psychopy.org | Reference | Downloads | Github

Bug in v3.22 when compiling path delimiters under Linux

#1

In a stimulus component, when I specify the path to an image in a subdirectory (e.g. stimuli/myimage.png) with a forward slash as the path delimiter as required under Linux, the experiment crashes.

The error message in the output window looks like
"OSError: Couldn’t find image stimuli\myimage.png; check path? (tried: /home/…/stimuli\myimage.png)

Compiling the builder script and looking at the result in coder I find that the forward slash has been converted to a double backslash. After editing this to replace the two backshlashes with a single forward slash the python script works.

#2

Well, this bug is still there in 3.2.3. Does no one else ever transfer .psyexec files from WIndows to Linux or vice versa, or is my observation due to a unique glitch in my installation?

#3

Hi @Detlef, I have just created a new task on a Linux machine running Ubuntu 18.04 and the path format seems correct (all forward slashes). Would you mind sharing your task so I can test on this machine?

#4

Hi @Detlef, I think one issue is that you have used backslash characters as your path separators in your image components e.g., in Bisection routine, your image component called TexturePreview_11 has a stim path of stimuli\noise_000.png. On Linux, you should use forward slash path separators e.g., stimuli/noise_000.png. Try changing all of your paths and give it another go.

#5

That’s embarrassing. However, I explicitely mentioned in my bug report that I had actually used forward slashes. That you see backward slashes may point into the right direction. My worklflow is that I make the builder scripts on my office pc under Windows, then transfer the files to a Linux machine in the lab and change the backslashes to forward slashes. I assure you that everything looked good in the Linux builder gui, but I nevertheless got the error.
Now after your post I opened the .psychexec file in the lab and found one (!) backslash. I edited that again and ran the script. The error was there again, but now for another image stimulus. So I edited that path again. I was not very systematic because initially I thought I overlooked something, but I think I had to edit and save and reload the script into builder maybe two or three times until I got rid of the error.
In a nutshell I suspect that the file from Windows was not (always) updated internally when I changed the backslashes in the gui, and thus they reappeared when the file was freshly loaded. I believe this is what you experienced when you opened my file. Does that make sense?