PCEP Practice Test 4 — 10 Questions

Question 1

A programmer needs to store a fixed set of error codes that should not change during program execution. Which data type is most appropriate for this purpose?

Accepted Answer

tuple. A tuple is an immutable sequence, so its contents cannot be altered after creation. This ensures that the set of error codes remains constant throughout the program's execution. While lists, dictionaries, and sets can hold multiple values, they are all mutable, meaning they could be accidentally modified. The immutability of tuples makes them the most appropriate choice for storing fixed data.

Answer

dictionary

Answer

set

Answer

list

Question 2

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 3

A developer defines a function and calls it as shown:

def greet(name, greeting='Hello'):
    return greeting + ', ' + name

print(greet('Ana'))

What is printed?

Accepted Answer

Hello, Ana. Default parameter values let a caller omit arguments that have sensible fallbacks. Because greet is invoked with only 'Ana', that value binds to name while greeting uses its default 'Hello'. The concatenation then yields the string 'Hello, Ana', which is printed to the console.

Answer

A TypeError is raised.

Answer

Hello, greeting

Answer

Ana, Hello

Question 4

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 5

A developer writes a function to log sensor readings. The function is defined as:

def log_reading(sensor_id, value, unit="C"):
    return f"{sensor_id}: {value}{unit}"

The developer calls log_reading("T1", 22, unit="F"). What is the result?

Accepted Answer

"T1: 22F". The function call provides two positional arguments ("T1" and 22) and one keyword argument (unit="F"). The keyword argument overrides the default value "C". The f-string then interpolates sensor_id, value, and unit, producing "T1: 22F". This demonstrates how default parameters can be overridden by explicit keyword arguments in a function call.

Answer

A SyntaxError because keyword arguments must come before positional arguments.

Answer

A TypeError because the function expects three arguments and only two positional arguments were given.

Answer

"T1: 22C"

Question 6

Which THREE statements about the break statement in Python are correct? (Choose three.)

Accepted Answer

It exits the innermost loop when executed.. The break statement, when executed inside a loop, immediately terminates the innermost loop it resides in, transferring control to the next statement after the loop. This is a fundamental behavior defined in Python's control flow documentation.

Answer

It can be used with an optional else clause.

Answer

It can be used in an if statement outside any loop.

Question 7

Which TWO of the following code snippets will produce the output '0 1 2'? (Choose two.)

Accepted Answer

for i in range(5): if i>2: break; print(i). The loop iterates over range(5) (0,1,2,3,4), but the break statement executes when i > 2, so the loop terminates after printing 0, 1, and 2. Option D is correct because range(3) generates exactly the sequence 0, 1, 2, and each value is printed in order.

Answer

for i in range(5): if i%2==0: print(i); else: continue

Answer

i=0; while i<3: print(i); i+=1; else: print('done')

Answer

i=0; while i<3: print(i)

Question 8

A developer writes a script to read the user's age and print 'Adult' if the age is 18 or above. The code outputs 'Adult' for age 9. What is the most likely cause?

Accepted Answer

The input was not converted to integer.. The most likely cause is that the input was not converted to integer. In Python, the `input()` function returns a string. When comparing strings lexicographically, '9' >= '18' evaluates to True because '9' is greater than '1' in the first character. Thus, the condition `age >= '18'` (or similar) would mistakenly output 'Adult' for age 9. Converting the input to an integer with `int()` ensures numeric comparison, where 9 >= 18 is False.

Answer

The if statement lacked parentheses around the condition.

Answer

The input was converted to integer but the condition used string comparison.

Answer

The condition used >= instead of >.

Question 9

Which TWO of the following Python data types are mutable?

Accepted Answer

list. Option A (list) is correct because Python lists are mutable sequence types: you can change, add, or remove elements in place (e.g., append(), item assignment) without creating a new object. Option E (dict) is correct because dictionaries are mutable mappings: key-value pairs can be added, updated, or deleted in place (e.g., d['k'] = v, del d['k']). The unmarked options are immutable: str (B) cannot be modified in place since strings are immutable sequences, tuple (C) is an immutable sequence whose contents cannot be reassigned, and int (D) is an immutable numeric type where any arithmetic produces a new object rather than modifying the original.

Answer

str

Answer

tuple

Answer

int

Question 10

A junior developer is writing a script to calculate the total cost of items in a shopping cart. The script uses variables item_price (float) and quantity (int). The code is:

item_price = 2.5
quantity = 3
total = item_price * quantity
print("Total: " + total)

When run, this code raises a TypeError. The developer is confused because the multiplication seems correct. What is the most likely issue and the correct fix?

Accepted Answer

The print function cannot concatenate a string with a float; convert total to string using str(total).. The `print` function in Python expects all arguments to be strings when using the `+` operator for concatenation. The variable `total` is a float (result of multiplying a float by an int), and Python does not implicitly convert it to a string. The error is a `TypeError: can only concatenate str (not 'float') to str`. The fix is to explicitly convert `total` to a string using `str(total)` before concatenation.

Answer

The variable total is being overwritten by the print statement; use a different variable name.

Answer

The multiplication should be written as int(item_price) * quantity to ensure integer result.

Answer

The variable names are too descriptive; rename them to a and b to avoid confusion.