, data))+"%",  "Average =", sum(data)//len(data),"%")

Вывод:

Bob 100% 90% 70% 80% 100% 90% 90% 90% 100% 80% 80% 100% 90% 90% Average = 89 %
Sue 80% 80% 80% 90% 40% 80% 90% 70% 80% 30% 100% 100% 70% 90% Average = 77 %
Jan 60% 60% 0% 50% 70% 90% 40% 70% 80% 50% 70% 10% 50% 90% Average = 56 %
Sam 80% 80% 80% 70% 70% 70% 90% 90% 90% 90% 80% 90% 100% 80% Average = 82 %
Tom 90% 90% 90% 90% 90% 90% 90% 90% 90% 100% 90% 90% 90% 90% Average = 90 %