Не профессор но стремлюсь к нему.

from tkinter import *

vikno = Tk()

vikno.title('Калькулятор')

vikno.geometry("380x200")

def plus():

   a = int(entry1.get())

   b = int(entry2.get())

   c = a + b

   entry3['state'] = "normal"

   entry3.delete(0, END)

   entry3.insert(0, c)

   entry3['state'] = "readonly"

def minus():

   a = int(entry1.get())

   b = int(entry2.get())

   c = a - b

   entry3['state'] = "normal"

   entry3.delete(0, END)

   entry3.insert(0, c)

   entry3['state'] = "readonly"

def multiply():

   a = int(entry1.get())

   b = int(entry2.get())

   c = a * b

   entry3['state'] = "normal"

   entry3.delete(0, END)

   entry3.insert(0, c)

   entry3['state'] = "readonly"

def divide():

   a = int(entry1.get())

   b = int(entry2.get())

   c = a / b

   entry3['state'] = "normal"

   entry3.delete(0, END)

   entry3.insert(0, c)

   entry3['state'] = "readonly"

def clear():

   entry1.delete(0, END)

   entry2.delete(0, END)

   entry3.delete(0, END)

   entry3['state'] = 'readonly'

label1 = Label(vikno, text="Перше число", font="Arial 16 italic")

label1.grid(row=0, column=0, columnspan=2, padx=10, pady=10)

label2 = Label(vikno, text="Друге число", font="Arial 16 italic")

label2.grid(row=0, column=3, columnspan=2, padx=10, pady=10)

entry1 = Entry(vikno)

entry1.grid(row=1, column=0, columnspan=2, padx=10, pady=10)

entry2 = Entry(vikno)

entry2.grid(row=1, column=3, columnspan=2, padx=10, pady=10)

button1 = Button(vikno, text="+", font="Arial 16 bold", command=plus)

button1.grid(row=2, column=0, padx=10, pady=10)

button2 = Button(vikno, text="-", font="Arial 16 bold", command=minus)

button2.grid(row=2, column=1, padx=10, pady=10)

button3 = Button(vikno, text="*", font="Arial 16 bold", command=multiply)

button3.grid(row=2, column=2, padx=10, pady=10)

button4 = Button(vikno, text="/", font="Arial 16 bold", command=divide)

button4.grid(row=2, column=3, padx=10