Duration of key is always None

Builder
1

OS (e.g. Win10):
PsychoPy version (2021.2.0):
**Standard Standalone? y
**What are you trying to achieve?:

I want to know how a long a key was held down for before being released

**What did you try to make it work?:

For any given key I called for the key.duration attribute

**What specifically went wrong when you tried that?:

That attribute is always None

See below the code I am using inside the Each Frames tab

print(_key_mod_allKeys)
if len(_key_mod_allKeys):
    print(_key_mod_allKeys[-1].name)
    print(_key_mod_allKeys[-1].tDown)
    print(_key_mod_allKeys[-1].duration)

And then some output

[<psychopy.hardware.keyboard.KeyPress object at 0x0000019722DABFD0>, <psychopy.hardware.keyboard.KeyPress object at 0x0000019722D9F160>]
right
281912.6402972
None
[<psychopy.hardware.keyboard.KeyPress object at 0x0000019722DABFD0>, <psychopy.hardware.keyboard.KeyPress object at 0x0000019722D9F160>]
right
281912.6402972
None
[<psychopy.hardware.keyboard.KeyPress object at 0x0000019722DABFD0>, <psychopy.hardware.keyboard.KeyPress object at 0x0000019722D9F160>, <psychopy.hardware.keyboard.KeyPress object at 0x0000019722D9F240>]
left
281912.7530118
None

You can see in this part of the output that I have just pressed a new key (the left key), having previously pressed the right key. I released the right key, and therefore the key.duration should not be None.

2 Likes
2

Hi There,

Do you have the keyboard set to end on press? this might be helpful too Measuring key lift time relative to stimulus onset - #3 by Becca

Becca

3

Hi Becca,

Thanks again for helping me out!

I donā€™t believe so, though Iā€™m not certain. I see an option for ā€œForce end of routineā€ that is not checked. Is that what you mean?

The link you shared is actually particularly prescient, since I will be deploying this experiment on Pavlovia as soon as this bug is worked out. However, if it is still the case for PsychoJS that I will need to manually write code rather than using something from the builder than I can push now with no code and then just go at it online. What are your thoughts on this?

Thanks again,

Peter

4

Hi Peter,

Aha ok if you are going online what I would suggest is still make your experiment in builder but use code components to monitor the key press - a bit like in the file shared in this post !

Becca

5

Okay, Iā€™ll do that.

Thank you so much!

Peter

6

Iā€™m having exactly this problem: key.duration remains None with pyglet even after the key is released. Unfortunately I cannot switch to PTB backend which does not seem to work with my MRI-compatible button box (cf. Buttonbox delay - Programming Help - Psychtoolbox).
Is there another way of checking whether a key has been released that would work even with pyglet?