calculator.py

from tkinter import *

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


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

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

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

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

def button_equal():
	second_number = entry.get()
	entry.delete(0,END)
	if math == "Addition":
		entry.insert(0, f_num + int(second_number))

	if math == "Subtraction":
	    	entry.insert(0, f_num - int(second_number))

	if math == "Multiplication":
	    	entry.insert(0, f_num * int(second_number))

	if math == "Division":	
 	    	entry.insert(0, f_num / int(second_number))

def button_sub():
	first_number = entry.get()
	entry.delete(0,END)
	global f_num
	global math
	math = "Subtraction"
	f_num = int(first_number)

def button_mul():
	first_number = entry.get()
	entry.delete(0,END)
	global f_num
	global math
	math = "Multiplication"
	f_num = int(first_number)

def button_div():
	first_number = entry.get()
	entry.delete(0,END)
	global f_num
	global math
	math = "Division"
	f_num = int(first_number)
		

button_1 = Button(root, text="1", padx=45, pady=20, command=lambda: button_click(1))
button_2 = Button(root, text="2", padx=45, pady=20, command=lambda: button_click(2))
button_3 = Button(root, text="3", padx=45, pady=20, command=lambda: button_click(3))
button_4 = Button(root, text="4", padx=45, pady=20, command=lambda: button_click(4))
button_5 = Button(root, text="5", padx=45, pady=20, command=lambda: button_click(5))
button_6 = Button(root, text="6", padx=45, pady=20, command=lambda: button_click(6))
button_7 = Button(root, text="7", padx=45, pady=20, command=lambda: button_click(7))
button_8 = Button(root, text="8", padx=45, pady=20, command=lambda: button_click(8))
button_9 = Button(root, text="9", padx=45, pady=20, command=lambda: button_click(9))
button_0 = Button(root, text="0", padx=45, pady=20, command=lambda: button_click(0))
button_add = Button(root, text="+", padx=43, pady=20, command=button_add)
button_equal = Button(root, text="=", padx=97, pady=20, command=button_equal)
button_clear = Button(root, text="Clear", padx=85, pady=20, command=button_clear)
button_subtraction = Button(root, text="-", padx=45, pady=20, command=button_sub) 
button_multiplication = Button(root, text="*", padx=45, pady=20, command=button_mul)
button_division = Button(root, text="/", padx=48, pady=20, command=button_div)

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_subtraction.grid(row=6, column=0)
button_multiplication.grid(row=6, column=1)
button_division.grid(row=6, column=2)

root.mainloop()