test preparation application, needs a excel file of question and answers, application asks one by one

test

from tkinter import *
import pandas as pd
import xdrlib
import random
from pynput import keyboard

from array import array as ar
def main():
    
      
    def startbutton():
        label1.text=lis.values[0]
        root.update_idletasks()       
    def c_list(selection):
      
        xl = pd.ExcelFile('C:/Users/erdem/Desktop/Comptia_Network_Plus.xlsx')
        lis=xl.parse('Sheet'+str(selection))
        
        return lis             
    def valu():
        

        def nextbutton(): 
            
            selection=var.get()
            test=a.get()
      
            #lis=c_list(selection)
            #if selection!=a.get():a.set(selection)
            ls=c_list(selection)
         
            if test>=len(ls)-1:a.set(-1)
            else:
                a.set(a.get()+1)
                test=a.get()
            #d=random.randrange(0, len(ls), step=1, _int=int)
            text.set(ls.values[test][0])
            definition.set(ls.values[test][1])
            
            #root.update_idletasks()
            
        
      
    
        
        text=StringVar()
        definition=StringVar()        
        Frame2= Frame(root,width=95,height=20,bg="#E1E1E1")
        
        label1 = Label(Frame2,width=95,height=5,fg="#6E2C00",bg="#B9B9B9",wraplength=600,font=("Helvetica",18),textvariable=text)
           
        label1.pack_propagate(0)
        label1.pack(fill=BOTH,expand=NO)
        Frame2.pack_propagate(1)
        Frame2.pack(fill=X,padx=15,pady=15,expand=NO)
        label2= Label(Frame2,width=95,height=15,bg="#E1E1E1",fg="#5B2C6F",font=("Helvetica",15),wraplength=600, textvariable=definition)   
        label2.pack(fill=BOTH,expand=NO)
        Frame1= Frame(root,width=95,height=5,bg="#E1E1E1")
        
        B = Button(Frame1,command=startbutton,width=42,height=2,bg="#B9B9B9", text ="Start")
        B.pack(side=LEFT)
        f = Button(Frame1,width=42,height=2,bg="#B9B9B9", text ="Exit",command=sys.exit)
        B.pack(side=LEFT)
        h = Button(Frame1,command=nextbutton,width=42,height=2,bg="#B9B9B9", text ="Next")
        h.pack(side=LEFT)
        f.pack(side=LEFT)
        Frame1.pack(fill=X,padx=15,pady=15)        
    root=Tk()
    global lis
    global selection,test
    global text,test
    global definition
    global var
    lis=ar('B')
    var=IntVar()
    selection=IntVar()
    test=IntVar()
    var.set(1)
    global a
    a=IntVar()
    a.set(-1)
    print (a,selection)
    PROGRAM_NAME="Network+ Exams"
    root.title(PROGRAM_NAME)
    root.config(bg="#808B96")
    menu_bar=Menu(root)
    f_menu=Menu(menu_bar,tearoff=0)
    file_menu=Menu(menu_bar,tearoff=0)
    for i in range(1,14):
        f_menu.add_radiobutton(label='Chapter '+str(i),variable=var,value=i,command=valu)
    file_menu.add_command(label='Import source file')
    file_menu.add_command(label='Export source file')
    menu_bar.add_cascade(label='File',menu=file_menu)
    menu_bar.add_cascade(label='Chapters',menu=f_menu)
    menu_bar.add_cascade(label='Settings')
    menu_bar.add_cascade(label='About')
    root.config(menu=menu_bar)
    root.geometry("900x600")
    root.resizable(0,0)

    global label1
    
    

    root.mainloop()
main()