Python Identifier

Validation

Matches a Python identifier (ASCII; PEP 8 ASCII recommendation).

/^[A-Za-z_][A-Za-z0-9_]*$/

How it works

Python 3 actually allows Unicode identifiers, but PEP 8 recommends ASCII for portability. This regex enforces ASCII-only, letters, digits, underscore, no leading digit.

Test Cases

Should Match

snake_case
_private
Class1
x

Should NOT Match

1abc
with-hyphen
spaces here

Quick Summary

Validates ASCII-only Python identifiers per PEP 8.