Scenario-Based Python Interview Questions and Answers (2025)

1. Scenario: You are given a list of integers. Write a Python function to find the two numbers that sum up to a target value.

Question:
You are given a list of integers, and a target value. Write a Python function that returns the indices of two numbers such that they add up to the target value.

Solution:

def two_sum(nums, target):

    seen = {}

    for i, num in enumerate(nums):

        complement = target - num

        if complement in seen:

            return [seen[complement], i]

        seen[num] = i

    return None

# Example usage

nums = [2, 7, 11, 15]

target = 9

print(two_sum(nums, target))  # Output: [0, 1]

Explanation:
This solution uses a hash map (seen) to store the previously visited numbers and their indices. This allows the algorithm to find the complement of the current number in constant time.

2. Scenario: You need to calculate the factorial of a number in Python, but the number is too large. How would you approach this using Python?

Question:
Write a Python function to calculate the factorial of a large number efficiently.

Solution:

import math

def large_factorial(n):

    return math.factorial(n)

# Example usage

print(large_factorial(100))  # Output: 9.33262154439441e+157

Explanation:
The built-in math.factorial function efficiently handles large numbers in Python by using an optimized algorithm and arbitrary-precision arithmetic.

3. Scenario: Given a string, write a Python function to determine if it is a palindrome.

Question:
Write a Python function that checks if a given string is a palindrome (reads the same forward and backward).

Solution:

def is_palindrome(s):

    return s == s[::-1]

# Example usage

print(is_palindrome("racecar"))  # Output: True

print(is_palindrome("hello"))    # Output: False

Explanation:
The function uses Python's slicing feature to reverse the string and compares it with the original string.

4. Scenario: You are tasked with reading a large CSV file and calculating the sum of all values in a specific column.

Question:
How would you write Python code to read a large CSV file and calculate the sum of a specific column?

Solution:

import csv

def sum_column(file_path, column_index):

    total = 0

    with open(file_path, mode='r') as file:

        reader = csv.reader(file)

        next(reader)  # Skip header

        for row in reader:

            total += float(row[column_index])

    return total

# Example usage

print(sum_column('large_file.csv', 2))  # Sum of column at index 2

Explanation:

This code reads the CSV file row by row, skipping the header, and sums the values in a specific column using float() to ensure proper type conversion.

5. Scenario: You need to write a Python function that finds the longest common prefix in a list of strings.

Question:
Given a list of strings, write a Python function that finds the longest common prefix among them.

Solution:

def longest_common_prefix(strs):

    if not strs:

        return ""

    prefix = strs[0]

    for string in strs[1:]:

        while not string.startswith(prefix):

            prefix = prefix[:-1]

            if not prefix:

                return ""

    return prefix

# Example usage

print(longest_common_prefix(["flower", "flow", "flight"]))  # Output: "fl"

Explanation:
The algorithm starts with the first string as the prefix and iteratively shortens it until it matches the start of all strings in the list.

6. Scenario: You need to write a Python function to sort a list of dictionaries based on a key.

Question:
Write a Python function that sorts a list of dictionaries based on a specific key.

Solution:

def sort_dicts_by_key(dict_list, key):

    return sorted(dict_list, key=lambda x: x[key])

# Example usage

data = [{'name': 'Alice', 'age': 25}, {'name': 'Bob', 'age': 30}, {'name': 'Charlie', 'age': 20}]

print(sort_dicts_by_key(data, 'age'))

# Output: [{'name': 'Charlie', 'age': 20}, {'name': 'Alice', 'age': 25}, {'name': 'Bob', 'age': 30}]

Explanation:

The sorted() function sorts the list of dictionaries by the value of the specified key using a lambda function.