20 Python One‑Liner Tricks for Concise and Readable Code

This article presents twenty useful Python one‑liner examples, each accompanied by a brief description and the exact code, illustrating how to perform common programming tasks such as loops, conditionals, data‑structure manipulation, functions, recursion, file I/O, and more in a single line.

1 One‑line For Loop

Use a list comprehension to filter values greater than 250 in a single line.

mylist = [200, 300, 400, 500]
# normal way
result = []
for x in mylist:
    if x > 250:
        result.append(x)
print(result)  # [300, 400, 500]
# one‑line version
result = [x for x in mylist if x > 250]
print(result)  # [300, 400, 500]

2 One‑line While Loop

Show two ways to write a while loop in a single line, including an infinite loop and a bounded loop.

# method 1 – single statement
while True: print(1)  # infinite 1
# method 2 – multiple statements
x = 0
while x < 5: print(x); x = x + 1  # 0 1 2 3 4

3 One‑line IF‑Else Statement

Demonstrate the ternary operator for a one‑line conditional expression.

# if‑else in one line
print("Yes") if 8 > 9 else print("No")  # No
# if‑elif‑else using nested ternary
E = 2
print("High") if E == 5 else print("数据STUDIO") if E == 2 else print("Low")
# single if in one line
if 3 > 2: print("Exactly")  # Exactly

4 One‑line Dictionary Merge

Combine two dictionaries using either the update method or dictionary unpacking.

d1 = {'A': 1, 'B': 2}
d2 = {'C': 3, 'D': 4}
# method 1
d1.update(d2)
print(d1)  # {'A': 1, 'B': 2, 'C': 3, 'D': 4}
# method 2
d3 = {**d1, **d2}
print(d3)  # {'A': 1, 'B': 2, 'C': 3, 'D': 4}

5 One‑line Function

Define a function in a single line using a regular definition with a ternary return or a lambda expression.

# method 1 – regular def with ternary
def fun(x): return True if x % 2 == 0 else False
print(fun(2))  # False
# method 2 – lambda
fun = lambda x: x % 2 == 0
print(fun(2))  # True
print(fun(3))  # False

6 One‑line Recursion

Implement a recursive Fibonacci function in a single line.

# one‑line recursive Fibonacci
def Fib(x): return 1 if x in {0, 1} else Fib(x-1) + Fib(x-2)
print(Fib(5))  # 8
print(Fib(15))  # 987

7 One‑line List Filtering

Filter even numbers from a list using a list comprehension.

mylist = [2, 3, 5, 8, 9, 12, 13, 15]
# normal way
result = []
for x in mylist:
    if x % 2 == 0:
        result.append(x)
print(result)  # [2, 8, 12]
# one‑line way
result = [x for x in mylist if x % 2 == 0]
print(result)  # [2, 8, 12]

8 One‑line Exception Handling

Execute a try‑except block in a single line using exec() .

# normal way
try:
    print(x)
except:
    print("Error")
# one‑line way
exec('try:print(x) \nexcept:print("Error")')  # Error

9 One‑line List to Dictionary

Convert a list to a dictionary using enumerate() and dict() in one line.

mydict = ["John", "Peter", "Mathew", "Tom"]
mydict = dict(enumerate(mydict))
print(mydict)  # {0: 'John', 1: 'Peter', 2: 'Mathew', 3: 'Tom'}

10 One‑line Multiple Variable Assignment

Assign several variables simultaneously in a single line.

# normal way
x = 5
y = 7
z = 10
print(x, y, z)  # 5 7 10
# one‑line way
a, b, c = 5, 7, 10
print(a, b, c)  # 5 7 10

11 One‑line Value Swap

Swap two variables without a temporary variable.

# normal way
v1 = 100
v2 = 200
temp = v1
v1 = v2
v2 = temp
print(v1, v2)  # 200 100
# one‑line swap
v1, v2 = v2, v1
print(v1, v2)  # 200 100

12 One‑line Sorting

Sort a list in place or obtain a sorted copy in a single line.

mylist = [32, 22, 11, 4, 6, 8, 12]
# method 1 – in‑place sort
mylist.sort()
print(mylist)  # [4, 6, 8, 11, 12, 22, 32]
# method 2 – using sorted()
print(sorted(mylist))  # [4, 6, 8, 11, 12, 22, 32]

13 One‑line File Reading

Read all lines from a file into a list without an explicit loop.

# normal way
with open("data.txt", "r") as file:
    data = file.readline()
    print(data)  # Hello world
# one‑line way
data = [line.strip() for line in open("data.txt", "r")]
print(data)  # ['hello world', 'Hello Python']

14 One‑line Class Definition

Define a simple class or equivalent structure in a single line using a lambda or namedtuple .

# normal class
class Emp:
    def __init__(self, name, age):
        self.name = name
        self.age = age
emp1 = Emp("云朵君", 22)
print(emp1.name, emp1.age)  # 云朵君 22
# one‑line using lambda
Emp = lambda: None; Emp.name = "云朵君"; Emp.age = 22
print(Emp.name, Emp.age)  # 云朵君 22
# one‑line using namedtuple
from collections import namedtuple
Emp = namedtuple('Emp', ['name', 'age'])("云朵君", 22)
print(Emp.name, Emp.age)  # 云朵君 22

15 One‑line Semicolon Usage

Execute multiple statements on a single line using semicolons.

a = "Python"; b = "编程"; c = "语言"; print(a, b, c)  # Python 编程 语言

16 One‑line Print

Print a range of numbers without an explicit loop.

# normal way
for x in range(1, 5):
    print(x)  # 1 2 3 4
# one‑line way
print(*range(1, 5))  # 1 2 3 4
print(*range(1, 6))  # 1 2 3 4 5

17 One‑line map Function

Apply a lambda to each element of a list using map() in a single line.

print(list(map(lambda a: a + 2, [5, 6, 7, 8, 9, 10])))  # [7, 8, 9, 10, 11, 12]

18 Delete Multiple Elements in One Line

Remove every second element from a list using slice deletion.

mylist = [100, 200, 300, 400, 500]
del mylist[1::2]
print(mylist)  # [100, 300, 500]

19 One‑line Pattern Printing

Print repeated emoji patterns without a loop.

# normal way
for x in range(3):
    print('😀')
# one‑line
print('😀' * 3)  # 😀😀😀
print('😀' * 2)  # 😀😀
print('😀' * 1)  # 😀

20 One‑line Prime Number Finder

Generate a list of prime numbers within a range using filter() and a lambda.

print(list(filter(lambda a: all(a % b != 0 for b in range(2, a)), range(2, 20))))  # [2, 3, 5, 7, 11, 13, 17, 19]

These concise snippets help reduce boilerplate, improve readability, and demonstrate Python's expressive power for everyday programming tasks.