Майкл Доусон. Викторина

def open_file(file_name, mode):
    try:
        the_file = open(file_name, mode, encoding = 'utf-8')
    except IOError as e:
        print("Невозможно открыть файл. ", file_name, ". Работа программы будет завершена.\n", e)
        input("\n\nНажмите любую клавишу")
        sys.exit()
    else:
        return the_file
 
def next_line(the_file):
    line = the_file.readline()
    line = line.replace("/", "\n")
    return line
 
def next_block(the_file):
    category = next_line(the_file)
    question = next_line(the_file)
    answers = []
    for _ in range(4):
        answers.append(next_line(the_file))
    correct = next_line(the_file)
    if correct:
        correct = correct[0]
        explanation = next_line(the_file)
    return category, question, answers, correct, explanation
 
def welcome(title):
    print("Добро пожаловать в игру 'Викторина'!\n")
    print("\t\t" + title + "\n")
 
def main():
    trivia_file = open_file("D:\\py\\g7\\tr.txt", "r")
    title = next_line(trivia_file)
    welcome(title)
    #test(trivia_file)
    score = 0
    category, question, answers, correct, explanation = next_block(trivia_file)
    while category:
        print(category)
        print(question)
        for i in range(4):
            print("\t", i + 1, " - ", answers[i])
        answer = input("Ваш ответ: ")
        if answer == correct:
            print("\nДа!", end = " ")
            score += 1
        else:
            print("\nНет.", end = " ")
            print(explanation)
            print("Счет: ", score, "\n\n")
            category, question, answers, correct, explanation = next_block(trivia_file)
    trivia_file.close()
    print("Это был последний вопрос!")
    print("Вы заработали", score, " очков!")
 
main()
input("Нажмите Enter, чтобы выйти.")

def next_block(the_file):
    category = next_line(the_file)
    question = next_line(the_file)
    answers = []
    for _ in range(4):
        answers.append(next_line(the_file))
    correct = next_line(the_file)
    if correct: # если истина
        correct = correct[0]
        explanation = next_line(the_file) # то объявляем explanation и присваиваем значение
    return category, question, answers, correct, explanation # как вернуть не объявленную explanation если выше условие ложь?