10 Python One-Liners That Will Make You Look Like a Pro

Python is famous for its readability and expressiveness. But many developers — even experienced ones — write Python like it's Java or C#, missing the elegant tricks the language was built for. Here are 10 one-liners that will change how you think about Python.

1. List Comprehension Instead of a For Loop

The most fundamental Python trick. Replace verbose for-loops with a single readable line:

# Instead of this:
squares = []
for n in range(10):
    squares.append(n ** 2)

# Write this:
squares = [n ** 2 for n in range(10)]

# With a filter:
even_squares = [n ** 2 for n in range(10) if n % 2 == 0]

2. Swap Two Variables Without a Temp

a, b = 5, 10
a, b = b, a  # a=10, b=5

This uses Python's tuple unpacking. It's not just shorter — it's also slightly faster than using a temporary variable.

3. Flatten a Nested List

nested = [[1, 2], [3, 4], [5, 6]]
flat = [x for row in nested for x in row]
# [1, 2, 3, 4, 5, 6]

4. The Walrus Operator (:=) for Assign-and-Test

New in Python 3.8, the walrus operator lets you assign a value and test it in the same expression:

# Read lines until we find one longer than 100 chars
while (line := file.readline()) and len(line) <= 100:
    process(line)

# Filter a list while computing a value once
results = [y for x in data if (y := transform(x)) > 0]

5. Dictionary Comprehension

# Map names to their lengths
names = ["Alice", "Bob", "Charlie"]
name_lengths = {name: len(name) for name in names}
# {'Alice': 5, 'Bob': 3, 'Charlie': 7}

# Invert a dictionary (swap keys and values)
inverted = {v: k for k, v in original.items()}

6. enumerate() — Never Use range(len()) Again

# Bad:
for i in range(len(items)):
    print(i, items[i])

# Good:
for i, item in enumerate(items, start=1):
    print(i, item)

7. zip() for Parallel Iteration

names = ["Alice", "Bob", "Charlie"]
scores = [95, 87, 92]

for name, score in zip(names, scores):
    print(f"{name}: {score}")

# Unzip (transpose) a list of tuples
pairs = [(1, "a"), (2, "b"), (3, "c")]
numbers, letters = zip(*pairs)

8. any() and all() for Readable Condition Checks

scores = [78, 92, 85, 61]

# Did anyone fail? (below 70)
has_fail = any(s < 70 for s in scores)  # True

# Did everyone pass?
all_pass = all(s >= 70 for s in scores)  # False

9. sorted() with a Key Function

people = [
    {"name": "Alice", "age": 30},
    {"name": "Bob",   "age": 25},
    {"name": "Eve",   "age": 35},
]

# Sort by age, youngest first
youngest_first = sorted(people, key=lambda p: p["age"])

# Sort strings case-insensitively
names_sorted = sorted(names, key=str.lower)

10. Ternary Expression (Inline If-Else)

# Instead of:
if score >= 60:
    result = "pass"
else:
    result = "fail"

# Write:
result = "pass" if score >= 60 else "fail"

# Works in list comprehensions too:
labels = ["pass" if s >= 60 else "fail" for s in scores]