calculator2.py

from Tkinter import *
from functools import partial


def button_pressed(value):
    expression_field_value.set(expression_field_value.get() + str(value))


def equal_pressed():
    try:
        result = eval(expression_field_value.get())
        expression_field_value.set(result)
    except ZeroDivisionError:
        expression_field_value.set("Division by zero error")


def clear_pressed():
    expression_field_value.set("")


if __name__ == "__main__":
    window = Tk()
    window.title("My Little Calculator")

    expression_field_value = StringVar()
    expression_field = Entry(window, width=30, textvariable=expression_field_value)
    expression_field.grid(row=0, column=0, columnspan=4)

    button_rows = [
        ["1", "2", "3", "*"],
        ["4", "5", "6", "-"],
        ["7", "8", "9", "+"],
        ["0", "/"]
    ]

    for row, buttons in enumerate(button_rows):
        for col, button_value in enumerate(buttons):
            when_pressed = partial(button_pressed, button_value)
            button1 = Button(window, text=button_value, height=3, width=3, borderwidth=1, command=when_pressed)
            button1.grid(row=row + 1, column=col if button_value != "/" else 3, sticky="ew")

    equal_button = Button(window, text="=", height=3, width=3, borderwidth=1, command=equal_pressed)
    equal_button.grid(row=4, column=1, sticky="ew")

    clear_button = Button(window, text="C", height=3, width=3, borderwidth=1, command=clear_pressed)
    clear_button.grid(row=4, column=2, sticky="ew")

    window.mainloop()