PCEP Computer Programming and Python Fundamentals Practice Test 3 — 15 Questions

Question 1

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.. The code snippet as shown uses unique.sort() to sort the list in-place and then writes the sorted list, so it would produce ascending order if executed exactly. The discrepancy between the expected ascending order and the reported descending order strongly suggests a deviation from the snippet, such as the developer accidentally calling sort() on a different list (for example, sorting the original numbers list or a temporary copy) and then writing the unsorted unique list. Option B captures this idea: the sort() method was called on a list that was not saved, leading to the unsorted list being written. The other options are not consistent with the provided code: A is incorrect because the numbers are correctly converted to integers; C and D misrepresent file behavior (the file is opened in write mode, not append, and reading does not truncate the file).

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 2

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

Accepted Answer

Write the script in a text editor, save the file with a .py extension, open a terminal or command prompt, navigate to the directory containing the script, run the script using the Python interpreter.. The process involves creating the script, saving it, opening a terminal, navigating to its location, and executing it with the Python interpreter.

Answer

Write the script in a text editor, save the file with a .py extension, open a terminal or command prompt, run the script using the Python interpreter.

Answer

Write the script in a text editor, open a terminal or command prompt, run the script using the Python interpreter, save the file with a .py extension.

Answer

Write the script in a text editor, open a terminal or command prompt, navigate to the directory containing the script, run the script using the Python interpreter.

Question 3

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

Accepted Answer

Open the file, read the file contents, process the data, then close the file.. The correct sequence for reading data from a text file in Python is: first open the file using the open() function, then read its contents (e.g., with read() or readlines()), process the data as needed, and finally close the file with close(). Opening establishes a file handle, reading retrieves the data, processing uses it, and closing releases resources. Common mistakes include closing before processing, processing before reading, or reading before opening.

Answer

Open the file, read the file contents, close the file, then process the data.

Answer

Open the file, process the data, read the file contents, then close the file.

Answer

Read the file contents, open the file, process the data, then close the file.

Question 4

Arrange the steps to slice a list in Python.

Accepted Answer

First create the list, then specify the start index, then specify the stop index, then optionally specify the step.. List slicing in Python uses the syntax [start:stop:step] within square brackets on an existing list. The correct order is to first have the list, then define the start index, then the stop index, and finally an optional step. Common mistakes include putting indices out of order or attempting to slice before the list exists.

Answer

First specify the start index, then create the list, then specify the stop index, then optionally specify the step.

Answer

First create the list, then specify the stop index, then specify the start index, then optionally specify the step.

Answer

First create the list, then specify the start index, then specify the step, then specify the stop index.

Question 5

Match each Python data type to its description.

Accepted Answer

int: Whole numbers. The correct matches are: A (int - whole numbers), B (float - numbers with decimal point), D (bool - Boolean values True or False). Option C (str) is incorrect because strings are immutable sequences of characters, not mutable collections. Option E (list) is incorrect because lists are mutable collections, not immutable sequences. Option F (tuple) is incorrect because tuples are immutable sequences, not mutable collections.

Answer

str: Ordered, mutable collection of items

Answer

list: Immutable sequence of characters

Answer

tuple: Ordered, mutable collection of items

Question 6

Match each Python keyword to its use.

Accepted Answer

break: Exits the innermost loop. The correct matches are: break is used to exit a loop prematurely; continue skips the current iteration; pass is a no-operation statement. Common mistakes include swapping the definitions of break and continue.

Answer

break: Skips the rest of the current iteration

Answer

continue: Exits the innermost loop

Question 7

Match each Python list method to its effect.

Accepted Answer

insert: Inserts an element at a given index.. The correct matches are: insert inserts at an index, remove deletes first occurrence of a value, pop removes and returns an element by index. Common confusions involve swapping append (adds a single element) and extend (adds elements from an iterable).

Answer

append: Extends the list by appending elements from an iterable.

Answer

extend: Adds an element to the end of the list.

Question 8

A developer writes code to calculate the area of a rectangle and prints it. The code is:
length = 10
width = 5
area = length + width
print('The area is', area)
If the width is accidentally assigned a string '5', what error will occur?

Accepted Answer

TypeError. In Python, adding an integer and a string is not a valid operation; it will raise a TypeError because Python cannot implicitly convert the string to an integer for arithmetic. Therefore, the code will raise a TypeError when executed.

Answer

ValueError

Answer

SyntaxError

Answer

NameError

Question 9

An application requires different messages based on temperature. Given:
temp = 25
if temp > 30:
    print('Hot')
elif temp > 20:
    print('Warm')
else:
    print('Cool')
What is the output?

Accepted Answer

Warm. The condition `temp > 30` is False (25 is not greater than 30), so the first `if` block is skipped. The `elif temp > 20` condition is True (25 > 20), so the `print('Warm')` statement executes, outputting 'Warm'. Option D is correct.

Answer

No output

Answer

Hot

Answer

Cool

Question 10

A QA engineer needs to run a test 5 times. Which loop construct is most appropriate?

Accepted Answer

for i in range(5): .... The `for i in range(5)` loop is the most idiomatic and concise way to repeat an action a fixed number of times (5 iterations) in Python. The `range(5)` generates a sequence from 0 to 4, and the loop body executes exactly 5 times, which directly matches the requirement to run a test 5 times without needing manual counter management.

Answer

do: ... while counter < 5

Answer

while counter < 5: ... counter += 1

Answer

def repeat(): ... repeat()

Question 11

A data scientist has a list: scores = [88, 92, 79, 93, 85]. They want to add 5 bonus points to each score and store the new scores. Which code accomplishes this?

Accepted Answer

scores = [s + 5 for s in scores]. Uses a list comprehension to create a new list where each element is the original score plus 5. This correctly generates the new scores without modifying the original list, which is the intended behavior.

Answer

scores = [s+5] for s in scores

Answer

for s in scores: s += 5

Answer

scores = scores + 5

Question 12

A developer wants to extract the file extension from a filename: 'report.pdf'. Which string method will return 'pdf'?

Accepted Answer

'report.pdf'.split('.')[-1]. The `split('.')` method divides the string at each period, returning a list `['report', 'pdf']`. Accessing index `-1` retrieves the last element, which is the file extension `'pdf'`. This is a common Python idiom for extracting file extensions.

Answer

'report.pdf'.replace('.', '')

Answer

'report.pdf'.split('.')[1]

Answer

'report.pdf'.removeprefix('report.')

Question 13

A function is defined as:
def add(a, b=5):
    return a + b
What is the result of add(10)?

Accepted Answer

15. The function `add(a, b=5)` defines a default value of 5 for parameter `b`. When called as `add(10)`, the argument 10 is assigned to `a`, and `b` uses its default value of 5. The function returns `10 + 5 = 15`, making option C correct.

Answer

10

Answer

5

Answer

Error

Question 14

A developer writes:
try:
    x = int('hello')
except ValueError:
    x = 0
except TypeError:
    x = -1
finally:
    x = x + 1
What is the final value of x?

Accepted Answer

1. The code attempts to convert the string 'hello' to an integer, which raises a ValueError. The except ValueError block catches this and sets x = 0. The finally block always executes, adding 1 to x, so x becomes 1. The TypeError except is never triggered because the error is a ValueError, not a TypeError.

Answer

0

Answer

-1

Answer

2

Question 15

Consider code:
def outer():
    x = 1
    def inner():
        nonlocal x
        x = 2
    inner()
    print(x)
outer()
What is printed?

Accepted Answer

2. The `nonlocal` declaration inside `inner()` binds the variable `x` to the `x` defined in the enclosing `outer()` function. When `inner()` assigns `x = 2`, it modifies that outer `x`, so after `inner()` returns, `print(x)` in `outer()` outputs 2.

Answer

1

Answer

Error

Answer

None