[visionegg] Re: Terminating a While Loop

Hi Jeff,
Here is some code I use that aborts my experiments with an escape key. It's a bit convoluted (others may have a better solution) but it gets the job done.
The code handles keypresses generally and is set as an event in my main Presentation object via this command: 
___________
myPresentation.parameters.handle_event_callbacks = (pygame.locals.KEYDOWN, keypress) 
___________
So the function called keypress is implemented every time there is a keypress event while the Presentation object is running. Now here's the function itself: 
____________
#Function for keypress event
def keypress(event):

   #Get key event.  If escape, end experiment
   kb=pygame.key.get_pressed()
   if kb[27] == 1: stim_update(4)
else: resps.append([pygame.time.get_ticks()-starttime,trialctr,pygame.mouse.get_pressed()]) 
_____________
So, according to the above code, if the escape key is pressed (e.g. element 27 in the get_pressed output is set to 1), a function called stim_update is called and passed the value 4. If the key wasn't escape, the keypress is added to a list alongside some other relevant info (reaction time etc.). I later process that list as a subject response.
But the main thing here is the stim_update function called when the escape button is pressed. Here is a snippet of the relevant code within that function: 
________________
def stim_update(evt):

...snip...

   if evt == 4:    #End of exp event
       #Exp. is ended by setting main presentation evt duration to 0
       myPresentation.set(go_duration=(0,'seconds'))
________________
So, in a nutshell, if the escape key is pressed, a function is called that sets the Presentation duration to 0, which in effect ends it. 

Hope this helps - john

Maher, Jeffrey wrote:

Hello,
Im currently working on the following code trying to determine a way to exit a 
while loop before the criteria is satisfied.
i=0 
        while i<eval(self.number.get()):
                p.go
                i=i+1
My goal is to set it to a certain key that will either pause the program, and then resume it once pressed again, or have it exit the program all-together, either/or would be acceptable. I had tried setting it to the "esc" key by doing the following code that I found while searching for an answer: 
      if msvcrt.kbhit() and msvcrt.getch() == chr(27):
           break
But that just causes the program to fail to start up.
I have also tried:
for event in pygame.event.get():
        if event.type == pygame.locals.KEYDOWN:
            if event.key == pygame.locals.K_ESCAPE:
                  sys.exit()
But this again just causes the program to fail to start up.
Any suggestions would be greatly appreciated. -Jeff 
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