Top 10 Python Interview Questions to Dominate Any Coding Round

Introduction

Although Python is one of the most popular programming languages, Python interview questions often test basic concepts that every programmer should know. Learning Python can mean the difference between walking into a coding interview with confidence and passing it with flying colors. Here is a collection of some of the most asked Python interview questions with their answers and solutions. In this website, if you wanna learn python star patterns i’ve made a post.

Step-by-Step Solutions to Popular Python Interview Questions

Swapping of Two Numbers Using a Third Variable

One of the most common Python interview questions is swapping two numbers using a third variable.

Explanation

• We use a temporary variable to hold one value while swapping.
• This method is simple and easy to understand.

Code

# Assigning values
a = 5
b = 8

# Using a temporary variable
temp = a
a = b
b = temp

print("After swapping: a =", a, "b =", b)

Output

After swapping: a = 8 b = 5

Step by Step Execution

1. Store a in temp (temp = a)
2. Assign b to a (a = b)
3. Assign temp to b (b = temp)
4. Print the swapped values

Swapping of Two Numbers Without Using a Third Variable

Another popular topic in Python interview questions involves swapping two numbers without using a temporary variable. This approach demonstrates your understanding of arithmetic operations or bitwise manipulation.

Explanation:

• We use addition and subtraction or bitwise XOR to swap values.
• This reduces memory usage.

Code

# Assigning values
a = 5
b = 8

# Swapping without a third variable
a = a + b
b = a - b
a = a - b

print("After swapping: a =", a, "b =", b)

Output

After swapping: a = 8 b = 5

Step-by-step Execution:

1. a = 5, b = 8
2. a = a + b → a = 5 + 8 = 13
3. b = a - b → b = 13 - 8 = 5
4. a = a - b → a = 13 - 5 = 8

Final Values: a = 8, b = 5

Reverse a String Using a Loop

In most Python interview questions, candidates are asked to reverse a string using a loop. Here’s a simple code to achieve that:

Explanation

• We iterate through the string in reverse order.

Code

# Input string
s = "hello"
rev = ""

# Loop through the string in reverse order
for i in range(len(s) - 1, -1, -1):
    rev += s[i]

print("Reversed string:", rev)

Output

Reversed string: olleh

Iteration Breakdown:

Understanding the iteration breakdown is crucial to solving Python interview questions effectively.

• Given string: "hello"
• len(s) = 5 → indices: 0 1 2 3 4

Iteration	i	s[i]	rev (Reversed String)
1st	4	‘o’	“o”
2nd	3	‘l’	“ol”
3rd	2	‘l’	“oll”
4th	1	‘e’	“olle”
5th	0	‘h’	“olleh”

Check Whether a String is Palindrome or Not

Explanation

• A palindrome reads the same forward and backward.

Code

# Input string
s = "radar"
n = len(s)
is_palindrome = True

# Check if first and last characters are the same
for i in range(n // 2):
    if s[i] != s[n - i - 1]:
        is_palindrome = False
        break

print("Is palindrome?", is_palindrome)

Output

Is palindrome? True

Iteration Breakdown:

• Given string: "radar"
• n = len(s) = 5
• Loop runs for n//2 = 5//2 = 2 times

Iteration	i	s[i]	s[n-i-1]	Check
1st	0	‘r’	‘r’	Match
2nd	1	‘a’	‘a’	Match

Since all comparisons match, "radar" is a palindrome.

Check Whether a Number is Palindrome or Not

Explanation

• A number is a palindrome if it reads the same backward.

Code

# Common Python interview questions to check palindrome
num = 121
original_num = num  # Store the original number
rev_num = 0  # Initialize reversed number to 0

# Reverse the number using a loop
while num > 0:
    digit = num % 10  # Get the last digit
    rev_num = rev_num * 10 + digit  # Add digit to reversed number
    num = num // 10  # Remove the last digit

# Check if original and reversed numbers are the same
if original_num == rev_num:
    print(original_num, "is a palindrome.")
else:
    print(original_num, "is not a palindrome.")

Output

121 is a palindrome.

Iteration Breakdown:

• Given number: 121
• Reverse the digits using modulo (%) and integer division (//).

Iteration	num	digit = num % 10	rev_num = rev_num * 10 + digit	num = num // 10
1st	121	1	0 * 10 + 1 = 1	121 // 10 = 12
2nd	12	2	1 * 10 + 2 = 12	12 // 10 = 1
3rd	1	1	12 * 10 + 1 = 121	1 // 10 = 0

Since original_num (121) == rev_num (121), it is a palindrome.

Fibonacci Series

Explanation

• The Fibonacci sequence starts with 0 and 1.

Code

# Number of terms
n = 5
a, b = 0, 1

# Print first two terms
print(a, b, end=" ")

# Generate next terms using a loop
for i in range(n - 2):
    next_term = a + b
    print(next_term, end=" ")
    a = b
    b = next_term

Output

0 1 1 2 3

Iteration Breakdown:

• First two numbers: 0, 1
• Generate n-2 = 3 more terms.

Iteration	a	b	next_term = a + b	Output Sequence
1st	0	1	0 + 1 = 1	0 1 1
2nd	1	1	1 + 1 = 2	0 1 1 2
3rd	1	2	1 + 2 = 3	0 1 1 2 3

Factorial Using Loop

Explanation

• The factorial of a number n is n! = n * (n-1) * ... * 1.

Code

# Input number
n = 5
fact = 1

# Loop through numbers from 1 to n
for i in range(1, n + 1):
    fact *= i

print("Factorial:", fact)

Output

Factorial: 120

Iteration Breakdown:

Iteration	i	fact = fact * i
1st	1	1 * 1 = 1
2nd	2	1 * 2 = 2
3rd	3	2 * 3 = 6
4th	4	6 * 4 = 24
5th	5	24 * 5 = 120

Check Whether a Number is Prime or Not

Understanding prime numbers is important because it forms the basis of many Python interview questions that assess logical thinking and problem-solving abilities.

Explanation

• A prime number has only two factors: 1 and itself.

Code

# Input number
n = 13
is_prime = True

# Loop from 2 to n-1
for i in range(2, n):
    if n % i == 0:
        is_prime = False
        break

if n == 1:
    is_prime = False

print("Is prime?", is_prime)

Output

Is prime? True

Iteration Breakdown for n = 13

The loop checks numbers from 2 to 12.

Iteration	i	n % i (Remainder)	Prime Check
1st	2	13 % 2 = 1 (Not divisible)	Prime
2nd	3	13 % 3 = 1 (Not divisible)	Prime
3rd	4	13 % 4 = 1 (Not divisible)	Prime
4th	5	13 % 5 = 3 (Not divisible)	Prime
5th	6	13 % 6 = 1 (Not divisible)	Prime
6th	7	13 % 7 = 6 (Not divisible)	Prime
7th	8	13 % 8 = 5 (Not divisible)	Prime
8th	9	13 % 9 = 4 (Not divisible)	Prime
9th	10	13 % 10 = 3 (Not divisible)	Prime
10th	11	13 % 11 = 2 (Not divisible)	Prime
11th	12	13 % 12 = 1 (Not divisible)	Prime

Since 13 is not divisible by any number in the loop, is_prime remains True.

Print Prime Numbers in the Given Range

One of the most common Python interview questions asks candidates to print prime numbers in a given range.

Explanation

• We check each number in the given range.

Code

# Input range
start = 10
end = 18

# Loop through numbers from start to end
for num in range(start, end + 1):
    # Check if number is prime
    for i in range(2, num):
        if num % i == 0:
            break
    else:
        # Print prime number
        if num > 1:
            print(num)

Output

11
13
17

Iteration Breakdown for Numbers Between 10 and 50

Let’s go step by step and analyze each number.

Step-by-step Execution for Each Number

Checking num = 10

• Loop runs: i = 2 to 9
• 10 % 2 == 0 → Not a prime number (loop breaks)

Checking num = 11

• Loop runs: i = 2 to 10
• 11 % 2 != 0, 11 % 3 != 0, 11 % 4 != 0, … (no divisors found)
• Prime number → 11 is printed

Checking num = 12

• Loop runs: i = 2 to 11
• 12 % 2 == 0 → Not a prime number (loop breaks)

Checking num = 13

• Loop runs: i = 2 to 12
• 13 % 2 != 0, 13 % 3 != 0, … (no divisors found)
• Prime number → 13 is printed

Checking num = 14

• 14 % 2 == 0 → Not a prime number

Checking num = 15

• 15 % 3 == 0 → Not a prime number

Checking num = 17

• Loop runs: i = 2 to 16
• No divisors found → Prime number → 17 is printed

Find Sum of Individual Digits

Explanation

• We extract digits and sum them.

Code

# Input number
num = 123
sum_digits = 0

# Loop through digits
while num > 0:
    digit = num % 10
    sum_digits += digit
    num //= 10

print("Sum of digits:", sum_digits)

Output

Sum of digits: 6

Iteration Breakdown:

Iteration	num	digit = num % 10	sum_digits += digit	num = num // 10
1st	123	3	0 + 3 = 3	123 // 10 = 12
2nd	12	2	3 + 2 = 5	12 // 10 = 1
3rd	1	1	5 + 1 = 6	1 // 10 = 0

Count Vowels and Consonants in a String

One of the easiest python interview questions is this.

Explanation

• We count vowels (a, e, i, o, u) and consonants separately.

Code

# Optimized approach for common Python interview questions
s = "hello world"
vowels = "aeiouAEIOU"
vowel_count = 0
consonant_count = 0

# Loop through each character
for char in s:
    if char in vowels:
        vowel_count += 1
    elif char.isalpha():  # Check if character is a letter
        consonant_count += 1

print("Vowels:", vowel_count)
print("Consonants:", consonant_count)

Output

Vowels: 3
Consonants: 7

Iteration Breakdown

Let’s analyze the loop character by character for "hello world".

Character	Is it a Vowel?	Is it a Consonant?	vowel_count	consonant_count
‘h’	No	Yes	0	1
‘e’	Yes	No	1	1
‘l’	No	Yes	1	2
‘l’	No	Yes	1	3
‘o’	Yes	No	2	3
‘ ‘ (Space)	No	No (Ignored)	2	3
‘w’	No	Yes	2	4
‘o’	Yes	No	3	4
‘r’	No	Yes	3	5
‘l’	No	Yes	3	6
‘d’	No	Yes	3	7

Final Counts

• Vowels: 3 → (e, o, o)
• Consonants: 7 → (h, l, l, w, r, l, d)

Tips to Solve Python Interview Questions Quickly

• Break down the problem into smaller steps.
• Identify possible edge cases and handle them carefully.
• Practice common Python interview questions to get familiar with different approaches.
• Use comments to explain the logic for better readability.

Conclusion

To ace the python interview questions. these are the Fundamental ideas of Python interviews. These solid fundaments help you to hear the concepts such as loops, conditionals, functions, and mathematical operations, which are essential for solving problems properly.

The main point of the article was:

• Swapping two numbers with and without the third variable
• Reversing a string with a loop
• Making two strings or two numbers palindromes
• Counting the number of vowels and consonants in a string
• Generating a Fibonacci series
• Finding factorial with loops
• Seeing if prime numbers are in a given series and print them Finding the sum of the individual digits of a number

These are some of the most frequently asked Python interview questions that can help you build a strong foundation in coding, and if you practice them, then your skills of problem-solving would also get better. Time complexity plays a vital role in solving Python interview questions effectively, ensuring optimal solutions. Besides, we have come up with an approach that can be used to check prime numbers in a way that would save time.

Frequently Asked Python Interview Questions with Solutions