python - Print and clear output on screen with Kivy -

i'm trying print words on screen kivy. i'm looking print first word sleep 2 seconds clear first word , print second word

what i'm doing:

from kivy.app import app kivy.uix.label import label kivy.uix.gridlayout import gridlayout  random import choice time import sleep  xwords = ["hello1", "hello2", "hello3", "hello4", "hello5"]  class test(gridlayout):     def __init__(self, **kwargs):         super(test, self).__init__(**kwargs)         self.cols = 1         x in xrange(2):             # want show frist word sleep 2 sec clear first word screen print second word             self.add_widget(label(text = "[b]"+choice(xwords)+"[/b]", markup = true, font_size = "40sp"))             sleep(2)         # clear words in screen         x in xrange(5):             # show new 4 words             self.add_widget(label(text = "[b]"+choice(xwords)+"[/b]", markup = true, font_size = "40sp"))  class testapp(app):     def build(self):         return test()  if __name__ == "__main__":     testapp().run() 

how can this?

don't use time.sleep, blocks gui because whole function doesn't return until time.sleep does.

use clock.schedule_once instead. below simple example call function called update in 2 seconds, can whatever want within function including scheduling one.

from kivy.clock import clock class test(gridlayout):     def __init__(self, **kwargs):         super(test, self).__init__(**kwargs)         clock.schedule_once(self.update, 2)  # 2 2 seconds     def update(self, *args):         self.clear_widgets()         # add more widgets here