Quiz in Tkinter

import tkinter as tk
import random
def show_frame(frame):
    frame.tkraise()

def validateReg(username, password):
    userstr = username.get()
    passstr = password.get()
    print("Username entered :", userstr)
    print("Password entered :", passstr)
    text_file = open("passdoc.txt", "w")
    text_file.write(userstr+"\n")
    text_file.write(passstr+"\n")
    text_file.close()

def close():
    root.destroy()

def FindLogin(username, password):
    userstr = username.get()
    passstr = password.get()
    text_file = open("passdoc.txt", "r")
    login_info = text_file.read()
    if login_info == username and password:
        commad=close
    text_file.close()

def show_question(question):
    global current_question
    current_question = question

    # configure the question label to display the question
    question_label.configure(text=question.question)

    # configure the radiobuttons to hold the answers
    answers = list(question.answers)
    random.shuffle(answers)
    for i in range(4):
        answer_radiobuttons[i].configure(text=answers[i])

    answer_var.set(-1)  # causes buttons to show as unselected

class Question():
    def __init__(self, question_string):
        subject, question,answer1,answer2,answer3,answer4 = question_string.split(":")
        self.subject = subject
        self.question = question
        self.correct_answer = answer1
        self.answers = (answer1, answer2, answer3, answer4)

def check_answer():
    choice = answer_var.get()
    choice = int(choice)
    answer = answer_radiobuttons[choice].cget("text")

    if answer == current_question.correct_answer:
        result_label.configure(text="Correct")
    else:
        result_label.configure(text="Incorrect")



window = tk.Tk()
window.state('zoomed')

window.rowconfigure(0,weight=1)
window.columnconfigure(0, weight=1)

register = tk.Frame(window)
login = tk.Frame(window)
subject = tk.Frame(window)
english = tk.Frame(window)
maths = tk.Frame(window)
science = tk.Frame(window)
computing = tk.Frame(window)
history = tk.Frame(window)
english_multiple = tk.Frame(window)
english_fill = tk.Frame(window)
english_quick = tk.Frame(window)
english_spag = tk.Frame(window)
difficulty = tk.Frame(window)
diff_ks2 = tk.Frame(window)
diff_ks3 = tk.Frame(window)
diff_ks4 = tk.Frame(window)
diff_adult = tk.Frame(window)

game = tk.Frame(window)
question_frame = tk.Frame(game)
game2 = tk.Frame(window)


for frame in (game,register,login,subject,english,maths,science,computing,history,difficulty,diff_ks2,diff_ks3,diff_ks4,diff_adult,english_multiple,english_fill,english_quick,english_spag,):
    frame.grid(row=0,column=0,sticky='nsew')


#================Register frame
register.configure(background='RoyalBlue4')
register_title = tk.Label(register, text='Register', fg='snow', bg='RoyalBlue4', font=('Chalkboard', 25))
register_title.pack(fill='x')
lblInst = tk.Label(register, text='Please choose username and password:', fg='snow', bg='RoyalBlue4', font=('Chalkboard SE', 25))
lbl = tk.Label(register, text="Username:", fg='snow', bg='RoyalBlue4', font=('Chalkboard'))
ent = tk.Entry(register)
lbl2 = tk.Label(register, text='Password:', fg='snow', bg='RoyalBlue4', font=('Chalkboard'))
ent2 = tk.Entry(register,show='*')
lblInst.pack()
lbl.pack()
ent.pack()
lbl2.pack()
ent2.pack()
register_btn = tk.Button(register, text='Next ->', font=('Chalkboard'), command=lambda:show_frame(login))
register_btn.pack()

#================Login frame
login.configure(background='RoyalBlue4')
login_title = tk.Label(login, text='Login', fg='snow', bg='RoyalBlue4', font=('Chalkboard', 25))
login_title.pack(fill='x')
lblInst = tk.Label(login, text='Please enter username and password:', fg='snow', bg='RoyalBlue4', font=('Chalkboard SE', 25))
lbl = tk.Label(login, text="Username:", fg='snow', bg='RoyalBlue4', font=('Chalkboard'))
ent = tk.Entry(login)
lbl2 = tk.Label(login, text='Password:', fg='snow', bg='RoyalBlue4', font=('Chalkboard'))
ent2 = tk.Entry(login,show='*')
lblInst.pack()
lbl.pack()
ent.pack()
lbl2.pack()
ent2.pack()
login_btn = tk.Button(login, text='Next ->', font=('Chalkboard'), command=lambda:show_frame(subject))
login_btn2 = tk.Button(login, text='<- Back', font=('Chalkboard'), command=lambda:show_frame(register))
login_btn.pack()
login_btn2.pack()


#================Subject frame
subject.configure(background='RoyalBlue4')
subject_title = tk.Label(subject, text='Subject selection', fg='snow', bg='RoyalBlue4', font=('Chalkboard', 25))
subject_title.pack(fill='x')
lblInst = tk.Label(subject, text='Please select a subject:', fg='snow', bg='RoyalBlue4', font=('Chalkboard SE', 25))
lblInst.pack()
lbl.pack()
fr = tk.Frame(subject, height=700, width=1200, bg='RoyalBlue4', borderwidth=30)
fr.place(relx=.5, rely=.4, anchor="c")
btnE = tk.Button(fr, text='English', command=lambda:show_frame(english), fg='gray4', bg='snow', height=2, width=30, font=('Chalkboard'))
btnM = tk.Button(fr, text='Maths', command=lambda:show_frame(maths), fg='gray4', bg='snow', height=2, width=30, font=('Chalkboard'))
btnS = tk.Button(fr, text='Science', command=lambda:show_frame(science), fg='gray4', bg='snow', height=2, width=30, font=('Chalkboard'))
btnC = tk.Button(fr, text='Computing', command=lambda:show_frame(computing), fg='gray4', bg='snow', height=2, width=30, font=('Chalkboard'))
btnH = tk.Button(fr, text='History', command=lambda:show_frame(history), fg='gray4', bg='snow', height=2, width=30, font=('Chalkboard'))

btnE.pack()
btnM.pack()
btnS.pack()
btnC.pack()
btnH.pack()

subject_button = tk.Button(subject, text='<- Back', font=('Chalkboard'), command=lambda:show_frame(login))
subject_button.pack()


#================English game type frame
english.configure(background='RoyalBlue4')
english_title = tk.Label(english, text='English game type selection', fg='snow', bg='RoyalBlue4', font=('Chalkboard', 25))
english_title.pack(fill='x')
lblInst = tk.Label(english, text='Please select a game type:', fg='snow', bg='RoyalBlue4', font=('Chalkboard SE', 25))
lblInst.pack()
lbl.pack()
fr = tk.Frame(english, height=700, width=1200, bg='RoyalBlue4', borderwidth=30)
fr.place(relx=.5, rely=.4, anchor="c")
btnMC = tk.Button(fr, text='Multiple choice', command=lambda:show_frame(difficulty), fg='gray4', bg='snow', height=2, width=30, font=('Chalkboard'))
btnMC.pack()
btnFitB = tk.Button(fr, text='Fill in the blank', command=lambda:show_frame(difficulty), fg='gray4', bg='snow', height=2, width=30, font=('Chalkboard'))
btnFitB.pack()
btnQf= tk.Button(fr, text='Quick-fire questions', command=lambda:show_frame(difficulty), fg='gray4', bg='snow', height=2, width=30, font=('Chalkboard'))
btnQf.pack()
btnSPaG = tk.Button(fr, text='SPaG mode', command=lambda:show_frame(difficulty), fg='gray4', bg='snow', height=2, width=30, font=('Chalkboard'))
btnSPaG.pack()
english_button = tk.Button(english, text='<- Back', font=('Chalkboard'), command=lambda:show_frame(subject))
english_button.pack()

#===============Difficulty selection
difficulty.configure(background='RoyalBlue4')
difficulty_title = tk.Label(difficulty, text='Difficulty selection', fg='snow', bg='RoyalBlue4', font=('Chalkboard', 25))
difficulty_title.pack(fill='x')
lblInst = tk.Label(difficulty, text='Please select a difficulty:', fg='snow', bg='RoyalBlue4', font=('Chalkboard SE', 25))
lblInst.pack()
lbl.pack()
fr = tk.Frame(difficulty, height=700, width=1200, bg='RoyalBlue4', borderwidth=30)
fr.place(relx=.5, rely=.4, anchor="c")
btn2 = tk.Button(fr, text='KS3', command=lambda:show_frame(game), fg='gray4', bg='snow', height=2, width=30, font=('Chalkboard'))
btn2.pack()
btn3 = tk.Button(fr, text='KS4', command=lambda:show_frame(game), fg='gray4', bg='snow', height=2, width=30, font=('Chalkboard'))
btn3.pack()
btn4 = tk.Button(fr, text='KS5', command=lambda:show_frame(game), fg='gray4', bg='snow', height=2, width=30, font=('Chalkboard'))
btn4.pack()
btnA = tk.Button(fr, text='Adult', command=lambda:show_frame(game), fg='gray4', bg='snow', height=2, width=30, font=('Chalkboard'))
btnA.pack()
difficulty_button = tk.Button(difficulty, text='<- Back', font=('Chalkboard'), command=lambda:show_frame(english))
difficulty_button.pack()


#==============Game Frame
game.configure(background='RoyalBlue4')
game_title = tk.Label(game, text='Multiple Choice!', fg='snow', bg='RoyalBlue4',font=('Chalkboard', 25))
game_title.pack(fill='x')
question_frame.configure(background='White')
questions = {"English": [], "Maths": [], "Science": []}
lblInst = tk.Label(game, text='Question 1:', fg='snow', bg='RoyalBlue4', font=('Chalkboard SE', 25))
lblInst.pack()
question_label = tk.Label(question_frame, width=80, anchor="c")


answer_var = tk.StringVar()

answer_radiobuttons = (
    tk.Radiobutton(question_frame, anchor="w", variable=answer_var, value=0, command=check_answer),
    tk.Radiobutton(question_frame, anchor="w", variable=answer_var, value=1, command=check_answer),
    tk.Radiobutton(question_frame, anchor="w", variable=answer_var, value=2, command=check_answer),
    tk.Radiobutton(question_frame, anchor="w", variable=answer_var, value=3, command=check_answer),
)
result_label = tk.Label(game)


question_label.pack(side="top", fill="x", anchor="c")
result_label.pack(side="bottom", fill="x")

for button in answer_radiobuttons:
    button.pack(side="top", fill="x", expand=True, anchor="n")

f = open("questions.txt","r")
for row in f.readlines():
    question = Question(row)
    questions[question.subject].append(question)
    show_question(question)
f.close()

question_frame.pack()

#game_button = tk.Button(game, text='Submit', font=('Chalkboard'), command=lambda:check_answer)
game_button2 = tk.Button(game, text='<- Back', font=('Chalkboard'), command=lambda:show_frame(difficulty))
#game_button.pack()
game_button2.pack()

show_frame(register)
window.mainloop()