[Tutor] Countdown Clock Programming Question

[Alan Gauld]

On 01/12/15 10:16, Alan Gauld wrote:

>>> def count_down():
>>>     # start with 4 minutes --> 240 seconds
>>>     for t in range(240, 120, -1):
>>>         # format as 2 digit integers, fills with zero to the left
>>>         # divmod() gives minutes, seconds
>>>         sf = "{:01d}:{:02d}".format(*divmod(t, 60))
>>>         #print(sf)  # test
>>>         time_str.set(sf)
>>>         root.update()
>>>         # delay one second
>>>         time.sleep(1)# create root/main window
> 
> Don't use time.sleep() in a Tkinter program use the after
> method instead. In this case it will look like
> 
> root.after(1000, count_down)

I just realized my advice is slightly contradictory.
If you add parameters to count_down you can't pass
it to after() directly. Instead you need to rewrite
count_down and use a little trick in after() like this:

def count_down(start, stop)
    sf = "{:01d}:{:02d}".format(*divmod(start, 60))
    time_str.set(sf)
    root.update()
    if start > stop:
       root.after(1000, lambda: count_down(start-1,stop) )

Notice it has no loop, instead after() subtracts 1 second
from the start value each time it calls count_down.

-- 
Alan G
Author of the Learn to Program web site
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