PCEP Practice Test 7 — 10 Questions

Question 1

Given the code: my_list = [1, 2, 3, 4, 5]. What is the output of print(my_list[-3:-1])?

Accepted Answer

[3, 4]. Python list slicing with negative indices counts from the end of the list. my_list[-3:-1] starts at index -3 (value 3) and goes up to but does not include index -1 (value 5), so it returns [3, 4].

Answer

[4, 5]

Answer

[2, 3]

Answer

[3, 4, 5]

Question 2

Which of the following correctly creates a tuple with a single element 5?

Accepted Answer

t = (5,). In Python, a tuple with a single element requires a trailing comma after the element. Without the comma, parentheses are treated as grouping operators for expression evaluation, not as a tuple literal. Thus, `t = (5,)` creates a tuple containing the integer 5.

Answer

t = (5)

Answer

t = (5)

Answer

t = (5, 5)

Question 3

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

Question 4

Which of the following is the most efficient (Pythonic) way to create a list of squares for numbers 0 through 9?

Accepted Answer

squares = [i*i for i in range(10)]. Uses a list comprehension, which is the most Pythonic and efficient way to create a list because it combines iteration and list construction in a single, readable expression. It avoids the overhead of repeated method calls (like `append`) and is faster than `map` with a lambda due to reduced function call overhead.

Answer

squares = []; for i in range(10): squares.append(i*i)

Answer

squares = list(map(lambda x: x*x, range(10)))

Answer

squares = (i*i for i in range(10))

Question 5

Which exception is raised when trying to access a dictionary key that does not exist?

Accepted Answer

KeyError. In Python, when you attempt to access a dictionary key that does not exist using square bracket notation (e.g., `my_dict['nonexistent']`), the interpreter raises a `KeyError`. This is the standard exception for missing dictionary keys, as defined in the Python language specification. The correct answer is A.

Answer

TypeError

Answer

ValueError

Answer

AttributeError

Question 6

A program needs to check if a number is both positive and even. Which expression correctly implements this?

Accepted Answer

if num > 0 and num % 2 == 0:. It uses the logical `and` operator to combine two conditions: `num > 0` (checks if the number is positive) and `num % 2 == 0` (checks if the number is even). Both conditions must be true for the overall expression to be true, which correctly implements the requirement of checking if a number is both positive and even.

Answer

if num > 0 or num % 2 == 0:

Answer

if num > 0 & num % 2 == 0:

Answer

if num > 0 and % 2 == 0:

Question 7

What is the result of bool(0) in Python?

Accepted Answer

False. The bool() function in Python converts any value to a Boolean. The integer 0 is considered a falsy value, so bool(0) returns False. This is because Python defines 0, None, empty collections, and False itself as falsy.

Answer

0

Answer

None

Answer

True

Question 8

Given the code:
```python
name = input('Enter your name: ')
print('Hello, ' + name)
```
If the user enters 'Alice', what is the output?

Accepted Answer

Hello, Alice. The `print('Hello, ' + name)` statement concatenates the string literal `'Hello, '` (which includes a trailing space) with the user input `'Alice'`, producing the output `Hello, Alice`. The `input()` function returns the exact string entered by the user without any extra quotes or formatting.

Answer

Hello,Alice

Answer

Hello, 'Alice'

Answer

Hello, Alice

Question 9

A Python program prompts the user for their age and stores it in a variable. Which is the correct way to convert the input to an integer?

Accepted Answer

age = int(input("Age: ")). The `input()` function in Python always returns a string, and to perform arithmetic operations or numeric comparisons, the string must be explicitly converted to an integer using the `int()` constructor. This is a fundamental requirement for type conversion in Python when handling user input.

Answer

age = str(input("Age: "))

Answer

age = float(input("Age: "))

Answer

age = input("Age: ")

Question 10

A server logs are stored as a list of tuples: `logs = [('2024-01-10', 'INFO', 'Started'), ('2024-01-10', 'ERROR', 'Disk full')]`. A developer wants to count how many ERROR logs exist. Which code snippet correctly counts them?

Accepted Answer

count = sum(log[1] == 'ERROR' for log in logs). Uses a generator expression with `sum()` to count how many tuples in the `logs` list have the second element equal to `'ERROR'`. The expression `log[1] == 'ERROR'` evaluates to `True` (which is treated as 1) or `False` (0) for each tuple, and `sum()` adds them up, giving the correct count of ERROR logs.

Answer

count = logs.count(('ERROR',))

Answer

count = [log for log in logs if log[1] == 'ERROR']

Answer

count = len(logs)