14 — Practice solutions

These are independently written explanations, not an official marking scheme.

14A

def count_large(values, limit):
    count = 0
    for value in values:
        if value > limit:
            count += 1  # Count each matching occurrence once.
    return count

Expected results: 2, 0, 0. Count matching items, including duplicate occurrences.

Reasoning

“number of values” requires a counter, and “strictly greater” excludes the value equal to limit. Both7s count independently. The code returns one integer, not a tuple containing an unrequested sum.

14B

def sum_before_stop(readings):
    total = 0
    for reading in readings:
        if reading == -1:  # Stop before adding the sentinel.
            break
        total += reading
    return total

Expected results: 1 and 0. Without a sentinel, all readings are summed. Checking for the sentinel after adding would wrongly include −1.

Reasoning

−1 terminates processing, but −2 is ordinary data. Test the sentinel before accumulation so it is excluded, and break so100 is never reached. Empty input or an immediate sentinel leaves the initial sum0.

14C

value	total before	total < 4?	total after
2	0	True	2
5	2	True	7
1	7	False	6
4	6	False	5

Final total is 5. The branch depends on the accumulated total before the update, so the same value may take a different branch in a different state.