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Internal error on a new computer

OS ( Win10):
PsychoPy version (2020-2.4):
Standard Standalone? (y)


I installed Psychopy and Python 3.9 on a new computer, and open an experiment that was built in an older version.
When I tried to run it online I received this error msg:

Traceback (most recent call last):
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\app\builder\”, line 1240, in onPavloviaRun
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\app\builder\”, line 719, in fileExport
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\scripts\”, line 73, in generateScript
compileScript(infile=exp, version=None, outfile=filename)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\scripts\”, line 242, in compileScript
_makeTarget(thisExp, outfile, targetOutput)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\scripts\”, line 214, in _makeTarget
script = thisExp.writeScript(outfile, target=targetOutput, modular=True)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\”, line 251, in writeScript
self_copy._currentRoutine.writeRoutineBeginCodeJS(script, modular)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\experiment\”, line 277, in writeRoutineBeginCodeJS
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\experiment\”, line 202, in writeRoutineStartCodeJS
self.writeParamUpdatesJS(buff, ‘set every repeat’)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\experiment\”, line 405, in writeParamUpdatesJS
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\experiment\”, line 399, in writeParamUpdates
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\experiment\”, line 435, in writeParamUpdate
valStr = str(val).strip()
TypeError: str returned non-string (type NoneType)

Tnx in advanced,


These errors happen when the value of one of your parameters cannot be converted to a string - usually because it doesn’t exist or shares a name with something else (e.g. a base Python function or the name of another component, parameter, etc.) so is overwritten

If you share the .psyexp file then I can use dev tools to track it down, this has popped up a few times so I’ve added in some code for the next version to add more information to the error message, hopefully making this easier to track down in future!