PCEP Control Flow, Loops, Lists and Logic Practice Question
A log file processing script uses a while loop to read lines until a specific pattern is found. The code currently hangs. The developer suspects an infinite loop. Which change is most likely to fix the issue?
⚠ Common exam trap
Python Institute often tests the misconception that adding a `break` statement is the universal fix for infinite loops, when in fact the root cause is usually a missing update to the loop condition variable, not the absence of an explicit exit command.
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
✓
Ensure the condition variable is updated inside the loop
An infinite while loop typically occurs when the condition controlling the loop never becomes false. In a log file processing script, the condition variable (e.g., a line counter or a flag indicating the pattern was found) must be updated inside the loop body. Without that update, the loop condition remains true indefinitely, causing the hang. Adding a `break` statement (option A) would exit the loop unconditionally after the first iteration, which is not the intended fix for a missing update.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Add a break statement after reading the line
Why it's wrong here
A break after reading executes only once per line, so it cannot terminate the loop on the pattern match; the loop still never exits if the pattern is absent. Break statements are for early loop exit on a condition, which is the right tool when the terminating condition is separate from the while test.
- ✗
Increase the sleep time in the loop
Why it's wrong here
Sleeping longer only delays each iteration; if the loop's condition never becomes false, it still never terminates. It is tempting because sleep is often used to throttle polling loops. The actual defect is a condition or read that never advances, which must be corrected instead.
- ✗
Replace while with for loop
Why it's wrong here
Swapping while for for changes iteration syntax, not the terminating condition; a for loop over the same unbroken sequence hangs identically. For loops suit bounded iteration over a known sequence, which is the correct choice when the number of iterations is fixed in advance.
- ✓
Ensure the condition variable is updated inside the loop
Why this is correct
An infinite while loop typically occurs when the controlling condition variable never changes, so the exit condition is never met. Updating that variable inside the loop body ensures the condition eventually becomes false, allowing termination.
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