INI File Section Header Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching ini file section header, ported and verified for Python. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your Python project — whether you're validating in a Django view, a FastAPI endpoint, or a standalone data processing script.

Python Implementation

# INI File Section Header
# ReDoS-safe | RegexVault — Dev & Systems > Config

import re

ini_file_section_header_pattern = re.compile(r'^\[([a-zA-Z_][a-zA-Z0-9_.\-\s]{0,254})\]\s*(?:[;#].*)?$')

def validate_ini_file_section_header(value: str) -> bool:
    return bool(ini_file_section_header_pattern.fullmatch(value))

# Example
print(validate_ini_file_section_header("[database]"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Dev & Systems > Config category and carries a ReDoS-safe certification. That matters for Python developers because particularly important in Python web servers where CPU-bound regex operations can stall concurrent request handling. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Group 1 = section name (may contain spaces). Inline comments with ; or # are accepted. The m flag treats ^ as start-of-line. Python configparser uses [DEFAULT] as a special fallback section.