PCEP Control Flow, Loops, Lists and Logic Practice Test 2 — 15 Questions

Question 1

Which TWO of the following code snippets will print the numbers 0, 1, 2, 3, 4?

Accepted Answer

for i in range(0,5): print(i). `range(0,5)` generates the sequence 0, 1, 2, 3, 4. The `range()` function with two arguments (start, stop) produces numbers from start inclusive up to, but not including, stop. Therefore, iterating with `for i in range(0,5): print(i)` prints exactly 0 through 4.

Answer

for i in range(5+1): print(i)

Answer

for i in range(0,5,2): print(i)

Answer

for i in range(1,6): print(i)

Question 2

Which THREE of the following are valid list operations?

Accepted Answer

my_list.extend([5,6]). 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 3

You are working on a network automation script that reads a configuration file containing firewall rules. Each rule is a dictionary with keys 'source_ip', 'dest_ip', 'action'. The script must iterate over the rules and print all rules where action is 'allow'. However, the script is not printing any output even though there are allow rules in the file. The code snippet is:

rules = [{'source_ip':'10.0.0.1','dest_ip':'10.0.0.2','action':'allow'},
         {'source_ip':'10.0.0.2','dest_ip':'10.0.0.3','action':'deny'}]
for rule in rules:
    if rule('action') == 'allow':
        print(rule)

What is the most likely cause of the problem?

Accepted Answer

The developer used rule('action') instead of rule['action']. In Python, dictionary values are accessed using square brackets (e.g., rule['action']) or the .get() method, not parentheses. Using parentheses like rule('action') attempts to call the dictionary as a function, which raises a TypeError and prevents the script from executing, so no output is printed even though allow rules exist.

Answer

The dictionary does not have an 'action' key

Answer

The developer used rule['action'] instead of rule.get('action')

Answer

The for loop syntax is incorrect; it should be for rule in rules:

Question 4

You are writing a script to parse a log file. Each line in the log contains a timestamp and a message separated by a colon. You need to extract only the messages that contain the word 'ERROR'. The script uses a list comprehension to filter lines. However, the script crashes with a 'ValueError: not enough values to unpack' when processing some lines. The code is:

lines = ['2024-01-01 12:00:00: INFO: all good', '2024-01-01 12:01:00: ERROR: something wrong']
errors = [msg for timestamp, msg in line.split(': ') for line in lines if 'ERROR' in msg]

What is the correct fix?

Accepted Answer

Rewrite as: [msg for line in lines if 'ERROR' in line for msg in [line.split(': ')[1]]]. It properly separates the filtering and unpacking steps. The original code attempts to unpack each line into timestamp and msg using `line.split(': ')`, but some lines may not contain exactly two parts after splitting (e.g., if the colon is missing or there are extra colons), causing a ValueError. Option D first filters lines containing 'ERROR', then safely extracts the message part by splitting and taking index [1] inside a nested comprehension, avoiding the unpacking error.

Answer

Rewrite as: [line for line in lines if 'ERROR' in line]

Answer

Change the list to a dictionary

Answer

Swap the order of the for clauses to: [msg for line in lines for timestamp, msg in line.split(': ') if 'ERROR' in msg]

Question 5

Arrange the steps to handle an exception in Python using try-except.

Accepted Answer

try block, then except block, then else block, then finally block. Exception handling wraps risky code in try, catches exceptions with except, and optionally includes else and finally.

Answer

try block, then except block, then finally block, then else block

Answer

try block, then else block, then except block, then finally block

Answer

except block, then try block, then else block, then finally block

Question 6

Arrange the steps to install a third-party Python package using pip.

Accepted Answer

1. Ensure pip is installed. 2. Run 'pip install package_name'. 3. Verify the installation by importing the package in Python.. Installing packages with pip involves checking pip, running install, and verifying.

Answer

1. Run 'pip install package_name'. 2. Check if pip is installed. 3. Verify the installation.

Answer

1. Verify the installation by importing the package. 2. Ensure pip is installed. 3. Run 'pip install package_name'.

Answer

1. Download the package manually from a website. 2. Run 'pip install' with the downloaded file. 3. Check pip version.

Question 7

Match each exception type to its description.

Accepted Answer

ValueError: Raised when a function gets an argument with correct type but inappropriate value. These are built-in exceptions in Python that indicate specific error conditions.

Answer

ValueError: Raised when an operation or function is applied to an object of inappropriate type

Answer

IndexError: Raised when a dictionary key is not found

Question 8

Match each Python concept to its description.

Accepted Answer

Module: A file containing Python definitions and statements. The correct matches are: Module is a single file; Package is a directory of modules; Class is a blueprint; Function is reusable code. Common mistakes are confusing module and package definitions.

Answer

Module: A collection of modules organized in a directory tree

Answer

Package: A file containing Python definitions and statements

Question 9

A junior developer needs to write code that processes a list of student scores and stops processing when a score of 100 is encountered, as that score represents a perfect score that should be treated separately. Which loop construct is most appropriate?

Accepted Answer

for score in scores: if score == 100: break ... further processing. The `break` statement immediately exits the loop when a score of 100 is encountered, which matches the requirement to stop processing further scores. The `for` loop iterates over the list naturally, and the `if` condition checks for the perfect score, making this the most straightforward and efficient construct for this scenario.

Answer

for score in scores: if score == 100: pass ...

Answer

for i in range(len(scores)): if scores[i] == 100: exit() ...

Answer

while scores: score = scores.pop(); if score == 100: continue ...

Question 10

A data analyst has a list of temperature readings in Celsius and wants to create a new list containing only readings that are valid (>= -273.15 and <= 1000). Which code correctly creates the filtered list?

Accepted Answer

valid = [temp for temp in temps if -273.15 <= temp <= 1000]. It uses a list comprehension with a chained comparison (`-273.15 <= temp <= 1000`) that correctly includes both boundary values. This syntax is Pythonic and ensures temperatures equal to -273.15 or 1000 are considered valid, matching the requirement exactly.

Answer

valid = [temp for temp in temps if temp > -273.15 and temp < 1000]

Answer

valid = [] for t in temps: if t > -273.15 and t < 1000: valid.append(t)

Answer

valid = list(filter(lambda t: t >= -273.15, temps))

Question 11

A developer is implementing a toggle switch feature. The variable flag starts as False. Which code snippet correctly toggles the flag and performs an action based on the new value each time the code is run? (Assume action1 is performed when flag is True, action2 when False.)

Accepted Answer

flag = not flag; if flag: action1() else: action2(). It first toggles the flag using `flag = not flag`, which flips the boolean value from False to True (or vice versa). Then it uses a conditional `if flag:` to check the new value and calls `action1()` when True or `action2()` when False, exactly matching the requirement to act on the new state each time the code runs.

Answer

if not flag: flag = True; action1() else: flag = False; action2()

Answer

if flag: flag = False; action1() else: flag = True; action2()

Answer

flag = not flag; if flag: action2() else: action1()

Question 12

Which code correctly and efficiently sums only positive numbers from a list?

Accepted Answer

for num in numbers:
    if num <= 0:
        continue
    total += num. It uses `continue` to skip non-positive numbers and then unconditionally adds the remaining numbers to `total`. This is both efficient (no unnecessary `else` branch) and correct: it sums only positive numbers without breaking the loop prematurely or adding zero/negative values.

Answer

for num in numbers:
    if num > 0:
        total += num
    else:
        break

Answer

for num in numbers:
    if num <= 0:
        pass
    else:
        total += num

Answer

for num in numbers:
    if num > 0:
        total += num
    else:
        continue

Question 13

A developer needs to iterate over a list of network interfaces and print only the names that start with 'eth'. Which code should be used?

Accepted Answer

for iface in interfaces: if iface.startswith('eth'): print(iface). The `startswith()` string method is the most direct and readable way to check if each interface name begins with the substring 'eth'. This approach avoids unnecessary slicing or substring membership checks, making the intent clear and the code efficient.

Answer

for i in range(len(interfaces)): if 'eth' in interfaces[i]: print(interfaces[i])

Answer

for iface in interfaces: if iface[:3] is 'eth': print(iface)

Answer

for iface in interfaces: if 'eth' in iface: print(iface)

Question 14

A programmer has a list of tuples representing (product, price) and wants to find the highest price. Which code correctly finds the maximum price?

Accepted Answer

max_price = max([price for product, price in prices]). Ly uses a list comprehension to extract all prices from the tuples, then passes that list to the built-in `max()` function, which returns the highest numeric value. This directly solves the problem of finding the maximum price without any unnecessary complexity.

Answer

max_price = max(prices, key=lambda x: x[1])

Answer

max_price = 0; for p in prices: if p[1] > max_price: max_price = p[1]

Answer

max_price = sorted(prices, key=lambda x: x[1])[-1]

Question 15

Which code correctly creates a list of squares for numbers 1 to 5 using a list comprehension?

Accepted Answer

squares = [x**2 for x in range(1,6)]. It uses the proper syntax for a list comprehension: `[expression for item in iterable]`. Here, `x**2` computes the square, and `range(1,6)` generates numbers 1 through 5 (since range excludes the stop value). This produces the list `[1, 4, 9, 16, 25]`.

Answer

squares = [x**2 for x in range(5)]

Answer

squares = [x^2 for x in (1,2,3,4,5)]

Answer

squares = [x^2 for x in [1,2,3,4,5]]