PCEP Practice Test 22 — 15 Questions

Question 1

A program contains a nested while loop. The inner loop should run as long as a condition is True, but the outer loop should stop after 3 iterations. Which code structure is correct? (Assume the inner loop condition is inner < 5.)

Accepted Answer

outer = 0
while outer < 3:
    inner = 0
    while inner < 5:
        # do something
        inner += 1
    outer += 1. Option D correctly implements a nested while loop where the inner loop runs while `inner < 5` and the outer loop runs while `outer < 3`. The inner loop increments `inner` to control its own termination, and the outer loop increments `outer` after the inner loop completes, ensuring exactly 3 iterations of the outer loop. This matches the requirement that the outer loop stops after 3 iterations while the inner loop runs as long as its condition is True.

Answer

for outer in range(3):
    inner = 0
    while inner < 5:
        # do something
        inner += 1

Answer

outer = 0
while outer < 3:
    for inner in range(5):
        # do something
        outer += 1

Answer

outer = 0
while outer < 3:
    inner = 0
    while inner < 5:
        # do something
        outer += 1
        inner += 1

Question 2

A developer runs the script and enters 'Alice' and '25'. What does it print?

Accepted Answer

Alice is 25 years old.. Option D is correct because the input() function returns strings, and the print() function with commas inserts spaces between arguments. The age '25' is printed as a string, not an integer, so no decimal point appears. The output is 'Alice is 25 years old.'

Answer

Alice is 25.0 years old.

Answer

Alice is  Alice  is 25 years old.

Answer

Alice is 25 years old. (with age as integer)

Question 3

A programmer needs to check if at least one element in a list of booleans flags is True. Which expression correctly does this?

Accepted Answer

True in flags. Option A is correct because the `in` operator checks membership in a list; `True in flags` returns `True` if at least one element in the list `flags` is the boolean `True`. Option D is also correct because the built-in `any()` function returns `True` if any element in the iterable is truthy, which for a list of booleans means at least one `True`.

Answer

all(flags)

Answer

flags.any()

Question 4

A function `def process(data):` modifies the dictionary passed as argument by adding a new key. The developer wants to avoid modifying the original dictionary. What should the function do?

Accepted Answer

Create a copy of the dictionary at the start: `data = data.copy()`. Option A is correct because dictionaries are mutable objects in Python, so passing a dictionary to a function passes a reference to the same object. Calling `data.copy()` creates a shallow copy of the dictionary, allowing the function to modify the copy without affecting the original dictionary. This is the standard Pythonic way to avoid side effects on mutable arguments.

Answer

Add the key, then delete it at the end.

Answer

Modify directly; changes to mutable objects are local only.

Answer

Convert the dictionary to a tuple before processing.

Question 5

Which THREE of the following are valid list operations?

Accepted Answer

my_list.extend([5,6]). Option B is correct because the `extend()` method appends each element of the iterable (here, the list `[5,6]`) to the end of the original list, modifying it in place. This is a valid list operation in Python that adds multiple elements at once.

Answer

my_list.add(5)

Answer

my_list.push(5)

Question 6

What is the output of this code?

Accepted Answer

RuntimeError: dictionary changed size during iteration. Option A is correct because modifying a dictionary's size (adding or deleting keys) during iteration over its keys, values, or items raises a RuntimeError. In this code, the loop iterates over the dictionary's keys while deleting them, which changes the dictionary's size and triggers the exception.

Answer

{}

Answer

{'b': 2}

Answer

{'a': 1, 'c': 3}

Question 7

A developer writes a function to calculate the average of a list of numbers, but the function sometimes returns a wrong result when the list contains non-numeric values. What is the best way to handle this?

Accepted Answer

Check that all items are numeric before calculation, and raise TypeError otherwise.. Option D is correct because it explicitly validates that all items are numeric before performing the calculation, raising a TypeError if any non-numeric value is found. This follows Python's principle of explicit error handling and ensures the function's contract is clear: it only works with numeric data. Returning None (A) or silently ignoring values (B) can lead to subtle bugs, while converting to strings (C) would produce a concatenated string, not an average.

Answer

Return None if any non-numeric value is encountered.

Answer

Use try-except to ignore non-numeric values and proceed with the remaining numbers.

Answer

Convert all values to string and concatenate them.

Question 8

A script uses a dictionary to store counts of words. The code `counts['apple'] += 1` raises a KeyError the first time because the key doesn't exist. Which approach best solves this?

Accepted Answer

Use `counts.setdefault('apple', 0)` then increment.. Option A is correct because `setdefault('apple', 0)` inserts the key with a default value of 0 if it does not exist, then returns the value (0). After that, `counts['apple'] += 1` increments safely. This avoids a KeyError without requiring an explicit check or exception handling, making it the most concise and Pythonic approach for initializing missing dictionary keys.

Answer

Use `try-except` to catch KeyError and then set the key.

Answer

Use `counts['apple'] = counts.get('apple') + 1`

Answer

Use `if 'apple' in counts:` before incrementing.

Question 9

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 10

A developer writes a function that takes a tuple as an argument and tries to modify an element inside the tuple. What happens?

Accepted Answer

The code raises a TypeError.. Tuples in Python are immutable, meaning their elements cannot be changed after creation. Attempting to modify an element (e.g., `my_tuple[0] = 5`) raises a `TypeError` because the tuple object does not support item assignment. This is a fundamental property of the tuple data type.

Answer

The tuple is converted to a list automatically.

Answer

The first element is modified successfully.

Answer

The code raises a ValueError.

Question 11

Which TWO of the following dictionary methods return a view object that changes when the dictionary changes?

Accepted Answer

`dict.keys()`. A is correct because `dict.keys()` returns a view object that dynamically reflects changes made to the dictionary. When the dictionary is updated, the view object automatically updates to show the new keys, making it a live view rather than a static copy.

Answer

`dict.get()`

Answer

`dict.copy()`

Answer

`dict.items()`

Question 12

A developer writes: a = 3; b = 4; c = a + b / 2. What is the value of c?

Accepted Answer

5.0. In Python, the division operator `/` always returns a float, and operator precedence dictates that division is performed before addition. Thus, `b / 2` evaluates to `4 / 2 = 2.0`, then `a + 2.0` yields `3 + 2.0 = 5.0`. Option D is correct because the result is a float value of 5.0.

Answer

3

Answer

3.5

Answer

5

Question 13

What is the output of the code?

Accepted Answer

None. Option A is correct because the code attempts to divide an integer by zero (2 / 0), which in Python raises a ZeroDivisionError. Since there is no try-except block to handle this exception, the program crashes before any value is assigned or returned, so the output is None (the default return value of a function that does not execute successfully).

Answer

inf

Answer

2.0

Answer

An unhandled TypeError is raised.

Question 14

Which THREE of the following expressions evaluate to True?

Accepted Answer

3 == 3. Option A is correct because the equality operator '==' compares the integer values 3 and 3, which are identical, so the expression evaluates to True. In Python, '==' checks for value equality, not identity, and since both operands are the same integer literal, the result is True.

Answer

1 < 0

Answer

4 > 5

Question 15

A developer writes a script that prompts the user for their age and stores it in a variable. Which code snippet correctly converts the input to an integer?

Accepted Answer

age = int(input("Enter age: ")). Option B is correct because it uses the `int()` function to convert the string returned by `input()` into an integer. The `input()` function always returns a string, so wrapping it with `int()` performs the type conversion needed for numeric operations.

Answer

age = int(input)

Answer

age = input("Enter age: ", int)

Answer

age = input(int("Enter age: "))