This webpage assigns consecutive participant numbers to experiments on Pavlovia.
Usage: If your experiment URL is https://pavlovia.org/a/b then use https://moryscarter.com/vespr/pavlovia.php?folder=a&experiment=b&id=c&researcher=d
Inputs id, session and researcher are optional but can be used to transfer a non-consecutive participant id and a variable that could be used as a password to access the experiment (to ensure that the participant information sheet has been viewed).
If you get a file not found error, it may be because your experiment isn't in the html folder. In that case add a / to the end of your experimnent name.
In PsychoPy you can use the participant number to assign participants equally to multiple conditions by using:
condition = int(expInfo['participant'])%x where x is the number of conditions. This will assign values 0 to x-1.