Pythonic Style & PEP 8

Simple Analogy 🏠

Think of writing code like organizing a kitchen. If every chef follows the same rules (knives here, spices there, pots below), anyone can walk in and cook. PEP 8 is the rulebook for making Python code consistent and readable across the entire community.

The Zen of Python

Type import this in a Python REPL. It reveals the guiding principles:

Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Flat is better than nested.
Readability counts.

PEP 8 — Python’s Style Guide

Naming Conventions

What	Convention	Example
Variables / functions	`snake_case`	`user_name`, `calculate_total()`
Constants	`UPPER_SNAKE_CASE`	`MAX_SIZE`, `DEFAULT_TIMEOUT`
Classes	`PascalCase`	`UserAccount`, `HttpClient`
Private (by convention)	`_leading_underscore`	`_internal_helper()`
Dunder (magic methods)	`__double_underscore__`	`__init__`, `__str__`

Code Layout

# ✅ GOOD — Follows PEP 8

# Two blank lines between top-level definitions
def function_one():
    pass


def function_two():
    pass


class MyClass:
    # One blank line between methods
    def method_one(self):
        pass

    def method_two(self):
        pass

Line Length

# Keep lines under 79 characters for code, 72 for docstrings

# ✅ GOOD — break long lines
total = (price * quantity
         + tax
         - discount)

# ❌ BAD — too long
total = price * quantity + tax - discount + shipping

Imports — Order Matters

# ✅ GOOD — three groups, separated by blank lines
# 1. Standard library
import os
import sys
from datetime import datetime

# 2. Third-party packages
import requests
import pandas as pd

# 3. Local application modules
from mypackage import mymodule

Pythonic Idioms

# Swap variables — no temp variable needed!
a, b = b, a

# Check if a list is empty
if not items:          # ✅ Pythonic
if len(items) == 0:    # ❌ Unnecessary

# Loop with index
for i, item in enumerate(items):
    print(i, item)

# Combine conditions
if 0 < x < 10:          # ✅ Pythonic
if x > 0 and x < 10:    # ❌ Overly verbose

# Default values
def greet(name="Guest"):     # ✅ Pythonic
def greet(name=None):
    if name is None:
        name = "Guest"       # ❌ Unnecessary

# File handling
with open("file.txt") as f:  # ✅ Pythonic — auto-closes
    content = f.read()

f = open("file.txt")         # ❌ Must remember to close
content = f.read()
f.close()

# String joining
result = ", ".join(items)            # ✅ Pythonic
result = items[0] + ", " + items[1]  # ❌ Painful

Linters and Formatters

Tool	What It Does	Example
black	Auto-formats code (opinionated)	`black myfile.py`
ruff	Fast linter + formatter (replaces flake8, isort)	`ruff check .`
mypy	Static type checker	`mypy myfile.py`
pylint	Analyzes code for errors + style	`pylint myfile.py`

# Install
pip install black ruff mypy

# Format your code automatically
black myfile.py

# Check for issues
ruff check myfile.py

🧠 In Simple Words

PEP 8 is Python’s official style guide — follow it so your code looks like everyone else’s
Use snake_case for variables/functions, PascalCase for classes
Keep lines under 79 characters, use meaningful names, organize imports properly
Write Pythonic code — use idioms like enumerate(), with statements, if not list
Use linters (ruff, black) to automatically enforce style — no memorizing needed