How to associate the same operation to a set of buttons programmatically in tkinter?

You are describing the behavior of a group of radiobuttons so you should use those.

Conveniently radiobuttons have an attribute indicatoron which

Normally a radiobutton displays its indicator. If you set this option to zero, the indicator disappears, and the entire widget becomes a “push-push” button that looks raised when it is cleared and sunken when it is set. You may want to increase the borderwidth value to make it easier to see the state of such a control.

thus, when set to zero it does precisely what you request.

You could simply return button and use it to access your buttons in press():

import tkinterwindow = tkinter.Tk()window.grid()# changed to integers so we can loop through the# values in press() and use them as indicesnumbers = [1, 2, 3, 4, 5, 6, 7, 8, 9]def buttonCreator(labels):    n = 0    button = []    for x in range(0, 3):        for y in range(0, 3):            if n <= len(labels) - 1:                button.append(tkinter.Button(window, text=labels[n],                                             command=lambda x=labels[n]:press(x)))                button[n].grid(row=x, column=y)            n += 1    return button # added a return statementdef press(value):    for x in numbers:        # index is x-1 because 1 is in button[0], etc        button[x-1]['relief'] = 'sunken' if x == value else 'raised'button = buttonCreator(numbers)window.mainloop()

Just for an example, I'll create two buttons with the reaction you wanted:

from Tkinter import *win = Tk()def press1():    button1["relief"] = "sunken"    button2["relief"] = "normal"def press2():    button1["relief"] = "normal"    button2["relief"] = "sunken"button1 = Button(win, text="Button 1", command=press1)button2 = Button(win, text="Button 2", command=press2)button1.pack()button2.pack()button1.grid(row=1, column=1)button2.grid(row=1, column=2)win.mainloop()

Should work. A second way:

from Tkinter import *win = Tk()def press(buttonnumber):    if buttonnumber==1:        button1["relief"] = "sunken"        button2["relief"] = "normal"    elif buttonnumber==2:        button1["relief"] = "normal"        button2["relief"] = "sunken"    else:         raise Exception("No Button Number \"%d\"" % buttonnumber)button1 = Button(win, text="Button 1", command=lambda: press(1))button2 = Button(win, text="Button 2", command=lambda: press(2))button1.pack()button2.pack()button1.grid(row=1, column=1)button2.grid(row=1, column=2)win.mainloop()