PCEP Computer Programming and Python Fundamentals Practice Test 9 — 15 Questions

Question 1

Which THREE of the following are valid ways to create a list in Python?

Accepted Answer

list((1, 2, 3)). The `list()` constructor can take an iterable, such as a tuple, and convert it into a new list. `list((1, 2, 3))` explicitly creates a list `[1, 2, 3]` from the tuple `(1, 2, 3)`. This is a standard and valid way to create a list in Python.

Answer

(1, 2, 3)

Answer

{1, 2, 3}

Question 2

Refer to the exhibit. What type of error occurred, and which line caused it?

Accepted Answer

ZeroDivisionError at line 3. The code attempts to divide by zero on line 3, which raises a ZeroDivisionError. In Python, any division where the denominator is zero (e.g., `x / 0`) triggers this runtime exception, and the traceback points to the exact line where the division occurs.

Answer

NameError at line 3

Answer

SyntaxError at line 1

Answer

ValueError at line 0

Question 3

You are a junior developer at a logistics company. Your team maintains a Python script that processes daily shipment data from a CSV file. The script reads the file, computes total weight per shipment, and writes results to a new CSV. Recently, the script started crashing sporadically with a 'ValueError: invalid literal for int() with base 10: 'NULL''. The CSV file sometimes contains the string 'NULL' in the weight column for missing values. The current code reads the weight column as: weight = int(row['weight']). Your team lead wants a robust fix that handles missing data gracefully without crashing, and also logs the line number for any problematic rows for later review. Which of the following approaches best meets these requirements?

Accepted Answer

Wrap the int conversion in a try-except block: try: weight = int(row['weight']); except ValueError: weight = 0; log the line number using a counter variable.. It uses a try-except block to catch the ValueError when int() fails on 'NULL', sets weight to 0 as a fallback, and logs the line number using a counter variable. This approach handles any unexpected non-numeric string (not just 'NULL'), making it robust against future data anomalies, and satisfies the requirement to log problematic rows for review.

Answer

Use the string method .isdigit(): if row['weight'].isdigit(): weight = int(row['weight']); else: weight = 0; no logging.

Answer

Read the entire file into a list, then use a list comprehension to convert weights: weights = [int(w) if w != 'NULL' else 0 for w in rows] without logging.

Answer

Add a check: if row['weight'] != 'NULL': weight = int(row['weight']); else: weight = 0; and log a warning. Do not use try-except.

Question 4

You are an IT support specialist for a university. A professor uses a Python script that analyzes exam scores from a text file. The script calculates the average score and prints it. Recently, the script outputs 'NaN' instead of a number. The relevant code is: scores = [float(line.strip()) for line in open('scores.txt')]; average = sum(scores) / len(scores); print(average). You inspect the scores.txt file and find that one line contains the word 'Absent' and another line is blank. The professor wants the script to ignore non-numeric lines and blank lines, and also print a warning if any line was skipped. Which of the following modifications to the script best achieves this?

Accepted Answer

Open the file, iterate over lines, use try-except to convert to float, if successful append to list else increment a skip counter. At the end, print the average and the number of skipped lines.. It uses a try-except block to safely attempt conversion of each line to float, incrementing a skip counter for lines that fail (e.g., 'Absent' or blank). After processing, it computes the average only from successfully converted scores and prints both the average and the number of skipped lines, meeting the professor's requirements exactly.

Answer

Read all lines, filter with a lambda that checks if line can be converted to int, then convert to float.

Answer

Use list comprehension with condition if line.strip() != '': scores = [float(line.strip()) for line in open('scores.txt') if line.strip() != '']

Answer

Check if line.strip().isdigit() before conversion, and skip if not.

Question 5

A developer writes a function that calculates the area of a rectangle and prints the result inside the function. Later, they need to use this area in another calculation. What should they do to make the function reusable and composable?

Accepted Answer

Modify the function to return the area instead of printing it.. Returning a value from a function allows the caller to capture and reuse that value in subsequent calculations, making the function composable and reusable. Printing the result inside the function (as in the original code) only outputs it to the console and discards the value, preventing further programmatic use. By modifying the function to return the area, the developer can assign the result to a variable and use it in other expressions.

Answer

Store the area in a global variable and access it later.

Answer

Keep the function as is and call it from inside another function.

Answer

Pass the area to the next calculation using a print function argument.

Question 6

While debugging a Python script, you see the following error: 'IndentationError: expected an indented block'. The code appears to be correctly indented with spaces. What is the most likely cause?

Accepted Answer

You mixed tabs and spaces for indentation.. Mixing tabs and spaces for indentation is a common cause of 'IndentationError: expected an indented block' even when the code appears correctly indented. Python 3 disallows mixing tabs and spaces; it uses the exact whitespace characters to determine block structure, and inconsistent usage triggers this error.

Answer

You used the wrong number of spaces (e.g., 2 spaces instead of 4).

Answer

You forgot to include a colon at the end of a compound statement.

Answer

The script has a logic error in the condition.

Question 7

A Python developer is creating a function that processes a list of dictionaries and needs to ensure the original list remains unchanged. They write the following code:

def process(data):
    for item in data:
        item['processed'] = True
    return data

What is the best-practice critique of this function?

Accepted Answer

The function modifies the original list elements, causing side effects.. The function mutates the dictionaries in the original list by adding the key 'processed' to each one. This violates the principle of avoiding side effects in functions, as the caller's data is changed unexpectedly. In Python, dictionaries are mutable objects, so modifying them inside a function affects the original list elements.

Answer

The indentation should be 2 spaces instead of 4 to conform to PEP 8.

Answer

The function should use a list comprehension instead of a loop.

Answer

The function returns a value but does not use it, which is acceptable.

Question 8

A junior developer is writing a script to read a number from input and double it. They write:

num = input("Enter a number: ")
result = num * 2
print(result)

When they test with input 5, the output is '55' instead of 10. What is wrong?

Accepted Answer

The input is treated as a string; they need to convert it to int.. The `input()` function in Python always returns a string, even if the user types a number. When you use the `*` operator on a string, it repeats the string, so `'5' * 2` yields `'55'`. To perform numeric multiplication, you must convert the input to an integer using `int(input(...))`.

Answer

There is a syntax error in the multiplication line.

Answer

The print function is incorrectly formatting the output.

Answer

The variable name 'num' conflicts with a built-in function.

Question 9

A team is writing a Python script that reads a large log file and counts occurrences of ERROR. The script works but is very slow. They profile it and find that most time is spent reading the file line by line. Which optimization technique is most appropriate?

Accepted Answer

Examine the inner loop logic for unnecessary operations per line.. Profiling shows that most time is spent on reading the file line by line, which indicates an I/O bottleneck. However, among the given optimization techniques, examining the inner loop logic (Option B) is the most appropriate, as it can uncover unnecessary per‑line operations (e.g., redundant string methods, repeated allocations) that, while not the primary bottleneck, may be compounding the I/O wait time. The other options are less suitable: Option A risks memory issues with large files, Option C typically provides negligible performance improvement, and Option D is a syntax enhancement with no performance impact.

Answer

Use .readlines() to load the entire file into memory at once.

Answer

Open the file in binary mode to reduce overhead.

Answer

Rewrite the script using the 'with' statement for file handling.

Question 10

Which TWO of the following are valid variable names in Python? (Choose two.)

Accepted Answer

my_var_2. Variable names in Python must start with a letter or underscore, and can contain letters, digits, and underscores. 'my_var_2' starts with a lowercase letter and uses only underscores and digits, making it a valid identifier.

Answer

1st_value

Answer

user@name

Answer

for

Question 11

Which THREE of the following code snippets will successfully print the string 'Hello, World!'? (Choose three.)

Accepted Answer

print('''Hello, World!'''). Triple-quoted strings in Python, using three single quotes ('''), can span multiple lines but also work for single-line strings. The code print('''Hello, World!''') outputs the string exactly as 'Hello, World!' without any syntax error, as the triple quotes properly delimit the string.

Answer

print("He said, "Hello!"")

Answer

print('It's a beautiful day')

Question 12

A Python script contains the following code:

x = [1, 2, 3]
y = x
y.append(4)
z = x.copy()
z.append(5)

After execution, which TWO of the following statements are true? (Choose two.)

Accepted Answer

x is equal to [1, 2, 3, 4]. `y = x` creates a reference to the same list object, not a copy. When `y.append(4)` is called, it modifies the shared list, so `x` becomes `[1, 2, 3, 4]`. This demonstrates that assignment in Python does not copy objects; it binds a new name to the existing object.

Answer

x and y refer to different list objects

Answer

x is equal to [1, 2, 3]

Answer

x is equal to [1, 2, 3, 4, 5]

Question 13

You are a junior developer at a small startup. Your team has a Python script that automates daily data processing. The script reads a CSV file, processes each row, and writes results to a new file. Recently, the script started crashing with a 'ValueError: invalid literal for int()' error. The error occurs on a line that converts a field to an integer using int() on a string value. The CSV file comes from an external source that sometimes contains non-numeric values like 'N/A' or empty strings. Which course of action is best to handle this robustly without stopping the entire process?

Accepted Answer

Wrap the conversion in a try-except block and handle the exception appropriately for each row.. Wrapping the conversion in a try-except block allows the script to catch the ValueError for each row individually, log or handle the problematic row (e.g., skip it or use a default value), and continue processing the remaining rows without crashing. This is the standard Pythonic approach for handling expected but unpredictable data quality issues in external input, as it separates error handling from the main logic and preserves the robustness of the batch process.

Answer

Add logging before the conversion to print the problematic value.

Answer

Use a regex to replace all non-digit characters before conversion.

Answer

Contact the external source to ensure no missing values are sent.

Question 14

You are maintaining a Python script that calculates team bonuses based on sales data. The script reads a dictionary where keys are employee names and values are total sales (float). It then applies a 10% bonus if sales exceed 5000. The code snippet is:

def calculate_bonus(sales):
    for name, value in sales.items():
        if value > 5000:
            print(f"{name} gets bonus")

However, the manager wants the script to return a list of employees who qualify, not just print them. They also want to avoid side effects. What is the best way to modify this function?

Accepted Answer

Build a list inside the function and return it at the end.. It modifies the function to build a list of qualifying employee names inside the function and returns that list. This avoids side effects (no global variables, no mutation of the input dictionary) and follows the principle of returning results rather than printing them, making the function reusable and testable.

Answer

Create a global list variable at the top of the script and append each qualifying name to it.

Answer

Keep the function as is and have the caller capture the printed names by redirecting stdout.

Answer

Use the dictionary's update method to mark bonus status in the original sales dictionary.

Question 15

You are a developer in a company that runs a Python script daily to generate reports. The script uses the os module to list files in a directory and process each. Recently, after a server migration, the script fails with 'PermissionError: [Errno 13] Permission denied'. The script runs under a service account that has read/write access to most folders, but the migration changed the permissions on certain subdirectories. The error is intermittent, occurring only for some files. You need to fix the script to continue processing other files even if one fails. Which approach should you take?

Accepted Answer

Use a try-except block inside the loop to catch PermissionError for each file and continue.. By placing a try-except block inside the loop that catches PermissionError specifically, the script can skip the problematic file and continue processing the remaining files. This approach handles the intermittent permission errors gracefully without halting the entire script. Option B is wrong because catching all exceptions silently would mask other critical errors (e.g., bugs in the processing logic). Option C is wrong because os.access() checks may not fully reflect actual runtime permissions due to race conditions and platform-specific behavior, and it requires additional calls that could still fail. Option D is wrong because it relies on external action and does not address the need for the script to be resilient to such errors.

Answer

Wrap the entire processing loop in a try-except that catches all exceptions and passes silently.

Answer

Before processing each file, use os.access() to check permissions and skip if not accessible.

Answer

Ask the server administrator to grant full permissions to the service account on all directories.