PCEP Control Flow, Loops, Lists and Logic Practice Test 9 — 15 Questions

Question 1

A quality engineer tracks defect counts per shift in a list called defects. She needs the running total of all defects after every shift, producing a list of cumulative sums with the same length as defects. Which approach produces that cumulative list?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

total = 0
cumulative = []
for d in defects:
    total += d
    cumulative.append(total). A running total requires an accumulator initialized before the loop, updated with each element, and recorded after the update. Appending after adding yields a cumulative value for every shift and keeps the output length equal to the input length. Appending before adding shifts all values by one position, and recomputing the whole-list sum each iteration produces a repeated grand total instead.

Answer

cumulative = []
for d in defects:
    cumulative.append(sum(defects))

Answer

total = 0
cumulative = []
for d in defects:
    cumulative.append(total)
    total += d

Answer

cumulative = [defects[i] + defects[i+1] for i in range(len(defects))]

Question 2

A Python developer is writing a function that takes a list of numbers and returns a new list containing only the numbers that are divisible by 3 or 5. The developer writes the following code:

def filter_numbers(nums):
    result = []
    for n in nums:
        if n % 3 == 0 or n % 5 == 0:
            result.append(n)
    return result

Which statement about this function is true?

Accepted Answer

The function correctly returns numbers divisible by 3 or 5, and it does not modify the original list.. The function iterates over the input list, checks each number for divisibility by 3 or 5 using the modulo operator and logical OR, and appends qualifying numbers to a new list. It does not modify the original list, and it correctly implements the specified filtering. The other statements are either incorrect or describe behavior that does not occur.

Answer

The function correctly returns numbers divisible by 3 or 5, but it will raise an error if the list contains a zero.

Answer

The function correctly returns numbers divisible by 3 or 5, but it includes duplicates if the input list has duplicates.

Answer

The function correctly returns numbers divisible by 3 or 5, but it uses a logical OR when it should use a logical AND to meet the requirement.

Question 3

A game developer writes a loop to process a list of player scores: `scores = [45, 82, 67, 91]`. She wants to print only the scores that are greater than 80. Which loop correctly accomplishes this?

Accepted Answer

for score in scores:
    if score > 80:
        print(score). To print only scores greater than 80, the loop must iterate over all scores and use an `if` statement with the `>` operator to print those that satisfy the condition. The correct snippet does exactly that, printing 82 and 91. Other options use incorrect comparison operators or misplaced print statements.

Answer

for score in scores:
    if score < 80:
        print(score)

Answer

for score in scores:
    if score >= 80:
        print(score)

Answer

for score in scores:
    print(score)
    if score > 80:
        break

Question 4

A developer is writing a Python script to process a list of integers representing inventory counts. The developer needs to iterate over the list and, for each element, perform an action, but also needs to be able to terminate the entire loop early when a sentinel value (0) is encountered. Which two statements about loop control in Python are correct? (Choose two.)

Accepted Answer

The continue statement skips the rest of the current iteration and proceeds to the next iteration of the loop.. The break statement exits the innermost loop immediately, which is suitable for stopping on a sentinel value. The continue statement skips to the next iteration without terminating the loop. These two control statements are fundamental for managing loop execution and are distinct from return, which exits a function.

Answer

The continue statement terminates the loop and resumes execution after the loop.

Answer

A for loop in Python automatically stops when it encounters a None value in the sequence.

Answer

The break statement can be used outside a loop to exit a function early.

Question 5

During a lab exercise, a student writes the following code to print a countdown from 3 down to 1, but the code enters an infinite loop and never stops. The code is:

count = 3
while count > 0:
    print(count)

Which change makes the loop terminate after printing 3, 2, and 1?

Accepted Answer

Add the statement count = count - 1 inside the loop body.. A while loop repeats as long as its condition stays true, so the counter must move toward the exit value on each pass. Reducing count by one each iteration makes the sequence 3, 2, 1 and then 0, at which point the condition fails and execution continues after the loop. Without such an update the condition never changes.

Answer

Add the statement count = count + 1 inside the loop body.

Answer

Change the condition to while count < 0:

Answer

Add the statement count += 0 inside the loop body.

Question 6

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?

Accepted Answer

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

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

Answer

for c in codes:
    while c != 'STOP':
        print(c)

Answer

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

Question 7

A developer is writing a Python script that should keep prompting for a password until the user enters the correct one. The script must not run forever if the user never guesses correctly, so it should give up after 5 attempts. Which loop construct is most appropriate for this scenario?

Accepted Answer

A for loop that iterates over range(5), checking the password inside and breaking when correct.. The requirement combines a fixed maximum number of attempts with the possibility of stopping early on success. A for loop over range(5) supplies the exact bound of five iterations, and a break inside ends the loop as soon as the password matches. The other constructs either loop forever when the user keeps failing or do not model repeated input attempts at all.

Answer

A for loop that iterates over the characters of the password string, comparing each character.

Answer

A while True loop with no break statement, relying on the password check to terminate.

Answer

A while loop that continues as long as the entered password is incorrect, with no attempt counter.

Question 8

A warehouse script stores stock quantities in the list levels = [4, 0, 7, 0, 2]. A developer wants to build a new list, in_stock, containing only the quantities greater than zero, preserving the original order. Which code correctly produces [4, 7, 2]?

Accepted Answer

in_stock = [q for q in levels if q > 0]. A comprehension of the form [expression for item in iterable if condition] walks the list in order and includes only items satisfying the condition. Testing q > 0 excludes the zeros while keeping 4, 7, and 2 in their original positions, and it builds a separate list rather than modifying the source.

Answer

in_stock = [levels[q] for q in levels if q > 0]

Answer

in_stock = [q for q in levels if q >= 0]

Answer

in_stock = [q if q > 0 for q in levels]

Question 9

A validation script defines a list named flags containing boolean values. The script must determine whether every flag is True and print 'All clear' only in that case; otherwise it should print 'Check needed'. Which code fragment implements this logic correctly?

Accepted Answer

if all(flags):
    print('All clear')
else:
    print('Check needed'). Determining that every element is True requires a check that inspects all elements and fails if any is falsy. The built-in all function does exactly that, returning True only when every element is truthy and False otherwise, which maps directly onto the two required messages.

Answer

if flags:
    print('All clear')
else:
    print('Check needed')

Answer

if any(flags):
    print('All clear')
else:
    print('Check needed')

Answer

if flags == True:
    print('All clear')
else:
    print('Check needed')

Question 10

A data analyst has a list named readings containing numeric sensor values. She needs to build a new list that contains only the values strictly greater than 10, preserving their original order. Which code fragment produces this result?

Accepted Answer

filtered = [x for x in readings if x > 10]. A filtering list comprehension keeps only the elements that satisfy the condition and preserves their original order. Writing the element expression as x and placing the comparison after if yields the desired numeric values. Using an inclusive comparison admits boundary values, putting the comparison itself in the expression yields Booleans, and appending a reverse slice destroys the original ordering.

Answer

filtered = [x for x in readings if x >= 10]

Answer

filtered = [x > 10 for x in readings]

Answer

filtered = [x for x in readings if x > 10][::-1]

Question 11

A data analyst has a list `readings` of numeric sensor values and needs to build a new list `scaled` that contains each reading multiplied by 2, but only for readings that are positive. Negative and zero readings should be excluded. Which code correctly produces `scaled`?

Accepted Answer

scaled = [r * 2 for r in readings if r > 0]. The correct comprehension uses a filter clause after the for to include only positive readings, then multiplies each by 2 in the expression. This produces a new list containing doubled values for positive readings only, excluding negatives and zeros. It matches the analyst's specification and uses idiomatic Python syntax.

Answer

scaled = [r * 2 for r in readings if r >= 0]

Answer

scaled = [r * 2 if r > 0 for r in readings]

Answer

scaled = [r for r in readings if r > 0] * 2

Question 12

A developer is writing a Python inventory reconciliation script. They need to examine each element of a list named `stock` and, for every element, execute a block of code that updates a running total. They do not want the loop to terminate early under any condition. Which statement should be placed at the beginning of the loop body to iterate over every element in order?

Accepted Answer

for item in stock:. Iterating over a list with `for item in stock:` visits every element in order and assigns each value to the loop variable, making it the direct way to process all entries without early exit. The alternatives misuse `range()`, `len()`, or `while` in ways that either raise errors or fail to traverse the list sequentially, so they cannot accomplish the reconciliation task.

Answer

for item in len(stock):

Answer

for item in range(stock):

Answer

while item in stock:

Question 13

A ticket system stores seat rows in the list rows = [[1, 2], [3, 4], [5, 6]]. A developer needs to print every individual seat number on its own line, in order, from 1 through 6. Which code accomplishes this?

Accepted Answer

for row in rows:
    for seat in row:
        print(seat). Traversing a list of lists requires nested loops: the outer loop yields each inner list, and the inner loop yields each element within it. Printing the inner element inside both loops emits every seat number in order, one per line, which matches the required output of 1 through 6.

Answer

print(rows)

Answer

for row in rows:
    print(row)

Answer

for seat in rows:
    print(seat[0])

Question 14

A Python programmer is reviewing a script that processes a list of order totals. The script must print each total that is greater than 100 and stop scanning entirely the first time it encounters a total of exactly 0. Which two statements about the loop logic are correct? (Choose two.)

Accepted Answer

A break statement placed inside the loop immediately terminates the loop when the total equals 0.. Stopping a scan at a sentinel value is the classic use case for break, which exits the innermost loop immediately. Pairing it with an if that compares the current total to 0 gives the required early termination. The continue statement only skips to the next iteration, and using exceptions for ordinary control flow is discouraged, so those approaches fail to meet the requirement.

Answer

Wrapping the loop in a try block and raising an exception at zero is the idiomatic way to stop iteration.

Answer

A continue statement placed inside the loop would stop the entire scan when the total equals 0.

Answer

The condition for printing must be checked before the zero check, or zero totals could be printed.

Question 15

A programmer is reviewing code that uses loops and conditional statements. Which TWO of the following statements about Python control flow are correct? (Choose two.)

Accepted Answer

An if statement can be nested inside a for loop, and a for loop can be nested inside an if statement.. The two correct statements are that a for loop's else runs only without a break, and that control structures can be nested arbitrarily. These reflect Python's actual semantics. The other statements mischaracterize continue, break, and while loop behavior, each of which is well-defined and different from the described behavior.

Answer

A while loop always executes its body at least once, even if the condition is initially false.

Answer

The break statement can be used outside a loop to terminate the program.

Answer

The continue statement exits the current loop entirely and resumes execution after the loop.