PCEP Control Flow, Loops, Lists and Logic Practice Question

A quality-control engineer stores defect codes in a list `codes` and wants to print each code until a sentinel value `'STOP'` is encountered, at which point the loop should end without printing `'STOP'`. Which loop correctly achieves this behavior?

⚠ Common exam trap

Many candidates confuse break with continue, or placing the print before the sentinel check so the sentinel is printed despite the intention to stop before it.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

for c in codes: if c == 'STOP': break print(c)

The correct loop checks each element for the sentinel before any output and uses break to exit the entire loop. Placing the break before the print ensures the sentinel is never displayed, and break ends iteration immediately so no later codes are processed. This matches the engineer's requirement precisely.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
for c in codes: if c == 'STOP': continue print(c)
Why it's wrong here
Using continue skips only the current iteration when 'STOP' is seen; the loop then proceeds to any remaining elements. This means codes after 'STOP' would still be printed, and the loop does not end at the sentinel. The scenario requires the loop to stop entirely, not merely skip the sentinel.
✓
for c in codes: if c == 'STOP': break print(c)
Why this is correct
This loop iterates over the codes, checks for the sentinel before printing, and breaks immediately when 'STOP' appears. Because the break occurs before the print statement, 'STOP' itself is never printed. It meets the requirement of printing each code until the sentinel and then terminating the loop cleanly.
✗
for c in codes: while c != 'STOP': print(c)
Why it's wrong here
The inner while loop never changes c, so if the first element is not 'STOP' it prints that same value forever, creating an infinite loop. If the first element is 'STOP', nothing prints and the outer for advances, but the logic is still broken. This does not correctly process the list or terminate at the sentinel.
✗
for c in codes: print(c) if c == 'STOP': break
Why it's wrong here
Here the print happens before the sentinel check, so 'STOP' is printed before the loop breaks. The scenario explicitly requires that 'STOP' not be printed, so this order of statements produces output that includes the sentinel and fails the requirement even though the loop does terminate.

Go deeper

PCEP Control Flow, Loops, Lists and Logic Practice Question

Why each option matters

Option-by-option breakdown

Related to this question