Master Python One‑Liners: 25 Handy Tricks for Variables, Lists & Files

Since writing my first line of Python, I have been fascinated by its simplicity and readability; this article showcases 25 practical one‑line Python tricks that cover variable swapping, multiple assignment, list operations, file handling, lambda functions, and more.

1. Swap two variables

a, b = b, a

2. Multiple variable assignment

a, b, c = 4, 5.5, 'Hello'

3. Sum of even numbers in a list

a = [1, 2, 3, 4, 5, 6]
s = sum(num for num in a if num % 2 == 0)

4. Delete multiple elements from a list

a = [1, 2, 3, 4, 5]
del a[1::2]  # removes elements at odd indices

5. Read a file into a list

lst = [line.strip() for line in open('data.txt')]
print(lst)

6. Write data to a file

with open('data.txt', 'a', newline='
') as f:
    f.write('Python is awesome')

7. Create a list with a range

lst = [i for i in range(10)]
print(lst)

8. Map a list or type‑convert an entire list

list(map(int, ['1', '2', '3']))
list(map(float, [1, 2, 3]))
[float(i) for i in [1, 2, 3]]

9. Create a set

{x**2 for x in range(10) if x % 2 == 0}

10. Fizz Buzz (1‑20)

[ 'FizzBuzz' if i%3==0 and i%5==0 else 'Fizz' if i%3==0 else 'Buzz' if i%5==0 else i for i in range(1,21) ]

11. Palindrome check

text = 'level'
ispalindrome = text == text[::-1]
print(ispalindrome)

12. Convert space‑separated integers to a list

lis = list(map(int, input().split()))
print(lis)

13. Lambda function (square)

sqr = lambda x: x * x
print(sqr(10))

14. Check existence of a number in a list

num = 5
if num in [1,2,3,4,5]:
    print('present')

15. Print a pattern

n = 5
print('
'.join('😀'*i for i in range(1, n+1)))

16. Find factorial

import math
n = 6
print(math.factorial(n))

17. Fibonacci sequence

fibo = [0,1]
[fibo.append(fibo[-2]+fibo[-1]) for _ in range(5)]
print(fibo)

18. Generate primes

list(filter(lambda x: all(x % y != 0 for y in range(2, x)), range(2,13)))

19. Find maximum value

findmax = lambda x, y: x if x > y else y
print(findmax(5, 14))
# or simply max(5, 14)

20. Scale list elements

def scale(lst, x):
    return [i*x for i in lst]
print(scale([2,3,4], 2))

21. Transpose a matrix

a = [[1,2,3],[4,5,6],[7,8,9]]
transpose = [list(i) for i in zip(*a)]
print(transpose)

22. Count occurrences with regex

import re
cnt = len(re.findall('python', 'python is a programming language. python is python'))
print(cnt)

23. Replace text

"python is a programming language. python is python".replace('python', 'Java')

24. Simulate a coin toss

import random
print(random.choice(['Head', 'Tail']))

25. Generate groups (Cartesian product)

groups = [(a,b) for a in ['a','b'] for b in [1,2,3]]
print(groups)