PyGTK

#!/usr/bin/env python

import pygtk
import gtk
import time

class SimpleButtonApp(object):

	def __init__(self):
		self.window = gtk.Window(gtk.WINDOW_TOPLEVEL)
		self.window.connect("destroy, self.quit")
		self.button = gtk.Button("Click Me")
		self.button.connect("clicked", self.update_button_label, None)
		self.window.add(self.button)
		self.button.show()
		self.window.show()

	def update_button_label(self,widget,data=None):
		self.button.set_label(time.asctime())

	def quit(self,widget,data=None):
		gtk.main_quit()

def main(self):
	gtk.main()

if __name__ == "__main__":
	s = SimpleButtonApp()
	s.main()