ttk.Label(mf, textvariable=meters, background='#E9D66B').grid(column=2, row
    =2, sticky=(W, E))
ttk.Button(mf, text='Calculate', command=calculate).grid(column=2, row=3,
    sticky=W)
ttk.Label(mf, text='feet').grid(column=3, row=1, sticky=W)
ttk.Label(mf, text='is equivalent to').grid(column=1, row=2, sticky=E)
ttk.Label(mf, text='meters').grid(column=3, row=2, sticky=W)
for child in mf.winfo_children():
    child.grid_configure(padx=5, pady=5)
feet_entry.focus()
root.bind('<Return>', calculate)
root.bind('red', callback_function)
root.mainloop()
Python Tkinter listener in text box