[Tutor] Making a function run every second.

[Dave Angel]

On 11/29/2011 10:52 AM, Mic wrote:
>
>
> -----Ursprungligt meddelande----- From: Dave Angel
> Sent: Tuesday, November 29, 2011 4:33 PM
> <SNIP>
>
>>>> -----Original Message-----
>>>> From: "Mic"<o0MB0o at hotmail.se>
>>>> Sender: tutor-bounces+bodsda=googlemail.com at python.org
>>>> Date: Tue, 29 Nov 2011 15:54:59
>>>> To:<tutor at python.org>
>>>> Subject: [Tutor] Making a function run every second.
>
>>>> Hi
>
>>>> I want a function to run every second , how do I do that?
>>
>>>> Say that the function look like this:
>>
>>>> def hi():
>> print("hi")
>
>> Without a clearer spec, there are too many possible answers. As Bobsda
>> says, you can't get it exactly one second apart. But you also have the
>> problem of whether a drift is okay. For example, if you have a global
>> you're incrementing each time that function runs, and you want it to
>> represent the total time the program has been running, then a simple
>> sleep() is totally wrong.
>
> Okay, I undestand. Hmm, what is a drift?
>
>> What I was concerned about is that perhaps this is for one of the
>> tkinter programs Mic is writing. For an event-driven program, sleep()
>> calls of even a second are unaccepable. And if you literally write a
>> while loop like that, your whole program would stop responding.
>
> Yes, this is one of my tkinter programs :) Why would the program stop
> responding using a sleep()?
>

I'm not that familiar with tkinter details.  But like all (almost??) 
GUI's it relies on an event loop.  Each event has to be "quick" for some 
definition of quick.  In the case of tkinter, I believe that eventloop 
is called mainloop().  That loop won't return till you hit the X button 
in the corner, or do something else that triggers program cancellation. 
  That loop is the thing that interacts with the OS, and calls various 
event handlers as things happen.   If you were to do a loop of  sleep() 
before you got to the mainloop() call, the GUI would never start.  If 
you do it inside some event, then the mainloop() never gets control again.

tkinter provides a couple of specific timer events, and I now see your 
reply to a message that said to use the after() method, which is a 
one-shot.  I believe there's another one that sets a periodic timer so 
you don't have to do an after() call each time it fires.

>> So Mik:
>> Tell us more about the real requirements. Is drift acceptable, is this
>> a console program or some gui environment, are there any other hidden
>> assumptions?
>
> Okay, this function approximately runs every second and check what the
> time is.
> (Well, every 30 second or every minute would be okay if that makes it
> easier)
> If the time is 15:00 it is supposed to remove a file. That should be all
> requirements!
>
> I have figured out how to make the function check what time it is and
> how to
> remove the file when the time is 15:00, but I don't know how to make it
> run every
> second or something like that.
>
>
> Thanks!
>
> Mic
>


-- 

DaveA