Error Finding Python Questions Class XI

Instructions:

Read each Python code snippet carefully.
Identify all errors in each question.
Rewrite the corrected Python code for each snippet.

Question 1

Find the syntax errors in the following code snippet:

Python

x = int(input("Enter a number: "))
if x > 10
    print("Greater than 10")
else
    print("Less than or equal to 10")

Question 2

Identify all syntax errors in the following Python program:

Python

def check_even(num)
    if num % 2 = 0:
        return True
    else:
        return False

print(check_even(8))

Question 3

Identify the syntax errors in the code below and explain why each error occurs:

Python

1st_name = "Alice"
for i in range(1, 5):
print("Count:", i)
break = True

Question 4

Locate the syntax errors in the given Python script:

Python

message = 'Hello, Python World!"
val = 25
if val > 20 and < 50:
    print(message)

Question 5

Find all syntax errors in the snippet below:

Python

items = ["apple", "banana", "cherry"]
for item in items
    if "a" in item:
        print(item + 10)

Question 6

Identify the syntax errors in the following code snippet:

Python

a = 0012
b = 5
c = a / b
Print("Result is: " c)

Answer Key

Answer 1

Errors Identified:

Line 2: Missing colon (:) at the end of the if statement header.
Line 4: Missing colon (:) at the end of the else statement header.

Corrected Code:

Python

x = int(input("Enter a number: "))
if x > 10:
    print("Greater than 10")
else:
    print("Less than or equal to 10")

Answer 2

Errors Identified:

Line 1: Missing colon (:) at the end of the function definition (def check_even(num)).
Line 2: Assignment operator (=) used instead of the relational equality operator (==) in the conditional expression.

Corrected Code:

Python

def check_even(num):
    if num % 2 == 0:
        return True
    else:
        return False

print(check_even(8))

Answer 3

Errors Identified:

Line 1: 1st_name is an invalid variable identifier because variable names cannot begin with a digit.
Line 3: Indentation error — statements inside the for loop body must be indented.
Line 4: break is a reserved keyword in Python and cannot be assigned as a variable name.

Corrected Code:

Python

first_name = "Alice"
for i in range(1, 5):
    print("Count:", i)
is_broken = True

Answer 4

Errors Identified:

Line 1: Mismatched string quotation marks (starts with single quote ' and ends with double quote ").
Line 3: Incomplete logical expression — and < 50 lacks a left operand; it must explicitly compare against the variable (and val < 50).

Corrected Code:

Python

message = "Hello, Python World!"
val = 25
if val > 20 and val < 50:
    print(message)

Answer 5

Errors Identified:

Line 2: Missing colon (:) at the end of the for loop header.
Line 4: String and integer concatenation (item + 10) causes an invalid type operation in Python (must convert integer 10 to string using str()).

Corrected Code:

Python

items = ["apple", "banana", "cherry"]
for item in items:
    if "a" in item:
        print(item + str(10))

Answer 6

Errors Identified:

Line 1: Leading zeros in numeric literals (e.g., 0012) are invalid syntax in Python 3.
Line 4: Print starts with an uppercase ‘P’ — Python is case-sensitive, so print() must be lowercase.
Line 4: Missing comma , separating the string parameter "Result is: " and variable c in print().

Corrected Code:

Python

a = 12
b = 5
c = a / b
print("Result is: ", c)

Here are 4 logical error identification questions tailored for Class XI Computer Science (Python) students, followed by the complete answer key at the end.

Question Paper: Find the Logical Errors

Instructions:

Logical errors occur when code runs without throwing a syntax or runtime error, but produces incorrect results due to flawed logic.
Identify the logical error in each question, explain why it produces incorrect output, and write the corrected Python code.

Question 1

A student writes the following program to calculate the average of three numbers, but the output generated is incorrect:

Python

a = 10
b = 20
c = 30

average = a + b + c / 3
print("The average is:", average)

Task: Identify the logical error, explain why the output is wrong, and write the corrected code.

Question 2

The following code is intended to compute the factorial of a given positive integer ($n! = n \times (n-1) \times \dots \times 1$). However, the program consistently outputs 0 regardless of the input:

Python

num = 5
fact = 0

for i in range(1, num + 1):
    fact = fact * i

print("Factorial of", num, "is:", fact)

Task: Point out the logical bug causing the output to remain 0 and write the corrected program.

Question 3

The following function is supposed to check whether a person is eligible to vote (age $\ge 18$) and has a valid voter ID. However, the program gives an incorrect output for a 20-year-old person who does not have a voter ID:

Python

age = 20
has_voter_id = False

if age >= 18 or has_voter_id == True:
    print("Eligible to vote")
else:
    print("Not eligible to vote")

Task: Identify why this logical condition fails and provide the corrected code.

Question 4

A student writes a function to find the maximum value in a list of non-positive integers (e.g., negative numbers). However, the program fails to find the correct maximum element:

Python

numbers = [-15, -42, -8, -23, -4]
max_val = 0

for num in numbers:
    if num > max_val:
        max_val = num

print("Maximum number is:", max_val)

Task: Identify the flaw in initializing max_val and provide the corrected code.

Answer Key

Answer 1

Logical Error: Operator precedence flaw. In Python, division (/) has higher precedence than addition (+). The expression a + b + c / 3 divides only c by 3 before adding a and b, yielding 10 + 20 + 10.0 = 40.0 instead of 20.0.
Fix: Enclose the sum in parentheses (a + b + c) so addition takes place before division.

Corrected Code:

Python

a = 10
b = 20
c = 30

average = (a + b + c) / 3
print("The average is:", average)

Answer 2

Logical Error: Initializing fact = 0. In multiplication, multiplying any number by 0 yields 0. Inside the loop, fact * i will always remain 0.
Fix: Initialize fact = 1 as the identity element for multiplication.

Corrected Code:

Python

num = 5
fact = 1

for i in range(1, num + 1):
    fact = fact * i

print("Factorial of", num, "is:", fact)

Answer 3

Logical Error: Incorrect boolean operator (or). Using or requires only one condition to be True. Since age >= 18 is True (20 $\ge$ 18), the entire condition evaluates to True even though has_voter_id is False.
Fix: Use the and logical operator so that both conditions must be satisfied simultaneously.

Corrected Code:

Python

age = 20
has_voter_id = False

if age >= 18 and has_voter_id == True:
    print("Eligible to vote")
else:
    print("Not eligible to vote")

Answer 4

Logical Error: Initializing max_val = 0. Since all elements in the list are negative numbers, none of them are greater than 0. Thus, num > max_val never evaluates to True, leaving max_val incorrectly as 0.
Fix: Initialize max_val with the first element of the list (numbers[0]) so the comparison works regardless of whether the list contains positive or negative numbers.

Corrected Code:

Python

numbers = [-15, -42, -8, -23, -4]
max_val = numbers[0]

for num in numbers:
    if num > max_val:
        max_val = num

print("Maximum number is:", max_val)