Problem with GUI

[KostisPanagiotou]

import sqlite3
from Tkinter import *
import tkMessageBox
global selected_tuple
import time



class DB:
        def __init__(self):
            self.conn = sqlite3.connect("new5.db")
            self.cur = self.conn.cursor()
            self.cur.execute(
                "CREATE TABLE IF NOT EXISTS seti (id INTEGER PRIMARY KEY, El_N INTEGER)" )
            self.conn.commit()

        def __del__(self):
            self.conn.close()

        def view(self):
            self.cur.execute("SELECT * FROM seti")
            rows = self.cur.fetchall()
            return rows

        def insert(self, El_N):
            self.cur.execute("INSERT INTO seti VALUES (NULL,?)", (El_N))
            self.conn.commit()
            self.view()

        def update(self, id, El_N):
            self.cur.execute("UPDATE seti SET El_N=? WHERE id=?", (El_N, id))
            self.view()

        def delete(self, id):
            self.cur.execute("DELETE FROM seti WHERE id=?", (id,)) 
            self.conn.commit()
            self.view()

        def search(self, El_N=""):
            self.cur.execute("SELECT * FROM seti WHERE El_N=?" , (El_N))
            rows = self.cur.fetchall()
            return rows


db = DB()

def get_selected_row(event):
    global selected_tuple
    index = list1.curselection()[0]
    selected_tuple = list1.get(index)
    e1.delete(0, END)
    e1.insert(END, selected_tuple[1])
       

        
        
def view_command():
        list1.delete(0, END)
        for row in db.view():
            list1.insert(END, row)


def search_command():
        list1.delete(0, END)
        for row in db.search(E_N.get()):
            list1.insert(END, row)


def add_command():
        db.insert(E_N.get()) 
        list1.delete(0, END)
        list1.insert(END, (E_N.get()))


def delete_command():
        db.delete(selected_tuple[0])


def update_command():
        db.update(selected_tuple[0], E_N)


window = Tk()

window.title("My Books")

def on_closing():
        dd = db
        if tkMessageBox.askokcancel("Quit", "Do you want to quit?"):
            window.destroy()
            del dd


window.protocol("WM_DELETE_WINDOW", on_closing)  # handle window closing

EL1 = Label(window, text="ELEGANCE")
EL1.grid(row=0, column=0,columnspan=2, pady = 15)

E_N=IntVar()   
e1 = Entry(window, textvariable= E_N)
e1.grid(row=1, column=1,sticky=W)
 

list1 = Listbox(window, height=6, width=35)
list1.grid(row=17, column=0, rowspan=6, columnspan=2)
    
sb1 = Scrollbar(window)
sb1.grid(row=17, column=2, rowspan=6)

list1.configure(yscrollcommand=sb1.set)
sb1.configure(command=list1.yview)

list1.bind('<<ListboxSelect>>', get_selected_row)
    
b1 = Button(window, text="View all", width=12, command=view_command)
b1.grid(row=17, column=3)
     
b2 = Button(window, text="Search entry", width=12, command=search_command)
b2.grid(row=18, column=3)
     
b3 = Button(window, text="Add entry", width=12, command=add_command)
b3.grid(row=19, column=3)

b4 = Button(window, text="Update selected", width=12, command=update_command)
b4.grid(row=20, column=3)

b5 = Button(window, text="Delete selected", width=12, command=delete_command)
b5.grid(row=21, column=3)

b6 = Button(window, text="Close", width=12, command=window.destroy)
b6.grid(row=22, column=3)

window.mainloop()

I cant understand why the El_N INTEGER does not cooperate with E_N IntVar