[solved] Key realease

Comments

• embodiment

  October 2012 edited February 2014

  Hi JasT.

  I had the same need in the past, so I can show you my solution (which requires a piece of python code).

  I used pyglet KeyStateHandler function inside psycho backend, so I don't know if you can use the same function inside another backend. This is a simple code that you can adapt to your needs.

  from psychopy import visual, core
  from pyglet.window import key
  response = key.KeyStateHandler()
  self.experiment.window.winHandle.push_handlers(response)
  win = self.experiment.window
  time = core.Clock()
  press = visual.TextStim(win, pos=(0,0), text='Hold down the SPACEBAR...')
  release = visual.TextStim(win, pos=(0,0), text='When you want, release the SPACEBAR')
  # spacebar not pressed
  while not response[key.SPACE]:
      press.draw()
      win.flip()
  t1 = time.getTime() # spacebar pressed! (first timestamp)
  while response[key.SPACE]:
      release.draw()
      win.flip()
  t2 = time.getTime() # spacebar released! (second timestamp)
  spacebar_time = t2-t1 # compute the key pressing time
  

  I don't know if there is a simpler method. Hope this helps.

  Andrea
• JasT

  October 2012 edited 4:18AM

  Thanks that's helpful - it makes sense to use a while loop to identify whether a key is no longer being pressed ">
• sebastiaan

  October 2012 edited February 2014

  Btw, in case you're not using the psycho back-end, here's a small code snippet that illustrates how you can accomplish approximately the same thing with the PyGame-based back-ends (legacy, expyriment, and opengl):

  import pygame
  key = None
  start_time = self.time()
  while key == None:
      time = self.time()
      for event in pygame.event.get():
          if event.type == pygame.KEYUP:
              key = event.key
  rt = time - start_time  
  print '%s was released after %d ms' % (key, rt)
  

  For more information, please see the PyGame documentation, and don't hesitate to post further questions!

  Cheers,
  Sebastiaan

  
  
  Check out SigmundAI.eu for our OpenSesame AI assistant!
  
• adamstone

  November 2014 edited 4:18AM

  Hi,

  I think this is a fantastic discussion; I have the same need for my study. I'm using sebastiaan's suggestion (for use with PyGame). However it doesn't seem to be recording the reaction time ("rt" variable). Or in fact, recording anything after the stimulus is presented. How do I get OpenSesame to record this part in logger?

  And...I'm a little uncertain how this works in the experiment workflow. Do I place this Python script after the keyboard_response item, before it, or does it entirely replace the keyboard_response item?

  Thanks,
  Adam
• adamstone

  November 2014 edited November 2014

  Never mind! Some more googling found me this comment, also by Sebastiaan.

  Basically, the python script needs to define the variable as well via exp.set() so there should also be a line like this:

  exp.set('keyreleaseRT', rt)

  All good now! Although I have no idea what the last print line is for, it doesn't seem to do anything.
• eduard

  November 2014 edited November 2014

  HI Adam,

  All good now! Although I have no idea what the last print line is for, it doesn't seem to do anything.

  The timing for each keypress should appear there, since this is were prints usually print to.
  Anyway, good to hear that it works now for you.

  Best,

  Eduard

  
• adamstone

  November 2014 edited 4:18AM

  The timing for each keypress should appear there

  What does "there" mean? Is the screen supposed to display the print line after I release the key? I'm not sure how that works since there isn't a text_render item around that part of the loop.

  Thanks,
  Adam
• eduard

  November 2014 edited 4:18AM

  Sorry! I think I rewrote my response and deleted something by accident. What "there" refers to is the debug window. If you print something, it does't appear on the screen, but the debug window.

  Sorry for the confusion.

  Eduard

  
• adamstone

  November 2014 edited 4:18AM

  Thank you, Eduard!
• mark

  November 2016

  Hi,
  Sorry for resurrecting an old thread, but I was wondering if anyone had any information on how reliable the RT is using the method Andrea (Embodiment) proposed above. Would it be anywhere near millisecond accurate (ignoring issues tied to the particular keyboard itself)? Is it tied to screen refresh (the win.flip seems to suggest that, but I'm not sure)?
  Thanks,
  Mark