For example, you may wish to bind a key to a button. This helps you streamline the control of an application. If you just have two input methods there could be a problem with things like arrows and backspace or delete messing up the calculator window.

import tkinter as tk
from tkinter import ttk

def press_eq(event):
    print('Equals key pressed.')

root = tk.Tk()

button1 = ttk.Button(root, text='=')
button1.bind('<Return>', press_eq)


button1.focus()
button1.pack(expand=True)

root.mainloop()