Code Explainer — illustrative example

INPUT
Explain this Python function and evaluate it for [-2, 0, 3, 1]:
def positives(values):
    return [value for value in values if value > 0]

RESULT
The comprehension tests each item against zero and builds a new list in input order.
positives([-2, 0, 3, 1]) returns [3, 1].
Zero and negative values are excluded. The input list is not modified. Items must support comparison with zero.

REVIEW
Explain code at the level needed for the task. Include inputs, output and assumptions, and distinguish intended behavior from behavior actually shown.

This is a teaching example, not a live execution record.