Writing Clean Python: PEP 8 and Why It Matters

Python PEP 8 is the official style guide for Python code. It was written by Python’s creator Guido van Rossum and exists for one reason: code is read far more often than it’s written. Consistent style makes code easier to understand, review, and maintain.

The Most Important PEP 8 Rules

Naming Conventions

# Variables and functions — snake_case
user_name = "kaikobud"
def calculate_total(price, quantity):
    return price * quantity

# Classes — PascalCase
class UserAccount:
    pass

# Constants — UPPER_SNAKE_CASE
MAX_RETRY_COUNT = 3
DATABASE_URL = "postgresql://..."

Indentation and Line Length

Use 4 spaces per indent (never tabs). Keep lines under 79 characters — some teams allow 88 or 100, but pick one and be consistent.

# Good
def process_order(order_id, user_id, items):
    total = sum(item["price"] for item in items)
    return {"order_id": order_id, "total": total}

# Bad — inconsistent spacing, too long
def processOrder( order_id,user_id,items ):
    total=sum(item["price"] for item in items); return {"order_id":order_id,"total":total}

Imports

# Good — one module per line, standard library first, then third-party, then local
import os
import sys

import requests
import flask

from myapp import models

Whitespace

# Around operators
x = 5 + 3       # Good
x=5+3           # Bad

# After commas
print(a, b, c)  # Good
print(a,b,c)    # Bad

# No space before colon in dicts/slices
d = {"key": "value"}  # Good
d = {"key" : "value"} # Bad

Tools That Enforce PEP 8 Automatically

You don’t need to memorise every rule. These tools check and fix your code:

• flake8 — linter that reports violations
• black — auto-formatter that rewrites your code to be PEP 8 compliant
• isort — sorts your imports automatically

pip install black flake8
black my_file.py  # Reformats the file
flake8 my_file.py # Reports issues

Conclusion

Following Python PEP 8 isn’t about being pedantic — it’s about writing code that other developers (and future you) can read easily. Install black and run it on every file you write. Consistent, readable code is one of the marks of a professional developer.

Read next: Python Virtual Environments: Why and How to Use Them

External resource: PEP 8 — Style Guide for Python Code