String variables for filenames in Builder?

Sorry about forgetting the error message! I’ve edited the post to include the full message.

When defining the string variable, I’ve included the .bmp extension, and when I print the stimulus list in the .py file, everything looks good. Here’s how I defined the strings in the .py file:

target = competitors[22]
target = target + ".bmp"

My syntax is probably off in the Builder. Thanks for the quick reply!