TypeError: bad operand type for unary -: 'unicode'
Dear all,
I am preparing an experiment, but it crashes irregularly after some trials (also when I put the sequence to sequential, it crashes at a seemingly random position).
I am using quite a lot of inline code, but this seems to all work, as can be seen during the working trials and logfile.
This is the message I get:
item-stack: experiment[run].counterbal[run].counterbal_proc[run].BlockList[run].BlockProc[run].TrialList[run].Trial[run].StimPres[run].StimSeq[prepare].SceneStims[prepare]
exception message: bad operand type for unary -: 'unicode'
time: Fri Dec 02 16:39:46 2016
exception type: TypeError
Not sure where it crashes, but I guess somewhere during SceneStims[prepare]?
This is the actual stimulus screen with a scene background and four object images superimposed.
I created the experiment in an older version of OpenSesame, but it throws the same error in the 3.1 version. Or might this be a Python version error? Any suggestions are welcome!
Thanks

Comments
Okay, found the issue. There was a typo (.....) in a variable name, such that one the coordinates did not get assigned. The coordinates were drawn from a randomized array, making the program stop at an unexpected location.