Error when running experiment on Psychopy3

Hello there!

I have been trying to run my experiment on PSYCHOPY3 (v2020.2.8), but this error keeps occurring. Could you please help?

ERROR:
Traceback (most recent call last):
File “C:\Users\Yasmine\Desktop\CSSL_C1\CSSL_C1_lastrun.py”, line 50, in
filename = thisDir + os.sep + u’data/%s%s_%s’ % (expInfo[‘participant’], expName, expInfo[‘date’])
KeyError: ‘participant’

Experiment ended.