This year (2018-2019) we teach the course with the Python3 version of PsychoPy, whereas last year (2017-2018) Python2 was used. There are some major differences between Python2 and Python3, even for basic functions such as division and dictionaries. So install a PsychoPy2 version to follow along with this course, or install a PsychoPy3 version and switch to the Python3 version of the course.
Note that this is the department version of the course, not the original course for the students (2017-2018).