Python Programming Naming Style Cheatsheet

Category	Case	Example
Modules	snake_case	import my_module
Packages	snake_case	from my_package import ...
Variables	snake_case	my_variable = 10
Constants	SCREAMING_SNAKE_CASE	MY_CONSTANT = 10
Functions	snake_case	def my_function(): ...
Methods	snake_case	def my_method(self): ...
Classes	PascalCase	class MyClass: ...
Exceptions	PascalCase	class MyException(Exception): ...
Properties	snake_case	@property def my_property(self): ...
Global Variables	snake_case	global my_global
Private Variables	_snake_case	_my_variable = 10
Private Methods	_snake_case	def _my_method(self): ...

Additional Notes

• Acronyms:
  • snake_case: Acronyms should be lower case. e.g., use my_id instead of my_ID.
  • SCREAMING_SNAKE_CASE: Acronyms should be all uppercase case. e.g., use MY_ID.
  • PascalCase: Acronyms are capitalized fully. For example, use HTTPServerError rather than HttpServerError.
• Numbers in Names:
  Use numbers as words in names.
  • Do not: version1 (snake case) or VERSION1 (screaming snake case).
  • Do: like version_1 (for snake case) and Version1 (for pascal case).

Type Variables and Covariant/Contravariant Behavior

When using type variables in Python (introduced in PEP 484), it's recommended to use CapWords for type variable names. Common examples include short names like T, AnyStr, or Num.

Additionally, when declaring covariant or contravariant behavior in type variables, you can use the suffixes _co for covariant types and _contra for contravariant types. Here's an example:

from typing import TypeVar

VT_co = TypeVar('VT_co', covariant=True)
KT_contra = TypeVar('KT_contra', contravariant=True)