Python Naming Conventions Cheat Sheet

A Programming › Python cheat sheet in English by CashM

Common Python naming conventions and their specific uses.

Python Naming-conventions

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Reference

Python Class (10-152-117)
Reference: PEP 8 - Style Guide for Python Code

The Python Quick Rule

Use in Python	Preferred Convention	Example
Variables	snake_case	total_cost
Functions and methods	snake_case	calculate_total()
Modules and packages	short snake_case	grade_tools.py
Classes	PascalCase	GradeCalculator
Exceptions	PascalCase	InvalidGradeError
Constants	UPPER_SNAKE_CASE	MAX_ATTEMPTS = 3

Use snake_case for most names, PascalCase for classes, and UPPER_SNAKE_CASE for
constants. Names should describe the value, behavior, or responsibility they represent.

Common naming conventions

Convention	Example	Where you may see it	Python status
lowercase	score	Simple names	Common
snake_case	student_score	Python variables, functions, methods, modules	PEP 8 preferred
PascalCase (CapitalCase)	StudentScore	Classes and exceptions	PEP 8 preferred
camelCase	studentScore	JavaScript, Java, C#	Avoid for Python names
UPPER_SNAKE_CASE (SCREAMING_SNAKE_CASE)	MAX_SCORE	Constants and configuration	PEP 8 preferred
kebab-case (train-case)	student-score	URLs, CSS classes, command-line options	Not valid for Python identifiers
dot.case	student.score	Module paths and attribute access	Not a single identifier
Title Case	Student Score	Headings and human-facing labels	Not a Python identifier
flatcase	studentscore	Occasional file names or labels	Rare; less readable
UPPERCASE	MAXSCORE	Acronyms or legacy systems	Rare; avoid for new Python names

Python-specific underscore conventions

Pattern	Example	Meaning
Leading underscore	_cached_result	Conventionally internal or non-public. from module import * does not import it.
Trailing underscore	class_	Avoids a conflict with a Python keyword or built-in name.
Double leading underscore	__balance	Python applies name mangling inside a class to help avoid accidental subclass conflicts.
Double leading and trailing underscores (dunder)	__init__, __len__	Special names defined by Python. Do not invent new dunder names.

Identifier rules

• Start with a letter or underscore, followed by letters, digits, or underscores.
• Do not start with a digit: 2nd_attempt is invalid.
• Do not use spaces or hyphens: student score and student-score are invalid.
• Python is case-sensitive: score, Score, and SCORE are different names.
• Do not reuse Python keywords such as class, for, if, or return.
• Prefer descriptive names: average_score is clearer than avg when space allows.

PEP 8 reminders

• Choose names that reveal intent: is_complete is clearer than flag.
• Use verbs for actions: save_file(), calculate_total(), and display_menu().
• Use nouns for values and objects: student_name, shopping_cart, and report.
• Use boolean names that read like questions: is_valid, has_access, and can_submit.
• Be consistent. A project using student_name should not also use studentName.

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