Master Python Readability: Essential PEP‑8 Coding Standards Explained

1. Coding Standards

PEP‑8 is the official Python style guide aimed at improving code readability; Guido van Rossum emphasized that code is read more often than written, so consistency across projects, modules, and functions is essential.

2. Syntax Standards

2.1 Comments

Comments explain code without affecting execution. Use single‑line comments starting with # and multi‑line comments with triple quotes ( ''' or """).

# This is a comment explaining the function
print('hello world')

'''\
This is a multi‑line comment.
It can span many lines.
'''\
"""
Another multi‑line comment.
"""

2.2 Indentation

Python relies on indentation instead of braces. Use four spaces per level; never mix tabs and spaces.

Configure editors to replace tabs with four spaces.

# Aligning parentheses
foo = long_function_name(var_one, var_two,
                         var_three, var_four)

# Hanging indent example
foo = long_function_name(
    var_one, var_two,
    var_three, var_four)

2.3 Semicolons

Semicolons are optional; each statement should ideally be on its own line, but multiple statements can be separated by a semicolon if needed.

2.4 Line Length

Limit lines to 79 characters; docstrings and comments should be wrapped at 72 characters. Exceptions include long import statements and URLs.

x = ('This is a very long string that would exceed the line limit '
     'so it is split using parentheses.')

2.5 Blank Lines

Separate top‑level functions and classes with two blank lines; use a single blank line between methods inside a class.

2.6 File Encoding

Source files should be UTF‑8 encoded. In Python 3 this is the default and explicit encoding declarations are unnecessary.

# -*- coding: utf-8 -*-

2.7 Imports

Place imports at the top of the file, after module docstrings and before global variables. Order imports as standard library, third‑party libraries, then local modules, separating each group with a blank line. Avoid wildcard imports.

import os
import sys
from subprocess import Popen, PIPE

2.8 Parentheses

Use parentheses only when necessary for line continuation or to create tuples; avoid unnecessary spaces inside parentheses.

# Correct
spam(ham[1], {eggs: 2})

# Incorrect
spam( ham[ 1 ], { eggs: 2 } )

2.9 Whitespace

Follow PEP‑8 spacing rules: no space before opening parentheses, one space after commas, and a single space around binary operators. Do not align operators vertically across multiple lines.

# Correct
x == 1

# Incorrect
x==1

Avoid compound statements that place multiple statements on one line.

if foo == 'blah': print(100)

2.10 Identifiers and Keywords

Identifiers consist of letters, digits, and underscores, cannot start with a digit, are case‑sensitive, and must not clash with Python keywords.

and as assert break class continue def del elif else except
exec finally for from global if import in is lambda not or pass
print raise return try while with yield

Naming conventions: use lowercase with underscores for functions and variables (e.g., student_name), CapitalizedWords for classes, and avoid Chinese pinyin.

3. Input and Output

3.1 Output

Standard output is typically handled with print() (details omitted).

3.2 Input

Use input() to read a line from standard input; it returns a string. To read multiple values, combine with eval() and separate with commas.

# Prompt for a username
input('Please enter username:
')

# Read three values at once
a, b, c = eval(input())