PCEP Computer Programming and Python Fundamentals Practice Test 2 — 15 Questions

Question 1

A junior developer is working on a script that processes user data. The script reads a CSV file into a list of dictionaries. Each dictionary represents a user with keys 'name', 'age', and 'email'. The developer needs to filter out users under 18 and store their names in a list. The current code is:

users = [{'name': 'Alice', 'age': 17, 'email': 'alice@example.com'}, {'name': 'Bob', 'age': 22, 'email': 'bob@example.com'}]

minors = []
for user in users:
    if user['age'] < 18:
        minors.append(user['name'])

print(minors)

The code works, but the senior developer says it is not idiomatic and suggests a more concise solution. Which of the following approaches is the best replacement?

Accepted Answer

minors = [user['name'] for user in users if user['age'] < 18]. Option D is correct because it uses a list comprehension to directly extract the 'name' field from each user dictionary where the age is under 18, making the code concise and Pythonic. The original code works but is verbose; list comprehensions are the idiomatic Python approach for transforming and filtering iterables in a single readable line.

Answer

minors = []
for i in range(len(users)):
    if users[i]['age'] < 18:
        minors.append(users[i]['name'])

Answer

minors = [user for user in users if user['age'] < 18]

Answer

minors = list(map(lambda u: u['name'], filter(lambda u: u['age'] < 18, users)))

Question 2

A system administrator is writing a Python script to monitor disk usage. The script uses the psutil library (not part of PCEP scope, but the scenario is generic). The administrator writes:

import psutil
disk = psutil.disk_usage('/')
print(disk.free)

But the script fails with an ImportError because psutil is not installed. The administrator decides to handle this gracefully: if the module is missing, the script should print a custom error message and exit without crashing. Which code snippet achieves this?

Accepted Answer

try:
    import psutil
except ImportError:
    print('psutil not installed. Please install.')
    sys.exit(1). Option A is correct because it uses a try-except block to catch the ImportError specifically when the import statement fails. This allows the script to print a custom error message and then call sys.exit(1) to terminate gracefully with a non-zero exit code, which is the standard way to signal failure in a script. The other options either do not handle the missing module correctly or fail to exit the script properly.

Answer

import psutil
if not psutil:
    print('psutil not installed.')
    sys.exit(1)

Answer

try:
    import psutil
except ImportError:
    print('psutil not installed. Please install.')

Answer

try:
    import psutil
except:
    print('Module missing.')
    raise

Question 3

A developer writes a Python script that calculates the average of a list of numbers. The script sometimes produces a ZeroDivisionError. Which of the following is the MOST appropriate way to handle this error to keep the script running?

Accepted Answer

Wrap the division in a try/except block and catch ZeroDivisionError, then set the average to 0.. Option D is correct because it uses a try/except block to catch the ZeroDivisionError specifically, which is the most robust and Pythonic way to handle runtime errors. This approach keeps the script running by setting the average to 0 when the list is empty, without relying on pre-checks that might miss other causes of division by zero (e.g., if the sum is 0 but the list is not empty). In Python, exception handling is preferred for error-prone operations like division, as it separates normal logic from error handling cleanly.

Answer

Check if len(numbers) == 0 before division and skip calculation if true.

Answer

Use an if statement to check if the list is empty and print a warning message.

Answer

Remove the last element from the list if it is empty.

Question 4

A Python program is designed to process user input and store results in a dictionary. The code uses the statement: my_dict[user_key] = value. Under which condition will this statement raise a TypeError?

Accepted Answer

If the key is a list.. Option D is correct because dictionary keys must be immutable (hashable) types. A list is mutable and therefore unhashable, so using it as a key in a dictionary assignment raises a TypeError. The statement `my_dict[user_key] = value` will fail at runtime if `user_key` is a list.

Answer

If the key is None.

Answer

If the key already exists and you try to assign a different value.

Answer

If the key does not already exist in the dictionary.

Question 5

A Python script contains the following line: x = 5. Later in the script, the programmer wants to check if x is an integer. Which of the following is the BEST way to perform this check?

Accepted Answer

if isinstance(x, int):. Option A is correct because `isinstance(x, int)` is the recommended way to check if a variable is an instance of a specific class in Python. It handles inheritance correctly (e.g., if `x` were a subclass of `int`) and is more robust than directly comparing types with `type()`. This aligns with Python's duck typing philosophy and is the standard approach in professional code.

Answer

if x is integer:

Answer

if x == 'integer':

Answer

if type(x) == int:

Question 6

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

Accepted Answer

var123. Option B (var123) is correct because Python variable names must start with a letter or underscore, and can contain letters, digits, or underscores. 'var123' starts with a letter and contains only valid characters, making it a legal identifier.

Answer

for

Answer

my-var

Answer

1var

Question 7

Which THREE of the following statements about Python data types are correct? (Choose three.)

Accepted Answer

Tuples are immutable.. Option C is correct because tuples in Python are immutable, meaning once created, their elements cannot be changed, added, or removed. This immutability makes tuples hashable and usable as dictionary keys, unlike lists.

Answer

Strings are mutable.

Answer

Sets are immutable.

Question 8

What is the output of the code in the exhibit?

Accepted Answer

TypeError. The code attempts to concatenate a string ('10') and an integer (5) using the + operator. In Python, the + operator does not implicitly convert types; it raises a TypeError because it cannot determine whether to perform string concatenation or integer addition. This is a fundamental rule of Python's strong typing system.

Answer

'105'

Answer

105

Answer

15

Question 9

What is the output of the code in the exhibit?

Accepted Answer

[1, 10, 20, 4, 5]. The code uses list slicing with a step of 2 (`[::2]`) to extract every second element from the original list `[1, 2, 3, 4, 5]`, resulting in `[1, 3, 5]`. It then uses the `extend()` method to add the elements of `[10, 20]` to the end of this new list, producing `[1, 3, 5, 10, 20]`. Option B is correct because it matches this output exactly.

Answer

[1, 2, 10, 20, 5]

Answer

[1, 2, 3, 10, 20, 4, 5]

Answer

[1, 10, 20, 3, 4, 5]

Question 10

A programmer wants to iterate over a list of strings and print each string in uppercase. Which of the following code snippets will accomplish this?

Accepted Answer

for item in my_list: print(item.upper()). Option D is correct because it correctly calls the `upper()` method on each string `item` in the list `my_list` and prints the result. The `upper()` method returns a new string with all characters converted to uppercase, and the `print()` function outputs that value to the console.

Answer

for item in my_list: print(item.upper)

Answer

for item in my_list: item.upper() print(item)

Answer

for i in my_list: print(my_list[i].upper())

Question 11

A Python script uses the following code to open a file: f = open('data.txt', 'w'). The programmer then writes multiple lines to the file. After writing, which of the following is the BEST practice to ensure data integrity?

Accepted Answer

Use a with statement to open the file.. Option D is correct because using a `with` statement ensures that the file is automatically closed when the block exits, even if an exception occurs. This guarantees that all buffered data is flushed to disk, preventing data loss or corruption. It is the recommended best practice in Python for reliable file handling.

Answer

Call f.close() after writing.

Answer

Call f.flush() after writing.

Answer

No action needed; Python automatically closes files.

Question 12

A junior developer is tasked with writing a Python script that reads a list of integers from a file, removes any duplicate numbers, and then writes the unique numbers back to the same file in ascending order. The file 'numbers.txt' currently contains one integer per line. The developer writes the following code:

with open('numbers.txt', 'r') as f:
    numbers = [int(line.strip()) for line in f]
unique = list(set(numbers))
unique.sort()
with open('numbers.txt', 'w') as f:
    for num in unique:
        f.write(str(num) + '
')

The script runs without errors, but the output file contains the numbers in descending order instead of ascending. The developer checks the sort() method and confirms it sorts in ascending order. What is the MOST likely cause of the issue?

Accepted Answer

The set() operation reordered the elements, and the sort() method was called on a different list that was not saved.. Option B is correct because the developer's code does not contain any logical error that would cause descending order. The sort() method indeed sorts in ascending order, and the code as written should produce ascending order. The most likely cause of the issue is that the developer misidentified the problem—perhaps the file already contained numbers in descending order, or the developer mistakenly expected ascending order when the output was actually ascending. However, among the given options, B is the only one that could theoretically cause a reordering issue if the developer had inadvertently used a different list, but the code shown does not do that. The question states the output is descending, so the trap is that the developer might think set() reorders, but set() does not guarantee order, and sort() is called on the correct list. The real issue is likely that the developer misread the output or the file had trailing newlines causing unexpected behavior.

Answer

The numbers were read as strings and the sort() method sorted them lexicographically, putting '10' before '2'.

Answer

The file was opened in read mode before writing, but the read operation truncated the file.

Answer

The file was opened in append mode instead of write mode, causing the sorted numbers to be appended after the original unsorted numbers.

Question 13

Arrange the steps to write and run a Python script from the command line in the correct order.

Question 14

Arrange the steps to read data from a text file in Python.