✅ 10 Essential Python Interview Code Snippets 🐍💼

1. Reverse a string

s = "hello"
print(s[::-1])  # Output: 'olleh'

2. Check if a string is a palindrome

def is_palindrome(s):
    return s == s[::-1]

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

3. Count word frequency in a list

from collections import Counter

words = ['apple', 'banana', 'apple']
freq = Counter(words)
print(freq)  # Output: Counter({'apple': 2, 'banana': 1})

4. Swap two variables

a, b = 5, 10
a, b = b, a
print(a, b)  # Output: 10 5

5. Fibonacci sequence using recursion

def fib(n):
    return n if n <= 1 else fib(n-1) + fib(n-2)

print(fib(6))  # Output: 8

6. Find duplicate elements in a list

lst = [1, 2, 3, 2, 4]
duplicates = set(x for x in lst if lst.count(x) > 1)
print(duplicates)  # Output: {2}

7. Check if a list is sorted

def is_sorted(lst):
    return lst == sorted(lst)

print(is_sorted([1, 2, 3]))  # Output: True
print(is_sorted([3, 2, 1]))  # Output: False

8. Flatten a 2D list

matrix = [[1, 2], [3, 4]]
flat = [num for row in matrix for num in row]
print(flat)  # Output: [1, 2, 3, 4]

9. Read a file line by line

with open('file.txt') as f:
    for line in f:
        print(line.strip())

10. Using lambda and map

nums = [1, 2, 3]
squares = list(map(lambda x: x**2, nums))
print(squares)  # Output: [1, 4, 9]

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💡 Pro Tip:
Practice variations of these snippets with lists, strings, dictionaries, and file handling. These are common patterns in Python interviews.