Measure duration of key press

Comments

• eduard

  August 2016

  Hi Charlotte,

  The reason nothing happened, is that you only broke out of the for loop, but not out of the while loop. YOu would need another break statement outside the for loop that is only executed once you broke out of the for loop. Alternatively, you can also get rid of the for loop entirely (assuming that your participants are not pressing multiple keys simultaneously). Below is an example of the code for when you remove the for loop. I also added the presentation of a the current key press duration for illustration purposes.

  var.start_response = None
  var.time_down = 0
  var.time_up = 0
  var.time_elapsed = 0
  ok = False
  t0 = clock.time()
  
  cv = canvas()
  while True:
          # used for displaying the current key presses duration
          if ok:
              cv.text(str(pygame.time.get_ticks()-var.time_down),0,0)
              cv.show()
              cv.clear()
  
          # assume only one event, if event is empty proceed with next one
          # otherwise do the checks below
          eve = pygame.event.get()
          if len(eve) == 0:
              continue
          else:
              ev  = eve[0]
          if ev.type == pygame.KEYDOWN:
              if ev.key == pygame.K_SPACE:
                  var.time_down = pygame.time.get_ticks()
                  # used to display the current key press duration
                  ok = True
          elif ev.type == pygame.KEYUP and var.time_down != 0:
              if ev.key == pygame.K_SPACE:
                  var.time_up = pygame.time.get_ticks()
                  var.time_elapsed = (var.time_up-var.time_down)
                  break
          # break the loop if nothing happend in 10 seconds
          t1 = clock.time()
          if t1-t0> 10000:
              break
  
  #var.time_elapsed = (var.time_up-var.time_down)
  RTs_three_hold.append(var.time_elapsed)
  print RTs_three_hold
  

  Does this make sense?

  Eduard

  
• sebastiaan

  August 2016

  @eduard is correct, of course. (You also mix up the name of the event, calling it event first and ev later.)

  But, just as a general remark, you can also use the for ... else pattern to deal with these kinds of nested loops, like so:

  while True:
      # Loop through all events and break the for loop when there is a KEYDOWN
      for event in pygame.event.get():
          if event.type == pygame.KEYDOWN:
              break
      # The else block is executed only when the for loop did *not* break. So
      # we continue the while loop if the for loop did *not* break.
      else:
          continue
      # If the for loop *did* break, we also break the while loop.
      break
  

  See:

  • https://docs.python.org/3/reference/compound_stmts.html#the-for-statement

  
  
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• Charlotte_

  August 2016

  Thank you so much, Eduard, it all works as it should now!

  And thank you Sebastian, I didn't even think about doing it that way, it's good to know that's a possibility!

  /Charlotte