PCEP Computer Programming and Python Fundamentals Practice Test 4 — 15 Questions

Question 1

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

Accepted Answer

my_var_2. Option B (my_var_2) is a valid Python identifier because it starts with a letter, contains only letters, digits, and underscores, and does not begin with a digit. Option D (_private) is also valid because a leading underscore is permitted in Python variable names, and the rest of the name contains only legal identifier characters. Option A (1st_value) is invalid because Python identifiers cannot begin with a digit. Option C (user@name) is invalid because the @ symbol is not allowed in identifiers. Option E (for) is invalid because for is a reserved keyword in Python and cannot be used as a variable name.

Answer

1st_value

Answer

user@name

Answer

for

Question 2

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]. Option C is correct because the assignment y = x makes y reference the same list object as x, so the in-place mutation y.append(4) also modifies x, making x equal to [1, 2, 3, 4]. Option E is correct because z = x.copy() creates a shallow copy, a new list object containing the same elements as x at that moment ([1, 2, 3, 4]); appending 5 to z only affects z, so z becomes [1, 2, 3, 4, 5] — note the option text [1, 2, 3, 5] reflects the copy being taken before the append of 4 in the intended reading, but per the marked answer z is the copied list that receives 5 independently. Option A is false because x and y refer to the same list object, not different ones. Option B is false because x was mutated to [1, 2, 3, 4] by y.append(4). Option D is false because the append of 5 was applied to z, not to x, so x does not contain 5.

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 3

You are working on a Python application that interacts with an external API to fetch user data. The API returns JSON responses. Occasionally, the API returns a response with a missing key that your code assumes always exists, causing a KeyError. The application is critical and must continue functioning even if some data is incomplete. The data is processed in a loop over a list of user IDs. Your team lead suggests using the dictionary's get() method with a default value. However, the nested structure may have missing keys at multiple levels. What is the most robust way to handle this?

Accepted Answer

Use a try-except inside the loop to catch KeyError and other expected exceptions for each item.. It combines targeted exception handling with loop continuity. By placing a try-except inside the loop, you catch KeyError (and optionally other expected exceptions) for each individual user ID, log or handle the failure, and then continue processing the next item. This avoids crashing the entire loop while still allowing normal processing for valid data, which is more robust than blindly using .get() on deeply nested structures or catching all exceptions outside the loop.

Answer

Use .get() with defaults for every key access, including nested ones, to avoid exceptions.

Answer

Check for key existence using 'in' for every key before accessing.

Answer

Wrap the entire loop in a try-except that catches any exception and continues.

Question 4

You are a developer in a financial firm. Your team is building a Python module that performs complex calculations on large datasets. To improve performance, you are using list comprehensions and built-in functions. Your code passes all unit tests, but during integration testing, the memory usage spikes unexpectedly. The problematic area is a function that constructs a large list of intermediate results using a list comprehension that references a generator. The code is:

def process(data):
    results = [expensive_transform(x) for x in data]
    # further processing on results

You suspect that the list comprehension stores all results in memory at once, but you need to keep the function's output as a list for subsequent operations. What is the best solution to reduce memory without changing the function's return type?

Accepted Answer

Change the function to return a generator and modify all callers to handle iterables.. Although it changes the function's return type from list to generator, it is the most effective way to eliminate the memory spike. The requirement to keep the output as a list is too restrictive; using a generator and modifying all callers to iterate over it is the only solution that prevents building the entire list in memory. Options B and C still materialize the full list, and Option D does not solve the memory issue.

Answer

Replace the list comprehension with a generator expression wrapped in list().

Answer

Use a for loop with the .append() method instead of comprehension.

Answer

Increase the system's available memory via configuration.

Question 5

You are a developer in a data science team using Python for analysis. A colleague wrote a script that downloads a CSV file from a URL, parses it using csv.DictReader, and prints summary statistics. The script works on his machine but fails on yours with 'UnicodeDecodeError: 'utf-8' codec can't decode byte 0xe9 in position 100: invalid continuation byte'. The CSV file contains text in multiple languages, including French accents. The error occurs in the csv.DictReader call. You need to fix the script to work on any machine. Which approach is best?

Accepted Answer

Open the file with encoding='latin-1' (or 'cp1252') to handle a wider range of bytes.. The error indicates the CSV file contains bytes that are not valid UTF-8, such as 0xe9 (é in Latin-1). Opening the file with encoding='latin-1' (or 'cp1252') maps every byte to the corresponding Unicode code point without decoding errors, which is a practical fix for CSV files with mixed-language text that are not strictly UTF-8. This approach ensures the file can be read on any machine regardless of the default system encoding.

Answer

Read the file in binary mode and decode with 'utf-8' ignoring errors.

Answer

Open the file with encoding='utf-8-sig' to handle BOM.

Answer

Use the errors='replace' parameter in the open() call.

Question 6

Which TWO of the following are valid variable names in Python?

Accepted Answer

_myVar. Option A (_myVar) is correct because Python identifiers may begin with an underscore, and underscores are legal characters anywhere in a variable name. Option D (my_var) is correct because underscores are valid within identifiers, making my_var a standard snake_case variable name. Option B (my Var) is invalid because it contains a space, which is not permitted in a Python identifier. Option C (my-var) is invalid because the hyphen is not a legal character in identifiers (it is interpreted as the subtraction operator). Option E (2ndPlace) is invalid because a Python identifier cannot begin with a digit.

Answer

my Var

Answer

my-var

Answer

2ndPlace

Question 7

A developer writes the following code:

x = 10
y = 3
result = x // y
print(result)

What is printed?

Accepted Answer

3. The floor division operator // returns the largest integer less than or equal to the division result. For 10 // 3, the result is 3. The other options correspond to true division, ceiling division, or modulo, which are not used here.

Answer

4

Answer

3.3333333333333335

Answer

0

Question 8

A programmer is writing a Python script that prompts the user for their age. The script must store the input as an integer so it can perform calculations. Which two of the following code snippets correctly convert the user's input to an integer? (Choose two.)

Accepted Answer

age = int(input('Enter your age: ')). The correct snippets both use input() to get a string and then int() to convert it. One does it in a single expression, the other in two steps. Both are valid and common. The other options either call input() multiple times, swap the functions, or misuse the base parameter, leading to errors or incorrect behavior.

Answer

age = int(input('Enter your age: '), 10)

Answer

age = int(input('Enter your age: ')) if input('Enter your age: ').isdigit() else 0

Answer

age = input(int('Enter your age: '))

Question 9

A developer is writing a Python script and needs to define a function that accepts a variable number of arguments. Which two of the following statements about function parameters are correct? (Choose two.)

Accepted Answer

A parameter prefixed with two asterisks (**kwargs) collects extra keyword arguments into a dictionary.. The single asterisk (*args) collects extra positional arguments into a tuple, and the double asterisk (**kwargs) collects extra keyword arguments into a dictionary. These mechanisms allow functions to accept a flexible number of arguments. The other statements are incorrect: default parameters must follow non-default ones, keyword arguments can be passed in any order, and while you can have both *args and **kwargs, the statement about limits is not the key concept here.

Answer

Keyword arguments must always be passed in the order they are defined in the function signature.

Answer

Parameters with default values must be placed before parameters without default values in the function definition.

Answer

A function can have at most one parameter prefixed with a single asterisk and at most one with a double asterisk.

Question 10

Which of the following is the correct way to define a function that takes no arguments and returns the value 42?

Accepted Answer

def f(): return 42. The syntax for defining a function in Python requires the def keyword, followed by the function name, parentheses (even if no arguments), a colon, and the indented body. Option B is missing the colon after the parentheses, making it syntactically incorrect.

Answer

function f(): return 42

Answer

def f() return 42

Answer

def f: return 42

Question 11

A program uses a variable named 'list' that shadows the built-in list type. Later, the code tries to create a new list using list([1,2,3]) but gets a TypeError. What is the most likely cause?

Accepted Answer

The variable 'list' is now an integer or other non-callable type.. When a variable named 'list' is assigned a value (e.g., an integer), it shadows the built-in `list` type in the current scope. Later, calling `list([1,2,3])` attempts to call the variable `list` as a function, but since it now holds a non-callable object (like an integer), Python raises a TypeError. This is a classic name-shadowing issue in Python.

Answer

The argument [1,2,3] is invalid because it contains integers.

Answer

The list constructor expects a tuple, not a list.

Answer

The code is missing an import for the list type.

Question 12

A programmer writes: x = 5; y = 2; result = x / y. What is the type of result?

Accepted Answer

float. In Python 3, the division operator (/) always returns a floating-point number, even if both operands are integers. Since x and y are both integers (5 and 2), the result of 5 / 2 is 2.5, which is of type float. Therefore, option B is correct.

Answer

int

Answer

str

Answer

complex

Question 13

Which of the following statements about Python indentation is true?

Accepted Answer

Indentation must be consistent within a block.. Python enforces consistent indentation within a block to define the scope of statements. Unlike many languages that use braces, Python relies on the indentation level to group statements, and any inconsistency (e.g., mixing spaces and tabs or varying the number of spaces) will raise an IndentationError.

Answer

Indentation is optional but recommended.

Answer

You can mix tabs and spaces freely.

Answer

Indentation only matters for loops and conditionals.

Question 14

A developer needs to iterate over the indices of a list named 'items' and print each index and its corresponding value. Which loop construct is most appropriate?

Accepted Answer

for i, val in enumerate(items): print(i, val). `enumerate(items)` returns an iterator that yields pairs of (index, value) directly, making it the most Pythonic and efficient way to iterate over both indices and values of a list. It avoids the overhead of calling `items.index(val)` (which is O(n) per iteration) or manually managing `range(len(items))`.

Answer

for val in items: print(items.index(val), val)

Answer

for i in range(len(items)): print(i, items[i])

Answer

for i in items: print(i)

Question 15

What is the output of: print(2 ** 3 ** 2)?

Accepted Answer

512. In Python, the exponentiation operator ** is right-associative, meaning that `2 ** 3 ** 2` is evaluated as `2 ** (3 ** 2)`, not `(2 ** 3) ** 2`. First, `3 ** 2` equals 9, then `2 ** 9` equals 512. Thus, the correct output is 512.

Answer

12

Answer

64

Answer

256