Thank you very much for answering my previous questions. I am new to psychopy, so I do have a lot 
I would like to counterbalance the task across participants so that odd IDs get task:
press q for yes and p for no
and even Ids get the opposite.
Therefore the “correct key” will be respectively opposite. The rest of the routines remain the same.
How can I do it as easily as possible?
Thousand thanks!