URL Fragment Extraction Regex for Python

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching url fragment extraction, 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

# URL Fragment Extraction
# ReDoS-safe | RegexVault — Web & Network > URL

import re

url_fragment_extraction_pattern = re.compile(r'^[^#\s]+#([^\s]*)$')

def validate_url_fragment_extraction(value: str) -> bool:
    return bool(url_fragment_extraction_pattern.fullmatch(value))

# Example
print(validate_url_fragment_extraction("https://example.com/page#section"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > URL 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

Capture group 1 contains the fragment string (may be empty for bare #). Fragments are client-side only — servers never receive them.