from tkinter import *

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

e=Entry(root, width=35,borderwidth=5)
e.grid(row=0,column=0, columnspan=3, padx=10, pady=10)

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

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

def button_add():
    first_number=e.get()
    global f_num
    global math
    math="addition"
    f_num=int(first_number)
    e.delete(0, END)

def button_equal():
    second_number=e.get()
    e.delete(0, END)
    if math=='addition':
        e.insert(0, f_num+int(second_number))
    if math=='subtraction':
        e.insert(0, f_num-int(second_number))
    if math=='multiplication':
        e.insert(0, f_num*int(second_number))
    if math=='division':
        e.insert(0, f_num/int(second_number))
        
def button_subtract():
    first_number=e.get()
    global f_num
    global math
    math="subtraction"
    f_num=int(first_number)
    e.delete(0, END)

def button_multiply():
    first_number=e.get()
    global f_num
    global math
    math="multiplication"
    f_num=int(first_number)
    e.delete(0, END)

def button_divide():
    first_number=e.get()
    global f_num
    global math
    math="division"
    f_num=int(first_number)
    e.delete(0, END)

# 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=91, pady=20, command=button_equal)
button_clear=Button(root, text='Clear', padx=79, pady=20, command=button_clear)

button_subtract=Button(root, text='-', padx=41, pady=20, command=button_subtract)
button_multiply=Button(root, text='*', padx=40, pady=20, command=button_multiply)
button_divide=Button(root, text='/', padx=41, pady=20, command=button_divide)

# place buttons

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

button_subtract.grid(row=6,column=0)
button_multiply.grid(row=6,column=1)
button_divide.grid(row=6,column=2)


root.mainloop()
