text: from tkinter import *
  
  root = Tk()
  root.title('Simple Calculator')
  e = Entry(root,width = 35,borderwidth=5)
  e.grid(row=0,column=0,padx=10,pady=10,columnspan=3)
  
  def buttonClick(number):
      #
      current_num = e.get()
      e.delete(0,END)
      e.insert(0,str(current_num)+str(number))
  
  def buttonClear():
      e.delete(0,END)
  
  def buttonAdd():
      first_number = e.get()
      global f_num 
      global math 
      math = 'add'
      f_num = int(first_number)
      e.delete(0,END)
  
  def buttonSub():
      first_number = e.get()
      global f_num 
      global math
      math = 'sub'
      f_num = int(first_number)
      e.delete(0,END)
  
  def buttonMul():
      first_number = e.get()
      global f_num 
      global math 
      math = 'mul'
      f_num = int(first_number)
      e.delete(0,END)
  
  def buttonDiv():
      first_number = e.get()
      global f_num 
      global math
      math = 'div'
      f_num = int(first_number)
      e.delete(0,END)
  
  def buttonEqual():
      second_number = e.get()
      e.delete(0,END)
  
      if math == 'add':
          e.insert(0,f_num + int(second_number))
  
      elif math == 'sub':
          e.insert(0,f_num - int(second_number))
  
      elif math == 'mul':
          e.insert(0,f_num * int(second_number))
  
      elif math == 'div':
          e.insert(0,f_num / int(second_number))
  
  
  
  
  
  
  # define buttons   
  button_1 = Button(root,text='1', padx=40,pady=20,command=lambda: buttonClick(1))    
  button_2 = Button(root,text='2', padx=40,pady=20,command=lambda: buttonClick(2))    
  button_3 = Button(root,text='3', padx=40,pady=20,command=lambda: buttonClick(3))    
  button_4 = Button(root,text='4', padx=40,pady=20,command=lambda: buttonClick(4))    
  button_5 = Button(root,text='5', padx=40,pady=20,command=lambda: buttonClick(5))    
  button_6 = Button(root,text='6', padx=40,pady=20,command=lambda: buttonClick(6))    
  button_7 = Button(root,text='7', padx=40,pady=20,command=lambda: buttonClick(7))    
  button_8 = Button(root,text='8', padx=40,pady=20,command=lambda: buttonClick(8))    
  button_9 = Button(root,text='9', padx=40,pady=20,command=lambda: buttonClick(9))    
  button_0 = Button(root,text='0', padx=40,pady=20,command=lambda: buttonClick(0))  
  
  button_add = Button(root,text='+', padx=39,pady=20,command= buttonAdd)    
  button_clear = Button(root,text='Clear', padx=79,pady=20,command= buttonClear)    
  button_equal = Button(root,text='=', padx=91,pady=20,command= buttonEqual)    
  button_sub = Button(root,text='-', padx=41,pady=20,command= buttonSub)    
  button_mul = Button(root,text='*', padx=40,pady=20,command= buttonMul)    
  button_div = Button(root,text='/', padx=41,pady=20,command= buttonDiv)    
  
  
  
  #grid the buttons to display
  button_1.grid(row=3,column=0)
  button_2.grid(row=3,column=1)
  button_3.grid(row=3,column=2)
  
  button_4.grid(row=2,column=0)
  button_5.grid(row=2,column=1)
  button_6.grid(row=2,column=2)
  
  button_7.grid(row=1,column=0)
  button_8.grid(row=1,column=1)
  button_9.grid(row=1,column=2)
  button_0.grid(row=4,column=0)
  
  button_add.grid(row=5,column=0)
  button_equal.grid(row=5,column=1,columnspan=2)
  button_clear.grid(row=4,column=1,columnspan=2)
  
  button_sub.grid(row=6,column=0)
  button_mul.grid(row=6,column=1)
  button_div.grid(row=6,column=2)
  
  
  
  root.mainloop()