Мой тестовый код показывает только использование одного CSV-файла: использование tkinter и python

Question

Мой тест в настоящее время распознает только один из трех CSV-файлов, отправленных с ним. это файл hardquestion.csv. Я пытаюсь иметь разные уровни сложности. Вот мой код:

import os
from tkinter import *
import tkinter.messagebox 
import random
#from PIL import ImageTk,Image
global score
score = 0
global count
global filename
count = 0
root = Tk()
root.title('Quiz')
root.config(bg = 'white')
root.geometry('770x555')

def menubutton():
    Easybutton = Button(root, text = 'easy', command = easy())
    Easybutton.pack()

    Mediumbutton = Button(root, text = 'medium', command = medium())
    Mediumbutton.pack()

    Hardbutton = Button(root, text = 'hard', command = hard())
    Hardbutton.pack()

# please read / the filename is always equal to hardquestion.csv / idk why??????

def easy ():
    global filename
    filename = "easyquestion.csv"

def medium():
    global filename
    filename = "mediumquestion.csv"

def hard():
    global filename
    filename = "hardquestion.csv"



class Question:
    def __init__(self, question, correct_ans):
        self.question = question
        self.correct_ans = correct_ans


def ask_quit():
    if tkinter.messagebox.askokcancel("Quit", "The quiz has finished now, would you like to quit?"):
        root.destroy()

def checkResult(letter):
    global score
    if letter == currentQuestion.correct_ans:
        score += 1
    if not len(questions) == 0:
        getNewQuestion()
    else:
        result()
        ask_quit()

def getNewQuestion():
    global count
    global currentQuestion
    currentQuestion = questions.pop()
    for i, var in enumerate((titleVar, aVar, bVar, cVar, dVar)):
        var.set(currentQuestion.question[i])
    count+= 1

def result():
    global score
    s = "your score is " + str(score)
    tkinter.messagebox.showinfo("Result", s)

def buttons():
    question = Label(root, textvariable=titleVar)
    question.pack()

    A = Button(root, textvariable = aVar, command = lambda: checkResult('A'))
    A.pack()

    B = Button(root, textvariable = bVar, command = lambda: checkResult('B'))
    B.pack()

    C = Button(root, textvariable = cVar, command = lambda: checkResult('C'))
    C.pack()

    D = Button(root, textvariable = dVar, command = lambda: checkResult('D'))
    D.pack()

menubutton()
file_handle = os.path.join(os.path.dirname(__file__), filename) 
print(filename)
count = 0
score = 0

questions = []

with open(filename, 'r') as file_handle:
    displayQ = []
    for line in file_handle:
        line_sections = line.strip().split(",")
        displayQ = line_sections[:-1]
        correct_ans = line_sections[-1]
        questions.append(Question(displayQ, correct_ans))

titleVar = StringVar()
aVar = StringVar()
bVar = StringVar()
cVar = StringVar()
dVar = StringVar()

currentQuestion = None
getNewQuestion()

canvas = Canvas(width = 100, height = 100, bg = 'black')
canvas.pack(expand = YES, fill = BOTH)

buttons()

root.mainloop()

Вам понадобятся 3 файла .csv с именами "easyquestion.csv", "mediumquestion.csv" и "hardquestion.csv", которые хранятся в та же папка. Они будут выглядеть примерно так

#easyquestion.csv
what is the smallest country in the world?,a) Monaco,b) Vatican City,c)Luxembourg,d)Maldives,B
what is the largest country in the world?,a)Russia,b)USA,c)India,d)China,A
what is the largest continent in the world?,a)Europe,b)Africa,c)Asia,d)Australia,C

#mediumquestion.csv
where is Genghis Khan from?,a)China,b)Nigeria,c)Mongolia,d)Kazakhstan,C
what is Newton's second law of motion?,a) F=ma,b)E=mc^2,c)mv-mu,d) v=u+at,A
who was the first man to walk on the moon?,a)Buzz Aldrin,b)Neil Armstrong,c)Charles Duke,d)David Scott,B

#hardquestion.csv
In Music what term is used to denote a gradual increase in loudness in a piece of music?,a)cresecendo,b)pitch rise,c)note amplification,d)crese rise,A
How many freds are there in a guitar?,a)29,b)25,c)20,d)22,B
What do the initials POTUS stand for?,a)politicians of the United States,b)prime minister of the United States,c)Parliament of the United States,d)president of the United States,D

Заранее спасибо!