The teacher posts a 15-line Python function on a class Padlet that should return the average of a list of test scores but contains four planted errors: a missing colon, = used instead of == in a condition, a loop over range(len(scores) - 1) that skips the last score, and a total that is reset inside the loop. Each student posts one bug to the syntax errors or logic errors column, giving the line number and a one-line explanation of what would happen when the code runs. The teacher watches the columns fill, notices which bug nobody has posted, usually the reset total, and asks the class to trace the loop by hand for a three-item list. The class then fixes each bug in order while the teacher edits the code live and runs it.
This page is one of a growing set of PICRAT examples by cell, subject and grade. Page maintained by Andy Perryer.