Crash in pilot mode

Builder
1

OS macOS Tahoe 26.61.
PsychoPy version 2026.1.3
Standard Standalone Installation? (y/n) y
Do you want it to also run online? (y/n) y
What are you trying to achieve?:

I use the following code to counterbalance groups in a research class experiment

index1 = []
index2 = []

if int(expInfo['participant']) % 2 == 0:
    index1 = list(range(5, 21)) 
    shuffle(index1)
    index2 = list(range(21, 37)) 
    shuffle(index2)
else:
    index1 = list(range(21, 37))
    shuffle(index1)
    index2 = list(range(5, 21))
    shuffle(index2)

index1.extend(index2)

Link to the most relevant existing thread you have found:

But this is rather old and I am not sure whether this still applies.

What specifically went wrong when you tried that?:
This code throws the following error in pilot-mode but not in run-mode

if int(expInfo['participant']) % 2 == 0:
ValueError: invalid literal for int() with base 10: 'pilot'

I am not sure whether it is related to running the experiment on a Mac.? It ran on a Win11-machine last semester without any problems.

Any hints?

Best wishes Jens

2

When you run an experiment in pilot mode the participant field is set to “pilot” instead of the given value (e.g. f"{randint(0, 999999):06.0f}"). You can suppress this behaviour via Preferences / Pilot mode / replaceParticipantID or deal with the pilot value explicitly in your code.

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3

Hello

I found my mistake. PsychoPy sets the participant number to “Pilot” when piloting. This cause the code to fail.

The following code circumvents this problem.

consent = 0
index1 = []
index2 = []

if expInfo['participant'] == 'pilot':
    participant_num = 0 
else:
    participant_num = int(expInfo['participant'])

if participant_num % 2 == 0:
    index1 = list(range(5, 21))
    shuffle(index1)
    index2 = list(range(21, 37))
    shuffle(index2)
else:
    index1 = list(range(21, 37))
    shuffle(index1)
    index2 = list(range(5, 21))
    shuffle(index2)
    
index1.extend(index2)

Best wishes Jens