from tkinter import *

root = Tk()
root.title("Simple Calculator")

e = Entry(root, width = 40, borderwidth = 5)
e.grid(row = 0, column = 0, columnspan = 3, padx = 10, pady = 10)

def button_click(num):
    current = e.get()
    e.delete(0, END)
    e.insert(0, str(current) + str(num))

def button_clr():
    e.delete(0, END)

def button_add():
    a = e.get()
    global first
    first = int(a)
    e.delete(0, END)

def button_equal():
  b = e.get()
  e.delete(0, END)
  e.insert(0, str(first + int(b)))
    
# define buttons

button_1 = Button(root, text = "1", padx = 40, pady = 20, command = lambda : button_click(1))
button_2 = Button(root, text = "2", padx = 40, pady = 20, command = lambda : button_click(2))
button_3 = Button(root, text = "3", padx = 40, pady = 20, command = lambda : button_click(3))
button_4 = Button(root, text = "4", padx = 40, pady = 20, command = lambda : button_click(4))
button_5 = Button(root, text = "5", padx = 40, pady = 20, command = lambda : button_click(5))
button_6 = Button(root, text = "6", padx = 40, pady = 20, command = lambda : button_click(6))
button_7 = Button(root, text = "7", padx = 40, pady = 20, command = lambda : button_click(7))
button_8 = Button(root, text = "8", padx = 40, pady = 20, command = lambda : button_click(8))
button_9 = Button(root, text = "9", padx = 40, pady = 20, command = lambda : button_click(9))
button_0 = Button(root, text = "0", padx = 40, pady = 20, command = lambda : button_click(0))
button_add = Button(root, text = "+", padx = 39, pady = 20, command = button_add)
button_equal = Button(root, text = "=", padx = 90, pady = 20, command = button_equal)
button_clr = Button(root, text = "clear", padx = 70, pady = 20, command = button_clr)

# put the bottons on the screen

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_clr.grid(row = 4, column = 1, columnspan = 2)
button_add.grid(row = 5, column = 0)
button_equal.grid(row = 5, column = 1, columnspan = 2)

root.mainloop()

