GUI for simple calculation

Simple Calculator with GUI

#Creator: Siba Moussa
#Date: March 4, 2020
#Purpose: Build a GUI for a simple calculator
from tkinter import *

import tkinter
import tkinter.messagebox


def proces():
    number1 = Entry.get(E1)
    number2 = Entry.get(E2)
    operator = Entry.get(E3)
    number1=int(number1)
    number2=int(number2)
    if operator=="+":
        answer=number1+number2
    if operator == "-":
        answer = number1 - number2
    if operator=="*":
        answer=number1*number2
    if operator == "/":
        answer = number1/number2
    Entry.insert(E4,0,answer)
    print(answer)

top=tkinter.Tk()
L1=Label(top,text="Siba's calculator").grid(row=0,column=1)
L2=Label(top,text="Number1",).grid(row=1,column=0)
L3=Label(top,text="Number2",).grid(row=2,column=0)
L4=Label(top,text="Operator",).grid(row=3,column=0)
L4=Label(top,text="Answer",).grid(row=4,column=0)
E1=Entry(top,bd=5)
E1.grid(row=1,column=1)
E2=Entry(top,bd=5)
E2.grid(row=2,column=1)
E3=Entry(top, bd=5)
E3.grid(row=3,column=1)
E4=Entry(top, bd=5)
E4.grid(row=4,column=1)
B=Button(top,text="Submit",command= proces).grid(row=5,column=1,)
top.mainloop()