PCEP Data Types, Variables, Basic I/O and Operators Practice Test 13 — 15 Questions

Question 1

A developer is writing a program to calculate the average of three test scores. The current code reads scores as integers: a=int(input()); b=int(input()); c=int(input()); avg = (a+b+c)/3; print(avg). For scores 7, 8, and 9, the output is 8.0, but the requirement is to print the integer average (8), rounded to the nearest whole number. Which modification should the developer make to meet the requirement?

Accepted Answer

Use round(avg): print(round(avg)). The requirement is to print the integer average rounded to the nearest whole number. Using `round(avg)` correctly rounds the floating-point result (8.0) to the nearest integer (8) and prints it as an integer, satisfying the requirement. Option D is correct because `round()` performs standard rounding (banker's rounding in Python 3) and returns an integer when called with a single argument.

Answer

Use integer division after multiplying sum

Answer

Use integer division: avg = (a+b+c)//3

Answer

Use int(avg): print(int(avg))

Question 2

A program asks for the user's age and then prints a message: age = input("How old are you? "); print("You are " + age + " years old."). A user enters "twenty five" and the program prints "You are twenty five years old." which is not the intended numeric age. The requirement is to ensure only numeric ages are accepted and to convert the input to an integer. Which modification is the best?

Accepted Answer

Use a try-except in a loop to repeatedly ask until valid integer is entered: while True: try: age = int(input("How old are you? ")) break except ValueError: print("Invalid."). Option D is correct because it uses a `while True` loop with a `try-except` block to repeatedly prompt the user until a valid integer is entered. The `int()` conversion raises a `ValueError` for non-numeric strings like "twenty five", and the `except` clause catches that error and prints "Invalid." without breaking the loop, ensuring only numeric ages are accepted and converted to an integer.

Answer

Use try-except to catch ValueError and print an error message, then exit.

Answer

Check if age.isdigit() before converting, and if not, ask again.

Answer

Assume the user will always enter a number; no changes needed.

Question 3

A company needs to calculate the average of three test scores entered by a user. The scores are integers. The programmer writes the following code:

s1 = input("Enter score 1: ")
s2 = input("Enter score 2: ")
s3 = input("Enter score 3: ")
avg = (s1 + s2 + s3) / 3
print("Average:", avg)

When run, the output is incorrect. What is the most likely cause?

Accepted Answer

The input() function returns strings, so concatenation occurs instead of addition.. Option D is correct because the `input()` function in Python always returns a string, even when the user types numbers. The `+` operator on strings performs concatenation (e.g., '5' + '3' + '2' becomes '532'), not numeric addition. Dividing the concatenated string by 3 then causes a `TypeError` (or produces an incorrect result if the string is implicitly converted), so the average calculation fails.

Answer

The division by 3 will cause a ZeroDivisionError because 3 is not a float.

Answer

The division operator / always returns an integer, but the sum is not an integer.

Answer

The variable names s1, s2, s3 are not allowed because they start with a letter.

Question 4

Which of the following are valid Python variable names? (Choose two.)

Accepted Answer

data_1. Option B (data_1) is correct because Python variable names can contain letters, digits, and underscores, but must not start with a digit. 'data_1' starts with a letter and includes an underscore and digit, all of which are allowed.

Answer

for

Answer

2nd_place

Answer

my-var

Question 5

Which of the following expressions evaluate to True? (Choose three.)

Accepted Answer

3 ** 2 == 9. Option A is correct because the exponentiation operator `**` computes 3 raised to the power of 2, which equals 9, and the `==` operator checks equality, so `3 ** 2 == 9` evaluates to `True`.

Answer

10 % 3 == 0

Answer

bool(0)

Question 6

Given the following code, which of the following statements are true after execution? (Choose three.)

x = 10
y = 3.0
z = x / y
w = x // y

Accepted Answer

The expression x % y is valid.. Option A is correct because the modulo operator % works with both integers and floats in Python. Here, x is an int and y is a float, so x % y is valid and returns a float result (the remainder of the division).

Answer

The type of w is int.

Answer

The expression x / y returns an integer.

Question 7

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).. Option D is correct because 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.

Question 8

A data analyst needs to read two integers from the user and compute their average as a float. The current code:

a = int(input())
b = int(input())
avg = a + b / 2
print(avg)

The output is always incorrect when a=5 and b=7 (expected 6.0, actual 8.5). The analyst cannot identify the bug. What is the root cause and correct fix?

Accepted Answer

The addition and division have wrong operator precedence; use parentheses: (a + b) / 2.. Option C is correct because in Python, the division operator `/` has higher precedence than addition `+`, so `a + b / 2` is evaluated as `a + (b / 2)`, not `(a + b) / 2`. For a=5 and b=7, this computes `5 + (7 / 2) = 5 + 3.5 = 8.5` instead of the expected `(5 + 7) / 2 = 12 / 2 = 6.0`. Adding parentheses around `a + b` forces the addition to occur first, yielding the correct average as a float.

Answer

The input function is not converting correctly; use float(input()) instead.

Answer

The print function is rounding the result; use print("{:.1f}".format(avg)).

Answer

The division operator / always returns an integer; use // instead.

Question 9

A system administrator writes a script to monitor disk usage. The script reads a percentage from a file as a string, e.g., "100". The code:

usage = open("usage.txt").read().strip()
if usage > 80:
    print("Warning: disk usage high")
else:
    print("Disk usage OK")

Even when usage.txt contains "100", the script prints "Disk usage OK". The admin expected "Warning". What is the problem and how to fix?

Accepted Answer

The file reading returns a string; convert usage to int before comparison.. Option C is correct because the `read()` method returns the file content as a string. In Python, comparing a string to an integer with `>` performs lexicographic (character-by-character) comparison, not numeric comparison. For example, `"100" > 80` evaluates to `False` because `"1"` (ASCII 49) is less than `80` (integer), so the condition fails and the script prints "Disk usage OK". Converting the string to an integer with `int(usage)` before the comparison ensures numeric comparison works as intended.

Answer

The comparison operator > is incorrect; use >= instead.

Answer

The file is not properly closed; use with statement.

Answer

The strip() method removes newlines but not spaces; usage may have extra spaces.

Question 10

A student is learning Python and writes a program to compute the area of a rectangle. The code:

length = input("Enter length: ")
width = input("Enter width: ")
area = length * width
print("Area:", area)

When the user enters 5 and 3, the program crashes with a TypeError: can't multiply sequence by non-int of type 'str'. The student is puzzled because they thought input returns numbers. What is the correct explanation and fix?

Accepted Answer

The input function returns a string, so use int(input("Enter length: ")) and int(input("Enter width: ")).. Option A is correct because the `input()` function in Python always returns a string, even if the user types a number. When you try to multiply two strings (or a string by a string), Python raises a `TypeError` because it cannot multiply sequences by non-integers. The fix is to explicitly convert the input to an integer using `int()` before performing arithmetic.

Answer

The error is due to variable names length and width conflicting with built-in functions; rename them to l and w.

Answer

The print function cannot handle the multiplication result because area is a string; convert area to int.

Answer

The error can be fixed by using the eval function to directly evaluate the input as Python code.

Question 11

A developer is building a simple calculator that accepts two numbers and an operator string. The code:

x = float(input("First: "))
y = float(input("Second: "))
op = input("Operator (+, -, *, /): ")
if op == "+":
    result = x + y
elif op == "-":
    result = x - y
elif op == "*":
    result = x * y
elif op == "/":
    result = x / y
print("Result:", result)

When the user enters 10, 3, and "/", the output is "Result: 3.3333333333333335". The developer wants to display only two decimal places. Which code change will achieve this without introducing errors?

Accepted Answer

Change print to: print("Result:", format(result, ".2f")). Option A is correct because the `format()` function with the format specifier `.2f` converts the floating-point result to a string rounded to two decimal places, which is exactly what the developer needs. This approach does not alter the original variable and works reliably for display purposes.

Answer

Change print to: print("Result: " + str(result)[:4])

Answer

Change print to: print("Result:", result.toFixed(2))

Answer

Change print to: print("Result:", round(result, 2))

Question 12

A beginner Python learner writes a script to swap two numbers:

a = 10
b = 20
a = b
b = a
print("a =", a, "b =", b)

The output is "a = 20 b = 20". The learner expected "a = 20 b = 10". Which of the following is the most Pythonic way to fix the code?

Accepted Answer

Use tuple unpacking: a, b = b, a. Option B is correct because tuple unpacking is the most Pythonic and idiomatic way to swap two variables. It leverages Python's ability to evaluate the right-hand side as a tuple before assignment, so the original values of `a` and `b` are captured simultaneously, avoiding the overwrite issue in the original code.

Answer

Use bitwise XOR: a ^= b; b ^= a; a ^= b

Answer

Use a temporary variable: temp = a; a = b; b = temp

Answer

Use integer arithmetic: a = a + b; b = a - b; a = a - b

Question 13

A programmer is writing a script to read a number, determine if it is even or odd, and then also use the number to calculate its square. The code:

num = input("Enter a number: ")
if num % 2 == 0:
    print("Even")
else:
    print("Odd")
square = num ** 2
print("Square:", square)

When run, a TypeError occurs on the modulo line. Which fix will resolve the error and allow the later calculation to work?

Accepted Answer

Change the input to: num = int(input("Enter a number: ")). Option D is correct because the `input()` function always returns a string, and the modulo operator `%` and exponentiation operator `**` require numeric operands. By converting the input to an integer with `int(input(...))`, both the modulo and exponentiation operations work correctly, resolving the TypeError and allowing the square calculation to proceed.

Answer

Change the condition to: if num // 2 == 0:

Answer

Change the condition to: if float(num) % 2 == 0:

Answer

Change the condition to: if int(num) % 2 == 0:

Question 14

A developer is working on a project that requires handling large numbers. They write:

x = 10000000000
y = 3.0
z = x / y
print(int(z))

The output is 3333333333. However, the developer expected 3333333333 (same). But they suspect that integer division might be better. They try:

x = 10000000000
y = 3
z = x // y
print(z)

Output: 3333333333. Both give same. Now they test with negative numbers:

x = -10
y = 3
z1 = x / y
z2 = x // y
print(z1, z2)

The output is -3.3333333333333335 and -4. The developer is confused why z2 is -4 instead of -3. Which of the following explains the behavior?

Accepted Answer

Floor division always rounds down toward negative infinity, so -10 // 3 = -4 because -3.33 floor is -4.. Option C is correct because Python's floor division (`//`) always rounds down toward negative infinity, not toward zero. For `-10 // 3`, the exact result is approximately -3.333..., and the floor (largest integer ≤ the value) is -4, not -3. This is consistent with the mathematical definition of floor division used in Python.

Answer

The division operator / rounds toward zero, while // rounds toward negative infinity.

Answer

Truncation division always rounds toward zero, so -10 // 3 should be -3, but Python has a bug.

Answer

The result depends on the types; using float y yields different result.

Question 15

A data scientist needs to read a list of floats from a file, one per line, and compute the sum. The current code:

total = 0.0
with open("data.txt") as f:
    for line in f:
        total = total + line
print(total)

When run, a TypeError occurs: unsupported operand type(s) for +: 'float' and 'str'. The scientist knows that line is a string. Which fix will correctly sum the numbers?

Accepted Answer

Change to: total = total + float(line.strip()). Option C is correct because `float(line.strip())` converts the string read from the file (after removing any surrounding whitespace, including the newline character) into a float, which can then be added to the float variable `total`. The original error occurs because Python does not allow implicit addition of a string to a float.

Answer

Change to: total = total + eval(line)

Answer

Change to: total = total + line.strip()

Answer

Change to: total = total + int(line)