Psychopy Error after removing experiment info fields

Builder
1

Hi! I’ve integrated my experiment with a an online subject repository. Since subjects will automatically provide their name when they follow the URL, I thought of removing the ‘participant’ field showing up at the beginning of the experiment. This was the only field present.

After removing this field I get a crash that doesn’t permit me to run the experiment, nor modify the experiment settings…nothing. I’m assuming having removed all experiment fields must be the issue since this was the only change I made prior to the crash… but I can’t be 100% sure!

Can someone help me dealing with this?

Thanks!

Traceback (most recent call last):
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\app\builder\builder.py”, line 1139, in setExperimentSettings
timeout=timeout)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\app\builder\dialogs_init_.py”, line 1842, in init
timeout=timeout)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\app\builder\dialogs_init_.py”, line 524, in init
ctrls = self.addCategoryOfParams(theseParams, parent=page)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\app\builder\dialogs_init_.py”, line 638, in addCategoryOfParams
valType=self.params[fieldName].valType)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\app\builder\dialogs_init_.py”, line 765, in addParam
advanced=advanced, appPrefs=self.app.prefs)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\app\builder\dialogs_init_.py”, line 131, in init
parent, val, order=[‘Field’, ‘Default’])
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\app\dialogs.py”, line 542, in init
raise AttributeError(msg)
AttributeError: The initial value for a ListWidget must be a list of dicts

Win10
PsychoPy 2020.2.3

2

This is an area we’ve not changed for a while, so this bug must have been there a while! Thanks for catching it, I’ll work on a fix now.

In the mean time, you can fix your experiment by opening the .psyexp file in a text editor (e.g. notepad) and replacing this line:

    <Param name="Experiment info" updates="None" val="{}" valType="code"/>

with this:

    <Param name="Experiment info" updates="None" val="{'participant':''}" valType="code"/>
3

Thanks so much!
Got it up & running!

Nicola