Aggregate Core.

Fourth class. The list is ready. Now we want summaries: average, minimum, maximum — classic aggregates.

average = sum(weights) / len(weights). sum adds every item; dividing by len gives the mean. For the lesson data [70.0, 72.0, 74.0, 75.0] the average is 72.75.

minimum = min(weights) and maximum = max(weights) are built-in functions. Do not write a hand-rolled min/max loop unless a lesson asks for it — here the goal is to use the language tools.

Mini example:

vals = [3.0, 1.0, 2.0]
print(sum(vals) / len(vals))
print(min(vals))
print(max(vals))

Print order matters for the checks: average, then minimum, then maximum — as in the task.

Common mistake: average = sum(weights) / 4 (a magic number instead of len); min/max on an empty list; printing only one of the three.