'NoneType' object has no attribute 'poll'

OS: Win10

PsychoPy version: 2020.2.4

Standard Standalone? (y/n) : y

What are you trying to achieve?:
It is a large and rather complex code for presentation of visual stimuli. It also involves EEG and eye tracking. I use different versions of this code for about a year.

What did you try to make it work?:
Nothing because the error appears only after installation of the new Psychopy version 2020.2.4.

What specifically went wrong when you tried that?:
On exit, either on “Esc” or on the end of the experiment, it gives the error and an invitation to report it to the developers:

Traceback (most recent call last):

File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\app\runner\scriptProcess.py”, line 118, in whileRunningFile

returnVal = self.scriptProcess.poll()

AttributeError: ‘NoneType’ object has no attribute ‘poll’

This is a known bug which will be fixed in 2020.2.5, it’s caused by closing the Runner and reopening it. Essentially, the app needs to have a value for “Runner” in order to run things - this is only set when you open the app with Runner open. So for the time being, make sure you have your preferences set to open all views (Builder, Coder and Runner) and restart Psychopy, this should solve the problem.