List Comprehension Tasks in Python List comprehension is one of Python’s most powerful and elegant features. It lets you create new lists from existing ones in a single, readable line of code. Basic Syntax # [expression for item in iterable if condition] squares = [x**2 for x in range(10)] print(squares) # [0, 1, 4, 9,…

Count Character Frequency in Python Counting how many times each character appears in a string is a fundamental problem with many real-world applications, from text analysis to compression algorithms. Best Solution: Using Counter from collections import Counter def char_frequency(s): return Counter(s) result = char_frequency(“hello world”) print(result) # Output: Counter({‘l’: 3, ‘o’: 2, ‘h’: 1, ‘e’:…

Check for Anagrams in Python Two strings are anagrams if they contain the same characters in the same frequency, just in a different order. For example, “listen” and “silent” are anagrams. Solution 1: Sort and Compare def is_anagram(s1, s2): return sorted(s1.lower()) == sorted(s2.lower()) print(is_anagram(“listen”, “silent”)) # True print(is_anagram(“hello”, “world”)) # False Solution 2: Using Counter…

Two Sum Problem in Python Given a list of numbers and a target value, find the indices of two numbers that add up to the target. This is one of the most popular LeetCode-style interview questions. Brute Force — O(n²) def two_sum_brute(nums, target): for i in range(len(nums)): for j in range(i + 1, len(nums)): if…

Remove Duplicates from a List in Python Cleaning a list of duplicate values is a frequent data processing task. Python offers several clean approaches depending on whether order matters. Fastest Method: Convert to Set (Order Not Preserved) my_list = [1, 2, 2, 3, 4, 4, 5] unique_list = list(set(my_list)) print(unique_list) # Output: [1, 2, 3,…

Find the Second Largest Number in a List in Python Finding the second largest element is a common interview problem. The key challenge is handling duplicates correctly. Solution 1: Remove Duplicates, Then Sort def second_largest(nums): unique = list(set(nums)) unique.sort() return unique[-2] print(second_largest([10, 20, 4, 45, 99, 99])) # Output: 45 Solution 2: Using sorted() and…

Check for Prime Numbers in Python A prime number is a number greater than 1 that has no divisors other than 1 and itself. Efficiently checking for primes is a classic coding problem. Efficient Solution (Check up to Square Root) import math def is_prime(n): if n < 2: return False for i in range(2, int(math.sqrt(n))...

Find the Factorial of a Number in Python The factorial of a number n (written as n!) is the product of all positive integers up to n. For example, 5! = 5 × 4 × 3 × 2 × 1 = 120. Using Recursion def factorial_recursive(n): if n == 0 or n == 1: return…

Check for Palindrome in Python A palindrome is a string that reads the same forwards and backwards, such as “racecar” or “madam”. This problem builds directly on string reversal. Simple Solution def is_palindrome(s): return s == s[::-1] # Examples print(is_palindrome(“racecar”)) # True print(is_palindrome(“hello”)) # False Case-Insensitive Check def is_palindrome_ci(s): s = s.lower().replace(” “, “”) return…

Reverse a String in Python One of the most common Python interview questions is reversing a string. Python makes this elegant with slicing. The Pythonic Way def reverse_string(s): return s[::-1] # Example print(reverse_string(“hello”)) # Output: “olleh” How It Works The slicing syntax s[::-1] means: start from the end, go to the beginning, step by -1…