Generate random number, save as variable, and use to call stimulus files

Builder
1

Hello,

I have four stimulus files for a counterbalanced set of trials, and I need Psychopy to randomly select one file to use without cycling through all four, as would happen in a loop. My current strategy is inspired by the advice about counterbalancing in another Psychopy article. I have four conditions files, named file1, file2, etc. Following those instructions, I was able to do this by having a “group” field at the beginning of the experiment, then manually typing in a number 1-4 at the beginning of the experiment, and assigning a file using:

$“group”+expInfo[‘group’]+".xlsx"

This worked well, but my supervisor wants Psychopy to generate the number randomly and internally, to save time on our end during data collection. I’ve inserted a code block before the trials in builder mode, where I’m trying to generate a random integer 1-4, save it as a variable (filepath), and then in the conditions field, call up the specific file using this text:

$“file”+thisExp[‘filepath’]+".xlsx"

Can I accomplish this using a code chunk in the Builder mode? Thank you!

2

Just use filepath as your variable name if you’ve defined it in a code component

3

Right thanks, that’s what I’m asking about. If possible, how do you generate a random number in the code chunk that saves as a variable that I can then use?

4

filepath=str(randint(1,4)) should set filepath as ‘1’, ‘2’ or ‘3’.

5

This seems to be working. Thank you very much for your help, on both this question and my previous one.

For anyone else reading this, I set each file with the orders of conditions to a number 1-4, then for my conditions file, specified $filepath+“.xlsx”, which seems to work.