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=0,pady=20)

#,padx=10,pady=10
def button_click(number):
    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)


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_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=40, pady=20, command=button_divide)

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)

#put 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_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()
