What Makes Code Truly Pythonic? 20 Idiomatic Examples Explained

What is Pythonic?

In Chinese, "pythonic" translates to "very Python" and conveys a special emphasis, meaning a way of writing code that only Python can do, distinct from other languages—essentially Python’s idiomatic and unique style.

Swapping Two Variables

Pythonic: a,b = b,a Non‑pythonic:

temp = a
a = b
b = temp

The tuple pack/unpack avoids a temporary variable and uses a single line.

Chain Comparison

Pythonic:

a = 3
b = 1
1 <= b <= a < 10  # True

Non‑pythonic: b >= 1 and b <= a and a < 10 # True The Pythonic form is clearer and shorter.

Truth Testing

Pythonic:

name = 'Tim'
langs = ['AS3', 'Lua', 'C']
info = {'name': 'Tim', 'sex': 'Male', 'age': 23}
if name and langs and info:
    print('All True!')

Non‑pythonic:

if name != '' and len(langs) > 0 and info != {}:
    print('All True!')

Direct truth testing reduces code and improves readability.

String Reversal

Pythonic:

def reverse_str(s):
    return s[::-1]

Non‑pythonic:

def reverse_str(s):
    t = ''
    for x in xrange(len(s)-1, -1, -1):
        t += s[x]
    return t

The slice notation is both elegant and efficient.

Joining a List of Strings

Pythonic:

strList = ["Python", "is", "good"]
res = ' '.join(strList)  # Python is good

Non‑pythonic:

res = ''
for s in strList:
    res += s + ' '
# Result has an extra trailing space

Using join is faster and avoids errors.

List Summation, Max, Min, Product

Pythonic:

numList = [1,2,3,4,5]
sum_val = sum(numList)
max_val = max(numList)
min_val = min(numList)
from operator import mul
prod = reduce(mul, numList, 1)

Non‑pythonic:

sum_val = 0
max_val = -float('inf')
min_val = float('inf')
prod = 1
for num in numList:
    if num > max_val:
        max_val = num
    if num < min_val:
        min_val = num
    sum_val += num
    prod *= num

Benchmarks show the Pythonic version can be twice as fast on large lists.

List Comprehension

Pythonic:

l = [x*x for x in range(10) if x % 3 == 0]  # [0, 9, 36, 81]

Non‑pythonic:

l = []
for x in range(10):
    if x % 3 == 0:
        l.append(x*x)

The comprehension is concise and expressive.

Dictionary Default Value

Pythonic:

dic = {'name':'Tim', 'age':23}
dic['workage'] = dic.get('workage', 0) + 1

Non‑pythonic:

if 'workage' in dic:
    dic['workage'] += 1
else:
    dic['workage'] = 1

get(key, default)

eliminates the explicit if…else check.

For‑else Loop

Pythonic:

for x in xrange(1,5):
    if x == 5:
        print 'find 5'
        break
else:
    print 'can not find 5!'

Non‑pythonic:

found = False
for x in xrange(1,5):
    if x == 5:
        found = True
        print 'find 5'
        break
if not found:
    print 'can not find 5!'

The for‑else construct handles the no‑break case without extra flags.

Ternary Alternative

Pythonic:

a = 3
b = 2 if a > 2 else 1

Non‑pythonic:

if a > 2:
    b = 2
else:
    b = 1

Using the inline conditional expression is clearer and avoids mis‑behaving logical tricks.

Enumerate

Pythonic:

array = [1,2,3,4,5]
for i, e in enumerate(array, 0):
    print i, e

Non‑pythonic:

for i in xrange(len(array)):
    print i, array[i]

enumerate

yields index and value directly and supports a custom start index.

Creating Key‑Value Pairs with zip

Pythonic:

keys = ['Name', 'Sex', 'Age']
values = ['Tim', 'Male', 23]
dic = dict(zip(keys, values))  # {'Name': 'Tim', 'Sex': 'Male', 'Age': 23}

Non‑pythonic:

dic = {}
for i, e in enumerate(keys):
    dic[e] = values[i]

zip

creates tuples that can be turned into a dictionary in one step.

References

Writing Idiomatic Python

Python Idioms

Code Like a Pythonista: Idiomatic Python

Code Style — The Hitchhiker’s Guide to Python