Python 3 Style Guide: Naming Convention

The goal of this Python 3 naming convention is to reduce the effort needed to read and understand code and variable scope by applying a consistent naming standard.

Good Practice

Avoid Characters I, l Or O

The single characters I (aka capital letter of i), l (aka lowercase of L) or O (aka capital letter of o) should not be used as variable names. These variable names could easily be mistaken as numerals 1 (one) and 0 (zero).

Meaningful Names

To help clearly document what the name is used for, choose meaningful and descriptive names that implies the intent and meaning of the code. Names can contain both letters, numbers and underscores. However, names cannot start with a number. Remember that names are case sensitive.

Variables

Use lower_case_with_underscores for naming variables, e.g. variable_name.

MCR Style Configuration Example

variable_name

Constants

Use UPPER_CASE_WITH_UNDERSCORES for naming constants, e.g. CONSTANT_NAME.

MCR Style Configuration Example

CONSTANT_NAME

Functions

Use lower_case_with_underscores for naming functions, e.g. function_name().

MCR Style Configuration Example

function_name()

Classes

Use UpperCamelCase (CapWords) for naming classes, e.g. ClassName. Capitalize all the letters of abbreviations, e.g. HTTPError.

MCR Style Configuration Example

ClassName

Reserved Keywords

Listed keywords (aka identifiers) below are reserved by Python 3 and must not be used when choosing names:

Python Code Example

Try code example below to view a list of all Python 3 keywords:

 import keyword
 print(keyword.kwlist)