@cvp the 361 one is the value I forget to change for testing.
I wrote a simple while loop to test button action. The result is the label will only show 10 after 10 seconds, but not get from 1 to 10 by each second. it just didn't show 1 to 9

def start2(sender):
	label = sender.superview['label1']
	num = 0
	while num != 10:
		time.sleep(1)
		num += 1
		label.text = str(num)

it seems like I can’t put a whole loop into button action, but I want to do a counter by time function.

I tried debug this code, and it worked correctly, but after I running this one, the whole app crushed.

def start(sender):
	def ani_pause():
		sender.image = ui.Image.named('iob:pause_32')

	def ani_play():
		sender.image = ui.Image.named('iob:play_32')

	global is_playing

	if is_playing is False:
		ui.animate(ani_pause)
		is_playing = True
		start_time = time.time()
		label = sender.superview['label1']
		label2 = sender.superview['label2']
		time_left = 0
		while int(label.text) != 131:
			time.sleep(0.01)
			time_now = time.time()
			duration = time_now - start_time
			time_left += 1
			label2.text = str(10 - time_left)
			if label2.text is '0':
				label.text = str(int(label.text) + 1)
				time_left = 361
		ui.animate(ani_play)
		is_playing = False
	else:
		is_playing = False
		ui.animate(ani_play)

@cvp oops, didn’t notice that. Let me try it.

@ccc you are right, I already changed it. It is still stuck though

Thank you, guys, just by adding 'iob:' makes it working.
Now I get another problem, I have a button action link to this function, and every time I press this button, the whole Pythonista will stuck.

state = False
def start(sender):
	def ani_pause():
		sender.image = ui.Image('iob:pause_32')

	def ani_play():
		sender.image = ui.Image('iob:play_32')

	global state
	if state is False:
		ui.animate(ani_pause)
		state = True
		start_time = round(time.time())
		label = sender.superview['label1']
		label2 = sender.superview['label2']
		while int(label.text) != '131':
			time_now = round(time.time())
			duration = time_now - start_time
			time_left = divmod(duration, 360)[1]
			label2.text = str(time_left)
			if time_left == 0:
				label.text = str(int(label.text) + 1)
			else:
				continue
		ui.animate(ani_play)
		state = False
	else:
		state = False
		ui.animate(ani_play)

How do I change the button image from 'play' to 'pause'?
Something like press button once, the image change to 'pause', then press it again, the image change back to 'play'.
What I did is

sender. Image = ui.Image.named('pause_32')

This will make the button blank, totally white